CHAPTER ONE

1.0 INTRODUCTION

Livestock production plays an important role in the life of farmers. It provides

food, employment and income and thus contributes to rural development. In a

nutshell, it enhances the standard of living of many farmers. The industry also

plays a crucial role in economic development, since in recent years, livestock

farming is shifting from subsistence farming to commercial farming.

Due to the high population growth in Africa (WHO, 2010) including Nigeria

whose population was estimated to be about 174.5 million people in 2013, and

with a population growth rate of 3% per annum (USDA, 2013).Although, the

population growth in Nigeria is rapid, Wiggins and Keats (2013) observed that

food production has not followed suit over the last 50 years. This population will

lead to an increasedrequirement of food especially the supply of protein in the diet

because of its important role in human wellbeing which includes growth,

maintenance of hormonal and enzymatic activities and improvement of the defense

mechanism of the body (Ademoluet al., 2004).

Owing to the increase in the demand of animal protein, there is need to look

inward and integrate into our farming system some non-conventional meat sources

(Ebenebe, 2000)of which snail is one of those sources when compared to poultry,

cattle, pig, sheep and goat which are all conventional animals farmed by man.
Snail farming (Heliciculture) has advantages over most other livestock which

includes; low capital requirement for its establishment and operation, less demand

of professional knowledge, very high fecundity and low mortality, less labour

requirement and availability of ready domestic and international markets etc.

(Akinbile, 2000). In addition to that, snail meat is a source of calcium, magnesium

and zinc. Thus, it is used in the treatment of anaemia and hypertension. The high

calcium content and polyunsaturated fatty acid of snail meat is the reason why it is

recommended for cases of rickets. The poor lipid content of snail makes it to be

about the only meat apart from fish to be recommended for a liver–diseased patient

(Mogboet al.,2013).Akannusi, (2002) also reported that the low content of fat

(1.3%) and low cholesterol level make snail meat a good antidote for vascular

diseases such as cardiac arrest, Hypertension, heart attack, stroke, high blood

pressure and other fat related ailments which are common in the tropical region.

Another benefit of snail farming is that snails are known to eat at least 500

different types of plants, fruits, vegetable, ornamental plants, tree barks etc. thus,

the ability of snails to utilize a variety of readily available feeding material to

achieve appreciable weight gain under intensive management makes it a suitable

and cheaper alternative to other animal protein sources (Okonta 2012; Boluet

al.,2009 and Alikweet al.,2013).

However, snails are usually found in the wild and snail production in the wild has

been on the decline due to the depletion of the rainforest, over harvesting of

snails,bush burning and the increased use of agricultural pesticides (Okorie and

Ibeawuchi, 2004).Also,another limiting factor is the fact that snails are very slow

growing animal with seasonal breeding pattern which severely affect their

productivity (Eze et al., 2010).

The tropical land snail belongs to a group called gastropod that belongs to

theMollusca Phylum.Although, there are several land snails in the world, but three

notable ones called Giant African land snails in the family of Achatinidae(Raut and

Barker, 2002)are farmed in Nigeria. They are., (i) Giant African land snail or East

African land snail scientifically called Achatina fulica, which weighs up to 32

grams (Cooling 2005). (ii)Achatina achatinacommonly calledthe giant Ghana or

tiger land snail are the largest land snails in the world and arewidely sought after

species, due to their size, distinct markings and lack of availability. Although, they

are believed to bemore difficult to breed than other African snails (James Rushton,

2012).

Reproduction is a pertinent aspect in the life cycle of every living thing. Snails are

hermaphrodites, having high rate of productivity, although they must fertilize each

other simultaneously before they layfertile eggs (SAkinnusi, 2004). Neiman,

(2006) reported that land snails carry out internal fertilization and observed that
courtship usually precedes mating. They also reported that snails depend on the

stimuli delivered by courtship behaviour and copulation to initiate and co-ordinate

reproductive function. Akinnusi (2004) further stated that snails are very

selectivein their mating partners. In addition, Omole and Kehinde (2005) observed

that snails are sometimes not interested in mating with other snails of the same

species. Akinnusi, (2004) has speculated the non-mating of black skinned and

white skinned strains of A.marginata because of the differences in their genetic

composition. It is based on the unique reproductive nature of snails that this study

is conducted to determine the phenotypic variation in the reproductive traits of

black and white skinned A. marginate snails and their crosses.

1.1STATEMENT OF PROBLEM

The natural habitat of African giant land snail is facing deforestation and

degradation due to human activities. Thus, there are growing efforts to

commercialize snail production to meet the animal protein demand. Snail farming

in large-scale especially the African giant land snail (Archachatinamarginata) has

paved way for demand for the snail in the local market to meet the protein intake

of the populace (Ejidike and Afolayan, 2010). The demand for snail despite the

cost has continue to increase and in meeting with this increase demand at low cost

by commercial farmers, they tend to source for alternative feeding materials for

snails. In addition to looking for feeding material, an important factor thesefarmers

should consider is the reproductive ability of these animals as reproduction plays a

vital role in the continuity of any specie.

The popularly farmed snail in Nigeria, A. marginatahas been classified on the basis

of foot colour into back and white by Akinnusi (2004) and Omole et al., (2007)

which can be termed a phenotypic kind of classification. Due to the unique

reproductive behavior of snails when compared to other livestock in the sense of

them being selective of mating partners (Omole and Kehinde 2005), it will be

imperative to study the reproductive potentials of the different species of A.

marginata so a farmer can decide which one to rear in order to meet maximum

production. Thus this study was aimed at determining the phenotypic variation in

the reproductive trait of black and white skinned A. marginatasnails and their

crosses.

1.2OBJECTIVES OF THE STUDY

The study is aimed at determining the

1. Effect of phenotypic variation on reproductive performance of two ecotypes of

A. marginata (Black and White skin) and their crosses.

2. To determine the Phenotypic correlation in black skinned and white skinned

Archachatinamarginata and their crosses.

 CHAPTER TWO

LITERATURE REVIEW

2.1 Reproduction in Snail

Molluscs are the second most numerous type of invertebrate with the majority of

them being gastropods (O’Connor and Crowe, 2005). Molluscs are a diverse group

of animals with respect to their morphological forms, presence in different

environments - water and land, feeding habit, also because of various patterns of

reproduction (Policansky, 1982). The main functions of their reproductive systems

includes: 1) production of gametes (sperm and ova), 2) nutrition and storage of

mature gametes, 3) transport of sperm produced by one specimen (autosperm) to

reproductive ducts of another specimen, 4) reception of sperm produced by the

same individual (allosperm), 5) providing appropriate environmental conditions for

the ovum fertilized by sperm, 6) covering of zygote by protective and nutrient

layers, 7) laying eggs (oviposition) and 8) resorption of remains and excess of

products of the reproductive process (Gómez, 2001). The mollucs can either be

dioecious (gonochorism or dioecism) having separate sexes (female and male

gonads occurring in different, separate individuals) or hermaphroditic (an

individual contains both male and female reproductive organs).

Achachatinamarginata which belongs to this Phylum: Mollusca; Class:

Gastropoda; Family: Achatinidae commonly called African giant snail are

nocturnal (active at night) and are mostly regarded as herbivorous, feeding

primarily on living and decaying vascular plant materials (Raut and Barker, 2002).

The form of reproduction seen in these species of animal is hermaphroditism

which is universal to pulmonate gastropod of which other species of Achatinadae

are included. Hermaphoditism refers to the presence of functional male and female

reproductive systems in the same individual (Chase, 2007). Thus,

Achachatinamarginatahas both male and female organs present in a single

individual. Hermaphrodites can be simultaneous, which means that an organism

has both male and female organs at the same time or sequential which means that,

during their life time their sexes change (Wilson and Harder, 2003). For the

changes of sexes during lifetime, there is protandry (male-to-female change) and

protogyny (female-to-male change), but the first one is more often in molluscs

(Larsen et al., 2013).

Chase (2007) recorded that in some species (example, Lymnaeastagnalis and Helix

pomatia), reproduction can be reciprocal (unilateral), where individuals play only

one role per mating which can however be switched in subsequent mating (Chase,

2007), while in some other species (example, Cornuaspersus), simultaneous

reciprocal mating occur with both members of the pair acting as male and female
simultaneously (Skelleyet al., 2010). Asamiet al. (1998) classified mating in the

majority of land snails and slugs to be either face-to-face or shell-mounting. Angus

and Peter (2014) stated that, four different modes of mating are possible because

sex is either simultaneous reciprocal or unilateral and classified those four to be;

Face-to-face-simultaneous reciprocal; Face-to-face-unilateral; Shell-mounting-

simultaneous reciprocal; and Shell-mounting-unilateral. The A. marginatawhich is

a hermaphrodite is involved in shell mounting that is simultaneous reciprocal

(Plumer, 1975).

2.2 Factors Affecting Reproduction in Snails

Reproduction is an essential aspect of the life cycle of every organism, thus,

conditions for reproduction must be favourable to ensure the survival of specie and

a diverse ecosystem. Several factors are known to affect reproduction in snails

which includes; nutrition (Abionaet al., 2012) and environmental factors

(temperature, humidity, photoperiod etc) (Cobbinahet al., 2008).

2.2.1 Nutrition as a Factor Affecting Reproduction in Snail.

Nutrition plays an important role in the life of an organism. Little wonder in

livestock production; cost of feed alone is responsible for 60-70 % of the total cost

of production (Omole et al., 2013). The function of individual nutrients has been

enumerated by several researchers. For example, protein plays a crucial role in the
diet of livestock for its wellbeing which includes growth, maintenance of hormonal

and enzymatic activities, reproduction and improvement of the defense mechanism

of the body (Ademoluet al., 2004). To understanding the role of nutrition in

reproduction in snails, several researchers have carried out several researches with

different feeding materials. There has been admittance to the influence of diets on

the reproductive performance of snails in captivity (Abionaet al., 2012).

Okonwoet al., (2000) showed that, snails fed ripe pawpaw fruits laid high number

of eggs when compared to snails fed old pawpaw leaves. Ademolu (2015) reported

a similar result in his publication (contribution of pawpaw plant (Caricapapaya) to

the performance of giant African land snail). They likened the effect to be the

inability of the old pawpaw leaves to meet the nutritional requirement of the

animal. Ayoola and Adeyeye, (2010) revealed that old and yellow pawpaw leaves

have low nutrients, minerals and vitamins composition which are necessary for egg

formation. In a study conducted by Olatunji and Michael, (2020) revealed that,

feeding of snails with unripe pawpaw and watermelon peel had the least

reproductive performance as compared to concentrate feed. Nyameasem and

Borketey-La (2014) in an earlier study also reported that layer mash (a concentrate

ration) when fed to snails supported reproduction in the snails better than pawpaw

fruit diet. Olatunji and Michael, (2020) in their stydy also reported that egg

hatchability, fertility, and average juvenile snails of snails fed a mixture of leaf
meal and concentrate diets performed better when compared to snails fed

concentrate only. Their result is in conformation with that of Ejidike (2007) and

Oyeaguet al. (2018) that reported that snails fed with diets containing concentrate

feed and herbs performed better than those that received only concentrate or herbs.

Similarly, Oyeaguet al. (2018) reported that inclusion of C. pubescens in

concentrate ration for snails increased the number of eggs laid, hatchability, and

fertility of eggs with a lesser mortality of the embryo.

2.2.2 Environmental Factors Affecting Reproduction in Snail

One major problem of domestication is the ability to copy perfectly the conditions

in the wild so as to maximize the growth and reproductive potentials of animals.

Ademoluet al. (2012) reported that much work still need to be done in

understanding the environmental requirement of snail as there exist a great gap

between snails in the wild and those reared commercially. Several environmental

factors are known to affect snail production. These factors include; soil type,

temperature, humidity, rainfall and photoperiod (Ejidikeet al., 2002, Ebenso,

2006).
  Temperature as an Environmental Factor Affecting Reproduction in

Snail

The influence of temperature on development and growth is of great importance in

determining an organism’s life strategy since growth rate and size at maturity are

key traits in life-history evolution (Stearns, 1992; Charnov, 1993). In

poikilothermic, growth, development rates and body size at adult age are functions

of environmental temperature. Atkinson (1995) reported that, in most

poikilothermic species studied, size at maturity decreases with increasing growth

temperature. The effect of temperature on reproduction of snails have been

observed and reported. Gomotet al. (1989), by using Cornuaspersumaspersa snails

observed that temperature of 20°C is the most favourable condition for egg-laying

and for the effective functioning of the ovotestis and the albumen gland, but noted

that, egg-laying is completely inhibited at 15°C and partially at 20°C; they

observed differentiation of gametes in the ovotestis of snails, but mature oocytes

were never released and thus degenerated. Saida et al. (2009) in their work with

Helixaperta land snail reported higher growth rates and higher weights at

temperature of 20°C which favoured fecundity. They also reported that, snails

reared at 20°C laid more eggs per clutch than those raised at 15°C. Furthermore,

rapid growth and larger body size are expected to be advantageous, not only in

fecundity but also in other aspects of life history for many organisms. However,
reduction in adult weights at lower temperature resulted in smaller numbers of

eggs per clutch because slower growth and the resulting smaller body size reduce

fecundity of each individual (Blanckenhorn, 2000). According to Ugwuet al.

(2011), temperature is one important factor on which hatchability of egg in snails

depends on. The optimal range of temperature for snail production in the tropics

which includes growth and reproduction, temperature above 30 oC is not favourable

(Cobbinahet al., 2008).

 Relative Humidity as an Environmental Factor Affecting Reproduction

in Snail

Relative humidity has to do with the amount of moisture in the air. There are

significant fluctuations in air humidity, which have a pronounced effect on the

reproductive characteristics of snails (Ebenso, 2006). Relative air humidity should

not be near saturation, because it would encourage the development of harmful

bacteria and fungi (Cobbinahet al., 2008) which may cause diseases in the flock.

Ugwuet al. (2011) stated that humidity is as important as temperature in ensuring

the hatchability of snail eggs. According to Cobbinahet al. (2008), the optimal

relative humidity range for snail production should not be below 70%. Mogboet al.

(2013) found this to be true in their work to determine the influence of housing on

the reproductive characteristics of snail to report that that the average relative
humidity for all the housing types were not below 70% which favoured egg

production and hatchability in snail.

 Photoperiod (Light) as an Environmental Factor Affecting

Reproduction in Snail

Lights duration and intensity play a pivotal role in the regulation and control of

production, reproduction, behavior and welfare of animals (Deep et al., 2010,

Schwean-Lardner et al., 2013). For reproduction in snails, the role of light has

been demonstrated. For example, Uguowoet al. (2019) reported that snails exposed

to 24 hour light period laid more eggs than those exposed to 18 hours and 12 hours

light period, they also had longer mating duration which was significantly different

from those in 12 hours light exposure but not significantly different from 18 hours

light exposure. Although, they didn’t report any difference in courtship duration,

but they saw that courtship in 24 hour light exposure had the highest duration.

Photoperiod has great influence on the number of matings and layings in snails.

Helix aperta Snails reared in long-day photoperiod had higher numbers of matings

and layings and longer periods of reproduction than those reared in short-days as

egg-laying stopped very early (after two weeks time) at 15°C and lasted only 6

weeks at 20°C (Saida et al., 2009). Enéeet al. (1982) reported that reproductively

active Cornuaspersumaspersasnails collected from natural habitats in France

stopped laying only after 4 weeks of exposure to short-days (6-12h of light),

whereas those exposed to long-days (18h light) did continue laying for as long as

13 weeks. Our results demonstrate the existence of an interaction between

temperature and photoperiod on matings and egg-laying in Helix aperta with a

predominant effect of photoperiod. Gomotet al. (1989) observed that oviposition

in snail was completely or partially inhibited under short-day photoperiods at 15°C

and 20°C, respectively. Saida et al. (2009) concluded that, the best conditions for

growth and reproduction of Helix aperta snails are the combination of temperature

of 20°C and a long-day photoperiod (16h Light: 8h Dark). Different species might

require varying exposure as that recommended by Uguowoet al. (2019) for

Achatina achatina is 24h light exposure while Saida et al. (2009) recommends 18h

light for Helix aparta.

 Soil type and Soil Depth as a Factor Affecting Reproduction in Snail

Snails dig into the soil at least two to five centimeters (2 – 5cm) deep to lay and

incubate their eggs (Cobbinahet al., 2008). Snail tolerance for soil differs. Loamy

soil (Garden soil) is reported to be the best for snail husbandry (Cobbinahet al.,

2008). Loose soils with 20% to 40% organic content (Thompson and Cheney,

1996) are, however, reputed to be better than compact soils with tendency to cake

(Ejidikeet al., 2002; Cobbinahet al.,2008). A study conducted by Ugwuet al.(2011)

to determine the effect of soil type and depth on the reproductive performance of
A. marginataand A. fulica showed that the different soil (sandy, loamy and clayey)

types studies had no effect on the hatchability of their eggs, while the 3cm depth

considered by them was favourable when compared to the 2cm and 1cm depth

respectively. They suggested that, the lack of difference noted in their study for

soil type must have been a result of the controlled environment in which the

different soils were placed for the experiment.

Naturally, sandy soil is known to be very porous and therefore, it is unsuitable for

hatching of snail eggs (Ejidikeet al., 2002, Cobbinahet al., 2008). Sandy soil also

heats faster but has poor heat retention capacity (cools fast) thus it is characterized

by constant fluctuation in temperature which is not good for incubation and

hatching of eggs. On the other hand, clay soil is too compact and heavy and has the

tendency to cake under low water content and to be water logged with the slightest

rain which will render it difficult for snails to burrow into to lay and hatch their

eggs (Thompson and Cheney, 1996). Generally, loamy soil is accepted to be most

suitable for rearing of snails and for hatching of snail eggs (Ebenso, 2006,

Cobbinahet al., 2008) due to its good water retention capacity and excellent

drainage potentials; moderate looseness of the soil particles, good organic content

(20% - 40%) and good temperature buffering ability (Thompson and Cheney,

1996). Amata, (2014) showed that top soil and river sand are good micro-habitats

for the hatching of the eggs of the giant African snail A.marginata as the resulted
to 100% hatchability but reported that they are not favourable in raising the

hatchlings when compared to the use of saw dust.

 Stocking Density as a Factor Affecting Reproduction

The number of animals kept in a particular area or square kilometer is known as

the stocking density. It is important to know the number of animals to keep in a

specific area for maximum production. In poultry, the spread of disease,

cannibalism and the number of birds culled increased when birds are densely

packed; also there is depression in feed consumption and final body weight at

higher stocking density (Agunbiade and Benyi, 1988). Ayodele and Asimalowo

(1999) reported that the amount of eggs laid and frequency of laying is reduced at

higher stocking rate in snail production. Omole et al., (2010) from their study to

determine the effect of stocking density of growth and reproduction performance

for breeding snails concluded that 1m square cage could house up to 15 breeding

snails without any adverse effect on growth, reproduction and state of health of the

breeding snails.

2.3 Reproductive Characteristics of Snails

Understanding the reproductive characteristics of animals is of great importance as

this helps farmers to manage their flock properly for higher production. It has also

helped in the classification of animals of the same species into different subgroups
as seen in snail (Ibom et al., 2008). The breeds of snail vary in their adaptability to

the environment, egg size, size at day old, size at maturity and growth rate

(Amusan and Omidiji, 1999), and these factors are used to identify the different

breeds of snails. The reproductive characteristics includes; egg characteristics (egg

weight, egg length, egg width) (Okonet al., 2013), clutch size (Ibom et al., 2012),

hatchling characteristics (shell length, shell weight, shell width, shell aperture)

(Okon and Ibom, 2012) amongst other.

2.3.1 Egg Characteristics of snails

Egg characteristics are important factors that affect Hatching results and

subsequent performances of an animal. The storage duration of eggs, the egg

internal and external quality parameters amongst other factors are seen affect

hatchability and performance of animals (Roberts and Nolan, 1997). For example,

one of the egg characteristics (egg weight) has been seen to have effect in poultry

production as it has an impact on broiler performance (Ulmer-Franco et al., 2010).

In poultry production, significant relationships between poultry egg weights and

hatching results have been observed. For example, Egg weight directly affects

hatchability, hatching duration, embryonic mortality, hatching weights and

subsequent performance of chicks (Çağlayanet al., 2009; Alabi et al., 2012).

Abiola et al. (2008) revealed that relatively heavier or lighter eggs are not
preferred as hatching egg, rather egg size within the intermediate range would

hatch better and that lower egg weights usually increases hatchability while heavier

weights reduces hatchability (UlmerFrancoet al., 2010; Alabi et al., 2012).

2.3.1.1 Egg Weight

The egg characteristics of snails have been described by many researchers.

Ubuaetal.(2012) described the egg characteristics of snail eggs of two subspecies

of A. marginata. According to them, the mean egg weight of A. marginata ovum

was 1.73g while A. marginatasaturalis had 1.57g values of egg weight. They

observed that, as hatching days keep decreasing during incubation, the egg weight

also decreases and this they say maybe as a result of environmental conditions.

Their observation corroborates the report of Ibom et al. (2008) that a decrease in

egg weight is attributed to exposure to relative humidity and temperature as well as

soil conditions which differ from the near constant uterine environment which they

belong before lay. On the other hand, Ibom et al. (2008) gave the average egg

weights of the black and white skinned ectotypes of A. marginata to be 1.80g and

1.05g while Okonet al. (2013) reported a mean egg weight of 2.00g for A.

marginataspecies.

2.3.1.2 Egg length

The egg length of snails have been reported by researchers for example, the mean

egg length of 15.59mm was reported by Ubuaet al. (2012) for A. marginata ovum

which differs with those reported by Ibom et al. (2008) and Okonet al. (2010) as

they reported 1.48mm and 14.32mm respectively for the same sub-specie. Ibom et

al. (2008) gave the average egg length of the black and white skinned ectotypes of

A. marginata to be 1.61mm and 1.43mm respectively.Okonet al. (2013) reported

the mean length to be 15.20mm for purebred black-skinnedA. marginata snails.

2.3.1.3 Egg width

Ubuaet al.(2012) reported that the mean egg width of A. marginata ovum was

13.53mm while A. marginatasaturalis was 12.13mm. Egg width of A. marginata

ovum obtained by Okonet al. (2010) was 10.78mm and is lower than that recorded

by Ubuaet al. 2012. However, earlier results of egg width of A. marginatasaturalis

obtained by (Awesu, 1980) which was 16mm is higher than the 12.132mm

obtained by Ubuaet al. 2013. Okonet al. (2010) reported that differences in egg

width exist among snails and may be due to the size of the snails and incubation

condition such as water uptake.On the other hand, Ibom et al. (2008) gave the

average egg width of the black and white skinned ectotypes of A. marginata to be

1.29mm and 1.05mm respectively.Okonet al. (2013) reported the mean egg width

to be 11.40mm for purebred black-skinnedA. marginata snails.

2.3.2 Hatchling Characteristics of Snails

In researches involving animal species, body weight gain is the most widely used

growth index from birth to maturity. Weight at hatch is the first indicator of

hatchling growth rate in snails and is useful as a starting point for measuring

subsequent indices, such as body parameters (body weight, shell width and shell

thickness). In addition to weight, shell aperture (shell ʻMouthʼ) parameters (shell

ʻMouthʼ length and shell ʻMouthʼ width) and the number of whorls can also be

taken at hatch and used in measuring subsequent snail growth rate (Okon and

Ibom, 2012). Records of these parameters for hatchlings are scarce as most of the

records taken are for juvenile snails that are used for performance experiment in

relation to determining the suitable feed for snails in commercial production

(Ukponget al., 2015).

Weight gain and shell growth correlate positively with feed intake in snails

(Amusanet al., 1998, Omole and Kehinde, 2005). The body traits of snails that can

be used in the assessment of growth rate are the phenotypic qualities, especially the

shell that is readily seen (Ibom, 2009). This can be measured in terms of length,

width and thickness, the author added. Omole and Kehinde (2005) reported that

snail shell increases as the body size increases and that the shell makes up 30 – 40

% of the whole body by weight.

 The shell length for hatchlingswas reported by okonet al. (2012) to be

14.3mm, 14.0mm and 14.9mm for the black skinned ectotype, whlte skinned

ectotype and their crosses respectively. Ibom and Okon (2012) reported

lower values of 1.41mm and 1.25mm for the black and white skinned

ectotypes respectively.

 Shell width for hatchlings as reported by Okonet al. (2012) revealed that the

black skinned ectotype had 11.8mm, the white skinned ectotype 10.3mm

and their crossed 9.96mm that are all higher than those reported by Ibom and

Okon (2012) which are 1.16mm, 0.99 for the black and white skinned

ectotypes of A. marginata.

 The body weight as reported by Okonet al. (2012) revealed that the black

skinned ectotype had 1.14g, white skinned ectotype had 0.77g while their

crosses had 0.73g in contrast to those recorded by Ibom and Okon (2012)

which had 1.08g and 0.69g for the black and white skinned ectotypes

respectively.

 Ibom and Okon (2012) recorded the shell mouth length of 1.05mm and

0.89mm and shell mouth width of 0.67mm and 0.56mm hatchlings of both

the black and white skinned ectotypes of A. Marginatarespectively.

2.3.3 Hatchability of Snails

Hatchability is the state of being able to produce hatchable eggs. Hatchability in

snail depends upon the prevailing soil conditions such as temperature, relative

humidity, dryness and water logging. Extremity in any of these conditions will

affect hatchability negatively (Ibom, 2009). The egg characteristics also have an

effect on hatchability. As observed in poultry that eggs that are too big will slow

down hatchability while those that are too small will quicken hatchability. Thus a

medium sized egg is preferable for incubation and hatching (Alabi et al., 2012). In

snails, the soil type have been demonstrated to have no effect on hatchability in a

controlled environment as reported by Ugwo et al., (2011) as they used sandy,

loamy and clayey soil in incubating snail eggs and observed no significant

difference. However, this may not be the case in the natural environment for the

different soils as sandy soil is very porous and is characterized by fluctuation in

temperature therefore, it is unsuitable for hatching of snail eggs (Ejidike et al.,

2002,Cobbinah et al., 2008), clay soil on the other hand can cake easily or be water

logged depending on the amount of water present and make it hard for snails to

burrow into the soil to lay eggs (Thompson and Cheney, 1996) and as such, loamy

soil is recommended to be the best soil for hatching of snails (Cobbinah et al.,

2008).
The role of temperature and relative humidity on the hatchability of snail eggs have

been described and records have shown that the best temperature for incubation

and hatching of snail eggs should not be less than 30 OC with a relative humidity

not below 70% (Cobbinah et al., 2008, Mogbo et al., 2013). Hatchability values

have been obtained by several researchers for A. marginata. Ogogo (1989)

recorded 68.4%, Akinnusi (1999) 70%, Ibom et al., (2012) 72 %, while that

recorded for the cross-bred of white skin and black skin ectotypes are 62% for

Ibom et al. (2011) and 66.9% for Awesu (1980).

2.3.4 Clutch Size of Snail

The clutch is the group of eggs laid at a time i.e. a single lay. To the lay man,

higher clutch can mean higher hatchlings.As more number of eggs are deposited,

many may be hatched if the condition is favourable. However, this is not so as the

hatching success does not depend on the number of eggs per clutch (Kramarenko,

2013). The Clutch sizes result of snails are affected by genetic composition,

therefore, varies among breeds and/or strains. Adegbaju (2000), Omole and

Kehinde, (2005), Ibom et al., (2008) and Okon et al. (2012) reported that a clutch

or cluster or batch of eggs contains 8-16 eggs, 4-18 eggs, 1-16 eggs, 4-6 eggs and

4-8 eggs for the black- skinned strains of A. marginate respectively. Whereas,

Ibom (2009) reported 2-13 eggs and 1-9 eggs as clutch sizes for black-skinned and
white-skinned strains of A. marginata respectively. Okon et al., (2009) reported 4-

6 eggs and 3-5 eggs respectively as clutch sizes for the same strains of A.

marginata. Ibom and Okon (2010) reported 2-4 eggs, and 1-3 eggs respectively as

clutch sizes for the same strains and Okon et al. (2010) reported 2-14 eggs as

clutch size for albino (white-skinned) strain of the same breed. Clutch sizes, in

combination with the eggs size, four groups of species with different reproductive

characteristics were distinguished among the pulmonate mollusks by Kramarenko,

(2013). From the above researches, it can be seen that clutch size can be used to

identify the different breeds, subspecies and ectotypes of snails. Snails lay 4 - 18

eggs (clutch) in 1 - 2 minutes (Omole and Kehinde, 2005, Ibom et al., 2008) unlike

hens that lay one egg per day. Akinnusi (1999) observed that A. marginata lays 5 -

11 eggs within the same period (1 - 2 minutes).

2.3.4 Number of Whorls of Snails

A whorl is a turn of the spire of a gastropod. The number of whorls on snails can

be taken at hatch and used in measuring subsequent growth rate in snails (Okon

and Ibom, 2012). A correlation have been found with other growth parameters

such as shell length, shell width and shell weight with the number of whorls

present on a snail (Etukudoet al., 2016). The results published by Etukudoet al.,

(2016) revealed the mean body weights of black-skinned ectotype to be 1.113g,

4.147g, 97.364g and 123.117g, while the body weights of white-skinned snails

recorded were 1.300g, 9.620g, 31.987g and 61.260g for 2, 3, 4 and 5 whorls of the

two ectotypes, respectively. Etukudoet al.,(2016)also reported the mean shell

length of white-skinned ectotype to be higher than the black-skinned ectotype for 2

and 3 wholes while that of the shell length of black-skinned ectotype were higher

than those of white-skinned ectotype for 4 and 5 whorls. The mean body shell

widths obtained by Etukudoet al. (2016) was 5.11cm for A. marginata black-

skinned snail whereas Okonet al. (2012) recorded a mean shell width of 4.97mm

for 4 whorls. This although might be due to the disparity in total number,

management practice and the initial weight of the snails used for the different

study. The number of whorls, length of whorl, width of whorl and whorl opening

can also be used to tell the age of snails as demonstrated by Samuel et al. (2013).

According to Venette and Larson (2004), fully grown snails have between 7 and 9

whorls.

2.4 Phenotypic Correlation

Phenotypic qualities are body traits of snails used in the assessment of growth rate

especially the shell as is readily seen (Ibom 2009). A correlation between body

parameters such as body weight and shell measurements can serve as important

factor in marketing, and breeders can use it as a guide to improve market value or
the quality of breeding stocks (Okon et al., 2012). Positive correlation for snail

eggs, hatchlings and adults has been reported by researchers (Ibom and Okon,

2012, Ibom et al. 2012, Ibom et al. 2019). The positive correlation in egg

characteristics was reported by (Ibom et al., 2012) which showed that egg length

(EL) and egg width (EH) had perfect positive relationship (r = 1.00) in the BS X

BS mating group. The pairs of egg weight (EW) and egg length (EL) and, egg

weight (EW) and egg width (EH) were mildly correlated (r = 0.49) in the same

mating group (Table 3). Egg width(EH) and egg length (EL) were closely

correlated (r = 0.89) in the WS X WS mating group, while egg weight (EW) and

egg length (EL) and egg weight (EW) and egg width (EH) were moderately

correlated (r = 0.59 and r = 0.70) respectively in the same mating group. Ibom,

(2009) and Okon et al. (2010) reported values similar to those reported Ibom et al.

(2012).

For hatchling/juvenile characteristics, strong positive correlation for body weight

and mouth length, body weight and shell width, body weight and shell length, shell

length and shell width, shell length and shell mouth width amongst others for the

black skinned and white skinned ectotype of A. marginata snails have been

reported (Ibom, 2009, Okon et al. 2010a, Okon et al. 2010a, Ibom and Okon

2012).
 CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 Experimental site

This experiment was carried out at the Niger Delta University Teaching and

Research farm,Amassoma,Bayelsa state– Nigeria. Amassoma is situated within

the geographical area between latitudes 5.6 0N and longitudes 6.70S of the South

South rain forest with an annual temperature and rainfall ranging from 26.5 0 C –

27.50 C and 2,000mm- 2,484mm respectively. Climatologically, there are two

seasons in Bayelsa State: the rainy season (April-October) and the dry season

(November-March).

The area is planted with trees like Ipil-Ipil (leucaenaleucocephala) and pawpaw

(carica papaya) and crops like cassava (manihot esculenta) and coco- yam

(Xanthosoma Sagittifolium). These trees and crops provided a micro-environment

similar to the natural habitat of snails as well as shade that protected the hutch used

for the study from direct sunlight. The trees and crops also protected the hutches

from direct impact of heavy rainfall.

3.2 Experimental materials

The materials used for this experiment includes the Archachatinamarginata snails

(white skinned and black skinned ectotype), forages (pawpaw leaves), concentrates

(compounded), water and petri dishes used as drinkers and feeders.

3.3 Experimental animals

Twenty four sexually matured Archachatinamarginata snails were used (12) each

from the black and white skinned ectotype , they were all gotten from snail vendors

in Bayelsa state, Nigeria. The snails were divided into groups according to their

treatments with each treatment having four replicates.

3.4 Construction of hutch

The snail hutch was made of wood and wire gauze containing series of cells known

as tubs each tub was measured 33cm (length) ×27cm (width) ×23cm (height).

Wire gauze was nailed to the wooden frame to form the top lid of the hutch to

allow ventilation.Net was also nailed to the wire gauze to prevent flies from

entering the cages and also to prevent snails from falling off and escaping. The

bottom cover was perforated to allow easy drainage of excess moisture. The hutch

was raised on wooden stands measuring 30cm from the ground. The stands were

immersed in containers of condemned oil to prevent ants and other predative

organisms from attacking the snails.

3.5 Preparation of soil

Loamy soil was collected loosened and sterilized to get rid of harmful soil micro-

organisms. The treated soil was allowed to cool off before pouring into the tubs to

29cm depth from the bottom.

3.6 Experimental diet

The snails were raised on mixed feeding regime of forage (pawpaw leaves) and

formulated concentrates and were fed ad libitum.

3.6.1 Collection of forage

The forage used for this experiment was pawpaw leaves and they were collected

within the farm.

3.6.2 Formulation of experimental diet

The feed used for this experiment was formulated to meet the requirement of 24%-

25% protein and 2200 - 2650 Kcal/kgME energy level recommended by Okonand

Ibom(2012).The percentage composition of the diet is shown in Table 1,

Table 1 Percentage composition of experimental diet

Ingredients % composition

Maize 40.00

Soy bean meal 30.00

Wheat offal 12.00

PKC 5.00

Crayfish dust 8.00

Bone meal 4.50

Mineral/ vitamin premix 0.35

Total 100.00

3.7 Management of experimental animals

This experiment was just in one phase namely the reproductive phase

The breeder snails were weighed for weight to ensure uniformity in average weight

for all the three mating groups (treatments). The initial weights of the snail eggs

were taken using S. Miller digital scientific scale having 0.1g sensitivity and 600 g
capacity. Other parameters measured include egg length (mm) and egg width(mm)

taken at lay using vernier caliper. At hatch initial body weights of snails were taken

using S.Miller digital scientific scale having 0.1g sensitivity and 600g capacity.

Other snail parameters measured include shell length, shell width, shell mouth

length, shell mouth width and shell thickness. The vernier caliper was used in

taking these measurements. This phase lasted for five months January to june2020

3.8 Data collection

The parameters measured during the reproductive phase include;

Number of eggs laid(i.e.clutch size):this was determined by counting the number

of eggs laid per snail during the period.

Number of eggs hatched (%hatchability): This was estimated using the following

formula.

%hatchability=Total number of snails survived

Number survived (%survivability): this was estimated using the following formula

%survivability=

Egg weight (g): this was obtained by placing the egg on a S.Miller®digital

scientific scale and then taking the displayed reading

Egg length(mm): this was obtained by measuring the longest dimension of the

snail egg from one end to the other end using vernier caliper.

Egg width(mm): this was obtained by measuring across the snail egg at right angle

of the snail egg length using a vernier caliper.

Snailet body weight at hatch(g):this was obtained by placing the snailet on the

S.Miller® digital scale and then taking the displayed reading.

3.9 Experimental design

The completely randomized design(CRD) was used.This experiment comprises of

three mating groups with each mating group consisting of four replicates. Each of

these replicates had two snails at each cell(tub).The model used for this experiment

is:

Yij= µ + Ri + eij

Where;

Yij= single observation

µ= common mean

Ri= effect genotype on reproduction

eij= random error effect (0,δ2)

3.10 Statistical analysis

3.11 Phenotypic correlations

Phenotypic correlations were estimated in some reproductive parameters such as

egg weight, egg length, egg width and clutch size using
 CHAPTER FOUR

4.0 RESULTS

4.1 Egg Parameters of the two Species of A. marginataand their Crosses

The result on table 4.1 on egg parameters for the black and white foot A. marginata

and their crosses showed no significant difference (P.0.05) for clutch size, egg

length and egg weight. However, there was a significant difference (P<0.05) for

egg width as white skinned ectotypewas significantly different from both the black

skinned ectotype and the crosses.

Table 4.1 Egg Parameters of the two Species of A. marginataand their Crosses

TREATMENT/ BS X BS WS X WS BS X WS SEM
PARAMETER

Cluth size 9.0 ± 0.707a 8.75 ± 0.48a 9.75± 0.479a

Egg length (cm) 2.43 ± 0.482a 2.53 ± 0.03a 2.48± 0.02a

Egg width (cm) 2.14 ± 0.019b 2.20 ± 0.00a 2.17 ± 0.02b

Egg weight (g) 1.57 ± 0.10a 1.86 ± 0.04a 1.64 ± 0.04a

Means that do not share a common alphabet are significantly different. (P<0.05)
BS = Black skinned A. marginata, WS = White skinned A. marginata and BS X
WS = Crosses
4.2 Hatchlings Parameters of the two Species of A. marginataand their Crosses

The result on hatchling parameters below showed no significant differences

(P>0.05) for body weight, shell length, shell width and shell mouth length but

showed a significant difference(P<0.05) for shell mouth width as white skinned

ectotype was significantly different from black skinned ectotypewhich was

different from the crosses of the black and white skinned ectotypes.
Table 4.2 Hatchlings Parameters of the two Species of A. marginataand their
Crosses

TREATMENT/ (BS X BS) (WS X WS) (BS X WS)

PARAMETER

Body weight (g) 1.01 ± 0.04a 1.46 ± 0.06a 1.00 ± 0.04a

Shell length (mm) 1.51± 0.03a 1.77± 0.04a 1.51 ± 0.02a

SHELL WIDTH (mm) 1.34 ± 0.02a 1.50 ± 0.02a 1.33± 0.18a

Shell mouth length (mm) 0.68 ± 0.01a 0.74 ± 0.14a 0.65 ± 0.01a

shell mouth width (mm) 1.09± 0.02b 1.24± 0.03a 1.01± 0.02c
Means that do not share a common alphabet are significantly different. (P<0.05)
BS = Black skinned A. marginata, WS = White skinned A. marginata and BS X
WS = Crosses
4.3 Correlation of body and shell traits of black and white skinned ectotypes
of A. marginata

The result in table 4.3 below showed that there were positive correlation for all the

traits considered for both the white and black skinned ectotypes. The result for the

white skinned showed a strong significant level (P<0.01) for the traits while the

black skinned ectotype show strong significance (P<0.01), weak significance

(p<0.05) and no significance (P>0.05). From the result it was observed that for the

white ectotype, the pair of the body weight to other traits was highly correlative

apart from body weight to shell mouth width when compared to the black skinned

ectotype.
Table 4.3 Correlation of body and shell traits of black and white skinned
ectotypes of A. marginata

WS X WS
SL SW SML SMW BW
SL - 0.92** 0.88** 0.71** 0.88**
SW 0.84** - 0.89** 0.55** 0.86**
SML 0.26 0.37* - 0.47** 0.94**
SMW 0.67** 0.66** 0.12 - 0.48**
BW 0.37* 0.41* 0.35 0.21 -
SL SW SML SMW BW
BS X BS
**. Correlation is significant at the 0.01 level (2-tailed).
*. Correlation is significant at the 0.05 level (2-tailed).
BS X BS = Black skinned ectotype, WS X WS = White skinned ectotype, SL= Shell Length, SW
= Shell Width, SML = Shell Mouth Length, SMW = Shell Mouth Width, BW = Body Weight
4.4 Correlation of Body and Shell Traits of the Crosses of Black and White
Skinned Ectotypes of A. marginata

The result in table 4.4 below showed that there were positive correlation for all the

trait considered for the crosses of white and black skinned ectotypesA. marginata.

The result showed strong significance (P<0.01), weak significance (p<0.05) and

no significance (P>0.05) for the traits considered. The highest correlation was seen

in the pair of shell width (SW) and shell length (SL) and the least was seen

between body weight (BW) and shell mouth width (SMW).

Table 4.4 Correlation of Body and Shell Traits of the Crosses of Black and
White Skinned Ectotypes of A. marginata

BW X WS
SL SW SML SMW BW
SL - 0.80** 0.54** 0.60** 0.62**
SW - - 0.52** 0.42* 0.73**
SML - - - 0.67** 0.66**
SMW - - - - 0.35
BW - - - - -
**. Correlation is significant at the 0.01 level (2-tailed).
*. Correlation is significant at the 0.05 level (2-tailed).
BS X BS = Black skinned ectotype, WS X WS = White skinned ectotype, SL= Shell Length, SW
= Shell Width, SML = Shell Mouth Length, SMW = Shell Mouth Width, BW = Body Weight
 CHAPTER FIVE

5.0 DISCUSSION

Understanding the reproductive ability of an organism is imperative to the

commercialization of this organism as reproduction ensures the continuity of live

of the organism and the profitability of the farm. In animals that give birth to their

young ones alive, the litter size, gestation period, fecundity amongst others are

used to determine the effective productive ability of the animal while for animals

that lay eggs, the clutch size, hatchability, egg size amongst others are factors that

are considered (Ibom, 2009). Thus in understanding the reproductive ability of A.

marginataectotypes, the egg and hatchlings characteristics were considered and

discussed in this research.

5.1 Egg Characteristics of two species of A. marginataand their Crosses

The result on the egg characteristics of two species of A. marginata and their

crosses showed no significant difference (P<0.05) for clutch size, egg length and

egg weight. The clutch is a group of eggs laid within a particular time and the

number of clutch does not determine the hatching success or the number of

hatchling according to Kramarenko (2013). The clutch has also been known to be

used to classify snails into different groups(Kramarenko, 2013). The clutch size

recorded in this study for both the black and white skinned species of A,
marginatafalls within the range recorded by Ibom (2008) as he recoreded 2-13

eggs and 1-9 eggs per clutch for the white and black skinned species of A,

marginatarespectively. The record from this study also falls within the range given

by Omole and Kehinde (2005) and Ibom et al. (2008) for the black skinned specie

while that of the white skin falls within the range recorded by Okonet al. (2010).

However, the record from this study is higher than the range recorded by Ibom and

Okon (2010) and Okonet al. (2009). In this study, no significant difference was

seen for clutch size, but the crosses had higher clutch size than both the black and

white skinned species while Ibom et al. (2012) recorded a significant difference

between the black and white skinned ectotypes in their study.

The egg weights of both the black and white skinned ectotype of A. marginata and

their crosses recorded in this study arenot similar to that recorded by other

researchers. Ibom et al. (2008) gave the average egg weights of the black and

white skinned ectotypes of A. marginata to be 1.80g and 1.05g which in this study,

the average weight egg weight ofr the black skinned and white skinned ectotypes

were 1.57g and 1.86g respectively.Okonet al. (2013) reported a mean egg weight

of 2.00g for A. marginataspecies which happens to be higher than the record for

both ectotypes in this study.Ibom et al. (2012) and Etukudoet al. (2015) recorded

significant differences for the black and white skinned ectotypes as they didn’t

consider their crosses, which this study recorded no significant difference. The
record from this study showed that the egg weight of the white skinned ectotype is

numerically higher that the black skin and their crosses as opposed to that recorded

by Ibom et al. (2008) and Ibom et al. (2012) where the egg weight of the black

skinned ectotype was higher that the white skinned ectotype.

The egg length obtained from this study as recorded in table 4.1 shows the mean

egg length for the black skinned and white skinned ectotypes to be higher than

those recorded by Ibom et al. (2008) who gave the average egg length of the black

and white skinned ectotypes of A. marginata to be 1.61mm and 1.43mm

respectively. However, Okonet al. (2013) have reported the mean length to be

15.20mm for purebred black-skinnedA. marginata snails that is way higher than

those recorded in this study for purebred black skinned ectotype.Etukudoet al.

(2015) recorded significant difference for egg length of black and white skinned

ectotypes of A. marginata while this present study recorded none. The mean egg

lengths from this study are higher than those recorded by Etukudoet al. (2015).

The egg width in this study recorded significant difference as the egg width of the

white skinned ectotype was significantly different from the crosses and the black

skinned ectotypes. Ibom et al. (2012) also recorded a significant difference

between the black and white skinned ectotpypes. However, Ibom et al. (2012)

recorded that the black skinned ectotype was significantly higher than the white
skinned ectotype which is not in line with this study as in this study the white

skinned was significantly different from the black skinned and the crosses. The

result on the egg width recorded in this study was higher than those recorded for

Ibom et al. (2012) for both ectotypes. The egg width recorded in this study was

higher than those recorded by Ibom et al. (2008) who recorded the average egg

width of the black and white skinned ectotypes of A. marginata to be 1.29mm and

1.05mm respectively.

5.2Hatchlings Characteristics of the two Species of A. marginataand their

Crosses

Ibom, (2009) reported that the weight of a juvenile snail at hatch is the first

indicator of hatchling’s growth rate and is used as a starting point for measuring

subsequent growth. According to the author, body parameters (shell length, shell

width and shell thickness) and aperture (shell “mouth”) parameters can be taken at

hatch and used to measure subsequent snail growth and growth rate.

The result on hatchling characteristics showed that, there were no significant

difference for body weight, shell length, shell width and shell mouth length. The

findings from this study does not agree with that recorded in Ibom et al. (2019)

who recorded that crosses between the black and white skinned ectotypeswas

significant difference for hatchling’s body weight, shell length and shell width than

the purebred back and white skinned ectotype. The values recorded in this study
for hatchling weight, hatchling shell length and hatchling shell width are way

lower than those recorded by Ibom et al. (2019) for the two ectotypes and their

crosses.

The result recorded by Ibom and Okon (2012) showed significant difference for

hatchling’s weight for the white and black skinned ectotype which is does not

support the result gotten from this study. The hatchling weight recorded for white

skinned ectotypeA.marginata is higher than that recorded by them which was

0.69g. There result corroborates with that gotten from this study with regards to

shell length and shell width which had no significant difference between the two

ectorypes and their crosses.

The result from this study showed that significant difference for hatchling shell

mouth width as white skinned ectotype of A. marginata was significantly different

from the crosses and the black skinned ectotype ofA. marginata.

5.3 Correlation between Body Weight and Shell Traits of White and Black

Skinned Ectotypes of A. marginata

The result in table 4.3 showed that all evaluated traits from this study had positive

correlation in both the white skinned and black skinned ectotype of A. marginata.

The correlation between the traits were highly significant (P<0.01), some slightly

significant (P<0.05) and others showed no significance. The result showed that in
the BS ectotype, the pair of shell length (SL) and shell width, shell length (SL) and

shell mouth width (SMW) and shell mouth width (SMW) and shell width (SW)

showed strong positive and significant correlation (r = 0.84, 0.67 and 0.66)

respectively. Body weight (BW) and shell length (SL), body weight (BW) and

shell width (SW) and, shell width (SW) and shell mouth length (SML) showed

weak positive and significant correlation (r = 0.37, 0.41 and 0.37) respectively;

while shell length (SL) and shell mouth length (SML), body weight (BW) and shell

mouth length (SML), body weight (BW) and shell mouth width (SMW) and, shell

mouth width (SMW) and shell mouth length (SML) showed very weak positive

correlation (r = 0.26, 0.35, 0.21 and 0.12) respectively. This result corroborates

with those recorded by Ibom (2009) and Ibom and Okon (2012) as they reported

positive correlation for body weight and shell trait of black skinned ectotype of A.

marginata. However, they reported a higher correlation value compared to that

recorded in this study.

The result for the white skinned ectotype shown in table 4.3 showed that the all the

traits showed high significance (P<0.01). The highest, strong positive correlation

was seen for body weight (BW) and shell mouth length(SML) and, shell length

(SL) and shell width (SW) (r = 0.94 and 0.92). The pair of shell width (SW) and

shell mouth length (SML) , shell length (SL) and shell mouth length (SML), body

weight (BW) and shell length (SL) and, body weight (BW) and shell width(SW)
showed very strong correlation that fall between the value (r = 0.86 to r = 0.89);

while shell length (SL) and shell mouth width (SMW) showed closely correlation

(r = 0.71) and shell mouth width (SMW) and shell width (SW), shell mouth width

(SMW) and shell mouth length (SML) and, body weight (BW) and shell mouth

width (SMW) showed weak correlation value between (r = 0.47 to r = 0.55).

positive correlation for body weight and shell traits of white skinned ectotype have

been reported by other researchers such asOkon and Ibom (2011), Ibom and Okon

(2012), Okonet al. (2012) and Ibom et al. (2019). However, Ibom and Okon (2012)

reported a correlation value (r = 0.99) for body weight and shell trait of white

skinned ectotype of A. marginata which is higher than the values obtained in this

study.

Table 4.4 showed the correlation for body weight and shell traits of hatchlings of

the crosses of black and white skinned ectotypes of A. marginata. The result

revealed that there was positive correlation for all the traits considered with

significant level (P<0.01) and (P<0.05). The result of the crosses showed that the

pair of shell width (SW) and shell length (SL) and, body weight (BW) and shell

width (SW) has strong significance (P<0.01) positive correlation(r = 0.73 to r =

0.80).The pair of body weight (BW) and shell mouth length (SML), body weight

(BW) and shell length (SL), shell mouth width (SMW) and shell length (SL), shell

mouth length (SML) and shell length (SL) and, shell mouth length (SML) and shell
width (SW) showed significance (P<0.01) and positive correlation value range (r =

0.52 to r = 0.66)while shell mouth width (SMW) and shell width (SW) showed

significance (P<0.05) and positive correlation (r = 0.42) and body weight (BW)

and shell mouth width (SMW) showed weakly positive correlation (r = 0.35). The

result gotten from this study agrees with that recorded by Okonet al. (2012) who

also reported positive correlation for traits of BS X WS crosses of A. marginata.

There values however, were higher than those recorded in this study.

The positive correlation values recorded among these traits indicates that the traits

are possibly influenced by the same genes in the same direction. The positive

correlations could also suggest that there are direct relationships between the traits,

and that weight increment in snails is as a result of increase in the size of

corresponding traits. The positive correlation among traits indicates that selection

for one trait will lead to improvement in the other trait. The variations in

correlations among measured traits showed that the influence of genes on the

different traits of A. marginata differ from one trait to another (Ibom, 2009, Ibom

and Okon, 2012).The results of this study supports the view of Ehiobu and Kyado

(2000) that correlation can be either high or low, positive or negative and/or no

correlation at all between traits.

 CHAPTER SIX

6.1 CONCLUSION

The study on the egg parametersand hatchlings parameters of black and white

skinned ectotypes of A. marginata and their crosses showed that there was no real

significant effect for the traits considered apart from egg width and shell mouth

width which the white skinned ectotype proved to be significantly higher than the

black skinned ectotype and the crosses. The close relation of the values obtained

proved that any of these ectotypes or their crossed can be selected and used

breeding stock in a snailry farm for maximum production.

The phenotypic correlation for all the traits considered for the two ectotypes and

their crosses showed a positive correlation for all the traits and as such,

improvement on one trait will lead to a direct improvement on the other trait.

However, the positive correlation varies from one trait to another, thus a careful

study of this correlation must be done by snail breeders so as to know the perfect

pair of trait to manipulate with minimal cost to achieving increase in snail protein

production by farmers.

6.2 RECOMMENDATION

The researcher recommended that any of the ectotypes or the crosses can be raised

in snailry farm and be used as a breeding stock. However, the researcher must
advise the study of these animals to sexual maturity to determine if discrepancies

might occur as they grow holder.

The researcher recommends that a thorough study of the reproductive

characteristics of the crosses be done so as to prevent a decline in subsequent

production as the breeding of F1 may reduce the productive ability of an animal

population. Thus inbreeding or back crossing with either the black or white

skinned ectotype may be done in determining the best combination for snail

reproduction.

The researcher recommends snail breeders to use the findings of this study to

improve the trait of snails, thus improving production of animal protein via snail.
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