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Reproductive Diversity in Fishes: - Parthenogenesis (Gynogenesis)

The document discusses reproductive diversity in fishes, highlighting modes such as parthenogenesis, hermaphroditism, dioecious, and various reproductive strategies including oviparity, ovoviviparity, and viviparity. It outlines the characteristics and examples of each mode, as well as generalizations regarding fecundity and egg size. Additionally, it describes reproduction as a cyclic event with distinct phases leading to the production and fertilization of gametes.

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18 views9 pages

Reproductive Diversity in Fishes: - Parthenogenesis (Gynogenesis)

The document discusses reproductive diversity in fishes, highlighting modes such as parthenogenesis, hermaphroditism, dioecious, and various reproductive strategies including oviparity, ovoviviparity, and viviparity. It outlines the characteristics and examples of each mode, as well as generalizations regarding fecundity and egg size. Additionally, it describes reproduction as a cyclic event with distinct phases leading to the production and fertilization of gametes.

Uploaded by

Orange Lemon
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Reproductive Diversity in Fishes

• Parthenogenesis (Gynogenesis)-
– Development without fertilization
– Sperm just initiates development of the egg
– Male does not contribute genetic material to
the offspring

• Example: Amazon Molly, Poecilla formosa


Types of Hermaphroditism
• Synchronous or simultaneous H
– Functions both male and female at the same
time
– Ovotestis – eggs and sperm are produced

Example: common in coral reef fishes


• Successive H
– Fish changes sex at some stage during its life
• Protandry (proto=first; andro=male)
• Protogyny (gynous=female)

• Ex. – Protandry – deep-sea fish, Gonostoma


gracile
-- Protogny -- grouper
• Dioecious (di=two;oecious=house)

• Gonochoristic (gonos=seed;chorisis=Separate)
• Eggs and sperm develop in separate female and
male sexes
• There is no sex change
• Sexual dimorphism is common
Reproductive Modes
• Oviparity
– Ovuliparous – eggs released prior to fertilization
– Zygoparous – internal fertilization, then release of eggs

• Ovoviviparity
– Fertilized egg is retained within the body of the female
until hatch
– Embryonic nutrition comes solely from the egg yolk
– (Lecithothrophy)
• Viviparity
– Fertilized egg is retained within the body of the female
until hatch
• Nutrition come from both the egg yolk and maternal
supplies (Matrotrophy)
– Ovulated eggs (oophagy)
– Slowly-developing siblings (embryophagy)
– ‘uterine-milk’ (nutrient rich-fluid)
– ‘yolk sac placenta’
Generalizations
• F is highest when eggs and sperm are
liberated freely in water
• Less in species that give some protection in
eggs
• Lowest in species which show parental care
• F and egg size are inversely related
• F is higher in oviparous than either
ovoviviparous and viviparous
Generalization
Species Rep. mode Fecundity Egg dia. Size of % adult
(mm) larvae length
(mm)
Atlantic cod, Gadus oviparous 2-9 x 106 1.1-1.9 3.5-4.5 0.3
morhua
Herring, Clupea oviparous 5-200 x 103 0.9-1.7 5.8 1.6
harengus
Spurdog, Squalus ovoviviparous 2-16 24-32 250-300 23
acanthias
Guppy, Poecilia viviparous 10-50 6-10 13
reticulata
Smoothbound, Mustelus viviparous 10-30 250 2.2
mustelus
Reproduction as a Cyclic Event
• Divisible into distinct phases that culminates in the
production of fertile gametes (milt in males, and
eggs in females) and fertilization of the eggs:
– Germ cell recruitment (gamete formation)
– Gamete development
– Gamete maturation
– Gamete release (related to spawning)
– Gamete fusion (resulting in egg fertilization)

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