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Unit 2: Biology of Aquarium Fishes
Common characters and sexual dimorphism of Fresh water and Marine Aquarium
fishes:
1. Guppy
2. Molly
3. Sword tail
4. Gold fish
5. Angel fish
6. Blue morph
7. Anemone fish
8. Butterfly fish.
1. Guppies (Poecilia reticulata)
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Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Family: Poeciliidae
Genus: Poecilia
Species: reticulata
Small tropical fish, native to South America in
The northeast coastal streams.
Robert John Lechmere Guppy
introduced
them into the aquarium trade.
Hence the name
“GUPPY”
MALE GUPPY
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Male
Sexually mature males exhibit an amazing
array of differently coloured spots and stripes,
Such that every male almost seems unique,
making the guppy one of the most
polymorphic vertebrates known.
Female
Although the females do not show such
coloration,
They vary in terms of their preferred mates
both within and between populations,
Making the guppy a powerful system for
studying sexual selection.
Female guppies are live-bearing
Like other members of the family Poeciliidae, such as swordtails and mollies,
Males fertilize the eggs using a stick-like
modified anal fin - Gonopodium.
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Variation is essential to understanding the genetics
underlying biological processes.
This variation has not been produced by mutagenesis screens,
but instead has been shaped by natural selection.
The guppy provides a huge amount of natural
variation that can be studied genetically.
Thus, combined with emerging genomic resources, the guppy
is an ideal organism for understanding the evolutionary
genetics and molecular basis of adaptation.
2. Molly
Genus Poecilia, known under the common name molly;
• to distinguish it from its congeners,
• it is called short-finned molly or common molly.
Short-Finned Molly or Common Molly: They inhabit fresh water streams and coastal brackish and
marine waters of Mexico.
Wild type:
The wild form is in fact quite rarely kept, as it has a rather plain silvery coloration suffused with
brown and green hues.
Aquarium/ Ornamental Mollies:
Black Molly: It is a melanistic breed which are black all over (most well-known aquarium fishes)
White Molly: A white colored molly.
Golden Molly: Nicknamed the "24 karat".
Balloon Molly: This fish has a deformed spine due to a genetic defect that gives it its appearance.
Lyretail Molly: A breed with an altered caudal fin structure.
Dalmatian Molly: A silver colored breed with black speckles
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White Molly Black Molly
Golden Molly Dalmatian Molly Lyretail Molly
Wild type
Balloon Molly
Sailfin Molly
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Sex differentiation:
• The female is much less spectacular, her colouring is subdued and the
dorsal fin is of normal size.
• In mature male, develops a intermittent organ called gonopodium.
Both the sexes should be separated before the fish are two months old
The molly can produce fertile hybrids with many Poecilia species
most important example:- Sailfin Molly
• Fish is viviparous one, giving birth to young ones.
• The female is fertilized by the merest touch of the gonopodium on her vent,
and one fertilization will last for several broods.
3. Swordtail
Common Name: Sword tail,
Scientific Name: Xiphophorus hellerii
Native Region :
• North and Central America (Veracruz, Mexico, to orthwestern Honduras)
Identifying features:
• The Swordtail comes in many different colors
•Males being easily identified by their signature sword like tail
Breeding Biology:
•They are livebearers which means that the baby fish come out free swimming.
• Swordtail is a prolific breeder and a female will give birth about once every 28 days
•Aggression among male swordtails when keeping multiples
•A good mix may be three females to one male.
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Male
Female
4. Carassius auratus auratus, Carassius carassius auratus.
Common Names: Gold fish, Fan tail
Original Distribution : Eastern Europe, East Asia, Siberia
Native range: Central Asia and China, Japan
Identifying Characters:
• Hard scale less, broadly triangular, snout longer than eye diameter.
• Metallic red- orange body with matching fins.
•The dorsal fin is high and the anal and caudal fins are doubled and free flowing.
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Common Names: Gold fish, Fan tail
Original Distribution : Eastern Europe, East Asia, Siberia
Native range: Central Asia and China,Japan
Carassius auratus auratus
Common Names: Gold fish, Fan tail
Original Distribution : Eastern Europe, East Asia,Siberia
Native range: Central Asia and China, Japan
Carassius carassius auratus
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Breeding Habit:
• Goldfish breeds most easily in large garden ponds-
• Also breeds easily in a spacious aquarium with plenty of oxygen and feathery-
leafed vegetation.
• A substrate spawner is necessary as the parent fish eat their own eggs.
• Sticky eggs, open water/ substratum egg scatterers.
• Non-guarders, Oviparous, with pelagic larvae.
• They last long in captivity.
• Fertilization external, spawning frequency is one season peak per year.
• Cold water necessary for proper ova development.
Classification
5 Kingdom: Animalia
(Freshwater angelfish) Phylum: Chordata
Class: Actinopterygii
Order: Cichliformes
Family: Cichlidae
Tribe: Heroini
Genus: Pterophyllum
Native Region:
• Southern Venezuela,
•Southeastern Colombia
Currently recognized species of this genus:
•Pterophyllum scalare (No Black Strip in the body)
•Pterophyllum altum (3 Complete Black Strip in the body) •extreme Northern Brazil.
•Pterophyllum leopoldi (3 Black Strip in the body: 2 Complete)
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Pterophyllum scalare
Pterophyllum leopaldi
Pterophyllum altum
Identifying features:
• Body compressed and disc-shaped;
• Dorsal spiny rays increasing in length from anterior to posterior part of the fin;
• first branched rays also very long;
• body height at anal fin level 1.07 to 1.29 times in SL
• body color silvery with dark vertical bars (7 in juveniles, 4 in adults)
Sexual dimorphism:
• Males have smaller, pointed genital papillae usually seen during spawning.
• Behaviour indicates males are likely to be more aggressive and territorial.
Reproduction Biology:
• Males court females during the breeding season.
• Both male and female guard the eggs.
• During the entire brooding cycle, the original pair of parents is
maintained -against aggression or potential rivals
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Classification
6. Amphiprion ocellaris
Kingdom: Animalia
Common Name: Clownfish or anemonefish
Phylum: Chordata
Native Region:
• Warmer waters of the Indian and Pacific Oceans Class: Actinopterygii
Order: Perciformes
• Including the Great Barrier Reef and Red Sea.
Family: Pomacentridae
Identifying Features:
Subfamily: Amphiprioninae
• stocky appearance and oval shape
•It is compressed laterally, with a round profile
• body is orange to reddish-brown
• It has three vertical white stripes outlined with a fine black line.
• 1st line passes just behind the eye
• 2nd line in the middle of the body widens forward to the head centrally
• 3rd line circles the caudal peduncle
• All the fins are also outlined with a fine black line.
Black line
Sea-anemone
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1
3
Black line
Black line
Black line
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Sexual Dimorphism:
• Females are larger than males.
• Males are more aggressive and territorial.
All individuals first develop into males and then later there is a possibility that they become
females (protandrous hermaphrodites) most often the alpha male.
Reproductive Biology:
• There is not much data on the reproduction of A. ocellaris.
• They have monogamous mating systems, and are territorial.
• Before spawning, the male prepares the nest near the anemone (so that the tentacles of
the anemone can protect the nest).
• Males become more aggressive during spawning.
• These Male behavior also changes to attract females: biting, chasing, fin extension.
•After the male chases the female to the nest, the female begins the spawning process.
• Female lays eggs for 1-2 hours, and leave the nest for the male to fertilize the eggs.
•The eggs take approximately 6-8 days to hatch
7. Butterfly fish Classification
Kingdom: Animalia
Phylum: Chordata
Butterfly fish are a group of conspicuous tropical marine fish
Class: Actinopterygii
family Chaetodontidae
Order: Perciformes
Native Region:
• Reefs of the Atlantic, Indian, and Pacific Oceans Superfamily: Percoidea
Family: Chaetodontidae
Identifying features:
• Smaller versions of angelfish, but they lack pre-opercle spines at the gill covers.
•Brightly coloured and strikingly patterned bodies, bearing shades of black, white, blue, red,
orange, and yellow.
•Many have eyespots on their flanks
• Dark bands across their eyes, not unlike the patterns seen on butterfly wings.
The approximately 129 species in 12 genera
The largest species, the lined butterflyfish (Chaetodont lineolatus) and the saddle butterflyfish
(Chaetodont ephippium)
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Chaetodont lineolatus
(Lined Butterfly fish)
Chaetodont ephippium
(Saddle Butterfly fish)
Sexual dimorphism:
• No sexual difference is noted for this species.
• Butterflyfish species studied till date indicates that these fish are gonochoristic -
meaning that each fish is either a male or a female and they do not change sex.
Reproductive Biology:
• This species has not been breed in captivity.
• In the wild butterflyfish are pelagic spawners
• Release many tiny eggs into the planktonic water column where they float with the
currents until they hatch.
• Once hatched the fry are in a post-larval state (body, extending from the head, is
covered with large bony plates).
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