Parental care in fishes

 

Population interaction - Intra-specific Association

Parental care in fishes

INTRODUCTION •

Looking after the eggs or young until they are independent to defend themselves from predators is known as parental care. 

Male and female giving food, shelter and protection to their off springs is parental behaviour.

 

Definition •Parental care behaviour is any behaviour performed after breeding by one or both parents, that contributes to the survival of their offspring.

Parental care is a form of altruism (unselfish concern for other) in spending time and energy to aid its offspring. The degree of parental care varies considerably, from species to species and depends upon the number of offspring produced.

Fishes as a group pay little parental care to their eggs and young. Most of them are content to ensure fertilization of their eggs but bestow little attention on them. •This lack of parental behaviour is correlated with production of great number of eggs and sperms. There are however, some notable exception in which the eggs and young are guarded with great solicitude mostly by the male parent

Fishes have adopted various devices to ensure proper development of the eggs into adults

The various modes of parental care in fishes are adopted as follows.

1.      Scattering eggs over aquatic plants     - Cyprinus carpio,

2.      Deposition of eggs in masses              - Yellow perch

3.      Laying of eggs at suitable places        - Salmon

4.      Nest building                                      - Male of many species                                                                                                 American cat fish (Male &female)

5.      Floating nest or foamy nest                - American cat fishes

6.      Egg brooding in mouth and intestine - Tilapia mossambica

7.      Coiling round the eggs                        - butter fish (Pholis gunnellus)

8.      Attachment of egg to body                - male nursery fish (Kurtus)   

9.      Formation of integument cups            - Male sea horse

10.  Placement of eggs in brood pouches  - lamp suckers

11.  Egg capsules                                       - Some of the type of sharks

12.  Viviparity                                            - Scoliodon

Scattering eggs over aquatic plants:

In some fishes such as pikes, Carps, Cyprinus carpio, Carrassius auratus etc. ,eggs are scattered usually over aquatic plants to which they are attached.

 

Deposition of eggs in masses of definite forms:

In many Carps, eggs are usually laid with some special sticky covering by means of which they are attached. yellow perch (Perca flavescens) deposit their eggs in single mass in hallow rope like structure. The eggs are held together and form floating bands.

 

Laying of eggs at suitable places

 Salmo solar,Acipenser,Oncorhyncus choose suitable place for spawning. • They dig excavation in gravel substrate, lay eggs in the pits, cover them with gravels.

 

Nest building •

The nest building provides suitable and safe place for the development of their young. Nests are bulit with various kinds of materials such as stones, aquatic vegetation , secretion of their body etc. •

Eg.

·         Male of many species such as darter (Etheostoma congregate), sunfishes and cichlids prepare a shallow basin like nest and the male remains on guard till the young ones are hatched.

·         In some species of North American cat-fishes (Amiuridae) both male and female prepare a crude nest in the mud for egg laying.

·         American cyprinids make a nest composed of large heap of stones

·         The sunfishes also scoop out a shallow basin-like nest from the bottom of which all pebbles are removed by male who guards the eggs till they hatch.

·         •The male bowfin (Amia calva) constructs a crude circular nest made of aquatic vegetation. The male stands on guard till the young ones are hatched. The young ones leaves the nest only under the protection of the father.

 

Floating nest or foamy nest: •

Floating nests are made by American cat fishes in which the eggs are suspended in a mass of bubbles and mucus .

•The male Siamese fighting fish (Betta splendens) builds a floating nest and sticks the fertilized eggs to the lower surface of foam.  It stays on guard and fights till death to defend it. Male Siamese fighting fish defending his nest

The most elaborate nest is made by Apelts quadracus its cup-shaped nest is attached to rooted plants close to the bottom. •After eggs are laid the male builds an extension of the nest up and over the eggs. •The second clutch of eggs are laid on the new floor. •This procedure is and several clutches of eggs are stacked within a single multitier nests

 

Egg brooding in mouth and intestine

The female Tilapia mossambica broods the fertilized eggs in her mouth. She allows the young to take refuge in her buccal cavity for some days after hatching.

•         North American male sea catfish (Galeichthys felis) carries eggs in the mouth for nearly six weeks. • The eggs are large and relatively few in number. • During period the brooder fish do not take any food, thus exhibiting great degree of self-sacrifice. •

•         Tachysurus keeps the fertilized eggs in its intestine till hatching occurs.

 

Coiling round the eggs:

The butter fish (Pholis gunnellus) rolls all eggs into a ball and curls around it. Very often it is done by male.

The eggs of skippers, Gar fishes and flying fishes have sticky threads, developed which serve to anchor them to foreign objects or become entangled with other eggs of the same species

 

Attachment of egg to body

The male nursery fish (Kurtus) of New Guinea, carries eggs held in cephalic hook. The cluster of eggs hang on the hooks with the help of string.

 

Formation of integument cups:

The cat fish Platystacus, the skin of the ventral surface of the body of the female becomes soft and spongy, during breeding season. •As soon as the eggs are fertilized the female presses her body against the eggs in such a manner that each egg are lodged in the small integumentary depressions. •Each egg is attached by a inconspicuous stalk. •They remain in this position till hatching.

 

Placement of eggs in brood pouches :

The male sea horse carry eggs in a brood pouch on the abdomen. •In sea horse (Hippocampus) fertilized eggs are transferred by the female into the brood pouch on the belly of the male. These eggs are carried by males until their hatching. •Eggs become embedded in the folds of the brood pouch and for the exchange of respiratory gases a sort of placenta is formed.

 

Egg capsules:

Some of the type of sharks and rays produce a special leathery case called mermaid purse. It is a shell secreted by the shell gland of oviduct. The shape of the purse varies in different groups but the function is the same that is protection

In the oviparous Elasmobranche such as rays and cat Sharks (Scyllium and Raja) fertilized eggs are laid inside protective horny egg capsules called Mermaids purse. This capsule remains attached to the aquatic weeds by their tendrils. The development proceeds inside the capsule until the yolk has been used up. The youngs hatch out after rupturing off egg case.

 

Viviparity: (True internal incubation) The highest degree of parental care is found in ovoviparous and viviparous fishes. In these embryos nutrition is obtained by forming yolk sac placenta in most case. Among the sharks, scoliodon is ovoviviparous. Some species like Zoarces, Gambusia and Poicilia, show internal fertilization.

Advantages of parental care in Fishes •

•         Protection

•         Survival

•         Contribute to reproductive fitness

•         Increased growth rate and quality

•         Better development