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
