Modes of Life of GASTROPODA

8/19/2019 Modes of Life of GASTROPODA

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Modes of Life of

Gastropoda


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Gastropods live just about everywhere on Earth - salt water,

fresh water, and on land. In the ocean, they live in bothshallow, intertidal areas and the deep sea.

The gametes released into the water for fertilization

to ta e place outside the female.

REPRODUCTION OFDIFFERENT SEXES


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The fertilized egg hatches into a free-swimming form!trochophore larva".

#pon the e$pansion of the ciliary girdle of thetrochophore larva into large, heavily ciliated lobes

!vela", the larva, called a veliger, undergoes torsion,a %&'( twisting of the body that brings the posterior part of the body to an anterior position behind the

head.


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In some species the swimming veliger stage persists for

wee s or even months. The veliger has a small shell intowhich the velar lobes and head can be withdrawn and a

larval heart that seems to e$ist solely to providecirculation in the velar lobes.


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)fter metamorphosis, the juvenile snail starts a typical pattern ofrapid growth until se$ual maturity, at which point growth eitherceases or is greatly slowed as energy is diverted to the productionof the ne$t generation.

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In some species, pallial reproductive tubes of male

and female become closed tubes, and a malecopulatory organ develops on the right side of thehead for transmission of sperm to the female.


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The trochophore and veliger stages are passed withinan egg mass or capsule provided with a food supply,rather than as free-swimming immature organisms thatmust find their own food.

)t first, provision of nutriment for the young probably involved laying eggs in a mucous mass.


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)s evolution progressed, more rigid capsules containingyol and with a protective cover might have been laidsingly or in masses. 1ome species currently provide

parental care of the eggs or egg mass.

0inally the eggs are retained inside a brood pouch orthe uterus of some species until the young are ready tohatch !ovoviviparity".


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)lmost all marine gastropods breathe with a gill, but many freshwater species,and the majority of terrestrial species, have a pallial lung

Respiration

Circulatory system

Gastropods have open circulatory system and the transport fluid ishemolymph. 4emocyanin is present in the hemolymph as the respiratory

pigment.

Excretory system

The primary organs of e$cretion in gastropods are nephridia, which produceeither ammonia or uric acid as a waste product. The nephridium also plays animportant role in maintaining water balance in freshwater and terrestrialspecies.

Modes of Life of GASTROPODA

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