Reproduction System in Fishes

By

Shweta Desai

Preface

Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The genital papilla is a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish often can be determined by the shape of its papilla. Oogonia development in teleosts fish varies according to the group, and the determination of oogenesis dynamics allows the understanding of maturation and fertilization processes. Changes in the nucleus, ooplasm, and the surrounding layers characterize the oocyte maturation process. Postovulatory follicles are structures formed after oocyte release; they do not have endocrine function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving the apoptosis of follicular cells. A degenerative process can also occur, but less frequently, in oocytes in other development stages. Some fish are hermaphrodites, having both testes and ovaries either at different phases in their cycle or, as in hamlets, have them simultaneously. In fish, fertilization of eggs can be either external or internal. In many species of fish, fins have been modified to allow internal fertilization. Similarly development of the embryo can be external or internal, although some species show a change between the two at various stages of embryo development. Lode described reproductive strategies in terms of the development of the zygote and the interrelationship with the parents; there are five classifications ovuliparity, oviparity, ovo-viviparity, histotrophic viviparity and homotrophic viviparity.

Contents

1 – Fatty Acid Content in Fish.

2 – Digestion in Fishes.

3 – Fish and Fishery Products: Risks and Controls Management.

4 – Developmental Plasticity in the Circulatory System in Fish.

5 – Fisheries Farming System: Planning, Operations and other Factors.

6 – Proteins and Amino Acids.

7 – Endocrine and Reproductive Systems.

8 – Fish Feed Formulation and Ingredients for Fish Feed.

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Prep./Ayman Ashry

Manage./ Mona Mahmoud

المصدر: Random Publications - New Delhi (India).

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