Physiology of Finfish and Shellfish (2+1)

5.2.19. Gonads

The hypothalamus produces gonadotropin-releasing hormone (GnRH. Gonadotropin releasing hormone (GnRH) is thought to stimulate the pituitary, a small gland located beneath the brain, to produce and release gonadotropin hormones (GtHs). Gonadotropin hormones (GTH) act on the ovaries and testes (gonads).

The hormones of the reproductive system of vertebrates (sex hormones) are steroids. In fish, sex hormones are produced by the gonads and these control maturation and development of secondary sexual characters. In male fish, hormones are believed to be secreted by the interstitial cells of the testis and these cells are involved in steriodogenesis. In the female, the post-ovulatory corpus luteum appears to be the source of sex hormones. LH stimulates the testes to produce several kinds of steroid hormones called androgens. One of these androgens is testosterone, the main sex hormone in males. LH stimulates the ovaries produce estrogen and progesterone, the female sex hormones.

A gonadectomised fish fails to develop the secondary sexual characters. Studies have shown that discharged follicles of teleosts are involved in steroid biosynthesis and young post-ovulatory follicles are capable of producing progesterone and testosterone in response to gonadotropins.

Estrogens ( AmE ), oestrogens ( BE ), or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals, and functioning as the primary female sex hormones. Natural estrogens are steroid hormones. Oestrogens are produced primarily by developing follicles in the ovaries, the corpus luteum, and the placenta. Luteinizing hormone (LH) stimulates the production of estrogen in the ovaries.

The hormones of the reproductive system of vertebrates (sex hormones) are steroids. In fish, sex hormones are produced by the gonads and these control maturation and development of secondary sexual characters. In male fish, hormones are believed to be secreted by the interstitial cells of the testis and these cells are involved in steriodogenesis. In the female, the post-ovulatory corpus luteum appears to be the source of sex hormones. A gonadectomised fish fails to develop the secondary sexual characters. Studies have shown that discharged follicles of teleosts are involved in steroid biosynthesis and young post-ovulatory follicles are capable of producing progesterone and testosterone in response to gonadotropins.

LH stimulates the testes to produce several kinds of steroid hormones called androgens. One of these androgens is testosterone, the main sex hormone in males. LH stimulates the ovaries produce estrogen and progesterone, the female sex hormones. FSH controls gamete (egg or sperm) production.