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Most male fish have two testes of similar size. In the case of sharks, the testes on the right side is usually larger [citation needed].The primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.
A gonad, sex gland, or reproductive gland [1] is a mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. [2] The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells
The primary sex organs are the gonads, a pair of internal sex organs, which diverge into testicles following male development or into ovaries following female development. [8] As primary sex organs, gonads generate reproductive gametes containing inheritable DNA. They also produce most of the primary hormones that affect sexual development, and ...
Ovary of a marine fish and its parasite, the nematode Philometra fasciati Birds have only one functional ovary (the left), while the other remains vestigial. In mammals including humans, the female ovary is homologous to the male testicle , in that they are both gonads and endocrine glands .
Sea urchins are dioecious, having separate male and female sexes, although no distinguishing features are visible externally. In addition to their role in reproduction, the gonads are also nutrient storing organs, and are made up of two main type of cells: germ cells , and somatic cells called nutritive phagocytes. [ 20 ]
Fish Gonads: CASI has also been observed in fish species where gonadal cells retain their sex identity independent of external hormonal cues. [ 39 ] [ 40 ] [ 41 ] The mechanisms underlying CASI highlight the diversity and complexity of sex determination processes across species.
This gene is expressed before gonads develop and differentiate. Mutations in this gene lead to sex reversal from male to female. While this gene plays a major role in sex determination in some fish species other species have variations of this gene as well as some versions of the Sox gene as seen in zebrafish. [12]
The anus is also located on ... Coprolites of both fish and cephalopods ... with individuals being either male or female. In most species, the gonads are located in ...