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Spermatocytes are a type of male gametocyte in animals. They derive from immature germ cells called spermatogonia. They are found in the testis, in a structure known as the seminiferous tubules. There are two types of spermatocytes, primary and secondary spermatocytes (Figure 1). Primary and secondary spermatocytes are formed through the process of spermatocytogenesis (Figure 3).〔 Primary spermatocytes are diploid (2N) cells containing 46 chromosomes. After Meiosis I, two secondary spermatocytes are formed. Secondary spermatocytes are haploid (N) cells that contain 23 chromosomes.〔 All male animals produce spermatocytes, even hermaphrodites such as ''C. elegans'', which exist as a male or hermaphrodite. In hermaphrodite ''C. elegans'', sperm production occurs first and is then stored in the spermatheca. Once the eggs are formed, they are able to self-fertilize and produce up to 350 progenies. ==Formation== At puberty, spermatogonia located along the walls of the seminiferous tubules within the testis will be initiated and start to divide mitotically, forming two types of A cells that contain an oval shaped nucleus with a nucleolus attached to the nuclear envelope; one is dark (Ad) and the other is pale (Ap), which can be seen in Figure 3. The Ad cells are spermatogonia that will stay in the basal compartment (outer region of the tubule); these cells are created to replenish the spermatogonia stores. Type Ap cells will mature and become type B cells, which have round nuclei and heterochromatin attached to the nuclear envelope and the center of nucleolus. Type B cells will move on to the adluminal compartment (towards the inner region of tubule) and become primary spermatocytes; this process takes about 16 days to complete. The primary spermatocytes within the adluminal compartment will continue on to Meiosis I and divide into two daughters cells, known as secondary spermatocytes, a process which takes 24 days to complete. Each secondary spermatocyte will form two spermatids after Meiosis II.〔 Although spermatocytes that divide mitotically and meiotically are sensitive to radiation and cancer, spermatogonia stem cells are not. Therefore, after termination of radiation therapy or chemotherapy, the spermatognia stems cells may re-initiate the formation of spermatogenesis.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Spermatocyte」の詳細全文を読む スポンサード リンク
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