Department of Zoology, University of Johannesburg, P.O Box 524, Auckland Park, Johannesburg, 2006, South Africa.
Research and Monitoring Division, KwaZulu-Natal Sharks Board, Private Bag 2, Umhlanga Rocks, Durban, 4320, South Africa.
Fish Physiol Biochem. 2021 Jun;47(3):713-723. doi: 10.1007/s10695-020-00871-z. Epub 2020 Sep 11.
Sharks are not only threatened, but also have a low fecundity as they are being overfished. The shark family, Sphyrnidae, consists of nine species of which three are found in South African oceans. One of the three Sphyrnidae species, the scalloped hammerhead (Sphyrna lewini) are the most common, but their biology and mode of reproduction are not extensively studied in terms of their reproductive biology. The aim of this study was to describe the germ cell development in the testes of sexually mature male scalloped hammerheads. Three individual male S. lewini were caught at Zinkwazi, KwaZulu-Natal, South Africa. The sharks and their reproductive organs were weighed and measured to collect the biometric data for the condition factor and the gonado-somatic index. Following standard necropsy, the testes were fixed in Bouin's solution and processed for histological assessment. The histological assessment revealed that the testes of S. lewini consist of seminiferous tubules which form part of a larger lobular structure with germ cells in different stages of development, from spermatogonia to mature spermatozoa. Seven stages of development were identified during the process of spermatogenesis, similar to what has been described for elasmobranchs. In conclusion, this study provides evidence that the testes of S. lewini are diametrical and polyspermatocystic and conforms to the testes structure of elasmobranch males.
鲨鱼不仅受到威胁，而且由于过度捕捞，繁殖能力也很低。鲨科（Sphyrnidae）由 9 个物种组成，其中 3 个在南非海域发现。这 3 种 Sphyrnidae 物种之一，也就是双髻鲨（Sphyrna lewini）是最常见的，但它们的生物学和繁殖方式在繁殖生物学方面并没有得到广泛研究。本研究的目的是描述性成熟雄性双髻鲨睾丸中生殖细胞的发育情况。在南非夸祖鲁-纳塔尔省的津克瓦齐，捕获了 3 条性成熟的雄性双髻鲨。对鲨鱼及其生殖器官进行称重和测量，以收集体况系数和性腺体指数的生物计量数据。在标准解剖后，将睾丸固定在 Bouin 溶液中，并进行组织学评估。组织学评估显示，双髻鲨的睾丸由生精小管组成，这些小管形成更大的小叶结构的一部分，其中生殖细胞处于不同的发育阶段，从精原细胞到成熟的精子。在精子发生过程中确定了 7 个发育阶段，与软骨鱼类所描述的阶段相似。总之，本研究提供了证据表明，双髻鲨的睾丸是直径的和多精囊的，符合软骨鱼类雄性的睾丸结构。
