Spermatozoon morphology, spermatogenesis and reproductive system of Acanthodasys australis (Thaumastodermatidae) were studied at ultrastructural level. The spermatozoon is a filiform cell formed by a cork-screw-shaped acrosome, a helical nuclear–mitochondrial complex and a long flagellum. The acrosome contains an axial tubular structure composed of a pile of electron-dense rings. The helical nucleus is thin and wraps a single, giant mitochondrion. A large and thick perinuclear helix surrounds the nuclear–mitochondrial complex extending for its whole length, except the two most basal coils. The flagellum with typical 9 × 2 + 2 axoneme is surrounded by a monolayered obliquely striated cylinder, in the terminal part of which the axoneme disappears. The general architecture of the spermatozoon of Acanthodasys species agrees with the general sperm model described for the family Thaumastodermatidae, and perfectly matches that observed in Acanthodasys aculeatus and Diplodasys ankeli, so confirming the great uniformity of the sperm ultrastructure morphology within the subfamily Diplodasyinae. Spermatogenesis includes the early and simultaneous development of acrosome and flagellum, the elongation of the nucleus and the fusion of mitochondria into a single giant mitochondrion, which later sinks into the nucleus, and the final appearance of a perinuclear helix and a peraxonemal striated cylinder. The process takes place through the same main steps already observed in all Macrodasyida species studied so far. The reproductive system consists of paired testes arrangement laterally to the intestine, a single ovary located dorsally to the posterior part of the intestine, a caudal organ located ventrolaterally to the intestine end, and, a dorsal frontal organ. The latter is in contact with mature oocyte posteriorly and with a compact cellular band connecting to the ‘rosette’ organ anteriorly. The general layout of the reproductive apparatus of A. australis perfectly matches that of the members of Diplodasyinae.

在超微结构水平研究了Acanthodasys australis（Thaumastodermatidae）的精子形态，精子发生和生殖系统。精子是由软木钉状的顶体，螺旋核线粒体复合体和长鞭毛形成的丝状细胞。顶体包含由一堆电子致密环组成的轴向管状结构。螺旋形核很薄，包裹着一个巨大的线粒体。一个大而粗的核周螺旋围绕核-线粒体复合体的整个长度延伸，除了两个最基础的线圈。具有典型9×2 + 2轴突的鞭毛被单层斜纹圆柱体包围，在轴突的末端部分消失。精子的一般结构Acanthodasys物种与描述的Thaumastodermatidae科的一般精子模型相符，并且与Acanthodasys aculeatus和Diplodasys ankeli中观察到的完美匹配。，因此证实了双龙亚科中精子超微结构形态的高度一致性。精子发生包括顶体和鞭毛的早期和同时发育，核的延长以及线粒体融合成单个巨大的线粒体，随后沉入核中，并最终出现核周螺旋和过轴心横纹圆柱体。该过程是通过迄今研究的所有Macrodasyida物种中已经观察到的相同主要步骤进行的。生殖系统由成对的睾丸横向排列在肠道两侧，位于卵巢后部背侧的单个卵巢，位于肠道末端腹侧的尾部器官以及额叶背侧器官组成。后者在后面与成熟的卵母细胞接触，并在前面与连接到“玫瑰花”器官的紧密细胞带接触。生殖器的总体布局A. australis与Diplodasyinae的成员完全匹配。