Ultrastructural research of spermiogenesis in two sponges, Crellomima imparidens and Hymedesmia irregularis (Demospongiae): new evidence of sperms with acrosome in sponges

Alexander Ereskovsky (1) , Daria Tokina (2)

1 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
2 SPBU - Saint Petersburg State University

Details of spermatogenesis and sperm organization are often useful for reconstructing the phylogeny of closely related taxa of invertebrates. Here, the spermiogenesis and the ultrastructure of sperm were studied in two marine demosponges, Crellomima imparidens and Hymedesmia irregularis (order Poecilosclerida). In C. imparidens and H. irregularis,we found bundles of microtubules arranged along the nucleus during spermiogenesis. These bundles derived from the basal body of axoneme, reaching the apical pole of the cell. In C. imparidens, the microtubules surround the nucleus, forming the manchette. In H. irregularis, the microtubules pass along only one side of the cell periphery. During spermiogenesis, the nucleus stretches and elongates. In both species, the nucleus is twisted into a spiral structure. We suppose that the manchette of microtubules could be responsible for controlling the elongation and shaping of the sperm nucleus to a helical form and for the twisting and/or condensation of chromatin in these sponges. The sper-matozoon of both species has an elongated shape. Its apical part has an acrosome, which is dome-shaped in C. imparidens and flattened and lenticular in H. irregularis.Thecyto-plasm of the spermatozoa contains some small mitochondria, and proximal and distal centrioles arranged at an angle to each other. There is a small volume of residual cyto-plasm with dark glycogen-like granules. The axoneme of the spermatid and the flagellum of the sperm of both sponges is located in the deep tunnel-like cytoplasmic depression. The comparison of spermatozoa morphology of different species of the order Poecilosclerida demonstrates that the knowledge of variation within genera and families can give valuable insights into the significance of many characters proposed for phyloge-netic studies of this order.

Mots clés: spermiogenesis; sponges; acrosome; ultrastructure

Domaines: Gamétogenèse; Zoologie des invertébrés

Alexander Ereskovsky, Daria Tokina. Ultrastructural research of spermiogenesis in two sponges, Crellomima imparidens and Hymedesmia irregularis (Demospongiae): new evidence of sperms with acrosome in sponges. Journal of Morphology, 2022, 283 (3), pp.333-345. ⟨10.1002/jmor.21446⟩. ⟨hal-03527256⟩