Some steps of spermatogenesis inHalichondria semitubulosa(Demospongiae, Halichondriidae)

Abstract

Spermatogenesis of the marine sponge Halichondria semitubulosa (formerly Pellina semitubulosa) has been investigated at the ultrastructural level. This process can be observed in March when, among the choanocyte chambers of the aquiferous system, spermatic cysts are visible. They are delimited by pinacocyte-like cells and include elements in progressive development: spermatocytes of the first and second order, spermatids and spermatozoa. The early phase of spermatogenesis was not detected. Spermatocytes of the first order show an elongated shape, several small mitochondria and patched chromatin; spermatocytes of the second order, frequently connected by bridges, show denser chromatin, a single large mitochondrion with numerous tightly adherent cristae, glycogen, and round-shaped inclusions with a central electron-dense core. In the spermatids the chromatin tends to be packed in the central region. Spermatozoa have a uniformly dense nucleus in close association with the large mitochondrion. Sperm maturation takes place synchronously within the same cyst but asynchronously within the same specimen.

Oogenesis and spermatogenesis in Paraleucilla magna (Porifera, Calcarea)

“…Unlike what has been seen in most species of Demospongiae that have been studied (see Reiswig 1983;Simpson 1984;Boury-Esnault and Jamieson 1999;Gaino et al 2007;Ereskovsky 2010) and to previous reports on spermatogenesis in calcarean species (Gatenby 1920;Sarà and Orsi 1975), in P. magna, as in Leucosolenia complicata (Anakina and Korotkova 1989;Anakina and Drozdov 2001), there is no arrangement of spermatic cysts. Spermatic cysts are usually characterised by the presence of pinacocytes or other flattened cells surrounding the male gametes, though in some species (Sycon ciliatum and S. raphanus) spermatozoa aggregates are surrounded only by collagen (Sarà and Orsi 1975).…”

“…This occurs through the Zoomorphology (2010) 129:249-261 257 elongation of cells and the shedding of their bases, as also happens in some Demospongiae (Tuzet and Pavans de Ceccatty 1958;Tuzet et al 1970;Gaino et al 1986;Barthel and Detmer 1990;Gaino et al 2007). In Demospongiae, the shape and size of choanocytes are more homogeneous than in Calcarea, and the beginning of spermatogenesis is usually recognised by changes in their shape.…”

The biology of choanocytes and choanocyte chambers and their role in the sponge stem cell system

“…In a wide range of sponge species, gametogenesis is known to occur within choanocyte chambers (Anakina and Korotkova, 1989;Kaye and Reiswig, 1991a;Gaino et al, 2007;Maldonado and Riesgo, 2008;Lanna and Klautau, 2010). Choanocytes are also known to be highly proliferative (De Goeij et al, 2009;Alexander et al, 2014).…”

“…Observations under light microscopy shows spermatogenesis in a number of species occurring inside a choanocyte chamber (Anakina and Korotkova, 1989;Barthel and Detmer, 1990;Kaye and Reiswig, 1991a;Gaino et al, 2007;Maldonado and Riesgo, 2008). In some species such as the calcareous sponge Paraleucilla magna, choanocytes are responsible for making both oocytes and spermatozoa (Lanna and Klautau, 2010).…”

“…To further explore this phenomena, one could isolate the choanocyte chambers undergoing spermatogenesis in species where this phenomenon is observable (e.g. Paraleucilla magna (Lanna and Klautau, 2010), Haliclona semitubulosa (Gaino et al, 2007), etc.) and sequence them along with other choanocyte chambers for comparison.…”