Oogenesis and embryogenesis in a cryptogenic species of calcareous sponge (Calcaronea, Heteropiidae) in the southwestern Atlantic

Abstract

Calcarea is a diverse group of sponges, in which individuals are generally small and found in cryptic habitats. These characteristics hamper the access to them and, consequently, the knowledge about several aspects of their biology, including reproduction. Little is known about many reproductive aspects of these sponges and broad generalizations are made upon few studied species. Therefore, investigations dealing with the oogenesis and embryogenesis of more species are still necessary. Sycettusa hastifera is an alien species in the southwestern Atlantic. Knowledge about its reproduction would not only help to improve our comprehension of reproduction in Calcaronea but would also help to understand the capacity of this exotic species to colonize. Histological and electron microscopy analyses of individuals sampled at Arraial do Cabo (Rio de Janeiro, Brazil) showed that oogenesis in S. hastifera was long (4-6 months) and nutrients were acquired by association with nurse cells and endocytosis of bacteria, yielding heterogeneous and complex yolk inclusions. Cleavage, inversion, and amphiblastula larvae were similar to what has been observed in other calcaroneans, except for the larval cavity lacking amoeboid cells and the relatively long swimming period of the amphiblastula (on average 12 h, but reaching 72 h). Our results indicate that the vitellogenic mechanism characterized as mixed (an ancestral characteristic of Calcaronea) is strongly influenced by autosynthesis; during cleavage, cell fates could be determined from embryo to larva; and inversion of the embryo (which will become the amphiblastula larva) directly into the choanocyte chamber is an ancestral characteristic of Calcaronea. Despite the absence of amoeboid cells or other structures to nourish the larva, the long swimming period suggests that vitellogenesis is sufficient for the maintenance of the embryo and larva until metamorphosis. This characteristic may facilitate the spread of this cryptogenic species to new regions.

Origin and development of primary animal epithelia

“…The motile flagellated blastula that arises contains a new cavity and, in some sponges, a few internalized cells. [153,154,155] Interestingly, maternal cell internalization is widespread in embryos of various sponge types including those of demosponges (Aplysina aerophoba). Cells migrate from the maternal follicle and become incorporated together with other bacterial symbionts into the embryonic cavity.…”

“…The motile flagellated blastula that arises contains a new cavity and, in some sponges, a few internalized cells. [ 153,154,155 ]…”

Ultrastructure of oogenesis in two tropical oviparous Demospongiae (Porifera): Cinachyrella apion and Tethya maza

“…This process is usually associated with accessory cells, which can be categorized in four groups: follicle cells; nurse cells, nutritive eggs, and other miscellaneous accessory cells related to nourishment role (Eckelbarger & Hodgson, 2021; Eckelbarger, 1994). Follicle cells (which provide mechanical support or protection for the oocyte or produce secondary compounds, synthesize metabolites or yolk precursors, and some are involved in resorption of the degenerating oocytes) and nurse cells (which may provide support for biosynthetic activities either by contributing pre‐yolk substances, synthesized yolk, or organelles such as mitochondria that help to synthesize yolk) are more commonly observed during the oogenesis in Porifera (Lanna & Klautau, 2010; 2022; Riesgo & Maldonado, 2009). In Porifera, as in other invertebrates, vitellogenesis can be described as a continuum from the production of the yolk by the oocyte itself to the complete external production of the yolk, which is then delivered to the gamete.…”