Spermatogenesis in the carnivorous sponge Lycopodina hypogea (Porifera, Demospongiae)

Abstract

The ultrastructural features of spermatogenesis of the carnivorous sponge Lycopodina hypogea displays unusual features in sponges. The male cells derive from large archaeocyte-like cells from the sponge body, the prospermatogonia, the ultrastructure of which is described. During its first divisions in spermatogonia, then in spermatids, the prospermatogonium is already surrounded by a thin follicle made by a single cell, at the origin of the spermatic cyst in which evolve the sperm cells. The spermatid nucleus progressively elongates and its granular chromatin condenses into twisted fibers. Spermatozoa, tightly packed inside the spermatic cyst, are long and narrow monoflagellated cells. They are unusual for sponges, i.e. dart-shaped, with an anterior filament, an electron-dense, rod-like outgrowth terminating in an acrosome, an opaque cone-shaped vesicle separated from the tip of the nuclear filament by a basal plate. The proximal region of the long flagellum is located within a cytoplasmic tunnel until about one third of the cell length. In the course of spermiogenesis, a secondary envelope made by several cells extraordinarily intertwined by their pseudopodia formed around the first unicellular envelope. Species-specific symbiotic bacteria are usually present between the sperm cells. During maturation, the sperm cyst, which may be termed spermatophore, migrates from the sponge body to the sponge filaments and acquires two bundles of special forceps spicules, included in the cyst envelope. The mature spermatophores are released from the filaments. These peculiarities of spermatogenesis in Porifera are discussed in relationship with the special characters of the carnivorous sponges, Cladorhizidae, i.e. absence of aquiferous system and choanocytes.

Exploration and discovery of sponge assemblages on the continental shelf and slope of the Catalano-Balearic Sea by means of non-invasive techniques

“…In the present paper, we report, for the first time, evidence of colonization of marine debris by the protected sponge Lycopodina hypogea (Vacelet & Boury-Esnault, 1996). This species is perhaps one of the most well-known sponges, as its first findings from a cave in Mediterranean French waters led to the discovery of the so-called "carnivorous sponges" .…”

“…-MEAN ± SD -MAX.) and are described below: Order Poecilosclerida Topsent, 1928Family Cladorhizidae Dendy, 1922 Lycopodina hypogea (Vacelet and Boury-Esnault, 1996) Description: Small, white, stipitate sponge, with a basal attachment area, followed by a long, thin stem made of styles, ending in a hirsute, drop-like body (Figs. 3 & 4).…”

“…Order POECILOSCLERIDA Topsent, 1928 Family CLADORHIZIDAE Dendy, 1922 Genus Lycopodina Lundbeck, 1905 Lycopodina hypogea (Vacelet & Boury-Esnault, 1996) Diagnosis Shape: Small, white, stipitate sponge, with a basal attachment area, followed by a long, thin stem made of styles, ending in a hirsute, drop-like body (Figs. 3 & 4).…”

“…Remarks: While currently there are ca. 200 carnivorous sponge species accepted worldwide , only two have been recorded in the Mediterranean so far; Lycopodina hypogea (Vacelet and Boury-Esnault, 1996) and the North Atlantic C. abyssicola, easily told apart from each other based on their external appearance and spicular set. Cladorhiza abyssicola is far less abundant than L. hypogea, having only been found five times in the Mediterranean prior to this study (Babiç, 1922;, being this its first report for the Catalan coast.…”