Spermiogenesis and seminal receptacles inAeolosoma singulare(Annelida, Polychaeta, Aeolosomatidae)

Abstract

Spermatogenesis, spermatozoa, seminal receptacles and the transformations of sperm after mating were examined for the first time in the polychaete annelid Aeolosoma singulare from Lake Baikal. The structure of the spermatozoon in the coelomic cavity is very similar to that already described for A. litorale, in particular in the presence of a cytoplasmic droplet containing lysosomelike vesicles around the nuclear basis. However, comparison of coelomic spermatozoa with those stored in the sperm receptacles revealed a progressive reduction of the cytoplasmic droplet. The cytoplasmic droplet can thus be considered as a sort of remnant of the spermiogenetic process in the mature spermatozoon. The seminal receptacles of A. singulare, like those of the other aeolosomatids, are epidermal formations; but in this species they have a multicellular organisation and penetrate the muscular layers to end deep inside the coelomic cavity. The spermatozoon of A. singulare was compared with those of polychaetes considered close to aeolosomatids, and was found to have characters in common only with potamodrilids.

Ultrastructure of spermiogenesis and synthesis of enigmatic cytoplasmic inclusions in the spirally shaped spermatozoon of the polychaete Spio setosa (Annelida: Spionidae)

“…Notable, however, is their complete absence from the sperm stored in the seminal receptacles of females. Instead, the midpiece of the stored sperm is full of what we interpret as glycogen, a feature reported for only a few polychaete species (Scharnofske 1986;Eckelbarger & Grassle 1987;Von Nordheim 1989;Westheide 1991;McHugh 1995;Marotta et al 2003;Rouse 2005). When the sperm midpiece of S. setosa loses the membrane-bounded inclusions and accumulates glycogen could not be determined, but it must occur after the sperm leave the coelomic cavity of the males.…”

Fauna Europaea: Annelida - Terrestrial Oligochaeta (Enchytraeidae and Megadrili), Aphanoneura and Polychaeta

“…Two families whose sister-group relationship is supported by morphological and molecular data (Purschke and Hessling 2002, Marotta et al 2003, Struck and Purschke 2005). Similar to clitellates in lacking parapodia, being hermaphroditic, and laying cocoons secreted by a specialized area of the body wall, features that for long time have suggested their inclusion in the Oligochaeta, either as the most primitive group or as a secondarily simplified, derived branch.…”

“…Similar to clitellates in lacking parapodia, being hermaphroditic, and laying cocoons secreted by a specialized area of the body wall, features that for long time have suggested their inclusion in the Oligochaeta, either as the most primitive group or as a secondarily simplified, derived branch. However, the possession of nuchal organs (Fauchald and Rouse 1997, Hessling and Purschke 2000), the construction of the central nervous system (Purschke and Hessling 2002) and pharynx (Bunke 1967), and the ultrastructure of spermatozoa (Bunke 1985, Bunke 1986, Marotta et al 2003) exclude any close affinities with clitellates. Molecular studies (Rota et al 2001, Struck and Purschke 2005, Rousset et al 2007) indeed indicate that the aphanoneurans are not closer to clitellates than any other annelid grouping.…”

Survival and Reproduction in Aeolosoma viride (Annelida, Aphanoneura)

“…Sexual reproduction has, however, been reported in a few species. Only one species, Aeolosoma singulare, reproduces exclusively by sexual reproduction (Marotta et al, 2003). Agametic reproduction occurs by paratomic fission with pygidial budding that begins at different stages of growth in the different species (Herlant-Meewis, 1950, 1951.…”