Studies on the polymorphic spermatozoa of a marine snail. 2. Genesis of the eupyrene sperm

Abstract

Spermiogenesis of the eupyrene sperm in the snail, Fusitriton oregonensis, was studied with light and electron microscopes. Endoplasmic reticulum, which encircles the nucleus in each spermatid, appears to connect with the Golgi body and to interconnect between adjacent spermatids via cytoplasmic bridges. It is suggested that as the Golgi body migrates around the nucleus the endoplasmic reticulum may circulate with it. The alignment of the proacrosome with the nucleus is effected by a 180° rotation of the Golgi body, after which it separates and migrates posteriorly with the residual cytoplasm. Each sperm possesses a well‐developed intracellular digestive system as indicated by multivesicular bodies, residual bodies, and myeloid figures. Autophagy begins in the residual cytoplasm before it is released from the middle piece. Microtubules are found outside the nucleus and mitochondria during the final stages of spermiogenesis, when elongation is almost complete. These microtubules appear to be involved in the final shaping and twisting process, in which torsion is locked in the nucleus and the mitochondria spiral around the axoneme. The annulus attaches the distal centriole to the plasma membrane in the early spermatid and as flagellar production begins they move towards the implantation fossa at the base of the nucleus. There are two centrioles in the early spermatid, the distal centriole and procentriole. The small procentriole fuses with the distal centriole in the intranuclear canal to form the centriolar cap of the basal body. This cap is pushed through the end of the nuclear tube and is separated from the subacrosomal space by only the nuclear membranes.

Ultrastructure of euspermatozoa and paraspermatozoa in the marine gastropod Adelomelon beckii (Caenogastropoda, Volutidae)

“…f TS of the endpiece, the axoneme is close to the membrane. an Annulus, ax axoneme, g putative glycogen granules, m mitochondrion, U U-shaped deWning edge of mitochondrial element the 'carrier type' described by Buckland-Nicks et al (1982b). We did not observe any physical association of euspermatozoa and paraspermatozoa in the testis and in the sperm duct of A. beckii.…”

Ultrastructural observations of eu‐ and paraspermiogenesis in the cottid fish Hemilepidotus gilberti (Teleostei: Scorpaeniformes: Cottidae)

“…Paraspermatozoa produced among invertebrates are classified into three types according to nuclear conditions and developmental process: spermatozoa with no chromatin, apyrene; those with very little chromatin, oligopyrene; those with an excess of chromatin, hyperpyrene (Meves, 1903;Sivinski, 1984; although these authors did not use the term paraspermatozoa). Paraspermiogenesis of most Gastropoda occurs with no or irregular maturation division; spermatocytes transform into apyrene sperm or into diploid or polyploid sperm by asymmetrical division (see, e.g., Buckland-Nicks et al, 1982;Okura et al, 1988;Hodgson, 1997). Those paraspermatozoa are formed along with euspermatozoa and often in the same areas of the testis (Healy and Jamieson, 1981;Hodgson, 1997).…”

Euspermatozoa and paraspermatozoa of the relict cerithiacean gastropod,Campanile symbolicum (prosobranchia, mesogastropoda)

“…The present study has revealed two types of paraspermatozoa in Campanile-one of which possesses a nuclear core (with axonemes attaching to the base of the head) and the other type lacking any apparent nuclear remnant (axonemes penetrating almost to the base of the acrosome-like structure, and evidently attaching to the blocks of the mosaic sheath). Although paraspermatozoal dimorphism has not been demonstrated in any other cerithiaceans, it is well known in viviparacean species (Yasuzumi & Tanaka, 1958;Nishiwaki, 1964;Tochimoto, 1967) and in certain other mesogastropod groups such as the Tonnacea and Epitoniacea (Nishiwaki, 1964;Tochimoto, 1967;Nishiwaki & Tochimoto, 1969;Buckland-Nicks et al, 1982). On balance, however, the paraspermatozoa of Campanile resemble those of families such as the Cerithiidae, Potamididae and also, apparently, Turritellidae (mosaic sheath of head, nuclear core [nucleate paraspermatozoa only], acrosome-like structure, tail tuft).…”