Maria Gloria Selmi

Further observations on the morphogenesis of the round headed human spermatozoa.

Sperm and testicular biopsies of an infertile human patient have been investigated using histochemical and electron microscopical technique. Spermiogram revealed a head defect, characterized with lacking acrosome and round and immature nucleoplasm, occuring in practically all cells and coiled tails in about a half of spermatozoa. EM study of spermatids has shown an abortive development of acrosome, whose primordium failed to attach the nucleus and expand, instead regressed. The nucleus failed in shaping and retarded in maturing, a disturbance apparently associated with the aplasia of hypoplasia of caudal manchette. The role of zinc in nuclear differentiation and the shape of head in the movement pattern are discussed.

Microsporidian Spore Wall: Ultrastructural Findings on Encephalitozoon hellem Exospore

A study of the spore wall of Encephalitozoon hellem was performed on thin sections, freeze‐fracture, and deep‐etched samples to obtain information on spore wall organization and composition. Our observations demonstrate that the spore wall is formed by an inner 30–35 nm electron‐lucent endospore and an outer 25–30 nm electron‐dense exospore. The exospore is a complex of three layers: an outer spiny layer, an electron‐lucent intermediate lamina and an inner fibrous layer. Freeze‐fracture and deep‐etching techniques reveal that the intermediate lamina and the inner fibrous layer result from the different spatial disposition of the same 4‐nm thick fibrils. In thin sections the endospore reveals a scattered electron‐dense material that appears in the form of trabecular structures when analyzed in deep‐etched samples. The presence of chitin in the exospore is discussed.

Spermathecae of Salamandrina terdigitata (Amphibia: Salamandridae): Patterns of sperm storage and degradation

The spermathecae of female Salamandrina terdigitata were observed using light and transmission electron microscopy during the fallspring period of sperm storage and secretory activity and during the summer stasis. When sperm are stored inside the spermathecae, the product synthesized by spermathecal epithelial cells is exported into the lumen, where it bathes the sperm. During sperm storage some spermatozoa undergo degradation by the spermathecal epithelium. This process, which includes sperm capture by the apical microvilli, formation of endocytic vacuoles and production of lysosomes, becomes prominent shortly after oviposition. In many instances, cells filled with vacuolized spermatozoa and/or residual bodies undergo desquamation from the spermathecal epithelium and enter the lumen together with residual sperm. Desquamated cells, together with residual sperm, are a common feature in the spermathecal lumina at the end of the egg‐laying season.

The morphological peculiarities of the typical spermatozoa of Theodoxus fluviatilis (L.) (Neritoidea) and their implications for motility.

A detailed examination of the typical sperm of Neritoidea shows it to be characterized by a unique flagellar structure. During the spermiogenesis of Theodoxus fluviatilis (L.), the flagellum breaks into two parts, one folded back on the other. The first length of the flagellum is constituted of a normal axoneme with a protein fiber associated with doublet 1. It is encircled by a cytoplasmic sheath containing two mitochondrial cylinders and numerous glycogen granules. This first part of the flagellum terminated in correspondence with a cap-shaped electron-dense body which gives origin to the second part of the flagellum which contains only the axoneme. The second half of the flagellum therefore develops parallel to the first but in the opposite direction. This particular conformation could account for the abnormal movement of this sperm, in which the tail precedes the head.

The fate of the endocytobionts of Blattella germanica (Blattaria: Blattellidae) and periplaneta Americana (Blattaria: Blattidae) during embryo development

Abstract In this paper we describe the behaviour of the symbiotic bacteria of Blattella germanica and Periplaneta americana during embryo development using transmission and scanning electron microscopy. In Blattella germanica, the bacteria are transferred by endocytosis to the egg cell and are sited in its peripheral cytoplasm; thence they begin to internalize in the yolk, using cytoskeletic structures which are probably only synthesized at this particular phase of their migration. In the 6–7‐day‐old embryo, the bacteria are in close contact with the vitellophages scattered in the yolk, where some of them appear to be in a degenerative phase. In Periplaneta americana, after the internalization of the bacteria, there is the formation of the mycetome which appears to be made up of a syncytial envelope, probably formed by the vitellophages, that contains a ball of symbionts of considerable number. During development, there is a progressive decline in the bacterial population, caused by complex lytic processe...

The seminal receptacle and sperm storage in Cochlostoma montanum (Issel) (Gastropoda: Prosobranchia)

Females of Cochlostoma montanum (Prosobranchia, Cochlostomatidae) have a seminal receptacle which is not a separate diverticulum of the oviduct. The seminal receptacle derives from a differentiated portion of the renal oviduct which has an inner wall composed of only one layer of cells. These cells are of two different types, both actively involved in secretory activity. One type is represented by goblet cells filled with large vesicles containing an electron‐dense, homogeneous, and partially paracrystalline material. This material is expelled into the lumen through macro‐apocrine or holocrine types of secretion. The other type is represented by ciliated cells rich in small vesicles containing granular material. Probably neither kind of secretion has a nutritive function; rather they serve as matrix for spermatozoa that immobilize them and prevent their expulsion from the receptacular portion of the oviduct. Spermatozoa are inserted in invaginations of the apex of both these epithelial cells. The sperm plasma membrane covering the acrosome forms long digitations which expand toward the corresponding invaginations of the receptaculum cells. This type of adhesion is a novelty for Mollusca and resembles that in seminal receptacles of some Annelida.

Sperm morphology of salamandrids (Amphibia, Urodela): implications for phylogeny and fertilization biology

Mature spermatozoa belonging to four salamander species, Salamandrina terdigitata, Triturus alpestris, Triturus carnifex and Triturus vulgaris, have been investigated by electron microscopy. The sperm ultrastructure of these species was compared with that of previously examined urodeles (36 species and 20 genera) and with that of anurans and caecilians. Many phylogenetic considerations may be inferred as a consequence of comparative spermatology. Urodela appears to be a monophyletic order characterized by three sperm synapomorphies: the acrosomal barb, nuclear ridge and marginal filament. Cryptobranchoidea are confirmed to form a monophyletic suborder having two synapomorphic characters: absence of mitochondria in the tail, and cylindrical shape of the tail axial rod. Within the family Salamandridae, sperm morphology confirms the phylogenetic distance between Salamandrina and Triturus, as already pointed out on the basis of molecular and morphological characters. The very complex ultrastructure of spermatozoa confirms a previous opinion that internal fertilization is the ancestral condition of the Amphibia.

The fine structure of the mature spermatozoon of Onchidella celtica (Cuvier) (Mollusca: gastropoda) and its phylogenetic implications

The spermatozoon of Onchidella celtica shows many peculiar features. The acrosome is formed by an apical vesicle and a pedestal consisting of a principal body which is flanked by two electron-dense elliptical elements. The mitochondrial derivative consists of three different components: peripheral layers of paracrystalline material, concentric cisterns, and two cylindrical compartments. The 9 + 9 + 2 axoneme shows 9 small deposits of glycogen granules in correspondence with the axonemal “spokeheads,” and a small assembly of possibly proteic material lying close to the two central tubules. Another intraaxonemal deposit of glycogen granules is present at the level of the “glycogen piece.” Most of the observed features are in substantial agreement with those of another species of the Onchidiidae. This confirms the constancy of sperm structure among the members of a single family of the Gastropoda.

The atypical spermatozoon of Theodoxus fluviatilis (L.) (Gastropoda, Prosobranchia)

The atypical spermatozoa of Theodoxus fluviatilis (L.) (Gastropoda, Prosobranchia, Neritoidea) can be divided into two classes of length even though they are identical in their internal structure. Each atypical spermatozoon is a monoflagellate cell completely lacking a nucleus. This would seem to result from an anomalous maturation of cells which in other respects resembles that giving rise to the typical line. The anomalous maturation becomes apparent at the spermatocyte stage. The final transformation of spermatid into spermatozoon is effected by an expulsion of the nucleus, enveloped in its own membrane, from the cytoplasm. The resulting mature atypical spermatozoon, is composed of a long flagellum encircled by a cytoplasmic sheath extending about one-seventh of its length.

Evidence of actin in the cytoskeleton of Microsporidia

Using transmission electron microscopy, fluorescence microscopy, immuno‐electron microscopy, and biochemical techniques such as 2‐D electrophoresis and immunoblotting, actin was found in all biological stages of the microsporidia Encephalitozoon hellem and Encephalitozoon cuniculi.