F-Actin and Tubulin During Spermatogenesis in Gamasid Mites (Acari: Parasitina)

Fine structure of the spermatophore and spermatozoa in inseminated females of Pergamasus mites (Acari: Gamasida: Pergamasidae)

This study describes the spermatophore of Pergamasus mites after transfer into the female endogynial sac and modifications of the structure of the female-penetrating spermatozoa. The spermatophore is saccular and contains largely unmodified spermatozoa and variously structured secretions. The spermatozoa that leave the spermatophore reach the inner (proximal) end of the vaginal duct where they presumably escape from the genital tract to continue their route through the hemocoel into the ovarian tissue where fertilization occurs. During this transit, the structure of such spermatozoa changes considerably, in particular when in contact with the ovary. These alterations include modifications of the cell periphery and of certain inclusion bodies. Furthermore, the spermatozoa form protrusions that fit into corresponding invaginations of the somatic tissue of the ovary.

Actin and major sperm protein in spermatids and spermatozoa of the parasitic nematode Heligmosomoides polygyrus

Nematode spermatozoa are amoeboid cells. In Caenorhabditis elegans and Ascaris suum, previous studies have reported that sperm motility does not involve actin, but, instead, requires a specific cytoskeletal protein, namely major-sperm-protein (MSP). In Heligmosomoides polygyrus, a species with large and elongate spermatids and spermatozoa, cell organelles are easily identified even with light microscopy. Electrophoresis of Heligmosomoides sperm proteins indicates that the main protein band has a molecular weight of about 15 kDa, as MSP in other nematodes, and is specifically labelled by an anti-MSP antibody raised against C. elegans MSP. A minor band at 43 kDa was specifically labelled by an anti-actin antibody. Reaction of anti-actin and anti-MSP antibodies is specific to, and restricted to, their respective targets. Actin and MSP localisation, studied by indirect immunofluorescence in male germ cells of Heligmosomoides polygyrus, are similar: spermatids show rows of dots, corresponding to the fibrous bodies, around an unlabelled central longitudinal core; spermatozoa are labelled strictly in an anterior crescent-shaped cap, at the opposite pole to the nucleus, which contains fibres of the MSP cytoskeleton. Phalloidin labelling shows that F-actin is present in spermatids, but absent in spermatozoa. Tropomyosin shows a distinct pattern in spermatids, but is located in the MSP and actin-containing cap in spermatozoa. It is hypothesized that actin plays a role in the shaping of the cell and in the arrangement of its organelles during nematode spermiogenesis, when MSP is present, in an inactive state, in the fibrous bodies. The concentration of actin and tropomyosin in the anterior cap is not compatible with previous theories about the MSP cytoskeleton, which is supposed to act in the absence of actin.