Morphogenesis of the decapitated and decaudated sperm defect in two brothers

The “decapitated sperm” defect, found in both of two sterile brothers, may be assumed to have a genetic origin. The present material suggests that the term “decapitated spermatozoa” is not exact, because detached heads and tails were found in the brothers' ejaculate that could be regarded as “decapitated tails” and “decaudated heads.” The present report describes frequent, more or less advanced stages of detachment. Both heads and tails showed a normal structure in which only the postnuclear region was deficient, lacking basal plate and implantation fossa. A break at a different level of the midpiece, and therefore three kinds of separation, were observed. The defect, according to the present research, must originate in the testicular region, whereas the detachment occurs in the epididymis.     

Ultrastructural studies of spermatozoa in three bivalve species with notes on evolution of elongated sperm nucleus in primitive spermatozoa

Sperm ultrastructure and spermiogenesis of the three bivalve species Musculus discors, Nucula sulcata, and Dreissena polymorpha have been studied. During spermatid differentiation in Musculus discors and Nucula sulcata the nucleus attains an elongated rod-like shape. The spermatozoon from Nucula sulcata was found to have a cup-shaped acrosome and five mitochondria surrounding two centrioles in the middle piece. The spermatozoa from Musculus discors has a long complex acrosome. From the distal centriole striated processes extend and attach to the plasma membrane. The spermatozoon of the fresh water species Dreissena polymorpha agrees in all main features with those of other invertebrate groups with external fertilization. It is thus of the primitive type with barrel-shaped nucleus and four to five mitochondria1 spheres in the middle piece. The acrosome is a prominant, complex structure at the apex of the mature spermatozoon. A comparison of sperm ultrastructure among bivalves indicates that there is a certain correlation between the evolution of the elongated sperm nucleus and large, yolk-rich eggs. In species with an elongated sperm nucleus the increased egg size has often led to a lecithotrophic or direct development. The elongated nucleus is a slight modification of the primitive type. There is a great variation in acrosome structure among bivalve spermatozoa, reflecting diverging functional demands at fertilization of the eggs.     

Challenges of External Insemination in a Tropical Sparid Fish, Acanthopagrus Berda

Duration of spermatozoa motility and proportion activated were tested under a range of salinities and temperatures in males of the tropical estuarine fish, Acanthopagrus berda, in both laboratory and novel field experiments. A. berda spermatozoa were activated under a wide range of salinities (5–60%) and showed the greatest duration of motility at approximately 30%) in both laboratory and field fish. The duration of activation exceeded 10 minutes at this salinity. However, relatively low activation rates were recorded (50–70%). The long duration of motility, wide range of activation salinities and low proportion of motile spermatozoa may reflect a reproductive style in A. berda of producing at least some motile spermatozoa despite the ambient conditions at spawning. This is discussed in relation to fishes from other habitats and the wide distribution of A. berda.     

Sperm morphology of scleractinians from the Caribbean

This study compares the sperm morphology of 2 hermaphroditic (Diploria strigosa, Montastrea annularis) and 2 gonochoric (Siderastrea siderea, Dendrogyra cylindrus) Caribbean reef corals. The spermatozoa of the gonochoric species are morphologically more specialized than those of the hermaphrodites. The cytological differences are apparent in the formation of a Spitzenkörper and pro-acrosomal vesicles, a mitochondrial mass (Nebenkern) and a large lipid vesicle in the gonochorists studied. Harrison (1985) first demonstrated that sperm morphology is correlated with sexual reproductive pattern and systematic position in scleractinian corals, and this is supported by the results of this study. The possible functional and phylogenetic bases of sperm morphology are discussed and a brief outline is given of further studies required.