Comparative sperm ultrastructure in Nemertea.

Although the monophyly of Nemertea is strongly supported by unique morphological characters and results of molecular phylogenetic studies, their ingroup relationships are largely unresolved. To contribute solving this problem we studied sperm ultrastructure of 12 nemertean species that belong to different subtaxa representing the commonly recognized major monophyletic groups. The study yielded a set of 26 characters with an unexpected variation among species of the same genus (Tubulanus and Procephalothrix species), whereas other species varied in metric values or only one character state (Ramphogordius). In some species, the sperm nucleus has grooves (Zygonemertes virescens, Amphiporus imparispinosus) that may be twisted and give a spiral shape to the sperm head (Paranemertes peregrina, Emplectonema gracile). To make the characters from sperm ultrastructure accessible for further phylogenetic analyses, they were coded in a character matrix. Published data for eight species turned out to be sufficiently detailed to be included. Comparative evaluation of available information on the sperm ultrastructure suggests that subtaxa of Heteronemertea and Hoplonemertea are supported as monophyletic by sperm morphology. However, the data do not provide information on the existing contradictions regarding the internal relationships of "Palaeonemertea." Nevertheless, our study provides evidence that sperm ultrastructure yields numerous potentially informative characters that will be included in upcoming phylogenetic analyses.

Light and scanning electron microscopy of fallow deer (Dama dama) spermatozoa.

No basic differences in size (mean +/- s.d. for at least 300 spermatozoa), shape and ultrastructure of the spermatozoa of fallow deer were detected (1) in comparison to other artiodactyls, (2) between different fallow bucks, and (3) between different months of the fertile season. The total length of the normal spermatozoon was 67.2 +/- 1.2 microns. The flat, paddle-shaped head was 8.2 +/- 0.3 microns long, 4.4 +/- 0.2 microns for the greatest width, 1.9 +/- 0.2 microns for basal width and, approximately 0.7 microns in thickness. The tail measurements were 13.7 +/- 0.3 microns for the midpiece, 0.5 +/- 0.1 microns for the diameter of the midpiece, 42.6 +/- 0.9 microns for the principal piece, and 2.7 +/- 0.6 microns for the endpiece. Spermatozoa with abnormalities such as cytoplasmic remnants and droplets, bent and coiled tails, as well as microcephalic forms were observed.