Spermatozoa of scorpions (Arachnida, Scorpiones) and their phylogenetic implications

KLANN, A., VIGNOLI, V., PERETTI, A. V., CARRERA. P., MICHALIK, P., TALLARICO, G. & G. ALBERTI

Sitges-Barcelona, España

Congreso; 23 European Colloquium of Arachnology; 2006

European Arachnological Society

Morphological characters of the spermatozoa have never been included in systematic studies of Scorpiones, mainly because there are only very few ultrastructural investigations on spermatogenesis and sperm cells. The present study aims to evaluate possible characters of the ultrastructure of mature spermatozoa and sperm packages, which can possibly be used for scorpion phylogeny. Several representatives of the families Buthidae, Bothriuridae, luridae and Euscorpiidae were investigated by means of transmission (TEM) and scanning electron microscopy (SEM). In general, scorpion spermatozoa are of the filiform-f1agellate type. Although they are morphologically not very diverse, certain differences could be observed which c1early differs between species of different families and genera. (1) Shape ofthe acrosomal complex, (2) position ofthe acrosomal complex, (3) presence or absence of the acrosomal filament, (4) shape of the nucleus, (5) axonemal pattem, (6) number of mitochondria, (7) shape of mitochondria and (8) shape of the sperm packages. Only in buthid representatives, a corkscrew shaped nucleus (at least in the anterior part), an acrosomal complex located at the side of the nucleus, a 9x2+2 axonemal pattern and two long mitochondria coiled around the axonema could be observed. Since the 9x2+2 axonemal pattem is considered plesiomorphic it confirms the systematic (basa!) position of this family. AII the other species investigated show a 9x2+0 pattern, a long thread-like nucleus and an acrosomal complex located at the tip of the nucleus. The number of mitochondria varies between 3 (in different bothriurid species), 5 (in an iurid species) and 6-8 in euscorpiid species. Mitochondria can appear as densely "condensated" organelles in the genera Brachistosternus and Timogenes, whereas they resemble more small f1ower-like structures in the genus Urophonius (all three species belong to the family Bothriuridae). In the investigated buthid species no sperm packages, respectively only loosely aggregated sperm cells could be observed. Sperm packages in bothriurid scorpions are long, sometimes surrounded by a secretion sheath at the anterior part, with curved tips to certain degrees depending on the species. Euscorpiid scorpions possess round, densely packed sperm packages, fully surrounded by a secretion sheath.