Ultrastructure of spermatozoa of Orsolobidae (Haplogynae, Araneae) with implications on the evolution of sperm transfer forms in Dysderoidea

LIPKE, E.; RAMÍREZ, M. J.; MICHALIK, P.

JOURNAL OF MORPHOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2014 vol. 275 p. 1238 - 1257

0362-2525

Haplogynae are highly diverse with respect to the primary male genital system and sperm characteristics. Additionally, all sperm transfer forms (STF) known for spiders are present. Besides individually transferred sperm (cleistospermia), sperm are transferred as sperm conjugates, both primary (synspermia) and secondary sperm conjugates (coenospermia, roleaux) occur. Nevertheless, the ultrastructure of spermatozoa and STF are described for few Haplogynae and often only one representative species was studied, resulting in a superficial insight in the evolution of these traits. In order to elucidate the evolution of STF within Haplogynae we investigated representatives of four genera of the dysderoid family Orsolobidae. Our data revealed the presence of synspermia (Orsolobus, Osornolobus, Hickmanolobus and Tasmanoonops) but also cleistospermia (Osornolobus). The occurrence of different STF within one family, or even genus is not described for any other spider group so far. Moreover, the synspermia of species of Tasmanoonops and Hickmanolobus were not covered by a secretion sheath suggesting a previously unknown strategy of transferring sperm that is possibly related to sperm residency time or female triggered processes after copulation. Based on serial ultrathin sectioning and subsequent 3D reconstruction, we obtained detailed measurements revealing remarkable size differences of STF. In order to evaluate a previously suggested correlation of these size differences with the most distal part of the spermophor inside the embolus, which is inserted into the female during copulation, we used micro51 computed X-ray tomography to obtain corresponding morphometric parameters. A similarity of dimensions of STF and diameter of spermophor was only found in two species.