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

Abstract

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 conjugates, both primary (synspermia) and secondary sperm conjugates (coenospermia, rouleaux) 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. To elucidate the evolution of STF within Haplogynae we investigated representatives of four genera of the dysderoid family Orsolobidae. Our data show the presence of synspermia (Orsolobus, Osornolobus, Hickmanolobus, and Tasmanoonops) and also cleistospermia (Osornolobus). The occurrence of different STF within one family or even genus has not been described for any other spider taxon 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. To evaluate the previously suggested correlation with the most distal region of the spermophor inside the embolus (intromittent part of the copulatory organ) we measured the diameter of the spermophor using micro-computed X-ray tomography data to obtain corresponding morphometric parameters. Based on these data only two species show similarity in STF and spermophor diameter.

Evolutionary Morphology of the Primary Male Reproductive System and Spermatozoa of Goblin Spiders (Oonopidae; Araneae)

“…Spider sperm need to be activated within the female reproductive system by female secretory products (Uhl, 1993;Herberstein et al, 2011b;Vö cking et al, 2013). Consequently, unsheathed sperm might bypass an initial triggering and avoid a direct female choice, as suggested by Lipke et al (2014). However, in this case the putative protective function during sperm induction and transfer into the female genital system should be correlated with additional secretions that achieve a protection during sperm induction and transfer (Lipke et al, 2014).…”

“…Recently, Lipke et al (2014) analyzed several representatives of Orsolobidae and revealed postcentriolar elongations having a similar length as the precentriolar part of nucleus, while the axoneme is longer than the precentriolar part of nucleus. The present study further complements knowledge on this issue (see table 1).…”

“…In contrast, in Neoxyphinus termitophilus, the very thin, loosely appearing sheath is not applied until they reach the ejaculatory duct. However, unsheathed STF (sensu Lipke et al, 2014) have been described for representatives of Caponiidae (Lipke and Michalik, 2012) and Orsolobidae (Lipke et al, 2014), as well as one theridiid, Phoroncidia sp. (Lopez and Boissin, 1975).…”

“…One potential evolutionary scenario illustrating the diversity of testis organization in Dysderoidea. Data of Caponiidae, Segestriidae, Dysderidae, and Orsolobidae were obtained from the literature (Michalik et al, 2004b;Michalik, 2009;Lipke and Michalik, 2012;Lipke et al, 2014;Michalik and Ramírez, 2014).…”

Copyright and the Use of Images as Biodiversity Data

“…Authors: Lipke, E., Ramírez, M. J. and Michalik, P Data type: multimedia Brief description: Orsolobus pucara (Orsolobidae), from Lipke et al (2014). This PDF file contains interactive 3D content.…”