Meeting Abstract
83.4 Sunday, Jan. 6 Insights into spermatozoon ultrastructure of lecanicephalidean tapeworms (Platyhelminthes: Cestoda) CIELOCHA, J. J.*; YONEVA, A.; JENSEN, K.; Univ. of Kansas; Bulgarian Academy of Sciences; Univ. of Kansas jjcielocha@ku.edu
Spermatozoon ultrastructural characters have shown to be informative in phylogenetic studies in many invertebrate groups. Comparative data exist on sperm ultrastructure of most cestode orders, though information for the elasmobranch cestode order Lecanicephalidea is limited. The only previous data on lecanicephalidean sperm ultrastructure came from a specimen of Tetragonocephalum (Justine, 2001). Mature spermatozoa of Tetragonocephalum were described as possessing a single axoneme, crested body, and parallel cortical microtubules. Based on these data, Levron et al. (2010) postulated a spiral nucleus. Specimens of Tetragonocephalum as well as three additional lecanicephalidean genera were collected from rays from the Solomon Islands and fixed for transmission electron microscopy (TEM). Posterior proglottids with well-developed external seminal vesicles were cut from the strobila of each individual and processed for TEM. Proglottids were embedded in Spurr’s resin. Ultrathin sections were cut on an ultramicrotome, mounted on copper grids, double stained with uranyl acetate and lead citrate, and observed with TEM. A single axoneme, crested body, parallel cortical microtubules and spiral nucleus were observed in individuals from all four genera. While spermatozoa of Cephalobothrium and Adelobothrium possessed a single crested body and ten parallel cortical microtubules medial to the rested body, Flapocephalus appears to have two crested bodies, and Tetragonocephalum possesses 20 parallel cortical microtubules peripheral to the crested body. In general, these characteristics are consistent with the minimal data available for species of closely related cestode orders, however the degree of variation was unexpected. The phylogenetic utility of spermatozoon ultrastructural characters can only fully be tested with a broader sampling of species within other cestode orders.
