SPERM ULTRASTRUCTURE OF 6 AUSTRALIAN HYLID FROGS FROM 2 GENERA (LITORIA AND CYCLORANA) - PHYLOGENETIC IMPLICATIONS

The spermatozoa of four fossorial (Litoria alboguttata, Cyclorana brev ipes, Cyclorana novaehollandiae and Cyclorana cryptotis) and two non-f ossorial australian hylid frogs (Litoria aurea and Litoria moorei) tog ether with previously examined Litoria (Hylidae: Anura) are compared. In spermatozoal ultrastructure (in particular the structure of the spe rm tail) Cyclorana includes species which appear derived (apomorphic) relative to non-fossorial species of Litoria while the fossorial L. al boguttata groups with Cyclorana. All hylid species examined here are u nited by the bufonoid synapomorphy of a conical subacrosomal cone cons isting of separate sheaves and the eubufonoid synapomorphy of a mitoch ondrial sheath or collar separated by a cytoplasmic canal from the cen triolar region and tail. Spermatozoal symplesiomorphies for the Eubufo noidea, seen in Litoria (with the exception of L. alboguttata), are th e well developed thin undulating membrane with juxta-axonemal and axia l fibre. L. alboguttata, C. novaehollandiae and C. brevipes appear mon ophyletic in the apomorphic modification of the undulating membrane as a thick, dense structure. In L. alboguttata and C. novaehollandiae th is structure retains a swelling, at the free edge, homologized with th e axial rod. C. brevipes has a further apomorphy as the undulating mem brane forms a parallel-sided dense structure with no separate differen tiation of an axial fibre. C. cryptotis, however, retains the plesiomo rphic sperm tail with a thin undulating membrane, juxta-axonemal and a xial fibre. That these differences in spermatozoal ultrastructure have phylogenetic significance is endorsed by the similarity of the fertil ization biology of the species examined. On the basis of sperm ultrast ructure three separate lineages are discerned within Cyclorana s. lat. : 1) C. cryptotis; 2) L. alboguttata and C. novaehollandiae; and 3) C. brevipes. The evidence of sperm ultrastructure, supported by previous ly published molecular, morphological and karyological data, clearly p laces Litoria alboguttata within the genus Cyclorana.