Molecular and morphological analyses in two genera of trichoniscidae with and without gland-piliferous organs (Isopoda, Oniscidea)

Species of genera Spelaeonethes and Titanethes (Trichoniscidae) bear two sexual gland-piliferous organs on the fourth pleon segment of the males. Sexual gland-piliferous organs in different parts of the body are present in many trichoniscid species but their function is still unknown. Several populations belonging to the genera Spelaeonethes and Titanethes have been analysed morphologically and from a genetic point of view, using mtDNA sequence data (COI and 16S) to reconstruct their molecular phylogeny and to clarify the relationships linked to the presence of these sexual organs on the pleon. The species T. albus, with sexual glandpiliferous organs on the pleon, showed a very high genetic distance (>23%) compared to species in the genus Spelaeonethes, demonstrating that such organs arose convergently from independent lineages. In Spelaeonethes 9-11% divergence in COI was observed among different species, while in Titanethes the divergence is very low (0.5%) and corresponding to interpopulation differences.