Genetic identity of two physonect siphonophores from Southern Ocean waters – the enigmatic taxonMica miculaandPyrostephos vanhoeffeni

Abstract

Based on some coincident morphological characters and distribution, it was believed for a long time thatMica miculawas the post-larval stage of a species ofBargmannia, a genus having a very wide geographic distribution. Recent studies, however, have shown that it is much more likely to be the post-larval form of the physonectPyrostephos vanhoeffeni, which is very common in both Antarctic and sub-Antarctic waters. Until now, molecular evidence to support this theory has been lacking. In the present study 34 nectophores ofP. vanhoeffeniand four colonies ofM. miculacollected from three areas in the Southern Ocean were analysed for the 16S rRNA gene. Five haplotypes were identified, which formed two clearly distinct lineages. Three haplotypes were found exclusively in Admiralty Bay and were shared between individuals of both studied taxa, confirming thatM. miculais indeed the post-larval stage ofP. vanhoeffeni. Two additional haplotypes were found in one open ocean locality and in Admiralty Bay.