Genetic diversity of Loma acerinae (Microsporidia: Glugeida) from different fish hosts and localities - Short communication.

Loma acerinae is a xenoma-forming fish microsporidium described from common ruffe Gymnocephalus cernua (Perciformes: Percidae) and also found in Ponto-Caspian gobies (Gobiiformes: Gobiidae). This casts doubt on the strict host specificity of this parasite. The largest subunit RNA polymerase II (rpb1) was used as a genetic marker of the parasite isolated from six host species of Perciformes (G. cernua from the Baltic Sea), Atheriniformes (Atherina boyeri from the Azov Sea) and Gobiiformes (Neogobius spp. and Zosterisessor ophiocephalus from the Black Sea and Ponticola kessleri from the Caspian Sea basin). Two major rpb1 haplogroups were found with 98.5% identity between the groups. Notably, Haplogroup I was associated with Neogobius spp. samples (n = 6) only, whereas Haplogroup II included the samples from other host species (n = 7). These findings confirm the broad distribution and host range of L. acerinae, but also indicate that certain patterns of host-driven intraspecific polymorphism may exist. Furthermore, the study revealed low similarity between the ribosomal RNA gene sequences of L. acerinae and the type species, Loma morhua (as well as other species of the genus). This suggests loose genetic association within the genus, and may raise the need for the taxonomic revision of L. acerinae.