Molecular insights into the identification and phylogenetics of the cosmopolitan marine fish blood parasite, (Adeleorina: Haemogregarinidae).

is one of the most prevalent haemogregarines of marine fishes and has long been considered an enigmatic and cosmopolitan species. However, to determine whether truly represents a single global species, or whether it should be partitioned into several species or subspecies, and to confirm its taxonomic status among the , molecular analysis is required. Here, we provide the first molecular characterisation of from one of its type hosts, , in the UK using 18S rDNA sequences. Phylogenetic and -distance comparisons of the newly generated sequences with those published from other haemogregarine taxa and related apicomplexans suggest that falls outside of the "" clade as well as the Adeleorina altogether, forming a separate apicomplexan marine clade, and appears to be in fact more closely related to other non-haemogregarine Apicomplexa genera. Further work including sequences of and -like parasites observed from fishes in other localities is now needed to investigate this further.