Synopsis of the Species of Coccidians Reported in Marine Fish

SIMPLE SUMMARY: Apicomplexa (Levine, 1970) are obligate parasites, of both vertebrate and invertebrate hosts, and may be responsible for important diseases. The majority of piscine apicomplexans are coccidians, which infect the cells of the alimentary tract and other extra-intestinal tissues. The goal of this work is to provide up-to-date information about the diversity of these parasites in marine fish. For this purpose, available information concerning Coccidia morphology and molecular profile, the hosts and the organs they infect, as well as their geographic distribution, was assembled. It is remarkable that from the 100 morphologically described species, only 6 have available genetic data. ABSTRACT: Eimeriid coccidians represent one of the largest groups of parasitic unicellular organisms and comprise many species of veterinary and medical importance. The aim of this work is to provide information, as complete as possible, concerning the oocyst phase of the species of coccidians (Apicomplexa: Eimeriorina) with four sporocysts, which were reported in marine fish. For each species, the accepted scientific name and respective authorities, its synonyms, reported hosts, site of infection (organ), and geographic distribution have been assembled. Available information on morphology (oocyst, sporocyst, and sporozoite) and GenBank accession numbers were also compiled. A total of 100 species of coccidians were described and reported from 60 families of marine fishes. Most species have been described from marine teleosts, with only 14 of the species described from marine elasmobranchs. Most of the species reported in marine fish belong to the genera Eimeria and Goussia, and only a handful belong to the genera Epieimeria, Calyptospora, and Crystallospora. Although marine coccidians have began to be described for more than one century, the collection of genetic data on marine fish coccidians only started in the 2010s and remains largely disconnected from the morphological analysis of specimens, which is available for only six formally described species.