A PARASITOLOGICAL SURVEY IN ELASMOBRANCHS FROM ADRIATIC SEA

Elasmobranches play a key-role as definitive hosts in the complex life cycle of several parasitic species being at the top of the food chain. Despite their biological importance, studies on the parasitofauna of sharks and rays are rather difficult to be carried out, as most of them are endangered species and specimens collection and examination are sporadic and mainly limited to biodiversity and environmental monitoring research projects. During 2013, in collaboration with the Lab of Marine Biology and Fishery, University of Bologna, located in Fano (Ancona province), Italy, a parasitological survey has been carried out on elasmobranchs caught in the Adriatic sea for stocks evaluation purposes. A total of 184 fish from georeferenced fishing stations and belonging to 10 species have been examined: 50 Galeus melastomus, 43 Scyliorhinus canicula, 34 Raja clavata, 27 Squalus acanthias, 11 Mustelus punctulatus, 8 Mustelus mustelus, 5 Raja miraletus, 3 Myliobatis Aquila, 1 Torpedo maculata, 1 Torpedo marmorata. All fish were weighed, measured and submitted to parasitological examination focused on the gastrointestinal tract. Parasites were cleaned in water and fixed in alcohol 70%, then mounted and clarified in Amman’s lactophenol for morphological identification. Prevalence (P) values, Mean Intensity (MI) and Abundance (A) have been calculated according to Bush et al,. 1997, J. Parasitol., 83: 575-583. All the individuals of the remaining species, Galeus melastomus, Myliobatis aquila, Torpedo maculata and Torpedo marmorata were negative for the presence of parasites. All the digenean trematodes have been referred to one species, Ptychogonimus megastomus (Rudolphi, 1819), already reported in M. mustelus and R. clavata but never described in Mustelus punctulatus. This represents to our knowledge a new host-record. Concerning cestodes, the specimens isolated belongs to two trypanorhinch species, in particolar Nybelinia lingualis in S. canicula and Eutetrarhynchus ruficollis in M. punctulatus, while the tapeworm isolated from S. canicula was not well preserved and impossible to be identified. Nematodes are the most represented endoparasites in our survey as they have been isolated from the intestine of all the six positive fish species. In S. canicula nematodes were identified as Proleptus obtusus, already reported in this fish species, while in R. clavata, S. acanthias, M. punctulatus, M. mustelus and R. miraletus, the parasites isolated seem referable to Pseudanisakis spp., but further morphological analyses need to be carried out to confirm this preliminary study. In addition in S. acanthias and M. mustelus, the presence of Hysterothylacium sp. and Acanthocheilus sp. has been respectively observed. The data collected during this survey give a preliminary sight on the parasitofauna present in elasmobranchs species not easy to be investigated and add new information on the host specificity of some parasitic species,such as Ptychogonimus megastomus, to our knowledge for the first time reported in M. punctulatus. Furthermore identification at species level and morphological data on nematodes such as Pseudanisakis spp., should contribute to improve the knowledge on this poorly known genus.