HIGH DIVERSITY OF Myxobolus spp. (MYXOZOA) IN AND BETWEEN JUVENILE Mugil cephalus INDIVIDUALS

Galit Sharon, Michal Ucko, Ben Tamir, Arik Diamant
 
Israel Oceanographic and Limnological Research, National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel
 

Grey mullet, Mugil cephalus is an important aquaculture species in the Mediterranean region. In this study we report high variability of Myxobolus Bütschli 1882 spp. (Myxosporea) in juvenile grey mullet received at our lab from Israeli aquaculture farms. The examined M. cephalus fingerlings originated from wild caught a. Ebro River Delta in Spain, fingerlings imported to Israel and b. River estuaries in northern Israel (Mediterranean Sea). Infections with Myxobolus spp. were recorded from both batches. Here we present light microscopy, electron microscopy and molecular analyses of the different Myxobolus spores found in multiple sites in these fish, as well as histological attributes of the infections. 18S rDNA sequence analyses indicated the presence of different species of Myxobolus in the examined grey mullet fingerlings. Clear differences in both spore morphology and 18S rDNA sequences was found between the Myxobolus spp. when the wild grey mullets from Spain ("Spanish") were compared to locally caught wild grey mullet fingerlings ("Israeli"). Nevertheless, spore morphology was similar amongst all Myxobolus recovered from the Spanish fish, while  their 18S rDNA sequences revealed species variability, between different infected organs (gills, tail, and internal organs) originating from the same fish as well as between individual fish from the same batch. The absence of records of these Myxobolus spp. in the GenBank database compounds the diversity of Myxobolus spp. which can be found on a single grey mullet host. It is noted that commercially caught wild fingerlings and imported stocks may contribute to this diversity by introducing and spreading new variants from remote geographical regions.