Composition and seasonal dynamics of the parasite communities of Scyliorhinus canicula (L., 1758) and Galeus melastomus Rafinesque, 1810 (Elasmobranchii) from the NW Mediterranean Sea in relation to host biology and ecological features

© 2017, Springer International Publishing Switzerland. The parasite communities of Scyliorhinus canicula and Galeus melastomus are studied for the first time in the Mediterranean. Their seasonal and geographical variations, and their relationship with environmental and fish biological data were tested. The parasite communities of both sharks were characterized by low richness and diversity, and high dominance. Infracommunity structure and composition differed between both species probably due to the consumption of different prey associated with their different bathymetric distributions. For G. melastomus, parasite infracommunity structure and the abundance of some parasites differed across seasons and/or localities due to different dynamics of intermediate hosts populations, in turn linked to different environmental conditions. While Ditrachybothridium macrocephalum was more abundant in juvenile specimens of G. melastomus as a result of ontogenic diet shifts, Grillotia sp. accumulated in adult hosts. The abundance of Proleptus obtusus was significantly higher in S. canicula, likely due to its shallower distribution coupled with higher consumption of reptantian decapods with respect to G. melastomus. Monogenean parasites were associated to high turbidity and temperature levels, which are known to enhance monogenean infection and reproductive success. Cestodes of G. melastomus were linked to high turbidity and O2levels, which increase zooplankton biomass, favouring the transmission of heteroxenous parasites.