Interactions of elasmobranchs with other taxa in iberian watersParasitism and agonistic relationships

Resumen

This doctoral thesis is devoted to the study of parasite helminth communities in elasmobranchs found in Iberian waters, both in the Atlantic and the Mediterranean, with comments on the agonistic relationships between blue sharks (Prionace glauca) and swordfish (Xiphias gladius), questions that hadn't been approached before by previous researchers. The present study provides, for the first time, a quantitative report on the cestode fauna in four elasmobranch species, i.e., the shortfin mako shark (Isurus oxyrhinchus); the blue shark (Prionace glauca); the marbled electric ray, (Torpedo marmorata), and the common torpedo (Torpedo torpedo), in Iberian waters (Northeastern Atlantic, Galicia; Western Mediterranean, Valencia). It also investigates the role of key host species-specific traits in providing structure at infracommunity level. This study also documents unexpected, but increasingly noticed, agonistic interactions between blue sharks and swordfish (Xiphias gladius) over recent years, discussing their functional meaning and population impact. Overall, this thesis shows how parasite communities of elasmobranchs have been mostly neglected in the past, how their infracommunities are driven by phylogeny, ecological and particular host's traits, and gives points of reference for future studies. Also, by pointing out the lack of ecological parasitic studies of elasmobranchs, it makes a call towards the development of this research field, proving that it would be beneficial for improving the current knowledge of both elasmobranch parasites and their host, hopefully contributing to their proper conservation and making sure they are worthily validated.