engleski

Feeding ecology of Illex coindetii (Cephalopoda): a link between helminth parasites and food composition

Predatory cephalopods, with their important role in marine food webs are significant intermediate/paratenic hosts in the transmission and life cycles of many parasites. Squids are especially frequent as paratenic hosts of helminth parasites, particularly to those that have elasmobranchs and mammals as final hosts. Among those parasite species, anisakid nematode larvae and cestode plerocercoids are most effectively transferred through the trophic chain by oegopsid squids, such as short-finned squid Illex coindetii. This species is a fast-growing, monocyclic squid that primarily feeds on fish, namely small mesopelagic sternoptychids and myctophids. In this study, a total of 439 I. coindetii specimens were sampled in the central part of the eastern Adriatic Sea in order to assess their helminth component community and parasite dynamics with respect to host sex, maturity, seasonality, and feeding behavior. Two helminths at their larval stages were isolated, i.e., larvae of Anisakis pegreffii, characterized by molecular tools at the species level, and plerocercoids of Phyllobothrium sp.. The overall prevalences of nematode and cestode were 30.5% and 2.3%, respectively. Highly significant seasonal variation in diet consumption, congruent with seasonal variation in anisakid intensity, was observed. This observation underlined the tight role of squid prey in the trophic transmission of parasite. The highest helminth prevalence and intensity of infection was recorded in autumn, when the fish prey, mostly myctophid Maurolicus muelleri, comprised the greatest proportion of diet. This helped to assign the Adriatic short- finned squid as a second paratenic host for the anisakid. Also, evidence from the helminth community of the Adriatic I. coindetii population indicated that ontogenic shifts in its feeding behavior are due to morphological change of beaks and not because of habitat change. The presence of larval A. pegreffii confirmed its previously reported zoogeographical distribution in the Mediterranean and Adriatic Seas. Finally, the consistent presence of two helminths in I. coindetii describes the feeding patterns of the squid, as well as clearly defined and coevolved predator–prey relationships.

Illex coindetii; helminthes; Anisakis pegreffii; diet; Adriatic

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