Low diversity of helminth parasites in Sardina pilchardus and Engraulis encrasicolus (Clupeidae) from the Bay of Biscay

Abstract

Parasitological data are increasingly used to provide information on host populations, trophic interactions and free-living biodiversity. In the present study, we investigated parasitic helminths in Sardina pilchardus and Engraulis encrasicolus from the Bay of Biscay (north-east Atlantic). In addition, helminths infecting E. encrasicolus were reviewed. Surprisingly, the field study revealed the occurrence of only three species of Ascaridoidea (Anisakis simplex s.s., Anisakis pegreffi and Hysterothylacium aduncum) in both fish species despite the high diversity of helminth parasites (mostly heteroxenous trophically transmitted) recorded throughout their distribution range (i.e. 39 and 15 taxa for S. pilchardus and E. encrasicolus respectively, with 12 shared taxa among them). This low diversity of helminth parasites in the Bay of Biscay may be indicative of a low free-living biodiversity. Moreover, similarities in the helminth parasites of S. pilchardus and E. encrasicolus, recorded both in the present field study and across their entire geographic distribution, suggest ecological and feeding similarities between these two planktivorous fish. However, the higher prevalence and mean intensity of Ascaridoidea in E. encrasicolus (v. S. pilchardus) in the Bay of Biscay also highlighted differences that were considered the result of its higher trophic plasticity.