Parasite community study of the undulate ray Raja undulata in the Rı́a of Muros (Galicia, northwest Spain)

Abstract

The parasites present in 75 undulate rays ( Raja undulata Lacepède, 1802) captured in the Rı́a of Muros, a coastal embayment (rı́a) in northwest Spain were studied. A total of five species of cestodes ( Onchobothrium uncinatum, Phyllobothrium lactuca, Echeneibothrium beauchampi, Acanthobothrium benedeni and Grillotia sp.), three species of nematodes ( Schulmanela [ Piscicapillaria] sp., Pseudanisakis rotundata and Cystidicolidae gen. sp.) and one acanthocephalan ( Acanthocephaloides propinquus) were detected. All species were elasmobranch-specific except Cystidicolidae sp. and Acan. propinquus, which can both be considered accidental in this host. Species diversity peaked over the period April–September (Shannon–Wiener diversity=1.9–2.2; Pielou evenness=0.8–0.9). The dominant species were cestodes, notably O. uncinatum (present in 73 of the 75 hosts, and accounting for 45% of all parasites detected), followed by A. benedeni, P. lactuca and Grillotia sp., all of which were present in more than 30% of the host individuals. All species detected were autogenous, and all individuals except those of Cystidicolidae gen. sp. were adults. The five species of cestodes were present in hosts of all sizes, though single-host species richness, single-host species diversity and overall intensity of infection increased with increasing host size. Nematodes appeared in larger individuals (body length >33 cm). Larval Cystidicolidae gen. sp. appeared only in the largest size class (>43 cm), probably because only rays of this size are capable of ingesting relatively large demersal fish, the usual intermediate hosts in this area. Analysis of the species compositions of single-host parasite communities, considering cestodes only, suggests that negative interspecific interactions do not occur, despite the typically large size and abundance of the parasites, and their spatial concentration in the spiral valve.