Aspects of ecology and biogeography of Acanthocephala in antarctic seabirds

Abstract

Four species of acanthocephalans are reported from seabirds, nototheniid fishes and gammaridean amphipods in the western Antarctic. Corynosoma hamanni (von Linstow, 1892) was found in Phalacrocorax atriceps King, Chionis alba (Gmelin), Larus dominicanus Lichtenstein, and Catharacta lonnbergi (Mathews). The complete life cycle of this acanthocephalan was elucidated : cysticanths develop in the haemocoel of a gammaridean amphipod, Pontogeneiella sp. of the family Eusiridae and presumably, following ingestion of parasitized amphipods, encyst in the body cavity of antarctic fishes of several species. Corynosoma singularis Skriabin and Nikol’skii, 1971 was found only in P. atriceps. Corynosoma bullosum (von Linstow, 1892) occurred in both P. atriceps and Pygoscelis papua (Forster). Neither of these species of Corynosoma had previously been reported from avian hosts. Corynosoma shackletoni Zdzitowiecki, 1978 was recorded only as a parasite of P. papua. The first known gravid females of this species were found during this study, indicating that C. shackletoni is a typical parasite of avian, rather than mammalian, final hosts. It is the first acanthocephalan known to typically occur in an avian definitive host in Antarctica. The host-distribution of Corynosoma spp. in birds suggested that these parasites were being acquired from piscine or possibly amphipod prey, generally in nearshore situations. Seabirds representing the zooplanktivore feeding guild were not infected. This indicates that pelagic food-webs, and other trophic pathways in which Euphausia superba Dana is a dominant prey organism, are probably not involved in the life cycles of Corynosoma spp. The host and geographic distributions of Corynosoma in piscine, avian, and mammalian hosts suggested that oceanographic factors, particularly the Antartic Convergence, could limit the ranges for some species of parasites. Host-parasite coevolution appears to have had an important influence on the species composition of the acanthocephalan fauna of seabirds and marine mammals in Antarctica.