VARIATION IN THE MORPHOLOGY OF ADULT APATEMON-GRACILIS RUDOLPHI, 1819(DIGENEA, STRIGEIDAE) REARED IN DIFFERENT AVIAN HOSTS

Adult Apatemon gracilis (Rudolphi, 1819) were reared experimentally in three different avian hosts: herring gulls Larus argentatus Gmelin, d omestic chicks Gallus gallus (L.) and eider ducklings Somateria mollis sima (L.). Comparisons of size, body proportions and fecundity were ma de between these and specimens obtained from a naturally infected goos ander Mergus merganser L. The eider duck proved to be a suitable exper imental host, rearing adults of comparable size and fecundity to those from the natural host. The growth and development of the parasite in domestic chicks and herring gulls were significantly reduced. Similar conditions are likely to exist in the natural environment and this sho uld be taken into consideration when choosing experimental hosts for u se in the laboratory or when identifying species.