Data on the adult marine and migratory phases in the life cycle of the southern hemisphere lamprey,Geotria australis Gray

Synopsis Large numbers of the Southern Hemisphere lamprey, Geotria australis, have been found in the regurgitated food of albatrosses breeding on South Georgia. This finding suggests that this lamprey is found in large groups at sea, presumably associated with its host, and can travel very large distances from its natal streams. The length and morphology of the individuals from South Georgia, which almost certainly represent a South American stock, were compared with those of representatives of the immediately pre- and post-marine trophic stages of G. australis caught in Western Australia. No significant differences could be detected either in the number of trunk myomeres or in the number and arrangement of the teeth. The mean length of the animals (± 95% confidence limits) from South Georgia was 45.9 ± 0.90 cm compared with 10.0 ± 0.23 cm and 62.5 ± 0.85 cm in G. australis collected from Western Australia just before they had entered and returned from the sea respectively.