Life history and osmoregulatory ability of Telmatogeton amphibius (Diptera, Chironomidae) at Marion Island
Although the non-crustacean arthropod fauna of the intertidal zone in the sub-Antarctic is both diverse and abundant, little is known about the biology of the species that occur in this habitat. Here, we provide information on the biology and osmoregulatory ability of the marine intertidal midge Telmatogeton amphibius (Eaton) (Diptera, Chironomidae) at Marion Island. Larval densities of this species in the lower shore zones can be as high as 16,000 individuals m-2 in their preferred habitat during peak abundance in summer. Winter abundances are substantially lower, and adults are much less abundant than larvae. Like other chironomids, this species has four larval instars and the flightless adult females have obligatory parthenogenesis. It is a strong osmoregulator. Larvae show little variation in body mass irrespective of whether they find themselves in freshwater or seawater, or are switched between the media. Haemolymph osmolality [ca. 400 milliosmol (mOsm)] varies by only 61 mOsm over a 1,520 mOsm range of the external medium. T. amphibius is similar in many respects to intertidal telmatogetonine midges found in other geographic regions. © Springer-Verlag 2004.