Temperature Adaptation of Acanthocephalus tenuirostris (Palaeacanthocephala: Echinorhynchidae) in the Postembryonic Development

Abstract

The larval development of a fish parasite, Acanthocephalus tenuirostris, has been studied under experimental conditions. This species is common in the eastern regions of Russia, from Primorye to the upper reaches of the Kolyma River. The material for the experiments has been collected from different areas of Magadan oblast, which is located mainly in the subarctic climate zone. In several series of experiments, intermediate hosts (Asellus hilgendorfii) are infected and maintained at a constant temperature of 15°C. In all cases, no more than 45 days are required for the formation of the final cystacanth stage. Along with cystacanths, a large number of other larvae at earlier developmental stages are simultaneously recorded in the hemocoel of the isopods. An additional experiment, carried out at 15°C for the first 45 days and 4–6°C for the next 207 days, has shown the possibility of the further development of larvae at low temperatures. A comparison with the available literature data on the timing of development of European Acanthocephalus species living in temperate climate has suggested that A. tenuirostris has adapted to cold climate conditions, which provides a twofold acceleration of the rate of its development compared to larval A. lucii in Europe.