Physiological constraints on the life cycle and distribution of the Antarctic fairy shrimp <Emphasis Type="Italic">Branchinecta gaini</Emphasis> |
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Authors: | T C Hawes M R Worland J S Bale |
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Institution: | (1) School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK;(2) Present address: Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand;(3) British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 OET, UK |
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Abstract: | Maturation to adulthood and successful reproduction in the Antarctic fairy shrimp, Branchinecta
gaini, must be completed within a physiologically challenging temporal window of ca. 2.5 months in the southern Antarctic Peninsula.
Although adults show considerable metabolic opportunism at positive temperatures, little is known of their tolerance of two
physiological insults potentially typical to pool life in the maritime Antarctic: sub-zero temperatures and salinity. B. gaini are freeze-avoiding crustaceans with temperatures of crystallisation (T
cs) of −5°C. No antifreeze proteins were detected in the haemolymph. Adults osmoregulate in relation to temperature, but rapid
mortality in saline solutions of even low concentration, indicate they cannot osmoregulate in relation to salinity. Survival
of ice encasement at temperatures above their T
c was found to be pressure but not time dependent: at severe inoculative ice pressures, there was little immediate survival
and none survived after 48 h below −2°C; at mild inoculative ice pressures, immediate survival was ca. 100% at −3°C, but <20%
after 48 h. There was no significant difference in survival after 1 and 6 h encasement at −3°C. Observations of ventilation
suggest that it is not low temperature per se, but ice that represents the primary cryo-stress, with ventilatory appendages
physically handcuffed below the freezing point of pool water. Both sub-zero temperatures and salinity represent real physiological
constraints on adult fairy shrimp. |
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Keywords: | Anostraca Ice encasement Salinity Osmoregulation Maritime Antarctic |
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