Temperature and relative humidity effects on water loss and hemolymph osmolality of Littoraria angulifera (Lamarck, 1822)
Abstract
Description
Desiccation stress is considered to be one of the more significant determining factors that
influence how organisms are distributed in the marine littoral. Gastropods living above
the high tide mark, referred to as eulittoral fringe gastropods are not wetted as regularly
and face unpredictable and prolonged periods of emersion. Consequently, adaptations
displayed by eulittoral fringe gastropods are aimed at minimizing water loss and
surviving prolonged periods of desiccation stress. Littoraria angulifera, is a tropically
distributed marine eulittoral fringe gastropod. Because L. angulifera spends a majority of
its time emersed there was interest in studying how the weight loss and hemolymph
osmolality of this species changed over a period of time in response to varying
environmental conditions. Hypotheses were that weight loss and hemolymph osmolality
would be dependent upon temperature and relative humidity with weight loss and
hemolymph osmolality being highest at high temperatures and low relative humidities.
Additionally, it was predicted that this species should also exhibit some form of
regulation of either weight loss or osmolality. Specimens ranging in size from 15.24 to
28.40 mm were collected from concrete marina bulkheads in Port Isabel, Texas. Weight
loss rate and hemolymph osmolality were examined at test temperatures of 15°, 25°, and
35°C and relative humidities (RH) of <5%, 33%, 53%, 75%, and >95%. Weight loss rates
were tracked for 5 individuals in each temperature/RH treatment. Hemolymph osmolality
of was determined at 0, 5, 10, and 15 days in each of the temperature/RH treatments. The
weight loss rates were significantly affected by test temperature and relative humidity and
varied significantly across each test temperature/RH combination. Hemolymph
osmolality was not significantly affected by test temperature but was affected by RH.
Results indicated that weight loss increased as temperatures increased and RH decreased
and hemolymph osmolalities generally increasing as relative humidity decreased.
Specimens did not seem to display any signs of osmoregulation, but this may have been
due to an experimental shortcoming. Behavioral responses to emersion that were
observed were consistent with the responses displayed by other eulittoral fringe species
displaying how this species’ is well adapted to life in its exacting habitat.
PDF; 34 pgs.
PDF; 34 pgs.