Lack of metabolic temperature compensation in the intertidal gastropods,Littorina saxatilis (Olivi) and L. obtusata (L.) |
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Authors: | Robert F McMahon W D Russell-Hunter David W Aldridge |
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Institution: | (1) Marine Biological Laboratory, 02543 Woods Hole, Massachusetts, USA;(2) Section of Comparative Physiology, Department of Biology, The University of Texas at Arlington, Box 19498, 76019-0498 Arlington, Texas, USA;(3) Department of Biology, Syracuse University, 13210 Syracuse, New York, USA;(4) Present address: Department of Biology, North Carolina Agricultural and Technical State University, 27411 Greensboro, North Carolina, USA;(5) 711 Howard Street, 21601-3934 Easton, Maryland, USA |
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Abstract: | Two intertidal snails, Littorina saxatilis (Olivi, 1972) (upper eulittoral fringe/maritime zone) and Littorina obtusata (Linnaeus, 1758) (lower eulittoral) were collected from a boulder shore on Nobska Point, Cape Cod, Massachusetts, in July
and acclimated for 15–20 days at 4 ° or 21 °C. Oxygen consumption rate (Vo2) was determined for 11–15 subsamples of individuals at 4 °, 11 ° and 21 °C with silver/platinum oxygen electrodes. Multiple
factor analysis of variance (MFANOVA) of lo10 transformed values of whole animal Vo2 with log10 dry tissue weight (DTW) as a covariant revealed that increased test temperature induced a significant increase in Vo2 in both species (P<0.00001). In contrast, MFANOVA revealed that temperature acclimation did not affect Vo2 in either L. saxatilis (P= 0.35) or L. obtusata (P= 0.095). Thus, neither species displayed a capacity for the typical metabolic temperature compensation marked by an increase
in Vo2 at any one test temperature in individuals acclimated to a lower temperature that is characteristic of most ectothermic animals.
Lack of capacity for metabolic temperature acclimation has also been reported in other littorinid snail species, and may be
characteristic of the group as a whole. Lack of capacity for respiratory temperature acclimation in these two species and
other littorinids may reflect the extensive semi-diurnal temperature variation that they are exposed to in their eulittoral
and eulittoral fringe/maritime zone habitats. In these habitats, any metabolic benefits derived from longer-term temperature
compensation of metabolic rates are negated by extreme daily temperature fluctuations. Instead, littorinid species appear
to have evolved mechanisms for immediate metabolic regulation which, in L. saxatilis and L. obtusata and other littorinids, appear to centre on a unique ability for near instantaneous suppression of metabolic rate and entrance
into short-term metabolic diapause at temperatures above 20–35 °C, making typical seasonal respiratory compensation mechanisms
characteristic of most ectotherms of little adaptive value to littorinid species. |
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Keywords: | acclimation Littorina obtusata Littorina saxatilis Littorinidae oxygen consumption respiration temperature effects |
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