Abstract
Temperature is one of the main factors that influences cardiovascular functioning in ectotherms. Hence this study sought to investigate heart rate responses of a freshwater crab species, Poppiana dentata, to different temperature exposures since the species generally reside in habitats of fluctuating physicochemistry. Heart rates were non-invasively determined in juvenile crabs for three temperature regimes, each over an 8-day session; A: temperature exposures of 26 °C (2 days) to 30 °C (3 days) to 26 °C (3 days), B: 26 °C (2 days) to 32 °C (3 days) to 26 °C (3 days) and C: a control at constant 26 °C. Heart rate variations were significant among the regimes (P < 0.05), with the median heart rate being highest for regime B (74 beats per minute or bpm) during the temperature insult (32 °C), relative to regime A (70 bpm) and the control (64 bpm). Notably, a suppression and inversion of the diurnal cardiac patterns occurred for regimes' A and B crabs respectively, with rates from the highest temperature insult not shifting back to pre-insult levels during recovery (26 °C). It is plausible that P. dentata may have compensatory cardiovascular mechanisms that account for these differential heart rate responses, possibly conveying adaptive strategies in its dynamic habitat conditions.
Highlights
Heart rate in crustaceans can be affected by different factors such as temperature, light, salinity and locomotive activity but each of these tends to influence this cardiac aspect in a different way
Heart rate variation occurred amongst regimes, along with cardiac diurnal patterns becoming altered for regime’s A and B during the temperature changes; this response is not atypical and was expected for brachyurans
A similar response in C. magister crabs was observed where heart rates varied in response to changes of an 8 °C increase (Wachter and McMahon, 1996)
Summary
Heart rate in crustaceans can be affected by different factors such as temperature, light, salinity and locomotive activity but each of these tends to influence this cardiac aspect in a different way. Most studies examining cardiovascular features have described baseline cardiac. Influence of temperature on heart rate of P. dentata physicochemical or biochemical stressor (Ansell, 1973; Florey and Kriebel, 1974; Wilkens et al, 1985; Frederich and Pörtner, 2000). While these studies have extensively examined cardiac responses to stress factors for the marine brachyurans, investigations involving freshwater counterparts have been relatively limited
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