PERFORMANCE PROCESSES IN MINUCA PUGNAX ACROSS TEMPERATURES AND IMPLICATIONS FOR NORTHERN RANGE EXPANSION
Date
2024-07-01
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Abstract
The Atlantic Marsh fiddler crab, Minuca pugnax, has migrated north of its historic range edge in Cape Cod, Massachusetts, and can be found in central Maine (Johnson pers comm.). The migration of M. pugnax leads toward the Gulf of Maine, a climate change hotspot. We studied the possible influences of expanded range temperatures on performance by investigating the effects of temperature on the respiration rate, running speed, and heart rate of M. pugnax. Both the respiration rate and running speed experiments were conducted in temperature-controlled chambers that were held at a single temperature for each trial. The temperature in the chamber ranged from 15°C to 35°C in increments of 5°C. Before the respiration rate experiment, each crab was placed in an individual glass beaker with a scannable sticker on the inside of the glass. Respiration rates were then measured using a PreSens Fibox 4, which recorded the oxygen consumption as a proxy for respiration rate over the course of an hour. Female M. pugnax did not show a significant change in respiration from 20°C to 35°C, while males had a peak respiration rate at 25°C. Running speed was measured using an entirely linear “racetrack” made of acrylic plexiglass, the surface of which was covered by a thin layer of damp sand to mirror the intertidal environment of M. pugnax. One crab was placed on a racetrack at a time to get individual running speeds and was encouraged to run by being “chased” using a popsicle stick. Female M. pugnax had a significantly higher running speed at 20°C through 35°C. Males had a peak running speed at 30°C. For both the running speed and respiration rate experiments, both male and female M. pugnax had significantly depressed performance at 15°C. Heart rates of M. pugnax were measured using voltage signal sensors connected to a Newshift AMP03 Heartrate Monitor over a 15°C to 35°C ramp. Both female and male M. pugnax showed no significant differences in heart rate. Our data implies that although the heart rate of M. pugnax may not be affected by the colder expanded range, issues for performance may arise in running speed and respiration rate.
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Ecology, Ecophysiology, Minuca pugnax, Range expansion