Relationship between age and thermoregulatory behaviour of Lithodes santolla (Molina, 1782) (Decapoda, Lithodidae) juveniles

Along its range of distribution, Lithodes santolla can be fished at sites with wide ranges of temperature (5 °C to 12 °C), suggesting a wider temperature tolerance than is observed for other members of the Lithodidae family. The present study aimed to evaluate the thermoregulatory behaviour of juveniles of L. santolla of different ages, maintained in laboratory conditions at 12 °C for 390 days and based on: i) temperature selected along a thermal gradient and ii) thermal window calculated as the tolerance temperature interval. Results demonstrate that age is a key factor to be considered in thermal tolerance studies, because the thermal tolerance can change, depending on the age and life cycle stages. The preferred temperature was 12 °C for animals aged between 45 d and 170 d and was 7.2 °C and 9.1 °C for crabs aged between 260 and 390 d, respectively. The critical thermal minimum (CTMin) significantly changed together with the age of crab; the highest value (4.2 °C) was for animals 260 d old and lowest for crabs 45 d old (1.5 °C). Critical thermal maximum values were also affected by age, with highest values for animals aged between 105 d and 170 d (27 °C to 27.6 °C). The temperature tolerance interval fluctuated between 20.5 °C and 25.5 °C. Crabs aged between 45 d and 260 d showed the narrowest interval (22.9 °C and 20.5 °C, respectively). Considering the thermal limits observed in the present study, a climate change scenario with an increasing frequency and intensity of extreme thermal events might affect the present distribution of the species. Temperature rises would allow L. santolla to explore higher latitudes, whereas a temperature decrease when juveniles are searching for a particular colder habitat, near to CTMin, might be detrimental to the population.