Effects of body size and lung type on desiccation resistance, hypoxia tolerance and thermal preference in two terrestrial isopods species.
Terrestrial isopods have evolved adaptations to reduce water loss, which is necessary for life in low humidity environments. However, the evolution of a waterproofed cuticle to prevent loss of water to the environment could also impede oxygen uptake from the environment. We therefore postulate an evolutionary trade-off between water retention and gas exchange in this group of soil animals. The outcome of this trade-off is expected to be affected by both differences across species (different types of lung) and differences within species (body size and resulting surface area to volume ratios). To test these ideas, we compared two sympatric isopods: Porcellio scaber and Oniscus asellus. While P. scaber possesses covered lungs typical for drier habitats, O. asellus has simple open respiratory fields which are in direct contact with external air. For each species, we assessed how individuals across a broad range in body size differed in their hypoxia and desiccation tolerance. In addition, we assessed how hypoxia and low humidity affected their thermal preference. We found clear effects of species identity and body size on tolerance to hypoxia and low humidity. Desiccation resistance was tightly linked to water loss rates (R2 = 0.96) and strongly resembled the interspecific pattern across 20 isopod species. However, our results did not support the postulated trade-off. Tolerance to hypoxia and low humidity covaried, both increasing with body size and being higher in P. scaber. Thermal preference was affected by both hypoxia and low humidity, but not by body size. Our study increases understanding of the ecophysiology of both species, which can be useful in explaining the geographical distribution and use of microhabitats of isopod species in a climate change context.
['Antoł|Andrzej|A|', 'Berg|Matty P|MP|', 'Verberk|Wilco Cep|WC|']
D000222:Adaptation, Physiological D000818:Animals D005075:Biological Evolution D049628:Body Size D057231:Climate Change D003681:Dehydration D017753:Ecosystem D006813:Humidity D000860:Hypoxia D033321:Isopoda D008168:Lung D012987:Soil D013696:Temperature
Crustaceans Physiological functional traits Pleopodal lungs Soil fauna Thermal biology