Thermal tolerance of the hermit crab <i>Pagurus samuelis</i> subjected to shallow burial events

Abstract

Abstract.Sedimentation and increasing temperature caused by human disturbances and global climate change are additive in their effects on coastal areas. To assess their influence on intertidal organisms, we studied the hermit crab, Pagurus samuelis, under acute temperature changes and shallow burial conditions. We applied three temperatures (5°C, 20°C, and 30°C) and two burial depths (3 cm and 6 cm) with a control at the surface (0 cm), and monitored survival, shell abandonment, and burial escape. Survival was primarily affected by temperature, with hermit crabs twice as likely to survive at 20°C than at 30°C, and at 5°C than at 30°C. The combined conditions of 30°C and 6 cm were the least favorable for survival. Hermit crabs which abandoned their shells were more likely to survive burial at 20°C and 30°C than those retaining their shells. Fewer hermit crabs abandoned their shells when exposed to 5°C than to 20°C and 30°C. Crabs buried at 6 cm were 85.0% less likely to abandon shells than those buried at 3 cm, and heavier shells were less readily abandoned than lighter shells. Although overall, 35% of hermit crabs escaped burial to the sediment surface, hermit crabs buried in the combined conditions of 30°C and 6 cm were significantly slower to reach the surface. Our results show that the combined stresses of temperature and burial can impact survival of hermit crabs in intertidal zones. While human activities, including dredging, industrial and domestic dumping, and coastal construction, result in relatively immediate increased inputs of sediment in coastal environments, climate change may endanger intertidal organisms, such as P. samuelis, living near their thermal tolerance over the long term, with both increasing temperature and sedimentation from more frequent storm events.

Lactate accumulation in the intertidal hermit crab, <i>Pagurus samuelis</i>, in response to burial-induced hypoxia

“…As previous preliminary oxygen saturation tests by Shives & Dunbar (2010) suggested, the longer hermit crabs were buried the more dissolved oxygen was consumed, causing hypoxia. These results are consistent with the rapid decrease in available oxygen during burial conditions measured by Valére-Rivet et al (2017), although they additionally investigated the combined impact of temperature on oxygen availability. When available oxygen was insufficient to support aerobic respiration, crabs relied on anaerobic fermentation, which was indicated by increasing lactate levels.…”

“…Burial also dramatically reduces diffusion rates of liquids and gasses, so that the supply of oxygen becomes limited to that accessible only in the immediate surroundings. As a result, burial by sediment may cause the immediate environment to become hypoxic (Nichols et al, 1978;Shives & Dunbar, 2010;Valére-Rivet et al, 2017). Several decapod species exhibit various physiological adaptations to short-term hypoxia, including increased scaphognathite Crustacean Research 46 (Anderson et al, 1991;Paterson & Thorne, 1995) or pleopod (Felder, 1979;Torres et al, 1977) beat frequency, and increased cardiac output (Thompson & Pritchard, 1969).…”