Meeting Abstract
Relatively little is known on the postprandial metabolic response, often termed specific dynamic action (SDA), in arachnids. In this study we wanted to investigate the effect of temperature on SDA in scorpions, and its possible consequence for post-feeding thermal preference. We hypothesized that the high increase in metabolic cost of digestion associated with infrequent feeding would translate to a behavioral thermoregulatory response, correlated with the expected higher prey energy utilization at higher temperatures. Adult Hottentotta judaicus (Buthidae) were collected, fed with grasshopper nymphs and acclimated to laboratory conditions (25˚C; 14L:10D), before being assigned to 25 (N=12) and 30˚C (N=14) temperature treatments. Following two-week food prevention at the experimental temperatures, standard metabolic rates were measured using closed-system respirometry, before the animals were offered prey. Following 5h (at 25˚C) or 4h (at 30˚C) of feeding, post-feeding metabolic rates were measured for up to 7 days. Additionally, scorpions acclimated to 25˚C were placed in a thermal gradient arena (105cm length; temperature range 17-46˚C) after two-week food prevention, and were photographed at 1min intervals for 10h during the night under red-light conditions, before a similar procedure was carried out for the same individuals post-feeding. Calculated SDA and SDA coefficient (CSDA=ESDA/Eprey×100) were significantly higher at 30 compared with 25˚C, but SDA duration was significantly shorter at 30˚C, despite larger meal sizes on average. Scorpions showed preference for significantly higher surface temperatures post-feeding (37.2±0.9˚C compared with 34.0±1.0˚C before). We conclude that post-feeding preference for higher temperatures, despite lower prey energy utilization, may benefit the energy budget of scorpions by shortening digestion time and thus maximizing foraging efforts.
