Meeting Abstract
P3.60 Monday, Jan. 6 15:30 Tarantulas vs. Scorpions: Digestive energetics and efficiencies of drinking versus eating BELANICH, JR*; SECOR, SM; U. of Alabama; U. of Alabama jrbelanich@crimson.ua.edu
The processing of any meal comes with a cost; a cost that impacts the net energy gained and therefore is incorporated into the efficiency by which energy is acquired. Animals differ in their mode of food handling and ingestion and thus will experiences differences in the tradeoff between energy intake and expenditure. Within the class Arachnida, tarantulas are liquid feeders using oral mastication and enzymes to produce an ingestible liquid sludge, whereas scorpions masticate and ingest small pieces of their prey. To a common meal, crickets, and body temperature, 30°C, we examined how these two arachnid groups differ in the cost of meal digestion and net energy efficiency.For three species of tarantulas (G. rosea, A. chalcodes, A. avicularia) and five species of scorpions (P. imperator, H. arizonensis, H. longimanus, H. trilineatus, C. sculpturatus), we measured their postprandial metabolic response and quantified from the metabolic profiles their SDA, which represents the accumulative energy expended on meal ingestion and assimilation. Both groups experienced a rapid postprandial increase in metabolic rate that peaked within 6-12 hours after feeding and returned to prefeeding values within two days. Tarantula and scorpion SDA averaged 20.8 kJ kg-1 and 42.2 kJ kg-1, respectively, and for each was highly dependent on meal size. Due to the variation in relative meal size (4.6-19.5% of body mass), we standardized SDA to meal energy. We found that when controlling for meal energy that scorpions expend 80% more energy on digestion and assimilation compared to tarantulas, however the differences in this SDA efficiency was not significant. We suspect that the lower SDA for tarantulas reflects their more liquid-like diet and less post-ingestion effort. Alternatively, the cost of meal digestion may be more similar between the two when including the cost for tarantulas of mastication and enzyme production.
