Influence of diet and temperature on physiological energetics of Chorus giganteus (Gastropoda: Muricidae) during reproductive conditioning

Abstract

The influence of two bivalve diets (Mytilus chilensis "chorito" and Tagelus dombeii "navajuela") at three temperatures (13, 15, and 18°C) was studied during the reproductive conditioning of Chorus giganteus (Lesson, 1829). Energy budgets were determined taking into account energy acquisition (ingestion and absorption) and energy expenditure (oxygen consumption, ammonia production, and energy placed into mucus production and egg laying). Relative physiological condition was assessed by calculating the scope for growth index (SFG). Diet and temperature both played key roles in the physiological energetic and reproductive conditioning of this snail. Tagelus was the preferred prey, probably because of its greater vulnerability to predatory attack by C. giganteus. The highest feeding rate was observed at 15°C, coinciding with optimal growth. Absorption efficiency was similar with both diets, despite the differential preference in prey. Temperature had no effect on oxygen uptake, but increased as the snails fed on Tagelus during the reproductive conditioning period. Diet was the main factor affecting SFG, and temperature, although significant, accounted for a lower percentage of variation in SFG. Highest growth rates were observed at 15°C on a Tagelus diet. Reproductive effort, measured as the proportion of the total energy budget of an organism that is allocated to reproduction, was highest at 18°C with a Tagelus diet. Energy would not be allocated for reproduction when the snails were fed with M. chilensis, as SFG was negative at all three temperatures.