Meeting Abstract

P3.140  Wednesday, Jan. 6  Elemental and Energy Assimilation in the round stingray, Urobatis halleri PAIG-TRAN, EWM*; LOWE, C; Univ. of Washington; California State University Long Beach mpaig@u.washington.edu

The elasmobranch digestive system contains a spiral fold that is believed to enlarge the exploitable surface area for digestion while maintaining a relatively short intestine. This leads to the question: does the addition of spiral folding have an effect on the elemental absorption efficiency of elasmobranchs? We addressed this question by measuring the elemental absorption and caloric assimilation of Urobatis halleri, the round stingray, fed a diet of de-shelled shrimp. Following total gut clearance, rays were fed 2% of their body weight in peeled shrimp and their subsequent feces collected. Both the food source and ray feces were dried, homogenized, and run through a CHN Elemental Analyzer. To calculate the average percentage of elemental assimilation in U. halleri, simple calculations were performed subtracting the average percentage of elemental carbon, hydrogen, and nitrogen found in fecal samples from the percentage of elemental abundance in the food source, and then dividing that by the initial food source. Ray elemental assimilation was approximately 75% of the available carbon and 90% of the available nitrogen. Shrimp and fecal samples were also subjected to semi-micro bomb calorimetry to determine total caloric (energy) uptake. Rays assimilated approximately 80% of the caloric energy available during these trials. Finally, three whole stingrays (a neonate, a juvenile, and an adult) were dried, homogenized and semi-micro bombed to assess the differences in total caloric value and to calculate the energy needed for somatic growth. There was an 828Cal/g difference between adult and neonatal stingrays. These results are similar to the high assimilation efficiencies of other carnivorous fishes including the lemon shark, Negaprion brevirostris, which has an energy assimilation efficiency between 62-83% and organic assimilation between 76-88%.