The effect of feeding frequency on consumption of food,absorption efficiency,and gonad production in the sea urchin Lytechinus variegatus

The frequency of feeding in the field is variable in sea urchins, ranging from nearly continuous to diel or intermittent. It is essential to know the effect of feeding interval on physiological and metabolic processes to understand the basis for production. Lytechinus variegatus (50 mm horizontal diameter) were collected in January 1999 and held in closed-circuit aquaria at 25 degrees C and 35 per thousand salinity. After 9 days without food, individuals were fed one of three treatments: food available ad libitum, food available for 1 day every 2 days or food available for 1 day every 4 days for 28 days. The rate of food consumption per day of all individuals was high the first week of feeding. It then decreased to a lower, constant rate in those fed ad libitum but remained high in those fed one day every 2 or 4 days. The total amount eaten was directly related to frequency of feeding. The apparent dry matter digestibility (absorption efficiency) did not vary with frequency of feeding. As the total amount of energy absorbed was directly related to the frequency of feeding, the increase in the rate of food consumption does not compensate for a decrease in frequency of feeding. Gonad production efficiency was directly related to frequency of feeding. Gonad gross production (assimilation) efficiencies were 8.4, 3.9 and 3.4% for individuals fed every day, or fed one day every 2 and 4 days, respectively. The corresponding gonad net assimilation efficiencies were 12.5, 5.5, and 4.8%. A decrease in frequency of food availability results in use of a greater proportion of the food consumed for maintenance and less for gonad production.