Evaluation of dietary feeding stimulants for the sea urchin Lytechinus variegatus
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Sea urchins shape their environment primarily through their feeding behavior. For Lytechinus variegatus this behavior is largely guided by the detection and response to chemical stimulus. The extent of which compounds and how these specific chemicals influence behavior in sea urchins has received only cursory investigation. The purpose of this study is to characterize the role of several amino acids in the feeding behavior of the sea urchin Lytechinus variegatus. Specimens of L. variegatus were collected from Cape San Blas within the Port St. Joseph Peninsula State Park, FL, USA (30 °N, 85.5 °W). Sea urchins were maintained in a semi-recirculating system and fed a standard reference diet (SRD) at ad libitum levels. This diet is used routinely in all sea urchin research at the Shrimp Mariculture Project. To standardize conditions for testing olfactory and gustatory response, a series of experiments were performed to evaluate the effects of water flow rate and hunger on the chemical response of L. variegatus. To characterize the effects of flow rate, feed consumption rate and travel speed was measured while the sea urchins were subjected to different current velocities. Lytechinus variegatus was subjected to different lengths of food deprivation to assess the effects of hunger on their feeding behavior. Finally, olfactory and gustatory response was evaluated by exposing L. variegatus to one of eight concentrations of six individual amino acids (L-alanine, L-arginine, DL-glutamate, glycine, L-leucine and L-tyrosine). Results from these studies suggest that Lytechinus variegatus is positively rheotactic and under the conditions of the study, increases feed consumption rate with increased flow rate. Also, during periods of prolonged food limitation, L. variegatus decreases physical activity but consumes larger amounts of food when it becomes available. Lytechinus variegatus also employ food-sourced amino acids to identify food sources and evaluate food palatability. These findings help expose components of scantily studied mechanisms that drive sea urchin navigation, foraging, distribution, food choice and interactions. These findings could also impact sea urchin aquaculture, affecting both feed formulation and sea urchin husbandry techniques.
Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy.