Evidence that hemolymph glucose in Aplysia californica is regulated but does not affect feeding behavior.

Abstract

Hemolymph glucose increased following a meal of a commercially available dried seaweed (laver) in Aplysia californica (Aplysia). Glucose injected into the hemocoel did not affect meal size, bite latencies, swallowing rate, or 24-hr food intake. The authors found that injection of a homogenate of nerves containing a putative Aplysia insulin-like substance decreased hemolymph glucose. The nerve homogenate, however, did not affect feeding behavior. Injection of 2-deoxy-D-glucose was found to increase hemolymph glucose, an indication of gluco-privation, but instead of increasing feeding it either had no effect or, at high doses, debilitated animals and interfered with feeding. These studies suggest that glucose may be physiologically regulated in Aplysia, but it does not appear to play a role in the control of feeding behavior.

An increase in insulin is important for the acquisition conditioned taste aversion in Lymnaea

“…This nerve homogenate, however, did not affect feeding behavior (Horn, Koester, & Kupfermann, 1998). In our study, the bovine insulin decreased the hemolymph glucose concentration; and interestingly the bovine insulin did not significantly alter the feeding response elicited by the CS in the pretest session.…”

Localization and Functional Characterization of a Novel Adipokinetic Hormone in the Mollusk, Aplysia californica

“…There was a reduction in hemolymph glucose over the course of the experiment [F(4, 32) = 8.456, p<0.0001] in both groups (Figure 5). This decrease was typical for repeated hemolymph sampling [32], [37].…”

“…diacylglycerol or trehalose) during times of high energy expenditure [7]. Since HP glycogen and hemolymph glucose are the primary forms of stored and circulating carbohydrates, respectively, in A. californica , we examined the effects of ap-AKH on these two parameters [32], [37], [38]. ap-AKH did not acutely alter circulating glucose (Figure 5), nor did it affect HP glycogen after repeated injections (Figure 7C).…”

“…All injections were 500 µl in volume and administered via 26-gauge needles through the posterior foot into the hemocoel. When food consumption was measured (Experiments 2 and 5), meal portions (∼7–13% body mass) and feeding durations (3 hours) were designed based on previously published studies [32]. The injection doses of ap-AKH were based on previously published ap-GnRH injection studies [27].…”

“…The main circulating sugar in A. californica is glucose [32], [37], [38], thus ap-AKH was tested for acute hyperglycemic activity. All animals were food-deprived for 24 hours before the study.…”