Dietary preferences of the opisthobranch mollusc Stylocheilus longicauda for secondary metabolites produced by the tropical cyanobacterium Lyngbya majuscula

Abstract

Pure compounds isolated from the cyanobacterium Lyngbya majuscula Gomont were evaluated in an artificial diet for their influence on the feeding preferences of the sea hare Stylocheilus longicauda (Quoy and Gaimard, 1824), which lives in and feeds on this filamentous cyanobacterium (blue-green alga). Microcolin B, ypaoamide, malyngolide and other natural products acted as feeding deterrents at natural concentrations. At lower concentrations, sea hares were indifferent to ypaoamide and malyngolide in their diets. In contrast, barbamide stimulated sea hare feeding at the concentrations normally found in L. majuscula. Malyngamides and majusculamides, the most common natural products found in samples of L. majuscula from Guam, increased sea hare feeding at low concentrations and inhibited feeding at the higher concentrations that occurred in some collections of L. majuscula. Dietary selection of cyanobacteria by S. longicauda may be regulated by the concentration of specific chemical cues produced by L. majuscula.