MEPS 147:21-29 (1997)  -  doi:10.3354/meps147021

Effects of repeated exposures to marine cyanobacterial secondary metabolites on feeding by juvenile rabbitfish and parrotfish

Thacker RW, Nagle DG, Paul VJ

Secondary metabolites isolated from marine algae and cyanobacteria can act as feeding deterrents to a variety of herbivores, but past studies have rarely considered the responses of herbivores to these compounds over time. We examined the influence of repeated preference tests on the responses of juvenile rabbitfish Siganusspinus and juvenile parrotfish Scarusschlegeli to malyngamide A, malyngamide B, and malyngolide, 3 secondary metabolites from the marine cyanobacterium Lyngbyamajuscula. We offered fish choices between control food and food treated singly with these compounds in series of 3 to 5 preference tests, during which fish were either fed only during tests (periodic feeding) or continuously fed. Each of the 3 compounds deterred feeding by juvenile rabbitfish and parrotfish, but the magnitude of deterrence varied over time and between the 2 feeding protocols. In the continuous feeding protocol, rabbitfish were more discriminating in later trials with malyngamides A and B, while parrotfish were more discriminating in later trials with malyngamide A. Levels of deterrence of malyngamides A and B did not change over time in the periodic feeding protocols, and were lower than in the continuous feeding protocols for both species. Malyngolide generated the same amount of feeding deterrence in each feeding protocol and the fishes showed no changes in their consumption of malyngolide over time. Changes in hunger level and the amount of experience with foods may influence whether fish learn to reject foods that contain feeding deterrents, though the extent of this learning varies among compounds and fish species. These behavioral mechanisms may lead to the consumption of broader diets when preferred foods are less abundant.

Chemical defense · Natural products · Learning · Cyanobacteria · Lyngbya · Siganidae · Scaridae

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