MICROENCAPSULATION AS A POTENTIAL CONTROL TECHNIQUE AGAINST SABELLID WORMS IN ABALONE CULTURE

We have developed a novel application for lipid-walled microcapsules ( LWMs) in the potential control of sabellid infestations in abalone aqu aculture. The use of LWMs takes advantage of the filter-feeding nature of the worms, versus the herbivory of the host abalone. Initial obser vations indicated that the pest was capable of feeding on particles ra nging from 3-30 mu m in size. Lipid-walled microcapsules were prepared using different combinations of lipids (tristearin, tripalmitin, and fish oil) to encapsulate water-based solutions. Feeding experiments us ing worm-infested shells indicated that in a relatively short time (30 -60 min) most of the worms (80-95%) fed on the LWMs and that large num bers of LWMs were ingested. Fecal pellets containing LWMs were observe d in the rectums of worms within 15-30 min. Feeding efficiency was exa mined using different concentrations of LWMs. The sabellid worm was an efficient feeder. At low particle densities (2.6 x 10(4) particles/mL ), 66.7% of the worms had eaten modest levels of LWMs. An asymptote in particle density in relation to feeding occurred at 2.6 x 10(5) parti cles/mL, with 83% of the worms feeding on large numbers of particles. In separate observations, LWMs composed of tripalmitin and fish oil we re observed in various stages of digestion in the stomach, rectum, and fecal pellets of the worms. Microcapsules were also observed in the d igestive tract of mud worms, Polydora spp. that were also inhabiting a balone shell. The utility of LWMs for delivery of toxins to the sabell id pest holds much promise in ridding the industry of this nuisance sp ecies.