An in vitro study of lipid preference in whaleworm (Anisakis simplex, Nematoda, Ascaridoidea, Anisakidae) third-stage larvae

The behavioural response of nematodes to chemical stimuli has been extensively investigated in some free-living and plant parasitic species. However, in animal parasitic species, little is yet known, particularly in regards to marine forms such as the whaleworm (Anisakis simplex). Previous studies showed that A. simplex L3-larvae tend to prefer fish tissue with high lipid content. The intention of this study was to investigate the behaviour of A. simplex L3 in response to different concentrations of fish lipid in further detail. This was done by an in vitro study based on larvae from cod (Gadus morhua). Ten larvae were placed in each of the culture containers containing agar that was separated into three segments of equal size. Three categories of agar were used containing 0, 2 and 7 % cod liver oil. A total of 900 larvae were included. The study consisted of three parts: The purpose of experiment I was to establish whether different lipid concentrations influenced the migration pattern at all. Experiment II was intended to examine whether A. simplex L3-larvae were able to actively search for lipids. Experiment III was set up to analyse the short-distance dispersion of the L3-larvae. Experiment I indicated that the L3-larvae move randomly but do not stop randomly since the tendency to move out of the start area was inversely correlated with lipid concentration. Experiment II indicates that the larvae are almost unable to select areas of high lipid concentrations when more than a few centimetres away. Experiment III showed that the L3-larvae prefer high-fat content and can seek it out over short distances.