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Abstract

Animals recognize the outside based on their own nervous systems. Some variations exist among nematodes, although there are many similarities in the structure of the nervous systems. What is the difference among nematodes in recognition mechanisms? The recognition mechanism of the predatory nematode Pristionchus pacificus has been studied in detail. It has been clarified that P. pacificus can distinguish the same strain from closely-related strains by chemical recognition. To understand the variations in recognition mechanisms of predator species, we have studied the recognition mechanism of the predatory nematode Seinura caverna belonging to Tylenchomorpha. First, we observed the predacious behavior of S. caverna against the same species, closely-related predatory species, and prey species. The results indicated that S. caverna was able to distinguish the same species from prey species, while S. caverna could not distinguish the same species from closely-related predatory species. Then, chemotaxis assays were carried out to investigate the attraction of S. caverna to nematode extractions followed by observation of the ultrastructure of the cuticle of S. caverna and related species. The results suggested that the S. caverna could distinguish same species and closely-related species from prey species on the basis of physical recognition rather than chemical recognition. These results indicate that S. caverna and P. pacificus have different recognition mechanisms.