Reference: Biol. Bull. 198: 101-109. (February 2000) Filamentous Fungi Associated With Holothurians From the Sea of Japan, Off the Primorye Coast of Russia MICHAEL V. PIVKIN Pacific Institute of Bioorgamc Chemistry. Fur East Branch of the Russian Academy of Sciences, 690022. Vladivostok. Russia Abstract. Holothurians (Holothurioidea, Echinodermata) are known to contain triterpene glycosides, which show antifungal activity. Nevertheless, fungi can be isolated from all organs of holothurians. During 1995-1996. mycelial fungi from several Far-Eastern holothurians Apostichopus japonic/is. Eupentacta fraiidutrix, Cuciinuiria japonica were collected from the Sea of Japan near the coast ot Primorye (Russia) and studied. Twenty-seven species of marine fungi, mostly facultative ones belonging to the mi-tosporic fungi, were isolated from the holothurians and identified. Fungi isolated from the holothurian surface were more diverse and abundant than those from internal organs and coelomic fluids. Of the holothurians studied. Ciicum-aria japonica was poorest in abundance and diversity of fungi. The fungi Cladosporium brevicompactum and C. sphaerospermum were common in the holothurian coelom. Because of their high proteolytic activity, these fungi may be pathogenic to holothurians. The detritovorus holothurian A. japonicus was shown to modify the fungal assemblages within the marine bottom sediments. Introduction Interest 'in the interactions between echinoderms and other species of marine organisms has intensified in the past few years. In addition to the trophic interrelationships of echinoderms within marine communities (Levin and Voronova. 1979) and diseases caused by bacteria, protists, and other parasites (Jangoux. 1987; Skadsheim etal.. 1995), benign, symbiotic interactions between echinoderms and bacteria have received much attention (Bauer and Agertr. Received 21 April 1998: accepted 10 September 1999. E-mail:
[email protected] 1994; McKenzie and Kelly. 1994; Newton and McKenzie, 1995: Kelly and McKenzie, 1995; Kelly el al. 1995; Thorsen, 1995). However, there is very little information about the fungi of echinoderms. Mortensen (1909) de-scribed a peculiar disease in the Antarctic cidaroid echi-noids, genera Rhynochocydaris and Ctenocidaris, which was caused by the fungus-like organism Echinophyces mirabilis. More recently, fungi were found to damage the spines of the sea urchins Diadema antillarum (Mortensen. 1940) and Strongylocentrotus franciscanus (Johnson and Charman. 1970). There is some evidence that fungi are present in the intestine of a sea cucumber. Apostichopus japonicus. from the Sea of Japan, but no data are available on their abundance or taxonomy (Levin, 1982). Despite the lack of data, the presence of fungi in holothu-rians is of potential importance. Holothurians are known to contain triteipene glycosides, which show fungitoxic, he-motoxic, and cytotoxic activities (Stonik and Elyakov, 1988). The diverse biological activities of the triterpene glycosides depend upon their specific binding to A-' sterols (Kalinovskaya etal. 1983; Kalinin et al. 1994, 1996). Such sterols are common in most fungi, but holothurian fungi must be assumed to contain some other sterols that will not bind to holothurian glycosides. In addition, fungi adapted to the effects of triterpene glycosides might produce secondary metabolites having a similar type of action. Thus, the iso-lation, in pure culture, of fungal strains from holothurians, and a definition of their species diversity would give us an insight into the biochemical mechanisms by which the fungi adapt to triterpene glycosides. This study had three aims. The first was to establish that fungi are found in and on holothurians a surprising phe-nomenon since holothurians are well known as producers of fungitoxic glycosides. The second aim was to prepare a list 101
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