Algae Aplysia species

Xeniolides A (152) and B (153) are a pair of lactones, related to the prenylated caryophyllene xeniaphyllenol and xenicin, which have been isolated from the soft coral Xenia macrospiculata. Hydroxydilophol (154) is a germacrene-like diterpenoid which has been obtained from the brown alga Dictyota masonii. The full paper, including an X-ray analysis, has appeared on dictyodial and dictyolactone which were obtained from various Dictyota and Aplysia species. A... 

Quite often the type of compound isolated from Aplysia species depends on the location from which they were collected, and therefore, on the algae upon which they feed. A. kurodai collected from Mei Prefecture of Japan was found to contain an extended diterpene (with a prenylated eudismane skeleton)-aplysiadiol [13] and its methyl derivative [14] (29). It could safely be assumed that a brown alga on which this prosobranch feeds was the actual source of aplysiadiol. Recently a biogenetic type synthesis of 14 has been reported (30). 

Some species of Aplysia also consume green algae and seagrass, mainly of the genera Codium, Ulva and Halo-phila, but there has been very little work on this type of food chain (Carefoot et al., 2000). 

The food chain between the Japanese species Aplysia kurodai and Laurencia concinna (Ceramiales) and Laurencia perforata yielded three closely related brominated diter-penes aplysin-20 was found only in the sea hare (Matsuda et al, 1967) isoaplysin-20 was identified in the mollusk and in Laurencia perforata and concinndiol was isolated only from Laurencia concinna. These three structures and their biosynthetic patterns are presented in Chapter 13. More recently, the food chain between the species Aplysia parvula and the red alga Laurencia filiformis, harvested in Tasmania, has led to similar comments (Jongaramruong et al, 2002). Other examples of brominated diterpenes found in Aplysia and Laurencia are presented in Chapter 13 (see also Komprobst and Al Easa, 2003). 

The Mediterranean species Aplysia depilans harvested in Spain preferentially consumes the green alga Ulva lactuca, and stores in its skin a series of 16- and 17-membered macrolactones derived from polyunsaturated adds with 16 or 18 carbon atoms and bearing a hydroxyl group at position 15 or 16. Aplyolides A-E are aU idithyotoxic (Spinella et al, 1997a). 

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