Clione antarctica

One example for a chemically defended zooplankton species is the Antarctic pteropod Clione antarctica. This shell-less pelagic mollusk offers a potentially rich source of nutrients to planktivorous predators. Nonetheless fish do not prey on this organism, due to its efficient chemical defense. In a bioassay-guided structure elucidation, pteroenone 37 could be isolated and characterized as the main defensive principle of C. antarctica [82,83]. If embedded in alginate, this compound is a feeding-deterrent in nanomolar concentrations. This unusual metabolite is likely to be produced by C. antarctica itself and not accumulated from its food, since its major food sources did not contain any detectable quantities of 37. 

In addition to protecting the pteropod, pteroenone 37 can also serve invertebrates as an indirect chemical defense (Fig. 2). The amphipod Hyperiella dilatata gains protection by carrying the pteropod Clione antarctica on its back. That this carrying behavior provides efficient protection is clear, since in all cases... 

Bryan, P. J., Yoshida, W. Y., McClintock, J. B., and Baker, B. J., Ecological role for pteroenone, a novel antifeedant produced by the conspicuous antarctic pteropod Clione antarctica (Gymnosomatia Pteropoda), Mar. Biol., 122, 271, 1995. 

The relationship described above might lead one to suspect that the reason that the hyperiid amphipod Plyperiella dilatata abducts and carries a chemically defended sea butterfly (Clione antarctica) is that it lacks the ability to synthesize or produce its own chemical defenses. Indeed, Hay et al.39 have also shown that amphipods may associate with chemically defended algae to provide defense against fish predators, rather than produce defensive compounds themselves. 

The pteropod Clione antarctica, a pelagic mollusc, produces the polyketide pteroenone (Structure 7.69).53 Pteroenone is distasteful to sympatric fish.54 C. antarctica are subject to capture by the amphipod Hyperiella dilatata, which holds them in place on its dorsum and is similarly avoided by the same fish predators (see Section III.A, below). 

Yoko, F. (2005) First synthesis of (+)-pteroenone A defensive metabolite of the abducted Antarctic pteropod Clione antarctica. Synlett., 635-636. 

Asao, H., Nakamura, Y, Furuya, Y, Kuwahara, S., Baker, B.J., and Kiyota, H. (2010) Synthesis of pteroenone and its stereoisomers, a defensive metabolite of the abducted Antarctic pteropod Clione antarctica. Helv. Chim. Acta, 93, 1933-1944. 

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