Fieldtrip to Rancho Marino Reserve

Image from Rancho Marino Reserve, Cambria, San Luis Obispo Co., CA, March 14-16, 2008

Acmaea mitra (duncecap limpet) with a pycnogonid (1 - 2 - 3 - 4) peaking out of the limpet's mantle cavity. The pycnogonid has been tentatively identified as Achelia chelata (Hilton, 1939) by pycnogonid expert, Dr. Roger Bamber. According to Dr. Bamber, the pycnogonid was first figured in 1940 by Dr. Joel Hedgpeth [Hedgpeth, J. W. 1940. A new pycnogonid from Pescadero, Calif., and distributional notes on other species. Journal of the Washington Academy of Sciences 30(2): 84-87], who described it as Ammothea euchelata before he became aware of Hilton's earlier proposed name. This pycnogonid was reported by Benson & Chivers (1960: A pycnogonid infestation of Mytilus californianus. The Veliger, 3 (1): 16-18; III.) to feed on another mollusc, Mytilus californianus, at Duxbury Reef, California, destroying ctenidial, gonadal and mantle tissue. In Hedgpeth's key to central California pycnogonids, this species is listed as: "Often in mussel beds and, in winter, parasitic on the ctenidia of Mytilus californianus" [Hedgpeth, J. W. 1975. Pycnogonida. Pp. 413-424, in (R. I. Smith and J. T. Carlton, eds.), Light's Manual: Intertidal Invertebrates of the Central California Coast. 3rd ed. Univ. of Calif. Press, Berkeley]. To my knowledge, no pycnogonid has previously been reported to be associated with a limpet and the extent of any association with or parasitism on limpets remains unknown.

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