Abstract
*Adamsia obvolva* is a new species of sea anemone (order Actiniaria, family Hormathiidae)
from the Gulf of Mexico, symbiotic with the hermit crab *Parapagurus pictus* (Smith, 1883). The pedal disc of the anemone enwraps the gastropod shell in which the hermit crab lives, and secretes a thin, chitinous carcinoecium that lies between the
pedal disc ectoderm of the anemone and the gastropod shell. The description of *A.
obvolva* n. sp. highlights many of the problems confounding the systematics of actiniarians
symbiotic with hermit crabs. *Adamsia obvolva*, which has been misidentified as *Paracalliactis involvens* (McMurrich, 1893), presents a suite of attributes that blur the distinction between the genera *Adamsia* Forbes, 1840, and *Calliactis Verrill*, 1869. We review definitions of these genera and emend *Adamsia* to include only those species that form a carcinoecium and have a lobed pedal disc. To better differentiate between
*A. obvolva* and *P. involvens*, we investigate the syntypes of *Adamsia involvens* McMurrich,
1893, which had been transferred to *Paracalliactis*, and of its putative synonym *Urticina consors* Verrill, 1882; we redescribe the species as *Paracalliactis consors* (Verrill, 1882). *Adamsia obvolva* and *P. consors* can be distinguished by tentacle number, the cinclides on the lower column of specimens of *A. obvolva*, and cnidae distribution and size. The taxonomic changes we propose are summarized in a diagnostic key to actiniarian families and genera that live attached to gastropod shells.
Description
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Citation
Daly, Marymegan, Adorian Ardelean, Ha-Rim Cha, Andrew C. Campbell, and Daphne G. Fautin. 2004. A new species, *Adamsia obvolva* (Cnidaria: Anthozoa: Actiniaria), from the Gulf of Mexico, and a discussion of the taxonomy of carcinoecium-forming sea anemones. Bulletin of Marine Science 74(2): 385-399.