Abstract
Several specimens of a small panopeid crab from coastal waters of the western Gulf of Mexico were long suspected to represent an undescribed species and are herein designated as representatives of a new genus. While the originally collected specimens from over four decades ago were not of gene-sequence quality, later collections from the same locality produced materials that yielded sequence data for inclusion in molecular phylogenetic studies. Building on results of those analyses, the present taxonomic description draws upon morphology to support the description of a unique species in which especially the male first gonopods differ from those of all other described panopeid genera. To date, the species remains known from only two western Gulf of Mexico sites, both of which are wave-washed intertidal rocky habitats where substrates are heavily burrowed by boring bivalves and sipunculans. While we cannot exclude the possibility that the species was introduced, recurrent collections show its populations to be at very least persistent, the species most likely being a long-overlooked among a confusing hard-substrate assemblage of small panopeid crabs.
References
Felder, D.L. (1973) An annotated key to crabs and lobsters (Decapoda: Reptantia) from coastal waters of the northwestern Gulf of Mexico. Publications of the Center for Wetland Resources, LSU-SG-73-02. Center for Wetland Resources, Louisiana State University, Baton Rouge, Louisiana, 103 pp., 179 figs.
Felder, D.L., Álvarez, F., Goy, J.W. & Lemaitre, R. (2009) Chapter 59: Decapoda (Crustacea) of the Gulf of Mexico, with comments on the Amphionidacea. In: Felder, D.L. & Camp, D.K. (Eds.), Gulf of Mexico Origin, Waters, and Biota. Vol. 1. Biodiversity. Texas A&M University Press, College Station, Texas, pp. 1019–1104.
Felder, D.L. & Martin, J.W. (2003) Establishment of a new genus for Panopeus bermudensis Benedict and Rathbun, 1891, and several other xanthoid crabs from the Atlantic and Pacific Oceans (Crustacea: Decapoda: Xanthoidea). Proceedings of the Biological Society of Washington, 116, 438–452.
Martin, J.W. & Abele, L.G. (1986) Notes on male pleopod morphology in the brachyuran crab family Panopeidae Ortmann, 1893, sensu Guinot (1978) (Decapoda). Crustaceana, 50, 182–198.
https://doi.org/10.1163/156854086X00205
Martin, J.W., Felder, D.L. & Truesdale, F.M. (1984) A comparative study of morphology and ontogeny in juvenile stages of four Western Atlantic xanthoid crabs. Philosophical Transactions of the Royal Society of London, B, 303, 537–604.
https://doi.org/10.1098/rstb.1984.0001
Martin, J.W., Truesdale, F.M. & Felder, D.L. (1985) Larval development of Panopeus bermudensis Benedict and Rathbun, 1981 (Brachyura, Xanthidae) with notes on the evolution of zoeal characters in xanthid crabs. Journal of Crustacean Biology, 5 (1), 84–105.
https://doi.org/10.2307/1548223
Rathbun, M.J. (1930) The cancroid crabs of America of the families Euryalidae, Portunidae, Atelecyclidae, Cancridae and Xanthidae. Bulletin of the U.S. National Museum, 152, i–xvi + 1–609.
https://doi.org/10.5479/si.03629236.152.i
Schubart, C.D., Neigel, J.E. & Felder, D.L. (2000) A molecular phylogeny of mud crabs (Brachyura: Panopeidae) from the northwestern Atlantic, and the role of morphological stasis and convergence. Marine Biology, 137, 11–18. https://doi.org/10.1007/s002270000325
Thoma, B.P. & Felder, D.L. (2012) Redescription of Hexapanopeus lobipes (A. Milne-Edwards, 1880), with reassignment to Milnepanopeus n. gen. (Crustacea: Decapoda: Panopeidae). Journal of Crustacean Biology, 32 (1), 141–152.
https://doi.org/10.1163/193724011X615415
Thoma, B.P., Guinot, D. & Felder, D.L. (2014) Evolutionary relationships among American mud crabs (Crustacea: Decapoda: Brachyura: Xanthoidea) inferred from nuclear and mitochondrial markers, with comments on adult morphology. Zoological Journal of the Linnean Society, 170, 86–109.
https://doi.org/10.1111/zoj.12093
Thoma, B.P., Schubart, C.D. & Felder, D.L. (2009) Molecular phylogeny of the western Atlantic representatives of the genus Hexapanopeus (Decapoda: Brachyura: Panopeidae). In: Martin, J.W., Crandall, K.A. & Felder, D.L. (Eds.), Crustacean Issues: Decapod Crustacean Phylogenetics. Taylor and Francis/CRC Press, Boca Raton, Florida, pp. 551–565.
Whitten, H.L., Rosene, H.F. & Hedgpeth, J.W. (1950) Invertebrate fauna of the Texas coast jetties; a preliminary survey. Publications of the Institute of Marine Science, University of Texas, 1 (2), 53–87.
Williams, A.B. (1965) Marine decapod crustaceans of the Carolinas. Fishery Bulletin, U.S., 65, i–xi + 1–298.
Williams, A.B. (1984) Shrimps, Lobsters, and Crabs of the Atlantic Coast of the Eastern United States, Maine to Florida. Smithsonian Institution Press, Washington, D.C., 550 pp.