BULLETIN OF MARINE SCIENCE, 74(2): 401–421, 2004 NEW TAXA PAPER TAXONOMY, CIRCUMSCRIPTION, AND USAGE IN ANTHOPLEURA (CNIDARIA: ANTHOZOA: ACTINIARIA) FROM THE GULF OF MEXICO AND CARIBBEAN Marymegan Daly and J. C. den Hartog ABSTRACT Inadequate descriptions and diagnoses of representatives of the sea anemone ge- nus Anthopleura from the Gulf of Mexico and Caribbean have led to confusion about species identity. Multiple names have been applied to a single species, and the same name has been used for multiple species, obscuring the distinction between species and confusing accounts of anatomy, life history, and ecology. Because Anthopleura krebsi Duchassaing and Michelotti, 1860, the type species of the genus, is among these spe- cies, reconciling taxonomy, anatomy, and biology is essential. We conclude from our investigation of live specimens, museum collections, and published records that the sea anemones in the Gulf of Mexico and Caribbean that have been considered members of Anthopleura belong to four valid species: A. krebsi, Anthopleura pallida Duchassa- ing and Michelotti, 1864, Anthopleura texaensis (Carlgren and Hedgpeth, 1952), and Isoaulactinia stelloides (McMurrich, 1889). We redescribe these species, providing differential diagnoses that use characters visible in the field and those evident after preservation; we also identify synonyms and reconcile published records of these spe- cies with our circumscriptions. Although all of the features that have been proposed as defining or diagnosing Anthopleura are seen in A. krebsi, a comprehensive study of spe- cies in Anthopleura, Aulactinia, Bunodactis, Bunodosoma, and Gyractis is necessary to evaluate the systematic value of currently used characters. Accurate accounts of the biology of an organism or of the biodiversity of a region de- pend on correct and consistent taxonomy. Discrepancies between the attributes of speci- mens to which a name is applied, and the definition of that name can lead to confusion about the variability of a species. Inaccurate or inappropriate application of names con- founds attempts to assemble information about these species and thwarts assessments of knowledge of an animalʼs biology. In the sea anemone genus Anthopleura, changes in nomenclature and circumscription have led to confusion about the identity of many species, including the type species of the genus, Anthopleura krebsi Duchassaing and Michelotti, 1860. Because A. krebsi is the type species of Anthopleura, clarifying usage and accurately documenting the histology, anatomy, and nematocyst signature of this species is essen- tial for resolving genus-level taxonomic problems. The definition and composition of Anthopleura have changed over time as the anatomy and variability of its constituent species have become known in greater detail (e.g., Verrill, 1869; McMurrich, 1889, 1901; Carlgren, 1949; England, 1987). In his catalog of the Actiniaria, Corallimorpharia, and Ptychodactiaria, Carlgren (1949) cited 29 species as belonging to Anthopleura; seven species have since been transferred from other genera, based on more complete informa- tion about anatomy and cnidom (e.g., Parry, 1951; Hand, 1955; Mathew, 1967; Schmidt, 1972; England, 1987). Anthopleura has been confused with and is in partial synonymy with Aulactinia Verrill, 1864, Gyractis Boveri, 1893, Bunodactis Verrill, 1899, and Bu- nodosoma Verrill, 1899 (e.g., Carlgren, 1949; Hand, 1955; Dunn et al., 1980; England, 1987; den Hartog, 1987); amendments to the definition of Anthopleura have been tar- geted towards more clearly differentiating it from these genera (e.g., Carlgren, 1949; Bulletin of Marine Science 401 © 2004 Rosenstiel School of Marine and Atmospheric Science of the University of Miami 402 BULLETIN OF MARINE SCIENCE, VOL. 74, NO. 2, 2004 England, 1987; Belém and Pinto, 1990). We reexamine criteria proposed as diagnostic for Anthopleura in light of our redescription of A. krebsi and discuss how well these criteria distinguish Anthopleura from its allies. The implications of inappropriate application of species names for specimens of An- thopleura from the Gulf of Mexico and Caribbean extend beyond taxonomy. Specimens attributed to these species have been used in studies of phylogeny and biogeography (e.g., McCommas, 1983, 1991; Geller and Walton, 2001), anatomy (e.g., Bigger, 1976, 1982; Belém and Pinto, 1990; Belém et al., 1996), and behavior (e.g., Bigger 1976, 1980). These studies are compromised because the specimens used may not belong to the species whose name was applied to them. GenBank contains sequences for 16S and cytochrome c oxidase subunit III genes from A. carneola (AF375806 and AF375791, respectively); unless the name associated with molecular sequence data is accurate, the results of sequence studies cannot be corroborated or used to interpret the evolution of life history or anatomy. Five species epithets have commonly been used for species of Anthopleura from the Gulf of Mexico and Caribbean: A. krebsi; A. carneola (Verrill, 1905); A. catenulata (Verrill, 1905); A. pallida Duchassaing and Michelotti, 1864; and A. varioarmata Watzl, 1922. Two other species that belong to genera often confused with Anthopleura, Buno- dactis texaensis Carlgren and Hedgpeth, 1952, and Isoaulactinia stelloides (McMur- rich, 1889), are also found in this region. In fact, two species originally described as subspecies of the species now called I. stelloides, Bunodactis stelloides catenulata Ver- rill, 1905, and Bunodactis stelloides carneola Verrill, 1905, are considered species of Anthopleura (e.g., Cairns et al., 1986). In addition, the name Aulactinia stella (Verrill, 1864), which belongs to a species considered a member of Anthopleura by some authors (e.g., Uchida, 1938, 1941), was applied to sea anemone specimens from the Caribbean (Duerden, 1897), although Verrill (1899) considered Duerdenʼs use of the name a misap- plication. McCommas (1983, 1991) used the name Anthopleura stellula (Hemprich and Ehrenberg, 1834), which refers to a Red Sea and tropical Indo-Pacific species, for speci- mens collected in Puerto Rico. In this paper, we attempt to disentangle circumscription, name usage, and taxonomy of the species of Anthopleura from the Gulf of Mexico and Caribbean. To accomplish this, we determine the number of species, identify the valid name for each species, and reconcile published records with the appropriate name. We find that the nine names used for members of Anthopleura from the Gulf of Mexico and Caribbean can be attributed to four species: A. krebsi, A. pallida, A. texaensis, and I. stelloides. We redescribe these species, synthesizing published information for senior and junior synonyms. Because the internal anatomy and histology of A. pallida has never been de- scribed in detail, we furnish additional details about this species. Anthopleura krebsi, A. pallida, A. texaensis, and I. stelloides can be distinguished from one another based on field characteristics like color and posture, and anatomical characteristics like tentacle number, arrangement of verrucae, and the size and distribution of cnidae (Table 1). Be- cause A. krebsi, A. pallida, A. texaensis, and I. stelloides have overlapping ranges and have been confused, we attempt to identify the species to which particular specimens mentioned in previous reports belong; unfortunately, some publications contain insuf- ficient information to determine the identity of the specimens studied. DALY AND DEN HARTOG: TAXONOMY AND USAGE OF ANTHOPLEURA 403 -mastigophores and basitrichs p Holotrichs and basitrichs Cnidae marginal of structures Macrobasic Holotrichs and basitrichs Holotrichs and basitrichs In rows, toIn mid-column rows, Verrucae arrangement In rows, toIn limbus rows, In rows, toIn limbus rows, In rows, toIn limbus rows, Elongate Column shape Stout Stout Stout from the Gulf Mexico and of Caribbean. Pale green to white Column color Cream to light brown Gray to pale pink Pale pink to wine, with red spots 48 96 100 – – – Anthopleura 48 24–48 24 80 Number of tentacles Anthopleura texaensis Table 1. Key to the Key species 1. of Table Species Anthopleura krebsi Anthopleura pallida Isoaulactinia stelloides 404 BULLETIN OF MARINE SCIENCE, VOL. 74, NO. 2, 2004 METHODS We examined preserved museum specimens and newly collected material. We corresponded with collectors and field workers to augment the information on museum labels or in published records because differences in microhabitat, life history, and behavior have proven essential to solving species-level problems in sea anemones (e.g., Fautin and Chia, 1986; Pearse and Francis, 2000). Living specimens of A. krebsi and A. pallida were collected in Sarasota, Florida. A chunk of rock bearing many specimens of both species was removed from just below mean low water at Point of Rocks, Siesta Beach (27º15ʹ45ʺ N, 82º32ʹ59ʺ W; coordinates taken from the National Oceanographic and Atmospheric Administration website <http://www.noaa.gov>. Approximately 30 live specimens of A. krebsi and 20 live specimens of A. pallida were ex- amined under a dissecting microscope and identified while alive. Specimens of A. krebsi were removed with forceps, allowed to expand, anaesthetized in 3.5 % MgSO4, and fixed in 10% buff- ered seawater formalin. Because A. pallida specimens could not easily be removed from the rock crevices, the rock was placed in a large dish containing 3.5% MgSO4; the anesthetic was drawn off and 10% buffered seawater formalin was added after the attached specimens were anaesthe- tized. Anthopleura pallida specimens