Proceedings of the Biological Society of Washington 115(4):868-877
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PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 115(4):868-877. 2002. Taxonomy, anatomy, and histology of the Hned sea anemone, Edwardsiella lineata (Verrill, 1873) (Cnidaria: Anthozoa: Edwardsiidae) Marymegan Daly Department of Biology, George Washington University, Washington, D.C. 20052, and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045 Abstract. —The lined sea anemone, Edwardsiella lineata (Verrill, 1873) is a common inhabitant of shallow waters of the North Atlantic from Cape Cod to Cape Hatteras. Its larval form, described as Edwardsia leidyi Verrill, 1898, is an endoparasite of the ctenophore Mnemiopsis leidyi and has been identified as the cause of sea-bather's itch. Although the biology and anatomy of the larval form are well documented, the internal anatomy and histology of adults has not been described. Confusion about the correct name for this species and about the identity of adults that produce the larvae have made identifying and monitoring this species difficult. In this study, I describe the anatomy of adult members of E. lineata, synthesize existing accounts of its development and life history, and detail the taxonomy of E. lineata and the genus Edwardsiella. Edwardsiella lineata is the valid name are undocumented. The lack of information for the species called Fagesia lineata (Ver- about internal morphology, and the absence rill, 1873) and E. leidyi Verrill, 1898. Ed- of clear differential diagnoses for E. lineata wardsia leidyi is the larval form of E. li- and other western North Atlantic species in neata (Crowell 1965, 1976). Although the the family Edwardsiidae make identifica- names of the larval and adult forms were tion and documentation of E. lineata pop- synonymized (Crowell 1965, 1976), the lar- ulations difficult. Because E. lineata has va continues to be cited as E. leidyi (e.g., been linked to sea-bather's itch in the North Gosner 1979, Kremer 1976, Meinkoth Atlantic (Freudenthal & Joseph 1992, 1995). Even publications that recognize the 1993), documenting the distribution of this synonymy fail to use the correct name for species is especially important. the species (e.g., Oviatt & Kremer 1977, Bumann & Puis 1996). Some of the no- Materials and Methods menclatural confusion is probably caused by Crowell's (1976) acknowledgment that For this study, I examined both live and the generic assignment given in the syn- preserved specimens of E. lineata. Live onymy was incorrect, as the genus Fagesia material was purchased from Marine Bio- was under revision at the time (see Manuel logical Laboratory (Woods Hole. Massa- 1981). chusetts); these specimens were collected Although the anatomy, ontogeny, and by SCUBA divers in Cape Cod Bay (E. ecology of the larval form are well char- Enos, pers. comm.). Coloration and external acterized (e.g., Mark 1884, Crowell 1976, anatomy were recorded prior to fixation. Crowell & Gates 1980, Bumann & Puis Freshly preserved material and museum 1996), and the external anatomy of the specimens from the Yale Peabody Museum adult is known (Verrill 1873), the internal (YPM 7642 Al and YPM 8802) and the anatomy and histology of adult E. lineata United States National Museum. Smithson- — VOLUME 115, NUMBER 4 869 ian Institution (USNM 53363) were used Systematic Account for histological studies. Serial sections of Family Edwardsiidae Andres, 1883 paraffin-embedded preserved specimens Genus Edwardsiella Andres, 1883 were stained in Masson's Trichrome (Schreibman 1964). Edwardsiidae with column differentiated In the following discussion of anatomy, into capitulum, scapus, and scapulus, three "distal" refers to the oral disc and tenta- or more cycles of tentacles. Tentacles hex- cles, "proximal" to the aboral end. The amerously arranged, those of innermost cy- terms "dorsal" and "ventral" are used to cle longest. Capitulum with ridges; nema- describe the orientation of the retractor tocysts of capitulum concentrated on ridges. muscles and mesenteries (e.g., Carlgren Scapus bears periderm but lacks nemathy- 1921, Stephenson 1935, England 1987); bomes and tenaculi. Aboral end not differ- more recent descriptions of actiniarian anat- entiated into a physa. Ciliated tracts of fil- omy employ "sulcular" rather than dorsal, ament short, discontinuous (modified from and "sulcar," rather than ventral (e.g., Sta- Stephenson 1935, Carlgren 1949, Manuel chowitsch 1992). I use the older terminol- 1981). ogy to facilitate comparison with descrip- tions of other edwardsiids; in no way is the Edwardsiella lineata (Verrill, 1873) use of the terms dorsal or ventral meant to Figs. 1-3 homologize the longitudinal axis of actini- Edwardsia lineata Verrill, 1873:421.—Ver- arians with that of bilaterians. rill & Smith, 1874:445.—Parker, 1900: Cnidae preparations were made by 750.—Hargitt, 1912:248.—Miner, 1950: squashing approximately 1 .0 mm^ of tissue 198.—Williams, 1981:350. on a slide. Smears were prepared from ten- Edwardsia leidyi Verrill, 1898:496.—Park- tacle, actinopharynx, mesenterial filament, er, 1900:750.—Hargitt, 1912:248.—Min- and capitulum tissues from several individ- er, 1950:198.—Gosner, 1971:154.—Kre- uals. Tissue smears were examined at mer, 1976:213—Oviatt & Kremer, 1977: lOOOX magnification with differential in- 236.—Gosner, 1979:95.—Williams, terference optics. ScanPro measurement 1981:349. software (Jandel Scientific Software) was Edwardsia sp. Verrill & Smith, 1874: used to measure the length and width of 504.—Mark, 1884: pi. xii. undischarged cnidae capsules projected Edwardsiella lineata Pratt, 1935:151. onto a Summa Sketch digitizing pad tablet Freudenthal & Joseph, 1992:101; 1993: (Summagraphics). Cnidae nomenclature 542. follows Mariscal (1974). Edwardsia sp. Mark Carlgren, 1949:23. Cnidae presentation is modified from Fagesia lineata Carlgren, 1949:25.—Gos- Dunn et al. (1980). The capsule with the ner, 1971:153.—Crowell, 1976:247.— smallest (or greatest) width is generally not Crowell & Gates, 1980:139.—Sebens, the capsule with the smallest (or greatest) 1998:20.—Williams, 1981:350.—Shick, length. Summarizing the range using four 1991:253.—Meinkoth, 1995:352.— measurements, providing a length by width Weiss, 1995:4.14. range, as is typical in cnidarian taxonomy, is imprecise (Fautin 1988) and can imply Adult external morphology. —Body capsule sizes not observed. I present the translucent white, with pale tan lines indi- range by citing the size of the shortest, nar- cating mesenterial insertions. Mesenterial rowest, longest, and widest capsule sepa- compartments proximal to capitulum rately. The sizes of these capsules define a streaked with opaque white. Oral cone space that includes the size coordinates of prominent, opaque white. Tentacles margin- all observed cnidae. al, filiform, 18-36, in 2-3 cycles, 6 tenta- 870 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON Fig. L External anatomy of preserved specimen of Echvardsiello lineata (USNM 53363). Scale bar = 3.0 mm. VOLUME 115, NUMBER 4 871 cles of innermost cycle longest. Tentacles mesenteries, forming capitular ridges. Ec- translucent white with opaque white flecks, toderm contains thin processes of mesoglea. each may bear longitudinal opaque mark on Cnidom. —Spirocysts, microbasic Z^-mas- oral side. tigophores, basitrichs, and microbasic Column 10-30 mm long, 2-5 mm in di- /7-mastigophores (Fig. 3). See Table 1 for ameter, divisible into 2 distinct regions: distribution and size information. short, ridged, capitulum and long, smooth, Larval morphology. —Young larva pink- scapus covered by rough periderm of mu- ish-tan, ciliated. Shape very changeable, cus, detritus, and sand grains (Fig. 1). Peri- most commonly ovoid, can be spheroid or derm sheath-like, not attached to column by vermiform. Parasitic juvenile 2.0—3.0 mm suckers or tenaculi, extending from scapus long, approximately 1 mm in diameter, aboral contracted to end; specimens appear translucent pink, with 4-8 tentacles (Mark entirely enclosed by periderm. Aboral end 1884, Crowell 1976). Larva becomes short- not ampullaceous, instead tapering or er and thicker after leaving host (Mark slightly rounded, with rugae, but without 1884, Crowell 1976). cinclides or central invagination. Development, distribution, and natural Internal anatomy. —Actinopharynx tan, history. —Although position of each mesen- partially visible through body wall. Six tery in larval coelenteron prefigured by fur- pairs mesenteries in primary cycle: two row in endoderm (Mark 1884), mesenteries pairs of directives and four pairs, each of develop from evaginations of endoderm which has one member complete and fertile (Mark 1884). Mesenterial folds ciliated. (= macrocneme) and one member minute, Ventrolateral mesenterial pairs arise first, imperfect, sterile (= microcneme). Second- followed by dorsolateral, ventral and dorsal ary and tertiary cycles, when present, mi- mesenteries (Mark 1884). Mesenteries more crocnemous; all microcnemes restricted to developed distally than proximally. Muscles distal capitulum. Single ventral siphonog- develop after all pairs present (Mark 1884). lyph. Trilobed ciliated filaments short, dis- Found along North Atlantic coast of continuous, present in region proximal to North America, from Cape Cod, Massachu- actinopharynx and in reproductive tract; setts to Cape Hatteras, North Carolina. Lit- gonochoric, oviparous. toral to sublittoral. Adults commonly inhab- Retractor muscles large, circumscript, it rock crevices, Zostera root mats, or bore- convex (Fig. 2A, B), with closely spaced holes created by