Anthopleura elegantissima ( Brandt, 1835 )

Vassallo-Avalos, Aurora, González-Muñoz, Ricardo, Acuña, Fabián H., Cervantes-Ramírez, Itzel Ittaí & Rivas, Gerardo, 2022, Intertidal sea anemones (Cnidaria: Actiniaria) from the west coast of the Peninsula of Baja California, Mexico, Zootaxa 5165 (2), pp. 151-179 : 162

Anthopleura elegantissima ( Brandt, 1835)

( Figure 4 , Table 3 , 4 )

Actinia elegantissima Brandt, 1835, p. 213

Anthopleura elegantissima ( Brandt, 1835) : Carlgren, 1952, p. 382 –384

Anthopleura elegantissima clonal Potts & Smith, 1987, p. 538–544

Bunodactis elegantissima ( Brandt, 1835) : Carlgren, 1949, p. 66

Cribrina elegantissima ( Brandt, 1835) : McMurrich, 1901, p. 18–23, 25, 37–38

[non] Anthopleura elegantissima Potts & Smith, 1987, p. 538 –544

Material examined. (See Appendix 1).

Short description.

External anatomy: oral disc smooth, flat, bulged, olive-green or emerald-green with greenish to brownish radial lines from the base of tentacles to mouth; mouth rounded. Tentacles shorter than oral disc, smooth, thin, conical, pointed, olive-green or greenish with pink, with purple or blue tips and some with yellow or white spots; tentacles arranged in six cycles (up to 120 tentacles in specimens examined), all similar length, contractile ( Figure 4A ). Deep fosse. Margin with endocoelic marginal projections, green to brown, and white acrorhagi atop each projection ( Figure 4B ). Column cylindrical, in preserved specimens 3–20 mm in height, 4–20 mm in diameter in preserved specimens, with endo- and exocoelic verrucae arranged in longitudinal rows from distal margin to limbus, distalmost part with compound verrucae; column pale green to beige, most distal verrucae dark green to brown ( Figure 4C ). Pedal disc well-developed, strong, 5–25 mm in diameter in preserved specimens, mesenterial insertions visible as light lines ( Figure 4D ). Preserved specimens light-brown to olive green in color.

Internal anatomy: mesenteries arranged in five cycles: first and second cycles perfect, others imperfect. Actinopharynx deeply sulcated with two pairs of directive mesenteries, each attached to a well-developed siphonoglyph. No gametogenic tissue observed in specimens examined. Retractor muscles well-developed, diffuse to restricted; parietobasilar muscles well-developed with free mesogleal pennon ( Figure 4E ); basilar muscles well developed. Endodermal marginal sphincter muscle circumscribed, pinnate ( Figure 4F ). Longitudinal muscles of tentacles ectodermal ( Figure 4G ). Zooxanthellate.

Cnidom: basitrichs, spirocysts, holotrichs, p -mastigophores A, p -mastigophores B1 and b -mastigophores ( Figure 4H–V ). See Table 4 for the sizes and distribution of cnidae.

Natural history. Anthopleura elegantissima inhabits the intertidal zones, in open and semi-protected sites on rocky shores, tidal pools and crevices. It can also be found along unsheltered coastlines, exposed directly to sun light. It is one of the most abundant species in the intertidal zone, forming large aggregations of just over 18 m. Generally covered with sand and remains of shells in a dense layer, camouflaged against the substrate when contracted. It is able to survive in polluted waters ( Haderlie et al. 1980; Rudy et al. 1983).

Distribution. Along the west coast of North America, from Alaska to Costa Rica; in Japan and southern part of Korea ( Carlgren 1952; Acuña et al. 2013; Daly & Fautin 2022a). This species has been previously recorded in Punta Banda, Baja California ( McFadden et al. 1997), but this is its first record in Punta Bandera, Punta Morro, La Chorera, Punta Baja, along the coast of Baja California; and in Punta Eugenia, Punta Abreojos and San Juanico, along the coast of Baja California Sur.

Remarks. A. elegantissima is distinguished from other species of Anthopleura in its color pattern of the oral disc, column, and tentacles, and in its verrucae, which are prominent and closely spaced on the distal column. In addition, there are some differences in the size-ranges of the cnidae. Anthopleura elegantissima has larger cnidae than A. artemisia , and has holotrichs in the column, unlike A. mariae . The sizes of the cnidae of the specimens examined were mostly within the range reported by Carlgren (1952), except for the holotrichs of the acrorhagi and the p -mastigophores A from the actinopharynx and the filaments, which were much larger in our specimens. Although the presence of two siphonoglyphs was observed in the specimens examined, this species has been reported with 1–3 siphonoglyphs due to asexual reproduction. Both A. elegantissima and A. sola have zooxanthellae, unlike A. artemisia and A. radians ( Table 3 ). Along the Baja California peninsula we could observe dense aggregations of A. elegantissima clones within tide pools, cracks, cavities, and channels that form at low tide. Generally, the aggregations found in exposed habitats showed dense layers of shells and debris adhering to the column, as well as the contracted body, which may favor water retention and prevent desiccation.

Figures

FIGURE 4. Anthopleura elegantissima. A) oral disc and tentacles. B) detail of acrorhagi. C) column with verrucae. D) pedal disc. E) cross section of column showing the retractor and parietobasilar muscles. F) longitudinal section of the distal column showing marginal sphincter muscle. G) longitudinal section of tentacle showing ectodermal muscles. (H–V) Cnidae. tentacles: (H) basitrich, (I) spirocyst; acrorhagi: (J) holotrich I, (K) holotrich II, (L) basitrich, (M) spirocyst; actinopharynx: (N) basitrich, (O) p-mastigophore A; column: (P) holotrich, (Q) basitrich; filaments: (R) basitrich I, (S) basitrich II, (T) p-mastigophore B1, (U) p-mastigophore A, (V) b-mastigophore. Abbreviations. acr: acrorhagi, dm: directive mesenteries, lm: longitudinal muscles, me: mesoglea, pbm: parietobasilar muscles, pd: pedal disc, rm: retractor muscles, sp: sphincter, t: tentacles, vr: verrucae. Scale bars: A–D: 20 mm; E–F: 500 µm, G: 200 µm; H–V: 20 µm.