Anthopleura artemisia (Pickering, 1846)

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 : 155-156

Anthopleura artemisia (Pickering in Dana, 1846)

( Figure 3 , Table 2 , 3 )

Actinia artemisia Pickering in Dana, 1846, p. 149 –150 [original description]

Anthopleura artemisia (Dana) : Carlgren, 1952, p. 384 –385

Bunodes Artemisia [sic]: Gosse, 1855, p. 274

Cereus artemisia: Milne-Edwards, 1857, p. 268

Cribrina artemisia (Pickering in Dana, 1846): McMurrich, 1901, p. 15, 23–26, 38

Evactis artemisia Verrill : Verrill, 1869, p. 471

Material examined. (See Appendix 1)

Short description. External anatomy: oral disc smooth, light-brown, reddish, purple, yellow, green, or orange, sometimes forming radial patterns and with mesenterial insertions visible as dark lines; outline of mouth circular ( Figure 3A ). Tentacles shorter than oral disc, smooth, thin, conical, pointed, olive-green, white, pink, purple, reddish, orange, or translucent, sometimes with whitish circular spots on its oral side ( Figure 3A ); tentacles arranged in five cycles (up to 72 tentacles in specimens examined), inner ones longer than outer ones ( Figure 3A–E ). Shallow fosse. Margin with endocoelic marginal projections, yellowish to dark-gray, with opaque acrorhagi atop each projection ( Figure 3B ). Marginal projections with three to six verrucae ( Figure 3C ). Column cylindrical, in preserved specimens 8–29 mm in height and 4–10 mm in diameter, elongate, light-brown, cream, or peach color, with endocoelic verrucae arranged in longitudinal rows extending halfway down the column, more prominent in the distal part, proximal part without verrucae or very few ( Figure 3D ). Pedal disc well developed, 9–13 mm in diameter in preserved specimens, adherent ( Figure 3E ). Preserved specimens light-brown to gray in color.

Internal anatomy: mesenteries hexamerously arranged in four cycles: first, second and third cycles perfect, others imperfect. No directive mesenteries observed in the specimens examined. Actinopharynx sulcated with two siphonoglyphs attached to non-directive mesenteries in the specimens examined ( Figure 3F ). No gametogenic tissue observed in specimens examined. Retractor muscles well-developed and strong, restricted; parietobasilar muscles weak with short mesogleal pennon ( Figure 3G ); basilar muscles well-developed. Endodermal marginal sphincter muscle circumscribed ( Figure 3H ). Longitudinal muscles of tentacles ectodermal. Azooxanthellate.

Cnidom: basitrichs, spirocysts, holotrichs, p -mastigophores A and b -mastigophores ( Figure 3I–Y ). See Table 2 for sizes and distribution of cnidae.

Natural history. Anthopleura artemisia lives in open shores, bays and estuaries ( Hand 1955). Inhabits the intertidal zone, occasionally at higher levels, strongly attached to rocks, in crevices.

Distribution. From Alaska to Southern California, and Japan ( Carlgren 1952; Hand 1955). This is the first record for the coast of Mexico; found in La Chorera and Punta Baja, Baja California.

Remarks. Taxonomic characteristics of the specimens examined agree well with those descriptions by Carlgren (1952) and Hand (1955), mainly in the coloration of tentacles, column, and the most distal verrucae. In addition, specimens examined had three to six verrucae for each marginal projection, the closest to the acrorhagi being whitish to yellow in color, such as those reported by Hand (1955). However, specimens examined were smaller than those previously reported, and external tentacles were relatively shorter than internal ones. In addition, the marginal sphincter was observed as circumscribed, but without being markedly pinnate due to the fact that the lamellae arise from a small mesogleal axis that is not located in the center of the muscle but is oriented towards one of its sides ( Fig. 2H ), coinciding with the mentioned by Hand (1955), who points out that the sphincter can be asymmetric, with more lamellae on one side than the other. Furthermore, no directive mesenteries were observed in the examined specimens, contrary to what was reported by Hand (1955), with one to three siphonoglyphs each attached to a pair of directive mesenteries. However, it has been reported in other species of Anthopleura that the absence of directive mesenteries can occur as a result of asexual reproduction ( Daly & Fautin 2004), and it is known that A. artemisia can undergo longitudinal fission ( Hand 1955). Some other differences were found in the size ranges of cnidae with those previously reported for A. artemisia . Basitrichs of tentacles and actinopharynx, and p -mastigophores of actinopharynx were smaller than those reported by Carlgren (1952) and Hand (1955), and basitrichs of the filaments were smaller than those reported by Carlgren (1952). In addition, Hand (1955) reported two categories of microbasic p -mastigophores, while only one was found in the specimens examined. The largest of the three categories of basitrichs from filaments reported by Hand (1955) may correspond to the b -mastigophores observed in the samples examined, as well as those of the single category of basitrichs reported by Carlgren (1952).

Of the other six species of Anthopleura reported from the northeastern Pacific ( Daly & Fautin 2022a), A. artemisia is distinguished primarily by the arrangement of the verrucae on the column, which range from the margin to mid-column; in Anthopleura dowii Verrill, 1969 , Anthopleura elegantissima ( Brandt, 1835) , Anthopleura mariae Vassallo-Avalos, González-Muñoz, Acuña & Rivas, 2020, Anthopleura sola Pearse & Francis, 2000 , and Anthopleura radians Spano & Häussermann, 2017 the verrucae range from margin to the limbus, whereas in Anthopleura xanthogrammica ( Brandt, 1835) they are not clearly arranged in rows ( Hand 1955; Vassallo-Avalos et al. 2020b). Anthopleura elegantissima , A. mariae , A. sola , and A. xanthogrammica present zooxanthellae, while these are absent in A. artemisia and A. radians and are unknown for A. dowii . Anthopleura sola and A. xanthogrammica do not reproduce asexually. Other characteristics to distinguish among the species of Anthopleura of the eastern Pacific region are compared in Table 3 .

Figures

FIGURE 2. A) Anthopleura dowii, B) Bunodosoma californicum, C) Bunodosoma grande, D) Isoaulactinia hespervolita, E) Phymactis papillosa.

FIGURE 3. Anthopleura artemisia. A) oral disc and tentacles. B) detail of acrorhagi in the margin. C) marginal projections with verrucae. D) detail of expanded column and pedal disc. E) column and tentacles slightly contracted. F) cross section of column at the level of the actinopharynx. G) cross section of column showing the retractor and parietobasilar muscles. H) longitudinal section of the distal column showing marginal sphincter muscle. (I–Y) Cnidae. tentacles: (I) basitrich, (J) spirocyst; acrorhagi: (K) holotrich I, (L) holotrich II, (M) basitrich, (N) spirocyst; actinopharynx: (O) basitrich, (P) p-mastigophore A; column: (Q) holotrich, (R) basitrich I, (S) basitrich II, (T) basitrich III, (U) spirocyst; filaments: (V) basitrich I, (W) basitrich II, (X) p-mastigophore A, (Y) b-mastigophore. Abbreviations. acr: acrorhagi, c: column, ep: epidermis, me: mesoglea, od: oral disc, pbm: parietobasilar muscles, pd: pedal disc, rm: retractor muscles, s: siphonoglyph, sp: sphincter, vr: verrucae. Scale bars. A–E: 20 mm; F, H: 200 µm, G: 500 µm; I–Y: 15 µm.