Actinostella californica ( McMurrich, 1893 )

Barragán, Yamaly, Rodríguez, Estefanía, Chiodo, Tommaso, Gusmão, Luciana C., Sánchez, Carlos & Lauretta, Daniel, 2024, Revision of the genus Actinostella (Cnidaria: Actiniaria: Actinioidea) from tropical and subtropical western Atlantic and eastern Pacific: redescriptions and synonymies, American Museum Novitates 2024 (4014), pp. 1-48 : 19-25

Actinostella californica ( McMurrich, 1893)

Figures 7–9, tables 1, 3

Oulactis californica McMurrich, 1893 .

Non Asteractis concinnata (Drayon in Dana, 1846): Pax 1912.

Phyllactis californica ( McMurrich, 1893) : Stephenson, 1922.

(?) Phyllactis bradleyi ( Verrill, 1869) : Carlgren, 1951.

(?) Phyllactis concinnata (Drayon in Dana, 1846): Carlgren, 1951.

Actinostella californica ( McMurrich, 1893) : Häussermann, 2003.

Actinostella californica ( McMurrich, 1893) : pro parte Barragán, 2015; Barragán, 2019; Barragán et al., 2019.

DIFFERENTIAL DIAGNOSIS: Actinostella with three cycles of mesenteries, first and second perfect, third imperfect. All mesenteries fertile including directives. Column and marginal ruff only with basitrichs and no p -mastigophores A.

EXAMINED MATERIAL: Actinostella californica : AMNH _ IZC 00361339 , AMNH _ IZC 00361340 , AMNH _ IZC 00361341 , AMNH _ IZC 00361342 , AMNH _ IZC 00361343 , AMNH _ IZC 00361344 , AMNH _ IZC 00361345 , AMNH _ IZC 00361346 , AMNH _ IZC 00361347 , AMNH _ IZC 00361348 , AMNH _ IZC 00361349 , AMNH _ IZC 00361350 , AMNH _ IZC 00361351 , AMNH _ IZC 00361352 , AMNH _ IZC 00361353 , AMNH _ IZC 00361354 ; USNM 1606851 ; USNM 17812 (syntype). See table 1 for material details .

DESCRIPTION: External anatomy (fig. 7): Well-developed pedal disc, to 25 mm diameter. Column elongate, to 65 mm height and 52 mm diameter, with 48 longitudinal rows of verrucae distally in each endo- and exocoel. Marginal ruff with rows of vesicles. Oral disc, to 38 mm

diameter. Fosse deep. Tentacles, 48, arranged in four cycles; simple, smooth, all of similar length, to 16 mm. Mesenterial insertions visible in pedal disc and column.

Internal anatomy (fig. 8): Same number of mesenteries distally and proximally. Twenty-four pairs of mesenteries hexamerously arranged in three cycles (6 + 6 + 12 = 24). First and second cycles perfect, third imperfect (fig. 8B). All mesenteries fertile including directives (fig. 8B). Two pairs of directives attached to two clearly distinct siphonoglyphs. Gonochoric, developed oocysts 0.08–0.18 mm in diameter (fig. 8E) in specimens collected in May and November 2013, and March 2016. Retractor muscles strong, diffuse to restricted; variability within studied specimens. Parietobasilar muscles well developed, with short free mesogleal lamella in juveniles, longer in adults (fig. 8F). Basilar muscles well developed, processes short and thin (fig. 8G). Endodermal marginal sphincter muscle weakly circumscribed (fig. 8A, C). Longitudinal muscles of tentacles ectodermal (fig. 8D). Zooxanthellae present in tentacles and marginal ruff.

Color (fig. 7): Variable in live specimens. Specimens with pedal disc and column pinkish, beige, or opaque orange; verrucae darker than column. Oral disc olive green with white radial lines. Marginal ruff olive green with lighter stripes and a brown ring closer to the mouth. Mouth light pink. Tentacles translucent greenish, brownish, or reddish, with white bases; white spots with brown dots along entire tentacles. Preserved material beige, oral disc and marginal ruff lighter.

Cnidom (fig. 9); Basitrichs, basitrichs S, b -mastigophores, p -mastigophores A, p -mastigophores B1 and spirocysts. Sizes and distribution in table 3.

GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION AND NATURAL HISTORY: Actinostella californica can be found in the Pacific Ocean from Mexico to Panama ( McMurrich, 1893; Carlgren, 1951). Although Carlgren (1951) cited A. bradleyi (= A. californica pro parte in this study) in the Pearl Islands ( Panama) he did not examine specimens from this locality, but he was referring to Verrill’s original description of A. bradleyi . Häussermann (2003) and Fautin (2016) considered the citation of Asteractis concinnata from Peru by Pax (1912) to correspond to A. californica ; however, Pax (1912) described his Peruvian specimens having 4–5 cycles of tentacles and without zooxanthellae, and thus we consider those specimens to be Oulactis concinnata . In Mexico, A. californica can be found in the Pacific side (west of Baja Peninsula) in Magdalena Bay, and in the Gulf of California it can be found in La Paz Bay and Concepcion Bay. In addition, this species was collected in Panama in the Pearl Islands. The specimens were found burrowed in sand, attached to a rock or shell, buried, or hidden in rock crevices with the marginal ruff above the substratum. They are often found in the intertidal to up to 12 meters in La Paz Bay (Gulf of California; see Barragán et al., 2019).

REMARKS: Actinostella californica is distinguished from congeners by the combination of having three cycles of fertile mesenteries, first and second cycles perfect, and only basitrichs in the marginal ruff and column (table 6). It was initially described by McMurrich (1893) as Oulactis californica without any mention of the cnidom (a common practice in those days). Later, Carlgren (1951) redescribed Phyllactis bradleyi and P. concinnata (Drayton in Dana, 1846; current valid name: Oulactis concinnata ) based on specimens from the Gulf of California, emphasizing they might need to be revised. Carlgren (1951) mentioned only the number of mesenteries (24) without describing their arrangement for the two specimens of P.bradleyi from the Gulf of California. The presence of only three cycles of mesenteries and the brief description of the cnidom suggest the two specimens might be A. californica . However, we cannot state confidently that the specimens of P.bradleyi from the Gulf of California redescribed by Carlgren (1951) are synonyms of A. californica because p -mastigophores A are easily overlooked unless surveying thoroughly; thus, we report this citation with a question mark (see synonymy list).

We agree with Haüssermann (2003) that Carlgren’s (1951) redescription of seven specimens from the Gulf of California as Phyllactis concinnata actually corresponds to specimens of Actinostella californica . Like Haüssermann (2003), we think that Oulactis concinnata and A. californica (both previously described as Phyllactis ) are clearly different species, with O. concinnata having many more tentacles and mesenteries (up to 400 tentacles), often acrorhagi and fighting tentacles (and thus holotrichs) but no zooxanthellae, whereas A. californica has only up to 48 tentacles and zooxanthellae, but lacks acrorhagi (see Haüssermann, 2003). The only attribute from Carlgren’s (1951) treatment that does not fit A. californica is the presence of three perfect cycles of mesenteries: in the type material from McMurrich (1893) and the other 22 specimens we studied, the third cycle of mesenteries is imperfect. We observed in the studied specimens longitudinal lines of tissue (corresponding to the third cycle of mesenteries) attached to the actinopharynx side distally, which might be interpreted as broken perfect mesenteries; it is highly unlikely that this artifact occurred in every single specimen examined, and most feasible that Carlgren’s (1951) observation might have been an artifact of observing the mesenteries distally. Consequently, we consider the third cycle in A. californica as imperfect. Alternatively, the specimens from the Gulf of California revised by Carlgren (1951) might have been juveniles of A. bradleyi with only three cycles of mesenteries developed (similar to the holotype of the species). Although the absence of p -mastigophores A in the marginal ruff and column suggests they were specimens of A. californica , we still consider this attribution an open question because it is also possible that Carlgren (1951) might have overlooked this cnida: we therefore reflect this in the synonymy list.