Actinostella flosculifera ( Le Sueur, 1817 )

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 : 31-35

Actinostella flosculifera ( Le Sueur, 1817)

Figures 13–14, tables 1, 5

Actinia flosculifera Le Sueur, 1817 .

Oulactis flosculifera [no author]: Milne Edwards, 1857.

Oulactis flosculifera (Lesueur) : Milne Edwards, 1857.

Oulactis flosculifera ( Le Sueur, 1817) : Duchassaing and Michelotti, 1860.

Actinostella formosa Duchassaing, 1850 .

Asteractis formosa ( Duchassaing, 1850) : Verrill, 1899.

Oulactis formosa Duchassaing and Michelotti, 1860 .

Asteractis flosculifera ( Le Sueur, 1817) : Verrill, 1899.

Cradactis fasciculata ( McMurrich, 1889) : Haddon, 1898.

Evactis flosculifera ( Le Sueur, 1817) : Andres, 1883.

Oulactis fasciculata McMurrich, 1889 .

Oulactis foliosa Andres, 1883 .

Actinactis [sic] flosculifera : Verrill, 1900.

Actinostella flosculifera ( Le Sueur, 1817) : McMurrich, 1905.

Phyllactis flosculifera ( Le Sueur, 1817) : Stephenson, 1922.

Oulactis conquilega Duchassaing and Michelotti, 1860 .

Actinostella conchilega ( Duchassaing and Michelotti, 1860) : McMurrich, 1905.

Asteractis conquilega ( Duchassaing and Michelotti, 1860) : Verrill, 1899.

Phyllactis conchilega ( Duchassaing and Michelotti, 1860) : Stephenson, 1922.

Phyllactis conquilega ( Duchassaing and Michelotti, 1860) : Carlgren, 1949.

Phyllactis conquilegia [sic] ( Duchassaing and Michelotti, 1860): Voss et al., 1969.

Metridium praetextum Couthouy in Dana, 1846.

Asteractis , n. sp.: Duerden, 1897.

Asteractis expansa Duerden in McMurrich, 1898.

Oulactis radiata Duchassaing and Michelotti, 1860 .

Lophactis radiata ( Duchassaing and Michelotti, 1860) : Andres, 1883.

Actinostella radiata ( Duchassaing and Michelotti, 1860) : McMurrich, 1905.

Phyllactis radiata ( Duchassaing and Michelotti, 1860) : Stephenson, 1922.

DIFFERENTIAL DIAGNOSIS: Actinostella with three cycles of mesenteries, first and second perfect, third imperfect; all fertile, including directives. Marginal ruff and column with p -mastigophores A and basitrichs.

EXAMINED MATERIAL: Actinostella flosculifera : AMNH Cat.Cnidaria 587, AMNH Cat. Cnidaria 694, AMNH Cat.Cnidaria 741, AMNH Cat.Cnidaria 1283, AMNH Cat.Cnidaria 1324,

AMNH Cat.Cnidaria 1330, AMNH Cat.Cnidaria 1352, AMNH Cat.Cnidaria 3585, AMNH Cat.Cnidaria 5308, USNM 1606852, USNM 1606853, USNM 1606854, USNM 1606855, USNM 1606856, USNM 1606857, USNM 1606858, USNM 1606859, USNM 1606860, USNM 1606861, USNM 1606862, USNM 1606863; MZUSP 8405; Phyllactis conquilega [= A. flosculifera ]: SMNH-1170 (holotype). See table 1 for material details.

DESCRIPTION. External anatomy (fig. 13): Well-developed pedal disc, to 29 mm diameter. Column, to 65 mm height and 38 mm diameter, with 48 longitudinal rows of verrucae distally in each endo- and exocoel. Marginal ruff with rows of vesicles. Oral disc, to 34 mm diameter. Fosse deep. Tentacles, 48, arranged in four cycles; simple, smooth, all of similar length, to 13 mm. Mesenterial insertions visible in oral disc, column, and pedal disc.

Internal anatomy (fig. 13): 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. All mesenteries fertile, including directives. Two pairs of directives attached to two clearly distinct siphonoglyphs. Gonochoric, developed oocysts 0.18–0.29 mm in diameter in specimens collected in May 2010, June 1966, and November 1899. Retractor muscles restricted and strong. Parietobasilar muscles well developed, with free mesogleal lamella. Basilar muscles well developed, processes short and thin. Endodermal marginal sphincter muscle weakly circumscribed, without central mesogleal lamella (fig. 13F–I). Longitudinal muscles of tentacles ectodermal. Zooxanthellae present in tentacles and marginal ruff.

Color (fig. 13): Variable in live specimens. Specimens from Panama with pedal disc and column pinkish, beige, or opaque orange; verrucae darker than column. Oral disc brownish with white radial lines. Marginal ruff white, green, or brown, with lighter stripes and a brownish ring near the mouth. Mouth light brownish. Tentacles translucent white, brownish, or reddish with lighter spots and dots along the entire aboral side of tentacles. Preserved material beige, oral disc, and marginal ruff lighter.

Cnidom (fig. 14): Basitrichs, basitrichs S, b -mastigophores, p -mastigophores A, p -mastigophores B1, and spirocysts. Sizes and distribution in table 5.

GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION AND NATURAL HISTORY: Actinostella flosculifera is distributed along the entire Caribbean Sea (from Bermuda to the Lesser Antilles), Gulf of Mexico, Colombia, and the South Atlantic off the coast of Brazil (see Schlenz and Belém, 1992; González-Muñoz et al., 2012, 2013; Durán-Fuentes et al., 2022; 2023). The species has been also reported in the east Atlantic in the Cameroon, Canary Islands, Cape Verde Island, and Senegal ( Ocaña and den Hartog, 2002; Ocaña et al., 2015) and the Gulf of Guinea ( Wirtz, 2003), but these records need to be checked to confirm species-level identification. Individuals in Bermuda have been described as viviparous ( Cairns and den Hartog, 1986).

REMARKS: Actinostella flosculifera is distinguished by the combination of having three cycles of fertile mesenteries in which only the first and second cycles are perfect and p -mastigophores A in the marginal ruff and column. All members of Actinostella except for A. bradleyi are known to have up to three cycles of mesenteries. Nevertheless, Ocaña (1994) described specimens from the Canary Islands (east Atlantic) as A. flosculifera with four or five cycles of mesenteries and four cycles of tentacles. Because having more cycles of mesenteries than cycles of tentacles is not a common condition in Actiniaria ( Stephenson, 1928) , we suspect this might be a mistake and consider it as such until the specimens are reexamined.

Actinostella flosculifera was formerly clearly distinguished within the genus by lacking an endodermal marginal sphincter muscle and bearing only two fertile (first and second) cycles of mesenteries ( McMurrich, 1905; González-Muñoz et al., 2012). However, after we reexamined the material (AMNH Cat.Cnidaria 5308) analyzed by González-Muñoz et al. (2012) and examined an additional 19 museum and 13 newly collected specimens from Panama (Atlantic side) (see table 1), an endodermal marginal sphincter muscle and gametogenic tissue in the third cycle were observed in all fertile specimens. Our observations of an endodermal marginal sphincter present in this species agree with those of Corrêa (1964), Schlenz and Belém (1992), and Ocaña (1994).

Corrêa (1964) did not report the presence of p -mastigophores A in the marginal ruff or the column of the material of A. flosculifera she studied. However, because capsules of p -mastigophores A in the ruff and in the column are not very abundant in specimens of A. flosculifera (and easy to miss unless looking for them specifically) and because we found this category of capsules in our examination of different specimens across the Caribbean and on those from Brazil (see tables 1, 5), we think Corrêa (1964) just overlooked this category of cnidae. Although this species has been redescribed a few times (e.g., Corrêa, 1964; Ocaña, 1994; González-Muñoz et al., 2012; Durán-Fuentes et al., 2022), the amount of revised material examined here allowed us to clarify the presence of an endodermal marginal sphincter muscle, all mesenteries fertile, p -mastigophores A in the marginal ruff and column, and S-shape basitrichs in column.