Amphianthus bathybium Hertwig, 1882

Targino, Alessandra K. G., De Melo, Yago A. & Gomes, Paula B., 2025, Deep-sea anemones (Cnidaria, Actiniaria) from off the northeastern coast of Brazil: new records and description of Stephanauge prima sp. nov., Zootaxa 5569 (2), pp. 328-344 : 335

Amphianthus bathybium Hertwig, 1882

( Fig. 4 ; Table 3)

MATERIAL EXAMINED. MNRJ 9077 (two specimens), South Atlantic Ocean, Potiguar Basin, Rio Grande do Norte , Brazil, station MT72 (04° 40.1817’S, 036° 23.8647’W), May 7, 2011, 908 m. MOUFPE-CNI 878 (two specimens) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT72 (04° 40.1817’S, 036° 23.8647’W), May 7, 2011, 908 m. LC 157 (one specimen) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT72-2 (04° 40.2981'S, 036° 23.7001’W), May 20, 2011, 960 m. MNRJ 9083 (two specimens), South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT73 (04° 37.6640'S, 036° 30.5400’W), May 5, 2011, 957 m. LC 158 (one specimen) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT73 (04° 37.6640'S, 036° 30.5400’W), May 5, 2011, 957 m. LC 159 (three specimens) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT74 (04° 34.1484'S, 036° 41.6035’W), May 5, 2011, 902 m. MOUFPE-CNI 877 (two specimens) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT75 (04° 28.8002'S, 036° 52.5554'W), May 3, 2011, 915 m. LC 154 (two specimens) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT84 (04° 25.8308’S, 036° 37.3678’W), May 6, 2011, 1964 m. LC 155 (two specimens) South Atlantic Ocean , Potiguar Basin , Rio Grande do Norte, Brazil, station MT85 (04° 21.3580’S, 036° 036° 44.2730’W), May 4, 2011, 2057 m .

SHORT DESCRIPTION. Individuals 5.6 to 8.7 mm in height and 16.6 to 24.1 mm in diameter. Number of tentacles corresponds to the number of mesenteries: 48 pairs of mesenteries and 48 tentacles arranged in four cycles. Most of the sampled specimens were attached to Acanella sp. and branches of Chrysogorgia tuberculata Cordeiro, Castro & Pérez, 2015 .

CNIDOM. Spirocysts, basitrichs, holotrichs, and microbasic p -mastigophores B1 ( Fig. 4I : a–e, Table 3).

GEOGRAPHIC DISTRIBUTION. North Pacific Ocean 2000-5285 m ( Hertwig 1888; Carlgren 1949), North Atlantic 1075–4851 m ( Riemann-Zürneck 1987; Iken et al. 2001; OBIS 2023). This is the first record for A. bathybium in the South Atlantic (Potiguar basin, RN, Brazil) 900–2000 m.

REMARKS. The individuals analyzed agree well with the previous descriptions of A. bathybium (e.g., Hertwig 1882; 1888; Riemann-Zürneck 1987). The morphological descriptions and cnidom of the individuals from the Potiguar Basin are highly similar to those provided by Riemman-Zürneck (1987) in her redescription of the type specimen of A. bathybium . Although the types and average sizes for cnidae that we recorded match fairly well with what Riemman-Zürneck (1987) described, we found an extra type of holotrich in the tentacle and smaller microbasic p -mastigophores B 1 in the filament. The holotrich is rare and was not found in all specimens.

Figures

FIGURE 4. External view, internal anatomy and cnidae of some sea anemones analyzed in this work. A) External view of Actinoscyphia saginata showing the bilobed oral disc. B) Specimen of Chondrophellia coronata. C) Amphianthus bathybium on Chrysogorgia tuberculata branch (arrow). D) Specimens of Amphianthus michaelsarsi, arrows showing rows of tubercles. E) Cross section of Actinoscyphia saginata column, showing cycles of mesenteries (roman numbers) and gametogenic tissue (arrows). F) Gametogenic tissue on A. saginata as viewed on the stereomicroscope (arrows). G) Mesogleal marginal sphincter band on Amphianthus bathybium (arrow). H) Cross section of mesenterial cycles present in C. coronata (roman numbers). I) Cnidae found in the sea anemones, a–e) Amphianthus bathybium; f–j) Amphianthus michaelsarsi; k–o) Actinoscyphia saginata and; p–s) C. coronata. Cnidae; a, f, k, p: Gracile spirocysts; b, g, l, q: Robust spirocysts; c, h, m, r: basitrichs; d, i, n: holotrichs; e, j, o, s: microbasic p-mastigophores B1. Abbreviations: oc, octocoral; tu, tubercles; gt, gametogenic tissue; ms, marginal sphincter. Scale bars: A: 20 mm; B, C: 5 mm; D: 2 mm; E–G: 400 μm; H: 300 μm; I: 20 μm.