Hydractinia dendritica Hickson & Gravely 1907

• Main Author: Peña Cantero, Álvaro L.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2015
• Subjects: Biodiversity; Taxonomy; Animalia; Cnidaria; Hydrozoa; Anthoathecata; Hydractiniidae; Hydractinia; Hydractinia dendritica; Antarctic; Ross Sea; Antarc*
• Online Access: https://zenodo.org/record/5671799; https://doi.org/10.5281/zenodo.5671799

Hydractinia dendritica Hickson & Gravely, 1907 (Figs 7 I–N, 8) Hydractinia dendritica Hickson & Gravely, 1907: 9, pl. 2 figs 7–10; Kramp, 1932: 11 M; Stechow, 1962: 417; Bouillon et al., 2006: 150; Stampar et al., 2006: 58 Hydronema dendritica — Stechow, 1921: 252; 1923: 67, fig. F. Halorhiza dendritica — Stechow, 1962: 417. Material examined. Discovery Antarctic Expedition 1901 -04: Holotype [NHM 1907.8. 20.5 (part)], W.Q. (Ross Sea), 21.III.1902, 10 fms, one long colony fragment, c. 85 mm long and c. 6 mm in maximum diameter, plus another erect colony fragment, c. 30 mm high, with gonophores; Paratype [NHM 1907.8.20.6], Locality unrecorded (label lost), several stem fragments, up to 28 mm long, with gonophores. Description (Holotype). A long colony fragment, c. 85 mm long and c. 6 mm in diameter (Fig. 8 A), and an erect colony fragment, c. 30 mm high (Fig. 8 B). Both irregularly branched, particularly the second one. Colonies with high density of polyps and gonozooids. With perisarc ridges throughout (Fig. 8 D), sometimes forming a sort of spine. Gastrozooids relatively large (c. 1700 µm high and c. 450 µm in maximum diameter), with cone-shaped hypostome and a distal crown of nine to ten filiform tentacles (Figs 7 I, 8 C, F). Some gastrozooids with extremely wide, flattened hypostome (Fig. 8 F). There are also evaginated gastrozooids. Gonozooids (Figs 7 K, L, 8 E, F) much smaller than gastrozooids (c. 570 µm high and c. 220 µm in maximum diameter with gonophores; c. 340 µm and 125 µm, respectively, without gonophores). Much varied in development, from barely developed (with none, one, two or three tentacles) (Fig. 7 K) to well-developed polyps with up to eight tentacles (Fig. 7 L). Incipient gonozooids apparently without mouth. Gonozooids with four to six gonophores (150–180 µm in diameter) situated at their base, resting on substratum, but attached to gonozooid (Figs 7 L, 8 E, F). Dactylozooids (Figs 7 N, 8 E) present in both fragments (at least three observed). Measurements (in µm). Cnidome: Type I ...