Dynamena disticha ( Bosc, 1802 )

Galea, Horia R., 2008, On a collection of shallow-water hydroids (Cnidaria: Hydrozoa) from Guadeloupe and Les Saintes, French Lesser Antilles, Zootaxa 1878, pp. 1-54 : 30-31

Dynamena disticha ( Bosc, 1802)

(fig. 5J–N)

Sertularia disticha Bosc, 1802: 101 , pl. 29 fig. 2.

Dynamena disticha — Calder, 1991d: 93, fig. 50.— Migotto, 1996: 62, fig. 12A–E.— Medel & Vervoort, 1998: 25.— Peña Cantero & García Carrascosa, 2002: 121, fig. 23C–E.

Dynamena cornicina — Leloup, 1935: 39, figs 22–23.— Calder, 1983: 9, figs 1–2.—Hirohito, 1995: 167, fig. 54.

Material examined. Stn. 1: 19.01.2008 —numerous fertile colonies, 6–8 mm high, on Thalassia testudinum ; 25.01.2008 —numerous fertile stems, 5–7 mm high, on T. testudinum ( MHNG INVE 60980); 18.03.2008 — several fertile colonies, ca. 8 mm high, on T. testudinum ; 20.03.2008 —several fertile colonies, ca. 8 mm high, on T. testudinum ; 21.03.2008 —several fertile colonies, up to 8 mm high, on T. testudinum . Stn. 2: 22.01.2008 —several fertile colonies, 2–4 mm high, on sponge and algae; 26.01.2008 —a few sterile colonies, 2–4 mm high, on algae and rock. Stn. 3: 26.01.2008 —numerous sterile stems, 2–4 mm high, on algae; 01.04.2008 — numerous sterile colonies, up to 6 mm high, on concretions and algae. Stn. 4: 22.03.2008 —one sterile colony, ca. 7 mm high, on ascidian. Stn. 6: 23.03.2008 —a sterile colony, ca. 7 mm high, on Halimeda sp.; 28.03.2008 —a sterile colony, ca. 7 mm high, on T. testudinum . Stn. 7: 25.03.2008 —several sterile colonies, up to 7 mm high, on various algae, a sponge, and concretions; 27.03.2008 —one sterile colony, ca. 8 mm high, on bivalve shell.

Type locality. Atlantic Ocean, no exact locality given.

Remarks. The material originating from calm waters has long stem internodes; they are comparatively shorter in specimens from agitated waters.

The gonothecae of D. disticha have been described either occurring on the stolon ( Calder 1991d) or arising from lower stem internodes ( Medel & Vervoort 1998), or both (Hirohito 1995). In the present specimens, the gonothecae are mainly borne on the stolon but, in some stems, peculiar gonothecae arise from the hydrothecal openings. These gonothecae did not retain any specific feature of the common type: they are sac-shaped, of variable length and width, with smooth to slightly undulated walls, but not ridges; the apical end is rounded and no aperture could be observed (see fig. 5M–N). The gonothecal content is a homogenous mass of tissue (male gonothecae?).

Distribution. Circumglobal in tropical, subtropical and temperate waters ( Peña Cantero & García Carrascosa 2002). The Caribbean records are summarized by Calder & Kirkendale (2005).