Lafoea dumosa ( Fleming, 1820 )

Peña Cantero, Álvaro L. & Horton, Tammy, 2017, Benthic hydroids (Cnidaria, Hydrozoa) from bathyal and abyssal depths of the Northeast Atlantic held in the modern Discovery Collections, Zootaxa 4347 (1), pp. 1-30 : 10

Lafoea dumosa ( Fleming, 1820)

( Fig. 3F–H )

Lafoea dumosa —Schuchert, 2001: 67–70, figs 54A–D, 55, 56 (synonymy).

Material examined. 51217#1, several stems up to 30 mm high, on bryozoan, and a few stem fragments up to 40 mm high, no coppiniae.

Description. Colonies with both stolonal hydrothecae and polysiphonic stems, at least 40 mm high. Stems little branched, straight. Hydrothecae irregularly arranged all around stem, practically without pedicel ( Fig. 3F ); frequently completely sessile, inserted directly into the branch. Hydrothecae cylindrical, basally narrowing into a short pedicel ( Fig. 3G ).

Measurements (in µm). Hydrotheca: diameter at aperture 190–200; length up to diaphragm 600–740. Cnidome: isorhizas ( Fig. 3H ), 13.5–15.5 x 5.0–5.5.

Remarks. In our material the hydrothecae are provided with a short pedicel or there is no pedicel at all. According to Schuchert (2001), L. dumosa has a complicated, not fully resolved, taxonomic history. He found distinct differences in relation to the size and shape of the hydrothecae, and the presence or absence of hydrothecal pedicel, even among colonies from the same locality. However, comparing enough material, he found that all forms ultimately intergraded, although he uncovered two “species” concerning the size of the isorhizas (mean, 23.6 vs 14.0 µm); the present material agrees with the latter. Moura et al. (2011) provided genetic evidence of the existence of cryptic diversity associated with this species.

Ecology and distribution. This is a cosmopolitan species, found from shallow waters to 3940 m (cf. Schuchert 2001); the present material was collected from the Porcupine Seabight at 150 m, on bryozoans.

Figures

FIGURE 3. Acryptolaria crassicaulis (Allman, 1888): A, hydrotheca; B, macrobasic mastigophore nematocyst (arrow). Cryptolarella abyssicola (Allman, 1888): C-D, hydrothecae; E, gonotheca. Lafoea dumosa (Fleming, 1820): F, hydrotheca; G, detail of basal part of hydrotheca; H, isorhiza nematocyst. Scale bars: 200 µm (A, C-F), 100 µm (G), 10 µm (B, H).