Schizotricha profunda ( Nutting, 1900 )

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 : 20

Schizotricha profunda ( Nutting, 1900)

( Fig. 8 )

Plumularia profunda Nutting, 1900: 66 –67, pl. 8 figs 2–3.

Not Polyplumaria profunda — Broch, 1918: 60 –62, figs 28–29 [= Schizotricha variabilis (Bonnevie, 1899) ]. Schizotricha profunda — Peña Cantero & Vervoort, 1999: 368 –371, fig. 3.

Material examined. 54907#3, four stems up to 18 mm high, on coral, with gonothecae.

Description. Stems polysiphonic, up to 18 mm high. Stem with alternately arranged cauline apophyses giving rise to hydrocladia ( Fig. 8F ). Stem divided into internodes with one to two cauline hydrothecae. Each at axil between cauline apophysis and internode and with three associated nematothecae ( Fig. 8A–B ): two flanking hydrothecal aperture and one under the hydrotheca. Cauline apophyses with one basal nematotheca ( Fig. 8B ). Hydrocladia unbranched, heteromerously divided into internodes with one or two hydrothecae. Each hydrocladial hydrotheca with three associated nematothecae ( Fig. 8C–D ): two flanking hydrothecal aperture and one infrathecal nematotheca. Hydrotheca elongate ( Fig. 8E ), length slightly increasing along hydrocladia (e.g. abcauline length from 230 to 290 µm).

Gonothecae inserted on cauline and hydrocladial internodes through a small pedicel ( Fig. 8E–F ); up to two gonothecae per internode ( Fig. 8E ). Gonotheca inverted pear-shaped ( Fig. 8F ), with circular diaphragm at basal fifth delimiting a basal chamber. Two nematothecae inserted at diaphragm. Gonothecal aperture wide, subterminal and adcaudally directed. Gonotheca 400 µm high and 240 µm in maximum diameter.

Remarks. Schizotricha profunda is the only species of the genus with unforked hydrocladia. These are typically branched once or several times in the remaining species of Schizotricha . Peña Cantero and Vervoort (1999: 369), who re-described the species after examining the type material, discussed the differences with the morphologically closest species of the genus.

Ecology and distribution. This is a bathyal species ( Peña Cantero & Vervoort 1999), previously reported from 491 to 792 m depth ( Nutting 1900); present material collected at 1060 m, distinctly increasing its lower bathymetric limit, on coral, and with gonothecae in May.

Hitherto , only known off the east coast of Florida (30°44’N 79°26’W and 30°53’N 79°42’30’’W) ( Nutting 1900). Our material, which represents the second record for the species, comes from the Porcupine Seabight.

Figures

FIGURE 8. Schizotricha profunda (Nutting, 1900): A – B, cauline internodes showing axillary hydrotheca and cauline apophysis; C – D, hydrocladial internodes; E, detail of hydrocladial internode, showing hydrotheca and basal part of two gonothecae; F, fragment of stem showing hydrocladial disposition and a gonotheca. Scale bars: 200 µm (C – D, F), 100 µm (A – B, E).