Symplectoscyphus interruptus ( Pfeffer, 1889 )

Galea, Horia R. & Schories, Dirk, 2012, Some hydrozoans (Cnidaria) from Central Chile and the Strait of Magellan, Zootaxa 3296, pp. 19-67 : 50-51

Symplectoscyphus interruptus ( Pfeffer, 1889)

(fig. 6D–F, table 7)

Sertularia interrupta Pfeffer, 1899: 55 .

Sertularella interrupta — Hartlaub, 1901: 43, pl. 1 fig. 2, pl. 2 fig. 26. — Hartlaub, 1905: 633, fig. Z3. — Jäderholm, 1910: 4, pl. 1 figs 3, 4.

Sertularella modesta Hartlaub, 1901: 42 , pl. 1 fig. 1, pl. 2 fig. 28 (syn. nov.). — Hartlaub, 1905: 634, fig. A4.

Symplectoscyphus modestus — El Beshbeeshy, 1991: 210, fig. 52G. — El Beshbeeshy, 2011: 163, fig. 52G.

Material examined. Stn. FSI — 08.i.2011, S01 (20 m): numerous stems detached from substrate, some bearing gonothecae (MHNG-INVE-79634).

Description. Colonies arising from creeping, tubular stolon. Stems slender, with thin perisarc, up to 2.0 cm high, monosiphonic, straight, unbranched. Basal part short, with twisted perisarc above origin from stolon. Remainder of caulus divided into internodes (up to 46 per stem) by oblique constrictions of the perisarc; nodes highly conspicuous on stem side opposite hydrotheca, appearing as deep incisions of the perisarc; slightly marked on opposite side; internodes short, widening abruptly in upper halves so as to accommodate insertion of hydrotheca; one hydrotheca per internode. Hydrotheca tubular, curved outwards and facing slightly upwards; abcauline and free adcauline walls distinctly convex; a plug of perisarc at junction between adnate adcauline side and base; a foramen below the hydrothecal base; rim with three conspicuous, pointed cusps, occasionally with 1–2 renovations. Hydranths with 18–22 filiform tentacles. Gonothecae inserted below hydrothecal bases; flask-shaped, perisarc more or less undulated, showing externally a number of transversal ridges; basal part merging proximally into indistinct pedicel; truncate distally and provided with a terminal funnel; the latter, short, constricted in middle region, widening apically at aperture. Stolonization occurring occasionally, either from the apical part of the stem or from within one of the distalmost hydrothecae; in both cases, stolons carry incipient erect stems.

Remarks. Symplectoscyphus modestus ( Hartlaub, 1901) from Ushuaia shows great similarities to the present species. When Hartlaub described his species, the gonothecae of S. interruptus were unknown, and he was not able to establish a reliable comparison between them. However, the peculiar characters of their trophosomes alone are striking. Additional material from South Georgia, the type locality of S. interruptus , allowed Jäderholm (1910) to describe for the first time its gonothecae. Although he recognized strong resemblance between the gonothecae of the two species, he argued that those of S. interruptus were provided with characteristic transversal ridges over their whole body. However, similar ridges were also distinctly figured by Hartlaub in his S. modestus (pl. 1 fig. 1), and are equally obvious in the present material from the Strait of Magellan.

Symplectoscyphus modestus , as described by Hartlaub (1901), forms monosiphonic stems, up to 2 cm high, while S. interruptus is said as occasionally sparingly branched ( Pfeffer 1889, Jäderholm 1910), with stems up to 4 cm high.

Distribution in Chile. Strait of Magellan (present study).

World records. South Georgia ( Pfeffer 1889, Jäderholm 1910), Ushuaia ( Hartlaub 1901, 1905, both as S. modestus ).