Sertularella curvitheca, Galea, Horia R. & Schories, Dirk, 2012

Galea, Horia R. & Schories, Dirk, 2012, Some hydrozoans (Cnidaria) from Central Chile and the Strait of Magellan, Zootaxa 3296, pp. 19-67 : 38-40

Sertularella curvitheca sp. nov.

(pl. 3E, fig. 4A–E)

Sertularella polyzonias — Leloup, 1974: 32, fig. 26. — Galea, 2007: 64, fig. 15A–D [not Sertularella polyzonias (Linnaeus, 1758) ].

Sertularella gayi — Galea, 2007: 62 [not Sertularella gayi (Lamouroux, 1821) ].

Material examined. Stn. CMZ — 13.vii.2010, S03 (40 m): two sterile stems, one mono-, the other slightly polysiphonic, 6.2 and 5.0 cm high, respectively (MHNG-INVE-79624). Stn. YBU — 09.iv.2007, S01 (20 m): colony composed of several monosiphonic stems, up to 4.0 cm high, growing on dead gorgonian and bearing male gonothecae; 25.iv.2007, S05 (20 m): holotype (MHNG-INVE-79665)—colony composed of several profusely branched, polysiphonic stems, up to 10.0 cm high, some bearing male gonothecae, epizoic on gorgonian; 01.vi.2009, DS120 (20–25 m): numerous sterile stems, both mono- and polysiphonic, up to 6.5 cm high, epizoic on gorgonian; 05.xi.2009, DS098 (35 m): fragmentary colony composed of a few polysiphonic stems, largest fragment 4.0 cm high, female gonothecae occur on some fragments, epizoic on gorgonian (MHNG-INVE-79625); 20.x.2009, DS028 (20–30 m): several fragmentary, monosiphonic stems, up to 4.0 cm high, growing on worm tubes and bearing numerous male gonothecae; 20.vi.2010, S05 (20 m): sterile colony composed of two polysiphonic, profusely branched stems, ca. 7.0 cm high; 11.vii.2010, S02 (25 m): a few sterile stems, both mono- and polysiphonic, up to 4.8 cm high, as well as several smaller fragments; S03 (25 m): several sterile colonies and fragments, up to 6.3 cm high, with both mono- and polysiphonic stems, epizoic on gorgonian; 12.vii.2010, S05 (41–43 m): a few polysiphonic stems epizoic on gorgonian and numerous fragments, up to 5.5 cm high, some incipient gonothecae on a side branch (MHNG-INVE-79626); S07 (42 m): a few mono- and polysiphonic stems, up to 5 mm high, and numerous fragments, all sterile, epizoic on sponge and calcareous bryozoan; 26.iv.2011, S07 (20 m): numerous sterile stems and fragments, up to 8.5 cm high, mostly polysiphonic, on dead gorgonian; S13 (20 m): several sterile stems and fragments, mostly monosiphonic, some possessing a few accessory tubes.

Description. Colonies coplanar, either mono- or polysiphonic, arising from creeping, branching stolon. Basal part of monosiphonic stems of variable length, devoid of hydrothecae, perisarc smooth, unconstricted at origin from stolon. Stems above composed of a succession of internodes delimited by rather indistinct, oblique nodes, occasionally well-marked. Each internode 880–1320 µm long, carrying a single, distal hydrotheca. Side branches almost alternate, rarely randomly arranged; generally three hydrothecae between successive side branches, but possibly 1 to 9. Up to third order branching. Stems and branches slightly zigzagging. First internode of a side branch comparatively longer (460–1930 µm) than subsequent ones. Hydrothecae tubular, distinctly curved outwards, adnate for about half their adaxial length. Abaxial wall 610–655 µm long, straight basally, and conspicuously curved below rim; free adaxial wall 410–450 µm long, slightly convex, perisarc smooth to wavy, in the latter case provided with 2–3 slight undulations, more consicuous basally; adnate part 375–495 µm; maximum width 340–395 µm. Hydrothecal aperture expanding just below rim; the latter 290–325 µm wide, provided with four acute cusps separated by moderately-deep, semi-circular embayments; operculum composed of four triangular plates, with concentric, close-set striations of the perisarc. Hydranths with abaxial caecum and up to 30 filiform tentacles. In fully fertile colonies, gonothecae arising every two hydrothecae or more, occasionally given off from bases of successive hydrothecae. Male and female similar, though of slightly different size: female 2105–2520 µm long, 810–915 wide in middle; male 2215–2750 µm long, 795–990 µm wide in middle. Gonothecae with 6–7 transverse ribs, the 3–4 distalmost well-marked, becoming less pronounced towards base; aperture mounted on a short terminal collar, truncate distally and provided with four, not very conspicuous, perisarc projections. Basal part of gonotheca excavated on side in contact with adjacent structures (internode and hydrotheca). Female gonothecae with acrocysts carrying about 30 developing larvae.

Remarks. In an earlier account (Galea 2007), one of us identified fertile material with monosiphonic stems as S. polyzonias (Linnaeus, 1758) , and sterile, polysiphonic colonies as S. gayi (Lamouroux, 1821) . The present specimens contain both mono- and polysiphonic colonies bearing gonothecae of both sexes. The gonotheca of S. gayi is characteristically provided with two apical "lips" of unequal development ( Ramil et al. 1992) and it is thus different from that observed in our material. Additionally, the hydrotheca of S. polyzonias is flask-shaped and its aperture is oriented outwards and upwards, while the hydrotheca of S. curvitheca is much more tubular in shape, and it obviously curves outwards.

The typical shape of the hydrotheca of this species leaves no doubt that Leloup's (1974) records of S. polyzonias belong to S. curvitheca .

Etymology. The specific epithet refers to the curved shape of the hydrotheca.

Distribution in Chile. Based on current knowledge this species is endemic to southern Chile, but its range does not extend southwards to the Strait of Magellan. It has been recorded from Reloncaví Sound (ca. 41.73° S) ( Leloup 1974) to Camello Island (ca. 49.18° S) (Galea 2007).