Symplectoscyphus subdichotomus

Symplectoscyphus subdichotomus (Kirchenpauer, 1884)

(fig. 17A–G, table 28)

Sertularella subdichotoma Kirchenpauer, 1884: 46, pl. 16 figs 1, 1B; Hartlaub, 1904: 6; Jäderholm, 1904a: 3; Nutting, 1904: 96, pl. 22 figs. 8–12; Hartlaub, 1905: 629, figs V 3 –W 3; Stepanjants, 1979: 77, pl. 17 fig. 7.

Symplectoscyphus subdichotomus: Ralph, 1961a: 813, fig. 20A–B; Blanco, 1969: 49, figs 1–18; Vervoort, 1972a: 140, figs 44B–D, 45; Leloup, 1974: 42, fig. 40; Blanco, 1976: 49, pl.6 figs 1–2; Millard, 1977: 37, fig. 11D–F; Hirohito, 1983: 53, fig. 25; El Beshbeeshy, 1991: 232, fig. 59; Hirohito, 1995 (English text): 222, fig. 75A–E; Vervoort & Watson, 2003: 234, figs 55F–H, 56A–F.

Material examined. Stn. MEL 02 – 06.iii. 2005, 15 m, S78: several sterile colonies and fragments, up to 5.5 cm high (MHNG INVE 53277). Stn. ANI — 01.iv. 2005, 2 m, S24: several fertile colonies and fragments, up to 5 cm high (MHNG INVE 53179). Stn. IMI — 15.iii. 2006, 22 m, S141: several fertile colonies ca 3.5 cm high (MHNG INVE 53435). Stn. CAD — 12.iii. 2006, 15 m, S113: several sterile, fragmentary colonies, up to 2 cm high. Stn. ICA — 13.iii. 2006, 12 m, S146: several fertile colonies, 2–3 cm high. Stn. PAB — 10.iii. 2006, 20 m, S85a: several fertile, fragmentary colonies, often less than 2 cm high (MHNG INVE 53300). Stn. CPA — 09.iii. 2005, 15 m, S170: several mass-like colonies, 3–4 cm high, with gonothecae in some parts. Stn. CPI — 07.iii. 2006, 24 m, S121: small, sterile colony growing on basal part of a stem of Synthecium robustum. Stn. GDA — 07.iii. 2006, 11 m, S126: several fertile colonies, up to 3 cm high. Stn. CVI — 06.iii.2006, S112 (15 m): a sterile, fragmentary colony, up to 3 cm high (MHNG INVE 53364); S142 (15–25 m): several fertile, fragmentary colonies, about 3 cm high; S86 (15–25 m): several fertile colonies, 3–4 cm high.

Type locality. Bass Strait, Australia.

Description. Colonies erect, monosiphonic, up to 5 cm high, light brown in color. Colonies of varied appearance: smaller ones pinnately ramified, larger ones pseudodichotomously branched; colonies growing in parallel planes and often anastomosing by the tips of branches; generally strongly interwoven, with reticulate appearance. Stems bent in zigzag fashion. Stem and side branches divided into internodes by oblique constrictions of perisarc, more or less marked in various parts of colony; no distinct nodes; internodes of variable length. Side branches arising laterally below stem hydrothecae, becoming axillar. Hydrothecae tubular, with ad- and abaxial walls slightly converging distally. Adcauline side ca ½ adnate, wall of free part straight. Abcauline side convex, with distinct flexure point in middle part, to nearly straight in some hydrothecae. Rim with three triangular cusps (one adaxial, slightly upturned, and two laterals) with rounded tips, delimiting three relatively deep, rounded embayments. Operculum composed of three triangular flaps. Gonothecae borne on internodes just below hydrothecal base, attached via a short pedicel. Gonotheca elongated ovoid. Wall with 9–12 transverse frills of perisarc, not spirally disposed; with semi-circular space between successive frills; periderm longitudinally striated. Apex of gonotheca, a small platform with central funnel, constricted basally and widening distally below the rim. Gonothecal content not seen; male = female?

Remarks. The shape of the terminal tube of the gonotheca is somewhat variable in different colonies, being obviously funnel-shaped in some specimens and nearly tubular in others, thus approaching the condition of S. filiformis. The variability in the morphology of gonotheca has been discussed in detail by Blanco (1969).

Vervoort & Watson (2003) regarded as doubtful all previous records of this species from South America, yet cited the records of Leloup (1974) from Chile. Nevertheless, several authors (Nutting 1904, Ralph 1961 a, Vervoort & Watson 2003) described in S. subdichotomus hydrothecae deeply immersed in the internode and with the free part of the adcauline side about half or less than that of the adnate part. Moreover, they described gonothecae as annulated rather feebly, with a distal flange-like, outer collar and a slender neck ending in a broad, rounded aperture. In some cases, both the collar and neck are absent, leaving only a broad aperture (Nutting 1904). The taxonomic status of S. subdichotomus must therefore be reevaluated.

Hydroid epibionts. Bougainvillia pyramidata (Forbes & Goodsir, 1851); Eudendrium cf. scotti Puce, Cerrano & Bavestrello, 2002; Campanulina pumila (Clark, 1875); Phialella cf. quadrata (Forbes, 1848); Filellum serratum (Clarke, 1879); Hebella cf. dispolians (Warren, 1909); Hebella striata Allman, 1888; Sertularella robusta Coughtrey, 1876; Parascyphus repens (Jäderholm, 1904); Orthopyxis mollis (Stechow, 1919); Clytia linearis (Thornely, 1900); Clytia paulensis (Vanhöffen, 1910); Clytia sp.; Obelia dichotoma (Linnaeus, 1758).

World distribution. Australia, New Zealand, Tierra del Fuego, Falkland Islands, Strait of Magellan, Cape Horn (Vervoort 1972a), Antarctica (Peña Cantero & García Carrascosa, 1999).

Records from Chile. Previous records of S. subdichotomus are from Corral, Calbuco, Guaitecas Islands, Canal Smyth, Strait of Magellan, Tocopilla, Canal Chacao, Seno Reloncavi, Golfo Corcovado (Leloup 1974), Punta Arenas (Hartlaub 1905). The present material was collected between 48°58' S and 52°09' S, and was never found north of Canal Messier.