Symplectoscyphus tuba Totton, 1930

Watson, Jeanette W., 2003, Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island, Memoirs of Museum Victoria 60 (2), pp. 151-180 : 171-172

Symplectoscyphus tuba Totton

Figures 21A–D

Symplectoscyphus tuba Totton, 1930: 186 , figs 37a, b.— Ralph,

1961: 816, figs 18f, g.— Leloup, 1974: 42, fig. 41.— Vervoort, 1993:

272, figs 67a–d. Sertularella tuba . — Stepanjants, 1979: 76, pl. 1 fig. 4.

Material examined. Stn 94, NMV F91323, specimen alcohol-preserved, NMV F 91349 malinol mounted microslide, fragments of colony detached from substrate. Stn 119, TM K2793, small fertile colony on primnoid gorgonian stem, specimen alcohol-preserved. Stn 120, TM K2794 many broken stems, longest intact stem 40 mm long, specimen alcohol-preserved. Stn 122, TM K2782, small infertile colony on Eudendrium , specimen alcohol-preserved.

Description. Hydrorhiza composed of sparse stolonal tubes. Stems monosiphonic, of same diameter as stolons, lower stem rather lax, almost straight proximally, narrowing a little distally. Stems branched alternately, branches widely spaced, usually simple but sometimes rebranched once or twice.

Primary branches up to 12 mm long, directed upward at an acute angle to stem; secondary branching (hydrocladia) if present, pseudodichotomous, forking from below a hydrotheca. Lower branch internodes sub-sympodial, this structure becoming more pronounced distally along hydrocladia. Some hydrocladia terminating in tendrils that rejoin other hydrocladia to form a loose meshwork. Internodes variable in length, slender, widening distally to accommodate hydrotheca, perisarc smooth, node a weak oblique constriction in perisarc sloping away from hydrotheca.

Hydrothecae alternate, distal on internode, short, contracting from base to margin, but sometimes almost tubular; directed upwards at an angle of 35–45° to internodal axis, abcauline wall straight to weakly concave, smoothly contiguous with internode, adcauline wall convex, adnate adcauline wall slightly longer than free wall, almost straight, wall becoming free at node, curvature greater than adnate wall, imparting a distinct angularity to wall. Floor of hydrotheca narrow, flat, a small subcircular foramen in perisarc below. Margin with 3 cusps, adcauline the longest, slightly everted, with 2 abcauline laterals, these less pronounced, rounded; some hydrothecal margins slightly thickened, many replicated. Hydranths with c. 12–16 short tentacles, not well preserved.

Gonothecae abundant, arising on a very short, bent pedicel inserted close beneath hydrothecae on stem and hydrocladia; gonotheca adpressed to hydrocladium, facing distally, ovoid with 8–10 deep, upturned flanges, proximal 2 or 3 shallowest, distalmost flange a collar surrounding orifice; gonothecal wall between flanges deeply concave and strongly vertically striated. Orifice central, wide, trumpet-shaped, upright. Remains of gonophores present in many gonotheca but sex indeterminate.

Colour. Colony colourless, transparent; gonophores may have been pink in life.

Measurements (µm)

Stem diameter?

Internode length 780–1260

diameter at node 88–120 Hydrotheca length of abcauline wall 416–440

length of adnate adcauline wall 296–360

length of free adcauline wall including replications 248–312

width across margin (lateral view) 192–216

width across floor 96–120 Gonotheca total length including pedicel 1120–1200

maximum diameter including flanges 760–800

diameter of orifice 240–280

length of tube 160–192

length of pedicel 80–112

Distribution. Northern New Zealand, 183 m ( Totton, 1930); Antarctica, 145–410 m ( Stepanjants, 1979); Chile, 30–60 m ( Leloup, 1974); New Caledonia, 650–680 m ( Vervoort, 1993).

Remarks. Although the width of the hydrothecal margin and diameter of the gonotheca are somewhat greater than measurements given by Totton (1930), Ralph (1961 a) and Vervoort (1993) for Symplectoscyphus tuba I have no doubt that the present material is referrable to that species. It is a rather delicate species, of which only small colonies or fragments of colonies have been previously reported. Its long, slender internodes, widely spaced hydrothecae and ovoid, deeply ridged gonothecae are characteristic.

Figures

Figures 21A–D. Symplectoscyphus tuba stn 120. A, single stem from colony. B, branch with axillar hydrotheca. C, hydrotheca. D, gonotheca. Scale bar: A, 10 mm; B, 1 mm; C, D, 0.5 mm.