Zygophylax sagamiensis Hirohito, 1983

Watson, Jeanette W., 2003, Deep-water hydroids (Hydrozoa: Leptolida) from Macquarie Island, Memoirs of Museum Victoria 60 (2), pp. 151-180 : 160-161

Zygophylax sagamiensis Hirohito

Figures 10A–F

Zygophylax sagamiensis Hirohito, 1983: 30 , fig. 11.— Rees and

Vervoort, 1987: 85.— Hirohito, 1995: 144, figs 44a–e, pl. 9 fig. C.

Material examined. Stn 44, TM K2775, infertile colony fragment 10 mm high, specimen alcohol-preserved. Stn 63, TM K2774, specimen alcohol-preserved, NMV F91335, malinol mounted microslide from fertile colony fragment 10 mm high on primnoid gorgonian stem. Stn 122, NMV F91316, specimen alcohol-preserved, NMV F91336 malinol-mounted microslide, complete branched colony 60 mm high and 50 mm wide, detached from substrate.

Description. Hydrorhiza a mat of stolons running along axis of gorgonian, bunching together at base of colony then passing upwards to become fascicular tubes of stem. Polysiphonic stems stiff, sparingly subalternately branched, primary branches widely spaced, occasionally secondary subdichotomous branching, one or two polysiphonic tubes running halfway to two thirds along branch or hydrocladium; branch and hydrocladia thereafter monosiphonic; a hydrotheca in axil of each branch. Hydrocladial internodes long, slender, perisarc moderately thick, smooth, nodes merely transverse constrictions, distinct when present, but often absent. Hydrothecae alternate to subalternate, widely spaced, facing frontally, 1 or 2 on internode, if one, about halfway to two-thirds up internode, if 2, one just below and the other just above node. Hydrocladial apophyses short, distal node transverse, deep.

Hydrothecal pedicel cylindrical, slender, variable in length, sometimes with one to several regenerations. Hydrothecae long, slender, slightly asymmetrical, adcauline wall convex, abcauline wall weakly concave, diaphragm distinct, clearly demarcated from hydrothecal wall, transverse or oblique (depending on angle of view) with central wide hydropore. Hydrotheca margin circular, transverse, rim distinctly everted, some hydrothecae with up to 8 marginal replications; perisarc of hydrotheca smooth.

Nematothecae numerous on peripheral tubes of fascicled stem, on hydrorhiza, on apophyses below hydrothecal pedicels, on surface of coppinia and on coppinial tubes; nematothecae small, vase-shaped, sometimes slightly asymmetric, pedicel very short, margin transverse, circular, rim slightly everted.

Coppinia (Stn 122) scarcely visible, embedded in polysiphonic tubes of stem between primary branches, marked by a faint swelling of the stem and numerous projecting nematophorous tubules. Gonothecae small, cylindrical, tightly packed, with low hooded semicircular orifice, a few with an apical peak, walls thick. Tubules issuing from coppinial mass, long, with one or two basal constrictions, some with one or two nematothecae, some with a few nodes along length and some incipiently branched.

Colour. Stems pale honey yellow, hydrocladia paler.

Measurements (µm)

Branch length of internode 360–392

width at node 36–52 Hydrotheca length of pedicel 108–120

length diaphragm to margin, including replications 392–600

diameter at diaphragm 56– 64

diameter at margin 116–148 Nematotheca length 76–108

diameter at margin 36– 40 Coppinia maximum length of tube 1050

diameter of tube 56–60

width of gonotheca 64–100

Distribution. Previously known from a depth of 300 m in Sagami Bay, Japan ( Hirohito, 1995).

Remarks. Branches are given off from just inside the peripheral tubes of the stem. Hydrothecae in the axils of branches usually have long, undulated or regenerated pedicels. Hydrocladial nodes may be faint or altogether absent. As there is only one coppinia in the sample and the gonothecae are deeply embedded in the mass, sex could not be determined. Nematothecae are so numerous on the hydrorhizal stolons and peripheral tubes of the lower stem region that they impart a rough, prickly appearance to these structures. Hirohito (1995) mentioned the presence of nematothecae on the peripheral tubes of the stem but not on the hydrorhiza.

In all but arrangement of the hydrothecae the present specimens resemble Zygophylax tottoni Vervoort, 1987 in which the branching is strictly planar and hydrothecae are not frontally directed. As the present specimens generally conform with descriptions and figures of Z. sagamiensis given by Hirohito (1983, 1995) the material is referred to that species. Differences with the present specimen are: (i) the fewer apical peaks on the gonothecae; and (ii) the numerous coppinial nematothecae.

Figures

Figures 10A–F. Zygophylax sagamiensis, stn 63. A, colony. B, distal part of branch. C, hydrotheca with multiple marginal replications. D, pedicellate nematotheca on hydrorhiza. E, coppinia. F, hooded gonothecae from coppinia. Scale bar:A, 25 mm; B, 0.5 mm; C, 0.2 mm; D, 0.1 mm; E, F, 0.25 mm.