Monotheca hyalina ( Bale, 1882 )

Watson, Jeanette E., 2011, Review of the genus Monotheca (Hydrozoa: Leptolida) from Australia with description of a new species and a note on Monothecella Stechow, 1923, Memoirs of Museum Victoria 68, pp. 71-91 : 78-80

Monotheca hyalina ( Bale, 1882)

Fig. 3A–I

Plumularia hyalina Bale, 1882: 41 , pl. 15, fig. 9.— Bale, 1884: 141, pl. 12, figs 4, 5.— Bartlett, 1907: 422.— Bedot, 1921: 28.— Trebilcock, 1928: 24, pl. 6, fig. 6.— Watson, 1975: 170, fig. 29.— Stranks, 1993: 11.

Monotheca hyalina . — Stechow, 1921: 260.— Watson, 1996: 78.— Watson, 1997: 529.— Bouillon et al., 2006: 368.

Not Plumularia hyalina .— Ralph, 1961b: 41, fig. 5a, b.— Ralph, 1961c: 109.

Not Monotheca hyalina .— Vervoort and Watson, 2003: 371, fig. 90F–I.

Material examined. NMV F59052, microslide; NMV F59053, microslide, Bale collection, Museum Victoria, locality Queenscliff, Victoria.

Material in author’s collection: Houtman Abrolhos Islands , Western Australia, infertile colony on Sargassum and red alga, depth 6–10 m, coll: J. Watson, 12 October 1986 ; Hopetoun , Western Australia, female colony on brown alga, depth 2 m, under ledge, coll: J. Watson, 13 January 1986 . Boatswains Rocks , South Australia, colony detached from substrate, coll: J. Watson, 27 January 1969 . Fluted Cape, Bruny Island , Tasmania, female colony, depth 16 m, on red alga, coll: J. Watson, 10 February 1972 . Lawrence Rocks, Portland , Victoria, infertile colony on red alga, depth 16 m, coll: J. Watson, 14 May 1969 . Walkerville , Victoria, infertile colony detached from substrate, depth 3 m, coll: J. Watson, 1 March 1968 . Nambucca Heads , New South Wales, infertile colony on coralline alga and ascidian, depth 13 m, coll: J. Watson, 11 January 1972 .

Description. Hydrorhiza of tubular rugose stolons reptant on substrate; stolons usually with internal flexion joints. Stems 3–10 mm high, monosiphonic, straight to weakly sympodial, up to four short basal internodes with transverse joints above hydrorhiza. Succeeding stem internodes variable in length, longer ones typically on taller stems, smooth, expanding a little distally with a strong oblique V-shaped proximal node and a transverse distal node, usually an internal transverse septum below distal node at level of apophysis.

Shorter stems with one, rarely two, short proximal athecate internodes, stem thereafter hydrocladiate; cauline internodes deeply and more or less irregularly septate with strong V-shaped proximal nodes and transverse distal nodes, and three or four strong transverse internal septa. Hydrocladia alternate, fairly long, given off in one plane from a short, strong apophysis distal on internode, apophysis curving smoothly out from internode, adcauline wall a shoulder with slightly oblique deep node, a cylindrical axillar hydrostatic pore on adcauline shoulder.

Athecate hydrocladial internode long, deeply inserted in shoulder of apophysis, with deep transverse distal node and several complete internal septa. Hydrothecate internode longer than athecate internode, terminating in a protuberance separating the twin lateral nematothecae, hydrotheca set deeply in internode, a large prehydrothecal chamber expanding from proximal node to floor of hydrotheca; hydrotheca deep bowl shaped, base convex with a large foramen connecting with prehydrothecal chamber; in lateral view abcauline wall convex, adcauline wall completely adnate to internode, in ventral view walls expanding in a smooth curve from base, narrowing just below margin, rim slightly thickened but not everted; margin hemispherical, wide in ventral view, abcauline side straight, adcauline side deeply concave, in lateral view, wall a broad sinous curve down to internode.

Three nematothecae on hydrothecate internode, hydrocladial median inferior about halfway along prehydrothecal chamber, small, bithalamic, moveable, adpressed to internode, base tapering, cup slightly adcaudally shortened, twin laterals of same shape as median, standing erect on each side of strong terminal protuberance of internode, tucked within hydrothecal margin, cup circular to slightly laterally compressed but not excavated; no cauline nematothecae.

Gonotheca large, one to several in a row on lower stem, conical, widening from a short indefinite pedicel inserted beside apophysis, walls of gonotheca smooth to obscurely undulated, truncated distally by a transverse, weakly concave aperture without operculum; female gonophore with 15–20 large ova.

Perisarc of slender stems thin, much thicker in shorter, robust stems.

Colour of live colonies where known, buff to yellow, gonophores yellow.

Figures

Figure 3. A–H, Monotheca hyalina. A, part of robust stem from cool temperate waters with intranodal septa; B, part of slender stem from temperate waters with no intranodal septa; C, hydrocladium and hydrotheca, lateral view; D, hydrocladium and hydrotheca, ventral view; E, gonotheca with female gonophore; F, apical stolonal plate; G, axillar hydrostatic pore; H, median inferior nematotheca; I, one of twin lateral nematothecae. Scale bar: A, B, 1 mm; C, D, 0.2 mm; E, 0.5 mm; G–I, 0.1 mm.