Monotheca obliqua ( Johnston, 1847 )

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 : 81

Monotheca obliqua ( Johnston, 1847)

Fig. 4 A–E

Plumularia obliqua Johnston, 1847: 106 , pl. 28, fig. 1.— Bale, 1884: 138, pl. 12, figs 1–3.— Bartlett, 1907: 43.— Mulder and Trebilcock, 1910: 116. — Mulder and Trebilcock, 1916: 76, pl. 11, figs 1–1e. — Jäderholm, 1919: 22, pl. 5, fig. 6.— Stechow, 1919: 113.— Bedot, 1921: 28.— Billard, 1927: 342.— Broch, 1933: 31, fig. — Leloup, 1934: 15.— Billard, 1936: 9.— Blackburn, 1938: 315.— Blackburn, 1942: 108.— Hodgson, 1950: 39, fig.68.— Rossi, 1950: 23, fig. 4b.— Pennycuik 1959: 180.— Watson, 1973: 189.— Millard and Bouillon, 1974: 9, 34, fig. 8A–D.— Millard, 1975: 396, fig. 125A–B.— Garcia-Corrales, Aguirre Inchaurbe and Gonzalez Mora, 1978: 56, fig. 25.— Millard, 1978: 196 et seq.— Watson, 1979: 234.— Boero, 1981a: 197.— Hirohito, 1983: 69. — Boero, 1984: 103, fig. 8.— Boero et al., 1985: 29.– Gili and García-Rubies, 1985: 48, fig. 5B.— Isasi and Saiz, 1986: 70.— Roca, 1987: 151.– Gili, Vervoort and Pagès, 1989: 89, fig. 17A.— Boero and Bouillon, 1989: 39, fig. 1. García Rubies, 1992: 265.— Park, 1992: 294 Cornelius, 1995: 142, fig. 33.— Bouillon et al,, 1995: 61.— Hirohito, 1995: 275, fig. 94d–f.— Watson and McInnes, 1999: 111.— Bouillon et al., 2006: 368.

Monotheca obliqua . — Stechow, 1923b: 17.— Leloup, 1932: 160.— Yamada, 1959: 78.— Rho and Park, 1986: 99.— Ryland and Gibbons, 1991: 538, fig. 9.— El Beshbeeshy, 1995: 404.— Medel and López-González, 1996: 202.— Watson, 1973: 529.— Watson and McInnes, 1999: 111.— Vervoort and Watson, 2003: 369.— Watson, 2005: 541, fig. 15.— Bouillon et al., 2006: 368.

Plumularia (Monotheca) obliqua . — Stechow and Uchida, 1931: 565.

Plumularia obliqua australis . — Stranks, 1993: 8.

Material examined. NMV F101686 , infertile colony, New Island, Archipelago of the Recherche , Western Australia, depth 20 m on red alga, coll: J. Watson, February 2003 . WAM Z29970 , fertile colony, New Island, Archipelago of the Recherche , Western Australia, depth 20 m, on brown alga, coll: J. Watson, February 2003 .

Material in author’s collection: fertile colony, Popes Eye reef, Port Phillip , Victoria, on stem of Macrorhynchia whiteleggei , depth 6 m, coll: J. Watson, 7 November 2009 . Infertile colony, Popes Eye reef, Port Phillip , Victoria, depth, 3 m, on thallus of Sargassum sp. , coll: J. Watson 29 December 2009 .

Description. Hydrorhiza reptant on substrate, tubular, somewhat rugose. Stems to 7 mm long, monosiphonic, straight to sympodial, internodes moderately long, widening to distal node; node transverse to slightly oblique, often a distinct shoulder in perisarc and an internal septum above, sometimes one to three strong internal septa in proximal part of internode. Apophysis of stem short, upwardly directed, situated well below node, widening to a strong distal shoulder.

Hydrocladia alternate, short, in one plane, distal on internode, athecate internode with one to three internal septa, distal node transverse. Hydrothecate internode almost completely occupied by hydrotheca, internode with one or two faint septa below hydrotheca, sometimes a short, faint septum passing into hydrotheca from distal septum; internode distally inflated, pushing base of hydrotheca upward, prehydrothecal chamber short, triangular with internal triangular septum.

Hydrotheca scoop shaped, abcauline and adcauline walls smoothly convex, margin cut obliquely back to internode, rim slightly everted, a thickening behind rim.

Cauline and hydrocladial median inferior nematothecae similar in shape and size, bithalamic, moveable, base moderately long, cup fairly wide, cauline nematotheca about one-third distance up internode on side opposite hydrocladium, standing out from internode, base connecting with a large foramen of internode, hydrocladial median inferior nematotheca adpressed to prehydrothecal chamber, just reaching floor of hydotheca; twin laterals directed outwards from an indentation in distal protuberance of internode, base short, stout, cup deeply adcaudally excavated; a nematotheca in axil beside apophysis; a dome-shaped axillar hydrostatic pore with small terminal aperture, sometimes also a small secondary pore on adcauline shoulder of apophysis.

Male and female gonothecae borne on the same colony but not on same stems, of same shape and size, large, conical, circular in section, perisarc fairly thick with tendency to proximal rugosity, typically one borne on a short, thin pedicel beside an apophysis near base of stem; aperture transversely truncate, occupying entire width of gonotheca, closed by a sheet of tissue. Female gonophore containing many large ova.

Perisarc of stems pale brown basally, becoming colourless distally, gonotheca pale brown, gonophores flesh-coloured.

Figures

Figure 4. A–E, Monotheca obliqua. A, part of stem; B, hydrocladium and hydrotheca; C, female gonotheca; D, twin lateral nematothecae; E, axillar nematotheca and hydrostatic pore. Scale bar: A, C, 1 mm; B, 0.2 mm; D, E, 0.1 mm. F–L, Monotheca pulchella. F, part of stem; G, hydrocladium and hydrotheca; H, female gonothotheca with ova; I, anterior view of gonothecal aperture with internal lobate submarginal cusps. J, median inferior hydrocladial nematotheca. K, one of twin lateral nematothecae. L, axillar nematothecae. Scale bar: A,C, 1 mm.; B, 0.2 mm; F, H, 0.5 mm; D–E, I–L, 0.1 mm.