Macrorhynchia whiteleggei ( Bale, 1888 ) Bale, 1888

Watson, Jeanette E., 2011, New species, new records and redescriptions of Thecate hydroids (Cnidaria: Hydrozoa: Leptothecata) from Southern Australia, Zootaxa 3122, pp. 1-36 : 13-15

Macrorhynchia whiteleggei ( Bale, 1888) comb. nov.

Figs 6 , 7 A–D

Aglaophenia whiteleggei Bale, 1888: 794 , pl. 21, fig. 8.– Stranks, 1993: 14, 26.– Watson, 1994: 67.– Vervoort & Watson, 2003: 336.

Material examined. NMV F171360, fertile colony on rock, Popes Eye reef, southern Port Phillip, depth 6 m, coll: J. Watson, 1/01/2010, colony alcohol preserved.

Description. Mature colonies large, up to 15 cm in height and 15 cm in width in a spreading plumose canopy complexly branched with up to 10 orders of branching. Hydrorhiza a bundle of tough rugose stolons firmly attached to rocky substrate. Stems strongly fascicled, lower stem ahydrocladiate, in large colonies ahydrocladiate stems up to 10 cm long and 2.5 mm wide, the polysiphonic tubes gradually reducing in number distally, typically a single tube near the end of each branch. Branching from main stem regularly subdichotomous, branch internodes short, nodes oblique, indistinct.

Hydrorhiza, stolon width 250–450 Branch (monosiphonic)

length of internode 344–416 width at node 184–200 Hydrocladium

maximum length 600–800 length of internode 360–440 width at node 130–160 Hydrotheca

length, axial 380–440 width at margin 200–240 anterior crest, length 120–140 Nematotheca

cauline, length 184–208 median hydrothecate, length 150–160 median, width at orifice 25–30 lateral, length 220–260 lateral, width at orifice 25–30 Gonotheca, mature

length 1900–2000 Width 1400–1600 Hydrocladia alternate, frontal, one proximal on each branch internode, moderately long, slightly recurved, length shortening distally along branch; hydrocladial internodes moderately wide, nodes transverse to weakly oblique, faint, a thick entire transverse intranodal septum at one third the distance from proximal end and a thinner, slightly oblique partial septum passing forward into the internode from the base of the lateral nematotheca.

Hydrotheca elongate, base lying along internode, posterior end pointed, anterior end facing upward at c. 40° from internode, a complete intrathecal septum passing almost vertically up through hydrotheca from intranodal septum. Margin with a prominent curved anterior rostrum and a long lozenge-shaped foramen behind rostrum; margin dentate with three pairs of lobate cusps, the anterior pair sharpest, the next pair rounded, the posterior pair shallowest and hidden behind the lateral nematothecae.

Median nematotheca tubular, narrow, following axial line of hydrotheca, orifice circular, level with hydrothecal margin, a small secondary orifice just above junction with anterior rostrum. Lateral nematothecae long, pointing forward, tubular, with a circular terminal orifice slightly ahead of hydrothecal margin, a small notch at base of nematotheca connecting with intranodal septum. Branch nematothecae similar to laterals, one at base of hydrocladium, usually one in fork of branch.

Gonotheca lenticular, without pedicel, large, several borne sparingly on a phylactocarp replacing a hydrocladium on higher branches, one hydrotheca on proximal internode of phylactocarp; usually one or two but sometimes up to five in various stages of development along primary phylactocarp; a short, straight secondary phylactocarp given off internode of primary at base of each gonotheca and closely adpressed to gonotheca, a single or a pair of nematothecae similar to laterals on each phylactocarpal internode, each with a circular terminal orifice and an inwardly facing orifice. Perisarc of gonotheca thick, rim conspicuously thickened, female containing several large ova.

Colour of live colonies silvery white, perisarc of stems brown, gonotheca grey with white scribbly lines, ova cream to mauve.

Remarks. This is the first description of the reproductive structure of the species, placing it in Macrorhynchia .

The material upon which Bale (1888) based his original description was a colony only 5 cm high, much smaller than mature colonies of the species. Bale split his hydroid collections between the Australian Museum, Sydney and the National Museum of Victoria, Melbourne (now Museum Victoria), usually depositing preserved material in the former and microslides in the latter. The Australian Museum holds preserved material labelled “ Aglaophenia whiteleggei , AM G10372, Green Point, Port Jackson” without collection data but with the note “Fig’d Proc. Linn. Soc. N.S.W. III (2) type ”. Other preserved material in the Australian Museum is labelled “Y99, N.S.W. Port Stephens, N.S.W., collected by J. B. Wilson” and “Y100 Green Point, Port Jackson, N.S.W.”. A microslide with Bale’s personal Catalogue No. 269 in the Museum Victoria collection is labelled “J.B.W. Port Phillip Heads, Jan. 1887 ”; a slide Catalogue No. 270 has the same locality and is labelled Dr Macgillivray, 1889; a third slide without catalogue number is labelled “Port Phillip Heads, Dr McGillivray, 1890”.

As the Port Jackson specimen (AM G10372) is apparently that described in his 1888 paper, and labelled type, this must be considered the type of the species. Stranks (1993) however suggested that a microslide in the Museum Victoria collection (NMV F587870) “from an unknown locality may be probable holotype ”. Without evidence that this is part of the AM G10372 specimen this supposition cannot be supported.

Macrorhynchia whiteleggei is a very common species in southern Port Phillip where the conspicuous silvery white colonies ( Fig. 6 ) grow on reef at depths to 6–30 m in strong current flow. Colonies grow from dormant hydrorhizae in late autumn (April–May) and mature over winter months at water temperatures of 13–16° C, becoming fertile in spring (September–October), regressing over the summer months.

Distribution. Southeastern Australian coast from Bass Strait to Port Stephens, New South Wales.

Figures

FIGURE 6. Macrorhynchia whiteleggei. Colony approximately 15 cm high, in situ photograph, Popes Eye reef, southern Port Phillip, depth 12 m, September 2008.

FIGURE 7. Macrorhynchia whiteleggei. A, hydrocladial internodes. B, hydrotheca. C, mature gonothecae, D, nematothecae on phylactocarp. Scale bar: A, B, D, 0.5 mm, C, 1 mm.