Halopteris urceolata, Watson, 2015

Watson, Jeanette E., 2015, A new species of Halopteris (Hydrozoa: Leptothecata) and redescription of Plumularia rotunda from Victoria, Australia, Memoirs of Museum Victoria 73, pp. 41-46 : 41-42

Halopteris urceolata sp. nov.

Material examined. NMV F207310 , holotype, malinol mounted microslide, infertile colony on the bryozoan Amathia tortuosa , coll: J. Watson, St Leonards pier, Port Phillip , 29/10/2012, depth 2 m ; NMV F207310 , remainder of holotype colony preserved in 70% ethanol .

Description. Hydrorhiza a smooth tubular stolon of same diameter as stem, running along branches of the bryozoan host, giving off single delicate stems at irregular intervals. Stems to 15 mm high, straight, monosiphonic, cylindrical, with one or two basal ahydrocladiate internodes with weakly oblique to transverse nodes, distalmost node strongly oblique, following internodes alternately athecate and thecate, athecate internode with transverse proximal and strongly oblique distal node.

Hydrocladia alternate, planar, basal hydrocladia opposite in some stems. Apophysis of stem cylindrical with transverse distal node. Hydrocladia with up to five hydrothecae, arising from behind frontal cauline hydrotheca, sometimes a short secondary hydrocladium bearing two or three hydrothecae given off from behind first hydrocladial hydrotheca. Hydrocladial internodes alternately athecate and thecate; thecate internode with oblique nodes, distal node sometimes reduced to a notch in perisarc, athecate internode with a single nematotheca about halfway along internode.

Hydrotheca seated about halfway along thecate internode at an angle of approximately 40° to hydrocladial axis, jug-shaped, abcauline wall almost straight to weakly concave, slightly thickened, adcauline wall distinctly concave, floor asymmetrically curved, margin circular in anterior view, transverse to hydrothecal axis, rim slightly thickened.

One or two large nematothecae on basal stem internodes and one halfway along athecate cauline internode, base of nematotheca long and slender, cup large, adcaudally foreshortened; nematothecae on hydrocladial internode, base of median inferior short and stout, cup adcaudally foreshortened, not reaching hydrothecal floor, base of paired laterals long, without pedicel, cup smaller than others, not reaching hydrothecal margin.

Cnidome comprising microbasic euryteles all of same size, capsule elongate oval, 10 x 5 µm, shaft 7 µm long, spinous.

Colony transparent white, perisarc thin.

Remarks. It was originally considered that the species may be Plumularia campanula var. geelongensis Mulder and Trebilcock 1916 , recorded by them only once from Corio Bay in Port Phillip. Careful search of the hydroid collections in Museum Victoria found no specimen of the variety geelongensis it is assumed that no specimens were ever lodged.

Their figure of var. geelongensis (p.76, pl. 11, figs 2, 2 a-c) shows a deep cup-shaped, straight-sided hydrotheca, suggesting that the specimen may have been a variant of Halopteris campanula (Busk, 1852) , a species common in Victorian oceanic habitat.

Ecology. The species occurs in sheltered habitat on jetty piles.

Etymology. Named for the jug-shaped hydrotheca.