Zygophylax concinna ( Ritchie, 1911 )

Watson, Jeanette E., 2019, Bathyal and abyssal hydroids (Hydrozoa, Leptothecata) from southeastern Australia, Memoirs of Museum Victoria 78, pp. 65-72 : 67

Zygophylax concinna ( Ritchie, 1911)

Figure 2 a, b

Zygophylax concinna Ritchie, 1911: 823 , pl. 88, figs 3, 4.

Record. QM G337986 , one microslide. Coll: off Bermagui , New South Wales, 36.418 S, 150.8 E, 3980 m, beam trawl, 26/5/2017 . QM G337446 , one microslide. Coll: off Byron Bay , New South Wales, 28.371 S, 154.6487 E to 28.3875 S, 154.617 E, 3825– 3754 m, beam trawl, 9/06/2017 .

Description. A broken, heavily fascicled and twisted stem originally about 15 mm long and one stem fragment 8 mm long with one undamaged hydrotheca.

Polysiphonic stem tubes parallel, giving off flaccid monosiphonic branches. Branch internodes long, thin, cylindrical, nodes transverse, narrow, a tumescence above and below node; one or two alternate hydrothecae on internode. Hydrotheca about halfway along internode, inserted on an inflated apophysis, distal node of apophysis transverse.

Pedicel of hydrotheca of one long, rarely two or three cylindrical segments expanding distally to diaphragm. Diaphragm a thin perisarcal ring situated high in hydrotheca; walls of hydrotheca above diaphragm more or less cylindrical or expanding a little to margin. Margin circular, transverse to hydrothecal axis, some slightly inclined, rim everted, often with several strong replications.

Perisarc of polysiphonic tubes thick, hydrocladia thinner, hydrothecae fragile, mostly broken.

Remarks. Zygophylax concinna was first recorded from a fine sandy bottom at a depth of 100 m off Sydney, New South Wales ( Ritchie 1911). Ritchie’s small colony ( Ritchie 1911, pl. 88, fig. 3) was probably young. The present specimens are probably parts of much larger complexly branched colonies; otherwise the material generally conforms to Ritchie’s description of Z. concinna .

Distribution. New South Wales, Australia. This is the second record of the species.

Figures

Figure 2. a–f. a, b, Zygophylax concinna. a, branch internodes with hydrothecae. b, hydrotheca. c, d, Amphisbetia ramifera sp. nov. c, stem with subopposite hydrothecae and axillar hydrotheca. d, branch with opposite hydrothecae. e, f. Lytocarpia parvispiralis sp. nov. e, holotype colony. f, hydrothecae, lateral view.