Lytocarpia megalocarpa (Bale, 1914)

Watson, Jeanette E., 2018, Some Hydroids (Cnidaria, Hydrozoa) from the Great Australian Bight in the collection of the South Australian Museum, Zootaxa 4410 (1), pp. 1-34 : 28-30

Lytocarpia megalocarpa (Bale, 1914)

Figure 12A–E

Aglaophenia megalocarpa Bale, 1914a: 45 , pl 4, fig. 1, pl. 6, fig. 5.— Stranks, 1993: 12. Lytocarpia megalocarpa .— Vervoort & Watson, 2003: 263.— Bouillon et al., 2006: 285.

Material examined. SAM H2338, preserved material; three microslides ( SAM H2600, H2601, H2602). PIRSA Stn QMP 5c.

Description. Branch 11 cm long, thick, part of a much larger colony, heavily fascicled, polysiphonic tubes running parallel almost to tip of branches.

Hydrocladia alternate, to 20 mm long, inserted on a wide frontal apophysis. Hydrotheca set high on hydrocladium at angle of about 40° to hydrocladial axis, body tubular, short, posterior rounded, divided almost into two by a thick septum passing backwardly about halfway through hydrotheca from base of lateral nematotheca, septum terminating in a large knob with a further upward extension as a faint indentation in perisarc; a tiny Vshaped protrusion of perisarc at base of hydrotheca into internode. Margin with a short bifid anterior cusp, abcauline wall thickened behind cusp down to orifice of median nematotheca, margin with three pairs of small pointed cusps, the first largest and most pointed and a third small, sharp hidden behind lateral nematotheca.

Median nematotheca short, tubular, adnate, reaching about halfway along hydrotheca, orifice scalloped and open down to hydrotheca. Lateral nematotheca tubular, reaching margin of hydrotheca, orifice open; two nematothecae on cauline internode, one above and one below apophysis, similar to laterals but orifice larger.

Colony pale honey colour (preserved material).

A, branch from colony. B, hydrothecae. C, hydrotheca, anterior view. D, median nematotheca. E, lateral nematotheca.

Remarks. The above description supplements that of Bale (1914a). A microslide (NMV F58666 ) in the Bale collection of Museum Victoria designated syntype by Stranks (1993) is labelled in Bale’s handwriting “312 Great Australian Bight, 1914”, and displays a stem with five corbulae. I select this slide as lectotype of Lytocarpia megalocarpa .

Distribution. Great Australian Bight; this is the second record of the species.

Ecology and Distribution. Distribution and sample data are given in Tables 1 and 24.

Hydroids studied in this collection were collected from shelf waters at depths of 59–180 m in the eastern Bight ( Tables 1, 24). The geographical area covered extends from Eucla (31,40.30 ° S, 128, 52.59° E) near the head of the Bight to Cape Catastrophe (34 59° S,136 0 10 ° E) on the eastern side of the Bight. The single exception is Cryptolaria gracilis recorded from the Cascade Seamount south-east of Tasmania. Locations given for the Southcott collection are only approximate as the surveys were undertaken prior to availability of GPS.

This report increases knowledge of the geographical range of some species already known from Pearson Island and the Nuyts Archipelago in the eastern Bight and the Archipelago of the Recherche in the western Bight (see Watson 1973; 2003; 2005). Although there is almost no information concerning the substrate on which the species were growing it is assumed that most were epilithic on reef (e.g. Clathroozoon wilsoni ) or epizooic on large reef invertebrates. Some, e.g. Gymnangium pusillum were dredged from a sedimentary substrate.