Lytocarpia carinifera (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 : 26-28

Lytocarpia carinifera (Bale, 1914)

Figure 11A–E

Aglaophenia carinifera Bale, 1914b: 181 , pl. 38, figs 1, 2.— Bale, 1915: 318.— Bedot, 1921: 341.— Blackburn, 1942: 110.— Stranks, 1993: 9.—Watson, 2003: 253.— Vervoort & Watson, 2003: 261.— Watson, 2005: 560, fig. 23 A–F.— Bouillon et al., 2006: 280.

Material examined. SAM H2330, preserved material; two microslides ( SAM H2598, H2599). PIRSA Stn QMP 5c.

Description. Largest colony consists of six infertile stems to 100 mm long attached to a hydrorhiza composed of several thick entwined stolons. Stems monosiphonic to lightly fascicled, one stem branched in lower region from a stolon twisted around the primary caulus.

Hydrocladia alternate, to 10 mm long, borne on a short frontal apophysis, hydrocladial nodes usually indistinct to absent, but where visible, weakly oblique. Hydrotheca at an angle of about 30°–45° to hydrocladium, elliptical, widening from base to margin, a septum passing obliquely in posterior third forward from floor almost to abcauline wall, a short extension passing from floor a short distance into internode. Margin of hydrotheca almost perpendicular to hydrothecal axis with a conspicuous bifid vertical anterior rostrum, (rostral cusps one above the other), followed by three pairs of marginal cusps, the the first pair the longest, pointed, a deep embayment separating it from anterior rostrum, the other pairs shallower, with shallow embayments between.

Median nematotheca tubular, straight, approx. two thirds length of hydrotheca, adnate, margin sinuously open down to hydrotheca. Lateral nematotheca tubular spanner-shaped, extending beyond hydrothecal margin, orifice deeply excavated down to junction with hydrotheca; one nematothecae on cauline internode just below apophysis.

Hydrocladial internode Hydrocladium

length of internode 400–464 depth below hydrotheca 200–280 Hydrotheca

length, base to tip anterior rostrum 464–480 width at margin 288–360 anterior rostrum length 144–160 Nematotheca

median length 352–376 median, width at orifice 72–88 lateral, length 200–224 lateral, width of orifice 72–88 A, whole colony SAM H2330. B, hydrothecae. C, hydrotheca, anterior view. D, median nematotheca. E, branch of another colony displaying a different colony form.

Remarks. Lytocarpia carinifera is well described by Bale (1914b), his figures showing the bifid hydrothecal rostrum but not the deep marginal excavation of the lateral nematotheca. Because of the similarity of their hydrothecae, especially the bifid rostrum, it is possible that L. carinifera is conspecific with Lytocarpia crucialis ( Lamouroux, 1816) .

A branch 40 mm long presumably from a much larger colony (submitted by the South Australian Museum after the main collection) was also examined. The branch has close-set flexuous hydrocladia to 20 mm long, contrasting with the relatively short widely spaced hydrocladia of the specimen described above. Although macroscopically very different ( Fig. 11E), the two specimens are virtually identical microscopically and in dimensions. It is possible although unlikely that these represent two different colony forms of the same species. Finding more, preferably fertile material of L. carinifera (as described above) may serve to distinguish whether one or two species are involved.

Distribution. Great Australian Bight.