Sertularella pinnata ( Lamouroux, 1816 )

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 : 12-13

Sertularella pinnata ( Lamouroux, 1816)

Figure 6A–C

Caberea pinnata Lamouroux, 1816: 130 .— Lamouroux 1824: 56.

Thuiaria lata Bale, 1882: 26 , pl. 13, fig. 2.— Bale, 1884: 120, pl. 7, fig. 4.— Stranks, 1993: 17. Sertularella lata Bale, 1915: 287 .— Bale, 1919: 337, pl. 16, fig. 5.— Blackburn, 1942: 115. Not Sertularella lata .— Nutting, 1904: 948.— Billard, 1907: 346, fig. 4.

Sertularella pinnata .— Gordon et al., 1998: 413, figs 1 b, 6.

Material examined. SAM H2323, preserved material; four microslides (SAM H2581, H2582, H2583, H2584). PIRSA Stn QMP5.

Description. Largest colony 200 mm high, infertile, with two branches and several pinnate stems 3 mm wide at base arising from a large tangled hydrorhizal mass. Branch internodes with three hydrothecae, one below hydrocladium, one above and one opposite, nodes when present, deep indentations sloping obliquely in opposite directions. Hydrocladia alternate on branch, to 12 mm long, straight, of same width throughout, without internodes, inserted on a short upwardly directed apophysis at an angle of approx. 40°.

Hydrothecae biseriate, loaf-shaped, sub-opposite, separated laterally across branch, but closer on hydrocladium, often adjoined and almost completely adnate to branch and hydrocladium, one row facing forward, opposite row facing outwards. Abcauline wall weakly concave, adcauline wall smoothly convex, thick, a knot of perisarc at base, floor open to internode. Margin subcircular, with four very low, thin cusps, shallow embayments between, rim slightly thickened, a small internal submarginal peg below abcauline cusp. Operculum of four thin triangular valves. Hydranth with abcauline diverticulum and c. 12 tentacles.

Remarks. The specimens conform to descriptions of Sertularella pinnata ( Bale 1882; 1919). S. pinnata was originally described as a bryozoan ( Caberea pinnata ) by Lamouroux (1816) but is now recognised as a hydroid (see Gordon et al., 1998).

Distribution. A common southern Australian oceanic species.