Symplectoscyphus pirsa, Watson, 2018

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 : 13-14

Symplectoscyphus pirsa sp. nov.

Figure 6D–F

Material examined. SAM H2335, holotype, preserved colony; one microslide ( SAM H2585) from holotype colony. PIRSA Stn IB1.

Description. Infertile stem 120 mm long, broken in two; hydrorhiza of fragmented tubular stolons. Basal stem section long, slender, monosiphonic, cylindrical, almost straight, several corrugations above hydrorhiza, stem ahydrocladiate to first branch at 80 mm from base, then indistinct corrugations at intervals to first branch, perisarc moderately thick.

Branching more or less planar, irregularly subdichotomous, in two or three orders at an upward angle, an axillar hydrotheca at base of branch. Branch internodes slightly geniculate, nodes variable from clearly visible to indistinct, sloping obliquely down from above base of free hydrothecal adcauline wall.

Hydrothecae biseriate, alternate, one distal on internode, flask-shaped, abcauline wall smoothly following line of internode, free adcauline wall proximally inflated then narrowing to margin, often following line of node, free wall longer than adnate wall, margin with three prominent pointed cusps, one adcauline, the other two lateral abcauline, rim internally thickened, a very small submarginal abcauline cusp just below rim, operculum of three delicate valves.

Remarks. In most hydrothecae the adnate adcauline wall merges in a continuous curve into a very short floor, thus the adnate length ( Table 11) often includes the floor. Although morphologically similar to Symplectoscyphus candelabrum Vervoort & Watson, 2003 from New Zealand, the hydrotheca of Symplectoscyphus pirsa is much larger. While caution is exercised in erecting yet another new species of Symplectoscyphus based upon infertile material, Symplectoscyphus pirsa does not match any known species of Symplectoscyphus from Australia, the western Pacific, Chile, Patagonia or Antarctica.

Etymology. Named to acknowledge the work of the South Australian Research and Development Institute (PIRSA), collector of the material.

FIGURE 6A–H.

6A–C. Sertularella pinnata ( Lamouroux, 1816) . A, part of branch. B, branch and hydrocladia. C, operculate hydrothecae. 6D–F. Symplectoscyphus pirsa sp. nov. D, holotype colony, SAM H2335. E, hydrocladium. F, hydrotheca showing thickened margin.

6G–H. Symplectoscyphus subdichotomus ( Kirchenpauer, 1884) . G, hydrothecate branch internodes. H, male gonotheca.

Stem, diameter 360–400 Branch (hydrocladium)

internode length 640–860 width at node 240–312 Hydrotheca

adcauline free wall length 504–520 adcauline adnate wall length 408–480 abcauline wall length 640–744 maximum width 408–456 width of margin 288–360