Eudendrium pennycuikae Watson, 1985

Watson, Jeanette E., 2015, Five athecate hydroids (hydrozoa: anthoathecata) from south-eastern australia, Memoirs of Museum Victoria 73, pp. 19-26 : 22

Eudendrium pennycuikae Watson, 1985

Figure 3A−F

Eudendrium album Pennycuik, 1959: 167 .

Eudendrium pennycuikae Watson, 1985: 183 , figs 5−8.

Material examined. NMV F202872 , jetty pontoon at Clifton Springs , Port Phillip, on ascidian Molgula ficus , depth 0.3 m, coll: J.Watson, 18/12/2013. Material examined alive, fixed in 4% formalin then transferred to 70% ethanol .

Description (from live material). Hydrorhizal stolons loosely reptant on ascidian. Hydrocaulus monosiphonic, of same diameter as stolon, to 16 mm high, sparsely and irregularly branched without definable main stem. Lowest branch with up to 15 wide annulations, upper branches with up to 10 proximal annulations at branch junction, younger branches smooth, older branches obscurely annulated or wrinkled but always smooth distally below hydranth.

Hydranth large, erect, terminal on branch, body constricted at base then becoming almost cylindrical, hypostome distinctly pedunculate, surrounded by 16-20 long tapering semiamphicoronate tentacles. No nematocyst rings or pads.

Developing female gonophore encircled by a moderately thick unbranched spadix, gonophores at various stages of maturity scattered singly or in clusters of two to five on blastostyle. Spadix lost at maturity, hydranth tentacles shortening and becoming resorbed, mature gonophores with approximately 20 ova attached to blastostyle on short peduncles. Male gonophores comprising two to four (usually three) linear bead-like chambers in clusters of up to 12 on a blastostyle without hydranth, distal chamber flat bun-shaped with scattered nematocysts; no apical nematocyst pad.

Cnidome comprising microbasic euryteles of one size, capsule elongate elliptical, 11−12 x 5−5.5 µm (undischarged), 8−9 x 4 µm (when discharged), shaft 4−6 µm long with a few spines, thread long; in tentacles and coenosarc.

Stolons and older stems pale honey brown, younger stems paler, hydranth body flesh pink, tentacles transparent, male gonophores almost white, spadix pale brown, female gonophores pale yellow.

Remarks. This is the first description of Eudendrium pennycuikae from live material, the original description of Pennycuik (1959) and Watson’s later redescription (1985) being from preserved material held by the Queensland Museum. The present record extends the range of E. pennycuikae from subtropical Queensland to cool temperate southern Australia.

The large elegant pink hydranths with a whorl of long subamphicoronate tentacles is a conspicuous character in live material, differing markedly from the small hydranths with a whorl of blunt tentacles typical of southern species of Eudendrium .

The capsule of the eurytele was found to shrink 15−20% during discharge; while capsules usually shrink about 10% at discharge (author’s obsv.) such a large reduction in size is unusual.