Cladocoryne minuta

Hydranths arising at intervals from an unbranched tubular stolon creeping up stem and along hydrocladia of host; caulus short, without demarcation from hydrorhiza, straight or bent, to 0.3 mm long, expanding a little distally below hydranth, perisarc weakly rugose or smooth, perisarc of stolon and caulus thin and fragile. Hydranths to 0.5 mm long (preserved), body cylindrical with dome-shaped hypostome surrounded by four to six rather short branched aboral tentacles in two whorls, each tentacle with three or four opposite pairs of short capitate side branches, a terminal capitalum on branch; four short capitate oral tentacles. Capitula 300-400 µm diameter composed of a globular cluster of nematocysts; some hydranths also with a few large scattered nematocysts enclosed in a blister of tissue between aboral and oral tentacles; same kinds of nematocysts also scattered throughout hydrorhiza and caulus.

Gonophore a globular fixed sporosac, one on hydranth on a short pedicel among basal aboral tentacles, gonophore 500 µm diameter (preserved), an aureole of large nematocysts (categories 1 and 3 below) scattered on top third of body.

Cnidome comprising three kinds of nematocysts:

1) Stenoteles, capsule subspherical to ovoid, 11-13 x 10 µm, in capitalum of tentacles and on gonophores.

2) Stenoteles, capsule subspherical to ovoid, 7 x 5 µm, in capitalum of tentacles.

3) Mesobasic euryteles, capsule oval, 3~34 x 18-21 µm, on body of hydranth, on gonophore, in coenosarc of caulus and hydrorhiza.

Colour: White

This species is named ‘minuta’ in recognition of its small size.

Holotype: NMV F101644, fertile colony on stem of Gymnangium ascidioides, Cape le Grand, Western Australia, depth 17 m. Paratype: WAM Z29950, infertile colony on stem of Gymnangium superbe, New Island, Western Australia, depth 20 m.

Western Australia.

Subtidal, epizoic on other hydroids.