Comprehensive DescriptionRead full entry
Colonies up to 20 mm in height.
Hydrorhiza tubular, wandering over and through the substrate, becoming erect at intervals as single stems.
Stems thick and smooth, unfascicled, sparingly and irregularly branched with up to 10 branches, rebranching common. Stems with 6-12 distinct proximal annulations, ringed at intervals throughout length, branches with 6-10 annulations just above origin.
Hydranths terminal on branches, pedicels indistinctly annulated at intervals, widening distally, sometimes terminating obliquely below hydranth. Hydranths large, with 24-30 tentacles (very long in life), a distinct proximal groove in the lower body of some, but not all hydranths.
Hypostome large, annular to clavate in preserved material.
Sexes on separate colonies, the gonophores scattered on all but the most distal branches. Male gonophores in all stages of maturity borne in a single crowded verticil below a hydranth with a fully-developed hypostome and a full number of partially-atrophied tentacles. Mature gonophore 3 or 4-chambered, immature gonophore with a rod-shaped spadix and a small apical knob without nematocyst pad. Mature gonophore globular or bun shaped, apical tubercule lost at this stage. Female gonophores borne low on stem, clustered in all stages of development below a hydranth with hypostome and a full number of partially-atrophied tentacles. Young gonophores on a long, thin pedicel, disk-shaped with unbranched spadix, mature gonophores retained below hydranth, oval, containing a single egg encased in a tough gelatinous pellicle.
Nematocysts, microbasic euryteles of two sizes present:
— Small microbasic euryteles, capsule 8-9 x 3-4 µm, shaft 6-8 µm long, with very long thread. Abundant in tentacles.
— Large microbasic euryteles, capsule 38-43 x 15-18 µm, bean-shaped, shaft discharging sideways, 30-36 µm long, distal end inflated and spirally annulated, with numerous bristles arising from the annulations, thread very long with distinct spines. Abundant around hypostome and scattered in groups over spadix of immature female gonophore.
Colour: Stems golden brown, body of living hydranth yellow or orange pink, tentacles pale yellow to pink, spadix of female gonophore purplish pink, mature eggs orange, male gonophores pearly pink, spadix orange pink.