''Hydractinia altispina'', or high-spined commensal hydroid, is a small colonial hydroid in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Hydractiniidae Hydractiniidae is a cnidarian family (biology), family of athecate hydroids. Genera The World Register of Marine Species includes the following genera in the family: *''Bouillonactinia'' Miglietta, McNally & Cunningham, 2010 *''Clava (cnidarian ...

Description

High-spined commensal hydroids grow as a fuzzy-looking orange coat usually on the shell of a

marine snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

, the scaly dogwhelk ''

Nucella squamosa ''Nucella squamosa'', common name the scaly dogwhelk, is a species of sea snail, a marine gastropod mollusk in the family Muricidae, the murex snails or rock snails. Description The scaly dogwhelk is a small brown whelk with many fine knobbly ...

''. Individual polyps grow to 0.4 cm in total height. The polyps are naked and cluster on the shell surface, interspersed with defensive spines and tiny ball-like reproductive structures.Millard, N.A.H. 1975. Monograph on the Hydroida of Southern Africa. ''Ann. S. Afr. Mus.'' 68:1-513

Distribution

This colonial animal is found only off the southern African coast from Luderitz to False Bay, Cape Town subtidally and to at least 30m under water.

References

Hydractiniidae Animals described in 1955 {{anthoathecata-stub