Halicnemia verticillata (Bowerbank, 1862)

Order : AXINELLIDA

Family : Stelligeridae

Form: Thin encrustations, lateral size up to 3.5 x 2 cm.

Colour: Lemon yellow

Consistency: Firm.

Surface: Granular.

Internal characters

Skeleton: Ectosomal : a dense mass of verticillate oxeas/strongyles. Choanosomal : single long tylostyles erect on the substrate, heads downward, pointed ends protruding beyond the surface; bundles of centrotylote oxeas surround these tylostyles.

Spicules: Tylostyles, with long, rounded tyle: 1900-2800 x 20-25 μm; centrotylote oxeas: 490-1600 x 12-25 μm; verticillately spined oxeas / strongyles: 90-120 x 4-5 μm; growth stages of the latter may be smoothly polytylote.

Habitat: Underneath overhangs on rock and also on pebbles, from 40 m downwards to 1000 m.

Distribution: Roscoff, SW Ireland, Shetlands, Orkney, Faroes, Norway.

Distribution Map: NBN map : National Biodiversity Network mapping facility, data for UK.

Identity: The only species with similar granular appearance and spiculation is Halicnemia patera. This is softer in consistency. The microxeas of that species are angularly bent and the spines are not in verticils.

Editors: Christine Morrow, Bernard Picton & Rob van Soest.