Description: This hydroid is most likely to be mistaken for Abietinaria abietina but is much smaller in all its parts. The main stem is unbranched or sparsely branched, with regularly spaced, alternate side branches in a flat plane. The hydrothecae are subalternate on both the stem and side branches. Typical colonies measure about 30mm in height, but can become elongate and branched to 100mm.

Habitat: Usually found attached to bedrock and boulders in strong wave action or tidal streams but can also grow on shells and cobbles.

Distribution: Widespread around the British Isles but more comon in the North.

Similar Species: Most likely to be confused with small colonies of Sertularia argentea which have not started to branch in three dimensions.

Key Identification Features:

• Subalternate hydrothecae borne on side branches and main stems
• Size and spacing of hydrothecae similar to Sertularia argentea and much smaller than Abietinaria abietina

Distribution Map from NBN: Abietinaria filicula at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Abietinaria filicula at iNaturalist World Species Observations database.

WoRMS: Abietinaria filicula at World Register of Marine Species. Accepted name: Abietinaria filicula (Ellis & Solander, 1786). AphiaID: 117871.

Classification: Biota; Animalia; Cnidaria; Medusozoa; Hydrozoa; Hydroidolina; Leptothecata; Sertularioidea; Sertulariidae; Abietinaria