Aplidium nordmanni (Milne-Edwards, 1841)

Aplidium nordmanni

Description: Colonies are usually thick crusts, divided into lobes. There are two colour forms, a white one and a pink one, this colour emanating from the test. The zooids are rather irregularly arranged around a series of large conspicuous cloacal openings in the upper surface of the colony. The six lobes of the oral siphon are heavily pigmented in white, as is the large atrial languet. The upper part of the branchial basket and endostyle are pigmented with white to a variable degree. 5mm thick x 20-50mm across.

Habitat: A typical surge-gully, upper infralittoral exposed water species. Usually on rock surfaces, also in more sheltered situations on vertical rock faces.

Ecology: Probably overwintering in a dormant form like most other polyclinids.

Distribution: Western coasts from Scotland to Cornwall and south to the Mediterranean. East coast records would be interesting.

Similar Species: The most distinctive, conspicuous and easily recognised polyclinid. Most likely to be confused with Botryllus schlosseri or Botrylloides leachii, or with Sidnyum elegans. Aplidium proliferum is considered to be a distinct species by some authors. If it is a distinct entity then it looks very like Sidnyum elegans but has only 6 papillae around the oral siphon.

Key Identification Features:

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

WoRMS: Species record : World Register of Marine Species.

iNaturalist: Species account : iNaturalist World Species Observations database

 Picton, B.E. & Morrow, C.C. (2016). Aplidium nordmanni (Milne-Edwards, 1841). [In] Encyclopedia of Marine Life of Britain and Ireland.
https://www.habitas.org.uk/marinelife/species.asp?item=ZD610 Accessed on 2024-07-13

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