Colour variation in the False Bay Cerianthids
Peter Southwood
Cape Town, 2005

On 28th September 2002 I dived at Photographers Reef (S34 deg 11.839. E018 deg 27.434.), at Boulders, Simon's Town. There I saw what is recorded in my logbook as "Things in tubes that look like anemones, but have short tentacles in the middle and retract when disturbed." Luckily I had a camera with me at the time, so I took a couple of photos. The photos came out OK, but I had no idea what these animals might be. They looked rather like anemones, but had short tentacles in the middle, and lived in floppy grey tubes, which seemed a bit odd for anemones, but the tentacles looked wrong for tubeworms.

In 2003 the False Bay Underwater Club hosted a series of lectures by postgraduate students from UCT on the local Marine ecology, and I mentioned these strange critters to one of the lecturers, Robyn Scott, and mailed her a photo. She showed it to Charles Griffiths at UCT and mailed me back to say "They are from an order called ceriantharia. This is an order of animals that are very much like anemones. They have greatly elongated bodies adapted for living with secreted tubes buried in sand or mud. There are no known species in S.A. The South African Museum in town has one specimen, and would appreciate any others. Charlie has photographed a Cerianthid in Table Bay, a large animal with white inner as well as outer tentacles. These little guys are different because of their long bodies, inner tentacles as well as the sand tube they build."

Over the course of the next few months we collected specimens of the False Bay cerianthids from Vogelsteen (S34 deg 10.302', E018 deg 50.355'), in Gordon's Bay, and Table Bay cerianthids from Cape Town harbour, and sent them to anemone taxonomist Dr. Fabian H. Acuna, at Departamento de Ciencias Marinas, Universidad Nacional de Mar del Plata, Argentina, who was able to identify the Table Bay specimens as Ceriantheopsis nikitai (see image on left). This was confirmed by Tina N. Molodtsova of the P.P.Shirshov Institute of Oceanology, in Moscow, who originally described the species from Namibia, and is now studying the as yet unidentified False Bay cerianthid which appears to be an undescribed species.

Cerianthids are classed as:
  • Kingdom Metazoa: Multi-celled animals.
  • Phylum Cnidaria: Stinging-celled animals; tissue-grade life, no organs, three cell layers.
  • Class Anthozoa: Single or colonial polyps; no medusa stage; no cover on stinging cells.
  • Order Ceriantharia: Tube anemones; no pedal discs; one ciliated mouth opening.

Distribution The False Bay cerianthids have now been recorded from a number if sites on both sides of False Bay, from Castle Rocks, Insanity Reef, A-Frame, Wave Rock/D-Frame, Photographer's Reef, Phoenix Shoal, Long Beach, Sunny Cove, Kalk Bay, Glencairn Quarry, Vogelsteen, Cow and Calf, Pinnacle, Troglodytes Cove, Tony's Reef, Rocky Bay, Bloukrans, Whirlpool Cove and Percy's Hole.

Colour variations A number of colour variations have been recorded. These include Blue, Lilac, Pink, Red-brown, Orange, Yellow, Beige and a combination of Brown and white.

Commensals A number of organisms have been found living in and on the tubes of the False Bay cerianthids. These include polychaete worms of at least two species, small brittle stars and what look like peanut worms, which were living in holes in the tubes.

Cerianthids are not really anemones despite their anemone-like appearance. They are more closely related to the black corals than to any of the true anemones or corals. They superficially resemble anemones, but the internal differences are so great as to group them in a different subclass (the Ceriantipatharia). They have a planktonic larval stage.
Unlike the true anemones, these animals lack a pedal disk for attachment to a substrate, and instead live in a tube which is buried in sandy or muddy sediments. This tube consists of a fibrous material similar to felt, which is formed by the discharge of special cnidae (the stinging cells of all cnidarians, with nematocysts being the most common kind) called ptychocysts which are found in only the cerianthids. Cerianthids have a crown of tentacles that consist of two whorls of distinctly different sized tentacles. The outer tentacle whorl consists of large tentacles that extend laterally. These tentacles taper to distinct points and are used primarily in food capture and defence. The smaller inner whorl tentacles are held more erect than the larger lateral tentacles and are used primarily for food manipulation and ingestion.

Photo of planktonic larval stage of a different cerianthid:
http://www.imagequest3d.com/pages/current/pictureoftheweek/tubeanemonelarva/tubeanemonelarva.htm
Technical information about similar organisms:
http://hercules.kgs.ku.edu/hexacoral/anemone2/index.cfm
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