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Rhizorhagium navis

Millard, 1959


Marco Faasse What was known as an extremely rare hydroid (Clavopsella navis) is probably an alien form North America: http://lancingwidewater.com/2012/11/370/ ...

Marco Faasse Its specific name 'navis', referring to the first find on a ships' hull in Cape Town, should have warned us ...

Andy Horton Location page: http://www.glaucus.org.uk/Brackish.htm All so called rare organisms in the lagoon are mostly thought to be absent or misidentifications. The 1997 survey failed to discover this hydroid. The species was added to Schedule 5 of the Wildlife and Countryside Act 1981 in 1998, after being penned for inclusion in August 1996

Carel Sartory Facebook Hi Marco, Sorry for a short, somewhat belated reply. I "discovered" this hydroid in Widewater lagoon in 1973 and after much searching through various tomes with Paul Cornelius at the Natural History Museum; we identified it as Clavopsella navis (Millard, 1959). She first called it Rhizorhagium navis when she found it in Cape Town docks. It was independently described by Thiel in 1962 as Clavopsella quadranularia when he found it in the Kiel Canal. I subsequently corresponded with Dr Millard who agrees that the unusual distribution is likely to be due to ship bourn transmission (as well as being a distribution map of hydroid nuts, rather than a true measure of its actual distribution!) What makes you think that North America is the source location? Over the next few years I regularly visited Widewater but failed to find C navis again. In 1972 it was very abundant on the algae in the lagoon. Also very abundant was Obelia Longissima growing on the concrete blocks enclosing parts of the lagoon. They were the largest O longissima I (or P Cornelius) had ever seen; some 400mm long. The lagoon also contained several Obelia medusae, presumably O longissima. After the so-called “clean up” of the lagoon in the early 1980s I didn’t find either species again, however due to its diminutive size and its ability to look like a mucus ‘blob’, it is easily overlooked! Was it found again in the lagoon in 1990? I cultured C navis in aquaria for over 3 years; studying its behaviour, and have a number of images of both live and preserved specimens. Sadly due to several moves and other commitments I never wrote"up my findings. Perhaps I should do so now. Please contact me at carel.sartory@orange.fr if you want any more information M & Mme SARTORY Carel 10 rue du 19 mars 1962 87210 LE DORAT France

Bernard Picton Marco Faasse, can you PM me Dave Fawcett's email address please? This does show that JNCC are spending money on obscure species where the basic taxonomy has never been done yet. I wonder if there is any sign of the anemone Edwardsia ivelli (presumed extinct).

Marco Faasse Hi Carel Sartory, Thank you very much for your reply. How nice to hear from the discoverer of Clavopsella navis in Europe. I will send you a an e-mail. I identified the species from The Netherlands after having seen its reproduction in captivity. At the moment I only knew about the finds in Cape Town, Widewater Lagoon and Kiel Kanal, while the species seemed to have disappeared at all these locations. Peter Schuchert, in his new Synopsis on NW Atlantic athecate hydroids suggests it may be identical with Pachycordyle michaeli. Calder (2012), writing on Hydrzoa of Sweden, stated Clavopsella navis is a junior synonym of Pachycordyle navis.

Marco Faasse Best wishes,

Marco Faasse Marco

Marco Faasse Bernard Picton, I asked Dave Fawcett whether E. ivelli has been seen recently; he knows of no recent records. I'll try to bring you into contact with him.

Marco Faasse Sorry, Carel Sartory, a correction: Calder (2012), writing on Hydrozoa of Sweden, stated that Clavopsella navis is a junior synonym of Pachycordyle michaeli (from North America)!

Carel Sartory FacebookHi Marco, When I was investigating C navis at Widewater, I also looked for E ivelli but without success. However I was not able to dredge or investigate the sediment bottom in the open water part of the lagoon, This is where I suspect it might have been if it was still extant from reading Ivells PhD thesis and from Richard Manual’s original paper, who named it. It is a small contractile animal living in soft mud and easily overlooked. I am not sure that C navis is identical to Pachycordyle michaeli but I have never had the opportunity to examine live P michaeli from America and I hesitate to question an authority like Calder. Carel M & Mme SARTORY Carel 10 rue du 19 mars 1962 87210 LE DORAT France E-mail: carel.sartory@orange.fr

Andy Horton A sea anemone was discovered at Widewater, but not Edwardsia ivelli. Do you have details please?

Andy Horton PS: I am far from sure that Edwardsia ivelli is/was a good species ???

Message posted on NE Atlantic Cnidaria on 18 Nov 2012
Taxonomy
Animalia (Kingdom)
  Cnidaria (Phylum)
    Hydrozoa (Class)
      Hydroidolina (Subclass)
        Anthoathecata (Order)
          Filifera (Suborder)
            Bougainvilliidae (Family)
              Rhizorhagium (Genus)
                Rhizorhagium navis (Species)
Associated Species