[Annelida] help on determination of Praxillella and Clymenura

Geoff Read via annelida%40net.bio.net (by g.read from niwa.co.nz)
Tue Oct 20 15:19:01 EST 2009


Those interested who don't know of Garwood (2007) can get it at:

http://www.nmbaqcs.org/scheme-components/invertebrates/literature-and-taxonomic-keys.aspx

Barbara,

This is not a part of the world I am experienced in but I can make some initial comments. If Garwood's nice indications for id'ing ant or post ends of (British Isles) maldanids don't get you an id then it probably can't be done. Pygidiums can be quite distinctive, and lacking them one can struggle. 

I don't know much about Praxillella. lophosetosa (a lapsus, actually lophoseta(?), originally apparently Clymene lophoseta Orlandi, 1898), and while WoRMS currently has an entry for that combination, another entry places it as a synonym of P. affinis. I do not know who made the synonymy or whether it is accurate, without doing further investigating, but it may partly originate from Hartman's catalogue (p.454), and she most likely would have got it from somewhere else. Unfortunately, as with all her placements,  such source information, which would be hugely useful today, was not included in the catalogue - it may have existed only in her head or on an index card somewhere.

http://www.marinespecies.org/aphia.php?p=taxdetails&id=130322

Geoff

>>> On 20/10/2009 at 10:20 p.m., Barbara Mikac <barbara.mikac from cim.irb.hr> wrote:
> Dear colleagues,
> 
> Can you advice me how can I determine Praxillella species based only on
> the front part of the animal containing the head (thus it's not possible
> to count the number of chaetigers). Sometimes I also have only pygidium,
> but then usually without the front part. In the Adriatic Sea there
> should be present: P. affinis, P. gracilis, P. praetermissa and P.
> lophosetosa. P. gracilis should be easy to determin because it should
> have distinctly elongated palpode on the prostomium. P. affinis should
> have ocelli and P. praetermissa not. But what about P. lophosetosa? Are
> the characteristics I mentioned above sufficient to distinguish the
> species anyway?
> 
> I also have a problem to determine Clymenura clypeata and C. tricirrata,
> that could be both potentially found on the stations I am working on.
> It's quite easy when I have the pygidium, because if it has muscular
> ring with three cirri originating from it, I know it's C. tricirrata. On
> the other hand if it only has a muscular ring forming a pygidial plate
> and an anal cone with a well developed ventral valve (Garwood, 2007) I
> know it's C. clypeata. Most of my animals unfortunately lack the
> posterior part/pygidium. Is there some way to distinguish two species
> based on the front part of the animal?
> 
> Thank you very much for your help!
> 
> Barbara
> 
> ________
> Barbara Mikac, M.Sc.
> Marine Research Centre 
> Rudjer Boskovic Institute
> G. Paliaga 5
> 52210 Rovinj
> Croatia


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