[Annelida] help on determination of Praxillella and Clymenura

Barbara Mikac via annelida%40net.bio.net (by barbara.mikac from cim.irb.hr)
Tue Oct 20 04:20:53 EST 2009

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 Mikac, M.Sc.
Marine Research Centre 
Rudjer Boskovic Institute
G. Paliaga 5
52210 Rovinj

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