Dear Fredrik et al,
Well, I can't argue cladistics but I have been taking a hard look at the
Nereididae and the Nereis/Neanthes/Hediste group in particular.
Traditionally, we have focused on setae and paragnaths in describing
these species and genera. Unfortunately, the numbers of paragnaths
appear to be related to environmental conditions, particularly salinity.
Looking at the STRUCTURE of the parapodial lamellae, on the other
hand, is extremely illuminating: Neanthes has a complex series of lobes
and folds surrounding the supra and sub-acicular bundles (interference
phase contrast needed, SEM helpful). Nereis has just a couple of simple
lobes. Hediste is more like Nereis in this regard but does have those
homogomph falcigers in the posterior neuropodia. More, it seems to
comprise a very morphologically similar set of sibling/cryptospecies from
euryhaline/freshwater littoral zones.
More research is needed but I am convinced it will bear out the
separation of these genera. Part of the problem seems to the extreme
"familiarity of the Nereididae: they are among the most common and
most frequently encountered polychaetes in shallow zones along the
coast (where most marine research is concentrated). We all "know"
what they look like. A really hard look might bring up some major
surprises, but will likely not end the controversy.
Judy Fournier
<110275.1004 at compuserve.com>
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