There is no doubt that even though the Mediterranean is well investigated,
its biodiversity is greater than presently indicated, with or without
introduced _Caulerpa taxifolia_. We can therefore expect a large number of
new and newly reported taxa as the different groups are critically reviewed
One of the reasons for this is that modern criteria often reveal that what
earlier was considered INTRAspecific variation is actually INTERspecific
such. Moreover, many older species descriptions in reality only describe
the genera, without sufficient information to permit accurate species
recognition. I have found this often in, e.g., _Pholoe_, cirratulids and
chaetopterids, many of which are very broadly defined. Most of the
Mediterranean species I have seen are either undescribed or newly reported,
yet many of them are hiding under well known names which may belong to
species not even present in the area. Within a restricted area it is
usually not a problem to recognize the individual species present. The
difficulties arise when local species must be differentiated from similar
ones from distant areas.
This brings in the problem of endemic and introduced species. Having seen
some Mediterranean cirratulid species that were uncomfortably close to ones
in other parts of the world, e.g., California, and not knowing if they were
the same or introduced one place or the other, I came to think of a paper
presented at the 1989 Long Beach polychaete conference by Thomas G. Douglas
and Ira Jones (1991. Parasites of California spionid polychaetes. -- Bull.
Mar. Sci. 48 (2): 308-317).
These authors point out that one of the ways one can recognize recently
introduced species is that they usually LACK their normal assortment of
endoparasites, thus the spionid _Pseudopolydora paucibranchiata_ had none,
suggesting a recent introduction to the coast of southern California. Among
the endoparasites present, at least for the gregarines the authors suggested
that there might be some species specificity and that it might be possible
to identify the polychaete species from its parasites.
This approach to distinguishing between native and introduced species would
seem to have an advantage over more traditional electrophoretic techniques
in that it not only would show a difference (with and without endoparasites)
but also would make clear which population was more likely to be the
original one. The difficulty is that it requires specialist knowledge that
most of us lack and would have to acquire.
Are there other recent studies on the use of endoparasites for
differentiating native and introduced populations of a species?
How much do such endoparasites (e.g., gregarines, coccidia, microsporidia,
mesozoans, bacteria) influence differences obtained by electrophoretic
comparisons of different populations? I have not used these techniques, so
my apologies for unenlightened questions, but I could imagine that the
presence or absence of certain bands might be due to the presence or absence
of certain parasites and not because of differences in the polychaetes.
Has anyone done anything with this? Are there standard techniques for
cleaning very small specimens before use to minimize or eliminate such
With greetings from Copenhagen,
Mary E. Petersen
Zoological Museum, University of Copenhagen
Universitetsparken 15, DK-2100 Copenhagen O, Denmark
Tel +45-35 32 10 67 Fax +45-35 32 10 10
E-mail: mepetersen at zmuc.ku.dk
Problems with Mediterranean (or other) cirratulids, ctenodrilids or
chaetopterids? Contact me at above E-mail for more information. Mary.