(by g.read from niwa.co.nz)
Sun Apr 22 19:24:54 EST 2007
Serge Utevsky wrote:
> Hirudo verbana and Hirudo medicinalis were distinguished based on
> morphological characters (see the pioneer work by Nesemann & Neubert
> 1999). The molecular analyses just corroborated that conclusion and
> revealed a new Hirudo species H. orientalis, which can be easily
> identified by its coloration pattern.
Thank you. While its tight focus didn't consider all available relevant
evidence on the species I see Siddall et al. 2007 as an interesting and
useful piece of research on which overall I would be pretty happy to
have my tax dollars spent. The title was "Diverse molecular data
_demonstrate_ that commercially available medicinal leeches are not
Hirudo medicinalis", and possibly then, disregarding for the moment the
significant "commercially available" qualifier, the outcome can be more
regarded as a reconfirmation of a problem rather than a first demonstration.
It is evident that there are several internal anatomy
medicinalis/verbana differences (including from Utevsky & Trontelj
2005, and possibly from Hetchel & Sawyer* 2002), known before the DNA
data. This is reassuring to a taxonomist/biologist. However, there is a
statement on the first page of the Siddall et al 2007 paper that "The
lack of clear internal anatomical differences has been an impediment to
accurately delimiting leech species ...". One would be mistaken then if,
as a reader only of this paper, one took from the context that the
generalisation also applied to the case of medicinalis/verbana, such
that there were no obvious (to experts) anatomical differences to match
the different colour patterns distinguishing the taxa. There is no
mention of anatomical differences in the scene-setting introduction.
Further, in the discussion it is only said that "recent work", cited but
nature undefined, pointed to more than one species.
As for the history of the taxonomy I wondered how categorically H.
Carena (1820) had first erected H. verbana, an aspect not discussed in
some recent papers. I don't have access to Nesemann & Neubert (1999) so
I quote Kutschera** (2006).
"Sixty years later [after H. medicinalis Linnaeus], a second, more
colourful thermophilic leech of similar size was discovered in Italy and
described in 1820 as a nova species (Carena***, 1820). In his Fig.6 on
plate 11 the author depicted a representative specimen in such splendid
detail that H. verbana (Locus typicus: Lago Maggiore, lat. Lacus
Verbanus) can be easily distinguished from H. medicinalis. The leeches
from Lacus Verbanus have a green-yellow basal colour with a
red/orange-pigmented longitudinal reticulum on the dorsal side and no
(or only very few) dark spots on the ventral surface that is
characterized by a pair of black marginal stripes."
*Hechtel, F.O.P. & Sawyer, R.T. (2002) Toward a taxonomic revision of
the medicinal leech Hirudo medicinalis Linnaeus, 1758 (Hirudinea:
Hirudinidae): re-description of Hirudo troctina Johnson, 1816 from North
Africa. Journal of Natural History, 36, 1269 - 1289.
**Kutschera, U. (2006) The infamous blood suckers from Lacus Verbanus.
Lauterbornia, 56, 1-4.
***Carena, H. (1820) Monographie du genre Hirudo ou description des
espéces de sangesues qui se trouvent ou qui sont en usage en piémont,
avec des observations sur la génération, et sur d'autres points de
l'histoire naturelle de quelques unes de ces espéces. Memorie della
Reale Accademiadelle Scienze die Torino, 25, 273-316.
Geoff Read <g.read from niwa.co.nz>
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