Thursday, 7 November 1996
Dear Johan,
You asked for information on the northern European species of Dodecaceria
Oersted. As you now must be aware, several of us are in total disagreement
with the taxonomy of Peter Gibson, including the "rather dramatic solution to
his problem in nomenclature" (Geoff Read, ANNELIDA, 7 Nov 1996) proposed by
Gibson & Heppell (1995). Five of us (Petersen et al., submitted) have sent
in a rebuttal to this application .
If your worms are in agreement with the figures in Hartmann-Schroeder 1971
(at least some spatulate neurochaetae as in fig. 127C), I'm pretty sure you
have the real D. concharum sensu Oersted, 1843 (= D. fimbriata sensu Gibson
1996). This is the type species of the genus and the only species at either
of the type localities (the Oeresund off Hellebaek, Denmark and the Kattegat
off NE Jutland, Denmark). It is also tolerant of lower salinities than D.
ater (= D. concharum sensu Gibson).
D. fimbriata (Verrill, 1879) (orig. as Heterocirrus fimbriatus) was
described from the Bay of Fundy, based on an epitokous individual; it is
either a junior synonym of the real, Danish D. concharum or a North American
sibling species of this. Terebella ostreae Dalyell, 1855 and D. caulleryi
Dehorne, 1933 (= D. concharum form B of Caullery & Mesnil 1898) are also
junior synonyms of D. concharum Oersted. Peter Gibson started using D.
fimbriata when he decided this was the same as D. caulleryi, which he
refused to believe was the only species in Danish waters and thus the real
D. concharum - he was convinced that there must be two species in Danish
waters (as in parts of UK) and that we just weren't looking the right
places. This is not the case, and intertidal habitats with "Lithamnion",
where Gibson has found the species in England, are not present in our
waters.
Oersted did not mention asexual reproduction in D. concharum, but since the
first record of this in polychaetes that I know of is in Kroeyer (1856), for
a sabellid, this is not so strange. We tend to see what we look for and
ignore things we don't understand.
D. concharum sensu Gibson is D. ater (Quatrefages, 1866), described from
material from northern France. The species is closely related to D.
saxicola (Grube, 1855) from the Mediterranean, and may be a junior synonym
of this, but apparent differences in reproduction of the two taxa suggest
that they should be kept separate until a more detailed picture of the
situation is available. Some of this is discussed in Petersen et al.
(submitted to BZN), which we were led to believe would have been published
in the June 1996 issue.
The two most common northern European species are easily told apart:
1. Body long and slender, middle segments often beadlike, posterior end
tapering; nuchal "slits" flat oval patches, inconspicuous; chaetae small and
inconspicuous, difficult to see at lower magnifications*; posterior segments
with spatulate neurochaetae, some or all of which with pronounced basal boss
(fig. 127c in Hartmann-Schroeder 1971); life history includes asexual
reproduction by fragmentation and when mature, male and female epitokes. . .
. . . . . D. concharum
*Epitokous capillaries of epitokes are easy to see; the above refers to
chaetae of the atokous individuals
-- Body short and broad, segments short throughout, not particularly
beadlike, posterior end broad and flattened; nuchal slits linear, usually
recognizable under a stereomicroscope; chaetae large and conspicuous, easy
to see; posterior segments with chisel-shaped (oar-shaped) spatulate chaetae
without basal boss (Fig. 1D in George & Petersen 1991); life history
incompletely understood, most mature individuals appear to contain
fertilized oocytes (parthenogenesis), but also sexually mature males,
apparently belonging to this species, with epitokous capillaries have been
found (McIntosh 1911) . . . . . . . . . . . . . D. ater
In the real D. concharum (= D. fimbriata sensu Gibson), most worms show
traces of asexual reproduction, usually as pigmentation differences, with
the regenerated portions paler, even in worms where the difference in size
between the original and regenerated segments is no longer conspicuous.
Chaetae are generally very inconspicuous and it is usually necessary to use
a higher magnification to see them, i.e., you will have trouble seeing or
counting acicular chaetae under a low power stereomicroscope. The basal
boss is most easily seen on neurochaetae of posterior segments or on
segments of the 2nd quarter of the body (there are 4 chaetal regions, with
the 2nd region starting about chaetiger 8-10). In Danish waters the species
is common in shells bored by Cliona and in dead shells of barnacles or
bivalves in Laminaria holdfasts. It does occur in subtidal "Lithothamnion",
but is not particularly common here. Color is variable, but young specimens
often are yellowish, older ones with more dark pigment but usually not
particularly black.
In D. ater (= D. concharum sensu Gibson), the body is relatively short and
broad, with short segments; in fixed material, the posterior end is broad
and flattened (if it is flattened in D. concharum it is slender). The
species is parthenogenetic, in some areas(?) also viviparous, and does not
reproduce asexually. Most of the specimens I have seen have contained
oocytes, but I have not seen a lot of material. This is the species that
does not tolerate lower salinity. I doubt you have this species. It is
often quite blackish.
Please note that while the above key will usually separate the two main
groups of Dodecaceria species in the Mediterranean, different species with,
inter alia, differences in reproductive biology and chaetal morphology,
appear to be involved. These species are currently under investigation by
me.
REFERENCES:
George, J.D. & M.E. Petersen. 1991. The validity of the genus Zeppelina
Vaillant. -- Ophelia Suppl. 5: 89-100, 1 fig.
Gibson, P.H. & D. Heppell. 1995. Case 2899. Dodecaceria concharum
O"rsted, 1843 and Heterocirrus fimbriatus Verrill, 1879 (currently D.
fimbriata) (Annelida, Polychaeta): proposed conservation of the specific
names by the designation of a neotype for D. concharum. -- Bulletin of
Zoological Nomenclature 52(1): 27-33.
McIntosh, W.C. 1911. Notes from the Gatty Marine Laboratory, St. Andrews,
No.XXXII. 3. On the British Cirratulidae. -- Annals and Magazine of Natural
History, ser. 8, 7: 151-162.
Petersen, M.E., J.D. George, J.A. Blake, K. Fauchald & K.W. Ockelmann.
(Submitted, December 1995) Comments to Case 2899. Recommendation that
Gibson & Heppell's requests to the ICZN in Case 2899 (deliberate
misidentification of type species of Dodecaceria Oersted, 1843 (Annelida:
Polychaeta) by designation of a neotype from a nontype locality and based on
a species not available to Oersted ) not be approved, with an appendix by
Mary E. Petersen with synonymies of the involved taxa. -- Bulletin of
Zoological Nomenclature.
******************
If this doesn't solve the problem, let me know where you need more
information. If nothing else, I can send you a few (small) specimens of D.
concharum from Danish waters.
Best wishes,
Mary
-------
Mary E. Petersen
Zoological Museum, University of Copenhagen
mepetersen at zmuc.ku.dk
**************************************************************
You wrote on 5 November:
>In our monitoring studies in the south-west of the Netherlands, ongoing
>since 1990, we found seven specimens of Dodecaceria. As Hartmann-Schroder
>(1971) only describes one species (D. concharum), we all identified them as
>such. Most of the species are found in the Grevelingen, a saline lake
>(chlorinity > 15.4 gCl/l, or a salinity of > 27.8 promille). But according
>to Gibson (1996), D. concharum is only found when the salinity is above 34
>promille. Therefore, we might have D. fimbriata instead of D. concharum.
>We checked some specimen using his description on p. 626: "the crotchets of
>D. fimbriata have a tooth at the proximal edge of the depression which is
>absent in D. concharum". We didn't see the tooth, however. Either, we
>misinterpret the description, or the specimen indeed are D. concharum.
>>Could anyone, therefore, give more information on the identifcation of both
>species. Where can we find descriptions with illustrations?
>>Thanks in advance,
>>Johan Craeymeersch
>craeymeersch at cemo.nioo.knaw.nl
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