The status of Aglaophamus neotenus Noyes

Igor Jirkov Jirkov at 1.hydro.bio.msu.ru
Fri Nov 15 11:13:22 EST 1996


Dear colleagues,
Sorry for silence, we was out.

Dr. Blake wrote
>Hilbig (1994: Taxonomic Atlas of the Santa Maria Basin
>vol. 4) determined that A. neotenus was a synonym of Nephtys cornuta
>Berkeley and Berkeley, 1945, and that the species agreed very well with
>the subspecies, N. cornuta franciscana Clark and Jones, 1955,
>originally described from San Francisco Bay.  Hilbig noted that N.
>cornuta ranged from the  eastern Pacific north to SE Alaska  and also
>occurred  in Maine,  the type locality for A. neotenus.  Hilbig noted
>that the characteristic bifid ventral antennae of N. cornuta also
>occurred in the specimens from Maine, but at a lower percentage
>suggesting to her that specimens from California and Maine represented
>two ends of a range of variability.  In other words, a kind of clinal
>variation.

>According to Dr. Jirkov, Aglaophamus neotenus is a valid species of
>Micronephthys and he compares it with M. minuta.  I do not see any
>indication in Jirkov's abstract that he found bifid ventral antennae;
>the distribution of branchiae and proboscideal papillae appear to be
>same as described by Hilbig for N. cornuta.

Dr. Hilbig wrote

>My feeling when I looked at a large number of specimens from both coasts
>of the U.S. was that maybe there are two species  in the making and they
>may be separated if I come back in a few thousand years to look again. The
>second antennae were not always clearly bifid, but they all had at least a
>basal thickening or a boss.


1. Studying Micronephthys from the White Sea, we found two species which
are very close each other. One seems to be identical to topotypes Nephtys
minuta Theel, 1879, earlier it became the type species of the genus
Micronephthys. As other species is very similar, we suppose it is
Micronephthys as well. This species is very similar to descriptions of
neotenus, that is why we supposed our species is M.neotena.

2. In our present article we wrote nothing about bifid antennae. Later we
found that large specimens of M.neotena have bifid lower antennae, lower
(smaller) branch is near 1/3 to 1/4 as long as larger branch. In smaller
worms small branch is smaller. The smaller worm the smaller branch and in
petit worms we can find only boss. The length of smaller branch seem to be
depend on contraction while fixation as well. So in this aspect (presence
of bifid antennae) our M.neotena is similar to Aglaophamus neotenus from
Main (this character did not mention in the original description).

3. As to M.minuta, our worms is not large and is not well preserved, and
the smaller branch of bifid antenna is very small, like boss.

Dr. Blake gave us choice:
our M.neotena is
>(1) A synonym of Nephtys cornuta
>(2) A valid species of Micronephthys

1. Is our worms M.neotena the same as Aglaophamus neotenus from Main? We
have not find any difference between them, but we did not compare worms.

2. Is our worms M.neotena the same as Nephtys cornuta? We cannot say.

3. But studying of available data on distribution of our two species we
can state, that M.minuta is arctic species, with south boundary of
distribution in the North European seas the East Barents Sea and the
arctic part of the White Sea. The M.neotena in our sense is the boreal
species distributed in the boreal part of the White sea and in the West
Barents Sea. There is no data from the Norwegian Sea, but in the North Sea
the new species of Micronephthys inhabits. This species is sharply differs
from both our species by setae and many other characters. (Paper is just
kindly checked by Mary and is ready for publishing). That is why we do not
believe that the same species occurs the North European sea and the
eastern Pacific.

Another question:
Dr. Hilbig wrote:
>By the way, having never seen a Micronephtys minuta, what exactly is
>Micronephtys?  It seems to me that the only character separating it from
>Nephtys is the small number of gills (or total absence thereof?).  If
>that is the case, I wonder if the genus is valid.

We can discuss it, but it seems to be too much for one message.
Wormly yours
Natalya & Igor

--- 
***************************************************
Igor A. Jirkov, Ph.D.
Scientific Researcher
Department of Hydrobiology,

Igor Jirkov <Jirkov at 1.hydro.bio.msu.ru>


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