Identification:
The major larger claw is always on the left side nearest the apex
of the adopted shell when viewed from the front.
The Hermit
Crab on the left is Diogenes pugilator with the major claw on the
left.
Similar species: Pagurus
bernhardus
Pagurus
cuanensis (CD-ROM ONLY)
Breeding:
Habitat:
Strandwerkgroep
file
Food:
Bionomics:
Range:
Additional Notes:
More Information
I was
interested in your recent find of a couple of Diogenes.
It is a species with an interesting distribution and interesting habits.
Some years ago I supervised at least two summer MSc projects on it. Since
I think MarLIN have yet to do a page
on it I thought you might be interested in a few comments.
The
distribution round Britain and Ireland is or was generally southwestern.
In the Irish Sea it comes up the Welsh coast as far as the
west
coast of Anglesey. Here it occurs commonly on certain flat slightly
exposed
beaches and just offshore from them. For example at Aberffraw I can
find
20 - 50 in a few minutes if I go at an evening LW in July and August
when
they are active and out of the sand. The distribution is clumped -
possibly
sexual activity rather than fighting for shells. Most are only in
ankle
deep water at this time so are easy to see. Although quite abundant
on
the right sort of beach on the west coast of Anglesey they do not as far
as
I know extend round to the east side of the island. There are no records
from
the east coast of Ireland but there are on suitable beaches in
Cardigan
Bay, Carmarthen Bay and Gower. Interestingly, the illustration in
Bell's
"Stalk-eyed Crustacea" is one from Rhosslli in Gower.
Virtually
all the beaches where I know of them in Wales are flat beaches
with
medium / fine sand and where the waves spill rather than curl when
breaking.
Diogenes burys rapidly and our hypothesis is that the south-paw
arragement
of the chelae is connected with burying. They seem to use the
major
chela as an anchor to stabilise the shell while digging themselves
into
the sediment. In some circumstances they can be seen using the major
chela
in such a way was to limit the rolling of the shell in the wave
swash.
If you have Pagurus and Diogenes together in similar shells,
the
Diogenes
become active after disturbance much more quickly. An adaptation
to
re- bury quickly.
Concerning
the distribution in the SW and English Channel. The MNCR
database
did not have any records from the north side of the SW peninsula,
not
counting the Scillies, but on the S side they had them as far east as
Lyme
Bay. Like several other things they did not normally seem to get past
Portland
Bill. This makes your Sussex record particularly interesting. On a
beach
near Plymouth (name forgotten) thety were sufficiently abundant to be
used
as test animals for dispersant toxicity at the time on the "Torrey
Canyon".
However on the French side of the Channel they seem to be abundant
at
least as far as the Straits of Dover. I know less of the French
literature,
but in August this year we were doing work in the Channel on
fish
habitats and found them abundant in a small mesh beam trawl at a depth
of
17m off Le Touqet. As in North Wales most were in Hinia shells.
For
the record, they were found in a few places on the west coast of
Ireland
as far north was Donegal in the Irish equivalent of the MNCR. These
are
the furthest N I know of in the British Isles.
Whereas
most Britsh records are from beaches, off S Spain and Portugal they
seem
to be common subtidally on sandy grounds to judge from the literature
on
their reproduction etc I have turned up.
Naturally
I would be interested in any more you find and in the types of
area
they come from.
Ivor
Rees
Reports:
6 October
2002
The
low tide on Lancing beach revealed my very
first discovery of the South-claw Hermit
Crab,
Diogenes pugilator, on the
Sussex coast. This Hermit Crab was discovered in knee depth water in the
sandy shallows below the low tide mark on the equinoctial spring tide,
receding below Chart Datum. They occupied
the empty shells of the Netted Dogwhelk, Hinia.
Full
Report
Links:
Hermit Crabs for the younger student (NE Atlantic
species only)
Information wanted: Please send any records of this crab, with
location, date, who discovered it, how it was identified, prevalence, common
name and any other details to
Shorewatch
Project EMail Glaucus@hotmail.com.
All messages will receive a reply.
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