http://www.collembola.org/publicat/restore.htm
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Last updated on
2008.10.26
by Frans Janssens
Frans Janssens,
Department of Biology, University of Antwerp, Antwerp, B-2020, Belgium
Ab H. Baas
European Invertebrate Survey - Nederland, Postbus 9517, 2300 RA Leiden, Nederland
Abstract
Tbd...
Introduction
It is known that Collembola are stimulated to moult in case of
a damaged appendage, such as a broken antenna.
We present here a case of Tomocerus vulgaris
that moulted in a culture after
severely being damaged while collecting it alive.
Materials and methods
On October 5, 2008, a humus sample was taken, by the junior author, from Hardenberg,
the Netherlands, at the
Collendoornerdijk 100m away from the roundabout of the Jachthuisweg, at the
right side between the trees
(UTM 32U 337059.80 m E 5828396.14 m N).
The sample was placed in a plastic culture box with a floor made of a mix of
plaster of Paris and charcoal.
The plaster was moisted and the culture was fed dried aquarium fish food.
The culture was kept at room temperature.
The sample contained several specimens of Orchesella cincta
and one specimen of Tomocerus.
Results
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Fig.2. Tomocerus vulgaris
Just after 1st moult
Specimen from Hardenberg, the Netherlands
2008.10.06 © Baas, A.H.
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Fig.1. Tomocerus vulgaris
Just before moulting
Specimen from Hardenberg, the Netherlands
2008.10.05 © Baas, A.H.
The scale cover of the Tomocerus specimen was severely damaged.
It was damaged up to the point
that it was not possible anymore to use the scale cover characteristics as a
diagnosis for a definitive identification at species level
based on a habitus inspection.
The specimen was tentatively identified by the senior author
as Tomocerus minor, based on the
subcylindric antennae and the fact that in previously collected samples
from the same region
other Tomocerus minor specimens have been found.
On October 5, 2008, the specimen remained immobile for several hours.
Apparently, it was in apolysis stage,
a pre-moulting stage in which the epidermis separates
from the cuticle of the previous instar.
An instar in such a state is said to be in pharate state, refering to an
instar cloaked within the cuticle of the previous instar, just before moulting.
In the early pharate state, the instar is immobile.
On October 6, 2008, the specimen was moulted. It turned out to be
Tomocerus vulgaris, not Tomocerus minor.
Discussion
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Fig.3. Tomocerus vulgaris
Just after 2nd moult
Specimen from Hardenberg, the Netherlands
2008.10.10 © Baas, A.H.
The Tomocerus vulgaris specimen was damaged in several ways (see fig.1):
1. the scale cover was almost removed completely. As such the specimen
is treathened by dehydration.
2. except for the collar, all the dorsal setae have been lost. In this way
the specimen is severely handicapped in its contact with the environment.
3. the right antenna is broken: the fourth antennal segment and the apical
part of the third antennal segment is lost. In this way the specimen lost
half of its food tasting capabilities.
4. the right proleg is missing.
These conditions will stimulate the specimen to shorten the normal
intermoult period and to go in an early pre-moulting stage.
This in order to restore the lost bodyparts and capabilities as soon as
possible.
In the moulted specimen (fig.2),
1. the scale cover is completely restored,
2. all dorsal setae are restored,
3. the right antenna is partly restored: the third antennal
segment has become longer then before the moult, an indication of a kind of
fused third and fourth antennal segment,
4. the right proleg is partly restored.
After a second moult, 4 days later, the right proleg is restored
completely (fig.3).
Conclusions
In Tomocerus vulgaris, damaged body parts are restored by the
regeneration of these damaged body parts in a series of subsequent moults.
A habitus inspection of Tomocerus specimens that have a severely
damaged scale cover is insufficient to identify the specimens at
species level.
References
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