http://www.collembola.org/publicat/eggdepos.htm
-
Last updated on
2016.12.24
by Frans Janssens
Frans Janssens,
Department of Biology, University of Antwerp, Antwerp, B-2020, Belgium
Marie Louise Huskens,
Opitterkiezel 223 bus 0.1, B-3960, Opitter, Belgium
Abstract
It was observed that in Sminthurides aquaticus,
the eggs are deposited in cuplike depressions
of the epidermis of Lemna minor. The cups have been chewn out by the
female, prior to laying the egg.
The egg is covered with a faecal pellet.
Introduction
In Collembola,
the eggs are fertilised within the female before laying using stored sperm
(Hopkin, 1997:140).
Once the eggs have been laid, they are subject to a wide range of predation
pressures, not least by Collembola themselves;
thus there is a strong selective pressure to hide the eggs in crevices and
make them as inconspicuous as possible.
(Hopkin, 1997:142).
Caretaking of the eggs by the females of Sminthurides aquaticus has
been observed already in 1907 : Lemna minor is chewn out
and eggs are deposited in it
(Klugkist 1907 cited from Schaller, 1970:50).
For this Sminthurides aquaticus was considered a parasite of
Lemna minor.
Material and methods
Specimens were collected from the surface of a pool in Opitter, Limburg, Belgium,
near to the Itterbeek and the Zuid-WillemsVaart.
At 2016.MM.DD the specimens were gently blown into a shallow container,
held tilted at the
water surface, using a mouth operated aspirator in reverse fashion.
The concentrated specimens were then transported to a small pond covered
with Lemna minor in the garden of the second author
and kept as such in culture for several months.
Observations were performed indoors on a staged set-up.
Photographs were made using a digital reflex camera Canon EOS 80D.
A Canon MP-E 65mm lens was mounted on the camera using a
set of Kenko extension tubes (12mm + 20mm + 36mm).
Illumination was provided by a Canon Macro Ring Lite MR-14EX
and a Falcon Eyes SLP-120LTV LED Lamp.
Results
The indoors stage was set-up and after a short aclimatisation period the
females started with their oviposition activities.
At first the epidermis of Lemna minor was chewn out to form a shallow
cuplike depression (fig.1). In such a cup, an egg was deposited (fig.2).
Afterwards, the egg was covered with a faecal pellet (fig.3).
 |
Fig.1. Sminthurides aquaticus ♀ chewing out a 'nest'.
Huskens, M.L. © 2016.07.28
 |
Fig.2. Sminthurides aquaticus ♀ depositing egg.
Huskens, M.L. © 2016.07.28
 |
Fig.3. Sminthurides aquaticus ♀ covering egg with faecal pellet.
Huskens, M.L. © 2016.07.28
At the end of the embryonic development, the
eggshell is completely transparant
revealing the fullgrown embryo ready to hatch
(Fig.4).
 |
Fig.4. Embryo's of Sminthurides aquaticus.
Huskens, M.L. © 2016.07.28
Discussion
After the courtship ritual and spermatophore uptake, the female must moult
before she can lay eggs (Falkenhan 1932 cited from Schaller, 1970:49).
Oviposition occurs in batches of 1 to 6 eggs
(Falkenhan 1932 cited from Schaller, 1970:49).
In each intermoult oviposition period, in average 25, at most 66,
eggs are laid
(Falkenhan 1932 cited from Schaller, 1970:49).
Eggs are deposited continuously when not moulting
(Waldorf 1971 cited from Hopkin, 1997:142).
Eggs are deposited in cuplike depressions
of the epidermis of Lemna minor (Fig.1,2).
The cups have been
chewn out
by the female.
After deposition, the egg is
covered by a faecal pellet (fig.3).
Conclusion
Tba.
Acknowledgements
Tba.
Bibliography
