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Pseudobiotus megalonys (Thulin, 1928)
Pseudobiotus megalonyx (Thulin, 1928) (Eutardigrada) is one of
the biggest tardigrades. Females can reach a body lenght of more than 1
mm. This tardigrade can be found quite numerous (up to 3.000 animals in
100 ml sediment) in the mud flats of the lower elbe river (germany). It
can tolerate low salinity.
- Phylum: Tardigrada Ramazzotti 1962
- Class: Eutardigrada Marcus 1927
- Order: Parachaela Schuster et al. 1980
- Family: Hypsibiidae Pilato, 1969
- Genus Pseudobiotus Nelson in Schuster et al. 1980
- Species: Pseudobiotus megalonyx (Thulin, 1928)
- Body length: male up to 500 µm, female up to 1000 µm, fresh
hatched young animals: 200 µm
- Environment: fresh water, esp. tidal mud flats of rivers and lowland
streams. Species can tolerate low salinity. and low oxygen
- Phototaxis: The animal has two eyes and shows a negative phototaxis.
- Nutrition: Algae
- Sexuality and breeding: Copulation occurs mostly
during summer. After a short preludium - the male crawls around the
female - the animals "kiss" each other several times at mouth
and other parts of the head. Then the male climbs on the females back
using the first and second pair of legs (the first pair of legs shows a
sexual dimorphism with short, thick and hook like claws, see also (1)).
Then the male crawls slowly backward with the last pair of legs, turning
90°, and positions its y-shaped cloac on the half rectangular
shaped cloac of the female. Inner insemination. Two to three days after
copulation the female moults. The exuvia is held with the claws of the
fourth pair of legs, forming a "backpack". Three days after
moulting the female deposites 8 to 12 eggs into the exuvia. Four to six
days after oviposition, the young tardigrades hatch from the eggs, crawl
4 to 6 hours inside the exuvia. Then they climb the mothers back, press
themselves between the front part of the exuvia and the females back
outside and stay a little time near the mother animal.
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