F-ACTIN AND β-TUBULIN LOCALIZATION IN THE MYXOSPORE STINGING APPARATUS OF MYXOBOLUS
PSEUDODISPAR GORBUNOVA, 1936 (MYXOZOA, MYXOSPOREA)
A. V. Uspenskaya,1 O. I. Raikova 2
1 Institute of Cytology RAS, and 2 Zoological Institute RAS, St. Petersburg,
Russia;
To understand the discharge mechanism of Myxozoan polar capsule (cnida) it is necessary to verify the role of major
cytoskeletal proteins in the process. With this aim F-actin and β-tubulin localization in spores of myxosporean developmental
phase (in myxospores) of Myxobolus pseudodispar Gorbunova, 1936 has been studied under confocal scanning laser microscope
using phalloidin fluorescent staining of F-actin and indirect anti-β-tubulin immunostaining. F-actin has been detected in walls of the
stinging tube invaginated into the polar capsule of myxospore. The fact suggests the contractile proteins involvement in the process of
myxozoan polar capsule extrusion. In addition, the cytoplasm of amoeboid sporoplasm inside the spore cavity is stained by phalloidin.
A polar cap with strong β-tubulin immunoreacton is observed at the front pole of fully mature myxospore above the outlets of the
polar capsule discharge channels. The role of the β-tubulin cap is supposed to be similar to that of the cnidarian cnidocil made
of microtubules. The weaker β-tubulin immunoreactivity has been found in stinging tubes, in polar capsule walls as well as in the
suture line of spore walls and in the cytoplasm of amoeboid sporoplasm. The involvement of cytoskeletal proteins in the process of
polar capsule extrusion is discussed. A hypothesis on the myxozoan polar capsule discharge mechanism is suggested. The mechanism
of myxozoan cnida discharge is compared with that of cnidaria.
Key words: actin, cnida, discharge mechanism, immunocytochemistry, Myxozoa, tubulin
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