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3 <strong>Molluscs</strong><br />
Theodoxus transversalis<br />
Striped Nerite<br />
Theodoxus<br />
transversalis<br />
Pfeiffer, 1828<br />
Striped Nerite<br />
Taxonomic classification:<br />
Order: Neritomorpha<br />
Family: Nerites, Neritidae<br />
Status: CR – Critically Endangered<br />
Striped Nerite<br />
(Theodoxus transversalis)<br />
J. Čačaný<br />
Morphology The shell is thick-walled, very hard,<br />
the disc covers about a third of the total shell length.<br />
The basic coloration is grey or yellow-grey with three<br />
longitudinal dark stripes. The suture (indentation<br />
where the whorls overlap) before the mouth prominently<br />
descends, making the disc prominent. The<br />
shell length is 7,8–8,2mm, the width 5,8–6,2mm. The<br />
species is little variable as for its size and coloration<br />
– the largest specimens reach 10mm. The individuals<br />
with plain black or yellow-brown shell are rare.<br />
Bionomics A reophile species inhabiting stone bottom<br />
of slowly flowing large rivers. It grazes on periphyton<br />
from the stones and other submerged objects, according<br />
to some authors also on decaying animal remnants.<br />
Distribution Endemic to the Danube river region:<br />
The Danube from Ingolstadt downstream; probably<br />
missing in lower reaches of the river. In places it penetrates<br />
into larger tributaries of the Danube.<br />
5
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