Biology Reference
In-Depth Information
5 mm
Lobatostoma
Digestive
gland
Figure 10.4. A juvenile Lobatostoma manteri (dotted) in a cavity of the digestive gland
of the snail Cerithium moniliferum. The same extended worm, dissected out of the
snail, to the right of the snail. Note the large size of the worm relative to that of the
snail. Redrawn and modified from Rohde (
1973
).
Worms from fish can be kept alive in dilute seawater for up to 13 days,
and they continue to produce eggs infective to snails. Juveniles from snails
stay alive in seawater and dilute seawater.
Electron microscopic investigations have shown that juvenile and adult
worms have 8 and possibly 14 types of sensory receptors, which differ in
the presence or absence of cilia, in the shape and length of cilia, and in the
presence or absence of ciliary rootlets. Juvenile Lobatostoma from snails,
on the basis of serial sections and scanning electron microscopy, were
estimated to have at least 8500 surface and numerous sub-surface receptors.
The function of the receptors is not known, but they are likely to play a role
in migration from the stomach to the small intestine, feeding, and mate
finding, and/or they may help in preventing damage to snail-host tissue.
There is evidence for intraspecific competition leading to density
dependence in Lobatostoma. The smallest of the three snail species found
to be infected, Cerithium moniliferum, almost always harbors only a single
individual parasite, coiled up in a cavity formed by the main and one (or
some?) side ducts of the digestive gland (Figure
10.4
), whereas Peristernia
