|
Two
trematode species were used in experiments: Cryptocotyle
lingua (Heterophyidae) and Himasthla
elongata (Echinostomatidae). Mature (cercariae producing)
daughter rediae (MDR) were extracted from hepatopancreas of
naturally infected periwinkles Littorina littorea.
For first ten days MDR exhibited high motility, especially
H. elongata rediae being originally more active than
C. lingua. They both produced motile cercariae.
Then, MDR gradually lost viability and died in 14 – 16th
day post-isolation. When pulsed with 14C–labeled aminoacids
mixture, they showed evident signs of high metabolic activity
and species-specific differences in protein synthesis.
Thus,
cultivation experiments revealed that rediae of both C. lingua
and H. elongata under axenic in vitro conditions
survived for similar time, as well as other redioid species
previously studied: Echinostoma caproni and Fascioloides
magna (Ataev et al. 1998; Laursen and Yoshino 1999). Moreover,
it seems that at least for a first week post-isolation, physiological
state of these parthenitae is more or less adequate to that
in vivo. Evident application of this in vitro maintenance
is a qualitative and functional analysis of secretory‑excretory
products that are free of host-derived contaminants. Another
important possibility is co-cultivation of rediae and periwinkle
haemocytes collected aseptically. Keeping in mind high concentration
of haemocytes in L. littorea haemolymph this experimental
model could serve as a valuable tool for investigating mechanisms
of interaction between snail internal defence system and trematode
parthenitae. On the other hand, comparative approach with
models of taxonomically distant prosobranch and pulmonate
species infected with closely relative echinostomatide trematodes
(Himasthla and Echinostoma)
could help to trace evolutionary aspects of snail/trematode
compatibility.
This study was supported by grant no. 00-04-49434 from Russian
Foundation for Basic Research.
|
