Am. Wegeberg et al., Effect of intermediate host size (Cerastoderma edule) on infectivity of cercariae of three Himasthla species (Echinostomatidae, Trematoda), J EXP MAR B, 238(2), 1999, pp. 259-269
Citations number
36
Categorie Soggetti
Aquatic Sciences
Journal title
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY
To understand prevalence patterns of parasites in marine host populations e
xperimental infection studies an required. Bivalves are important host orga
nisms to a variety of trematodes species and in our study area (Wadden Sea)
three different Himasthla species co-occur in cockle populations. These sp
ecies are morphologically very similar but differ with respect to various m
orphometric dimensions. To study the possible functional importance of diff
erences between Himasthla cercariae (the free-living stage shed from prosob
ranch snails and encysting as metacercariae in bivalves), we experimentally
measured the infectivity of the three congeners in regard to different siz
e groups of juvenile cockles. The smallest species, N. interrupta, has a hi
gh infectivity in small cockles (optimum around 4 mm), whereas the two othe
r congeners H. continua and H. elongata exhibit low infection efficiencies
in cockles less than 6 mm and higher efficiencies in larger cockles. Behavi
oural experiments were performed to identify proximate causes underlying th
e observed infection patterns. parasite avoidance behaviour of the cockle v
aries in a host-parasite size-dependent manner so that a large cercaria ten
d to provoke an avoidance response in a small cockle. The possible conseque
nces of the observed host size preferences in relation to definitive host s
pecies (waterbirds) are discussed and it is suggested that one or more of t
he parasite species an adapted to other host species and that their sympatr
ic occurrence in cockles in our study area is a result of a spinoff from th
eir main cycle mediated through migratory birds. (C) 1999 Elsevier Science
B.V. All rights reserved.