Data from: Echinorhynchus salmonis Müller, 1784 (Acanthocephala: Echinorhynchidae) from the Bothnian Bay, Baltic Sea: morphological variability and radial asymmetry of proboscis hooks

Echinorhynchus salmonis is a common parasite of salmoniform and other
fishes, occurring in fresh and brackish waters throughout the Holarctic.
Presented here is the first analysis of the morphometric and meristic
variation in a Palaearctic population of E. salmonis, collected from
whitefish Coregonus lavaretus L. and smelt Osmerus eperlaus (L.) from the
Bothnian Bay, northern Baltic Sea. Morphological data were compared with
published descriptions of congeneric taxa. Nearctic populations of
salmonid echinorhynchids considered by some to represent a distinct
species, E. coregoni Linkins in Van Cleave, 1919, did not show any
morphological divergence from Palaearctic populations, indicating that the
name E. coregoni should be suppressed. Similarly, E. alpinus Linstow, 1901
has been considered to be a junior synonym of E. salmonis. However, E.
alpinus should be regarded as a valid species, because it has a longer and
more elongate body. The armature of the acanthocephalan proboscis
typically displays radial symmetry. However, in E. salmonis the hooks on
the dorsal surface of the proboscis are smaller than those on the ventral
surface. Size differences between dorsal and ventral hooks are most
pronounced at the base of the proboscis. The systematic and functional
significance of radial asymmetry of proboscis hooks is discussed.