Náttúrufræðingurinn - 1977, Blaðsíða 21

Jónsson, Lúðvik. 1971: Skeldýranýjungar.
Náttúrufr. 41: 41—47.
Muus, B. J. 1963: Some Danish Hydro-
biidae with the description o£ a new
species Hydrobia neglecta. Proc.
Malac. Soc. London 35: 131—138.
Muus, B. J. 1967: The fauna of Danish
estuaries and lagoons. Distribution
and ecology of dominating species in
the shallow reaches of the mesohaline
zone. Meddelelser fra Danmarks Fisk-
eri- og Havundersögelser. Ny serie 5
(1): 1-316.
S U M M A R Y
Hydrobia ventrosa recorded
in Iceland
by Ingimar Óskarsson,
Marine Research Institute, Reykjavik,
Agnar Ingóljsson and Arnthor Gardarsson,
Institute of Biology, TJniversity of Iceland.
Hydrobia ventrosa (Montagu, 1803)
(Prosobranchia, Gastropoda) is recorded
as new to Icelancl. An earlier record o£
Hydrobia idvae in Iceland (Jónsson 1971)
should be regarded as probably relerring
to H. venlrosa. The species is now known
to have a wide but local distribution along
the west and southwest coasts of lceland
(Fig. 1).
In Iceland H. ventrosa is found in
brackish ponds (often with Ruppia mari-
tima) in Puccinellia salt marshes at sal-
inities varying from to 26.4%0, inter-
tidal lagoons, and in mucl flats with
higher and less variable salinities of about
33%0. At some of the localities the species
is very abundant (up to 23,000 individu-
als/m2).
Large numbers of live II. ventrosa from
most of the known Icelandic localities
were examined. All agreed well witli
European descriptions of this species in
structure of shell (Fig. 2), penis (Fig. 3)
and radula. Comparison of live Icelandic
material with a detailed description of
the North American Hydrobia totteni
Morrisson (Davis 1966) revealed no dif-
ferences in anatomy, but Davis’s descript-
ion was more detailed than any in the
European literature. In particular, the
Icelandic specimens were characterized by
ciliary ridges on the outer edge of the
left antenna (Fig. 4). Examination of live
Danish and Norwegian specimens ol' H.
ventrosa revealed that these also had
idcntical ciliary ridges not previously de-
scribed in II. ventrosa, but considered
diagnostic of H. totteni (Davis loc. cit.).
We therefore consider tlie North Ameri-
can Hydrobia totteni Morrison 1954, syn.
H. minuta (Totten, 1834), synonymous
with H. ventrosa. This species, therefore,
has a wide boreal amphi-atlantic distribu-
tion.
Icelandic populations vary considerably
in pigmention (Fig. 4) and in size. The
largest and darkest specimens were found
in brackish pools at Álftanes (Gálga-
hraun), SW-lceland, and the smallest and
least pigmented in intertidal lagoons at
Stokkseyri on the south coast.
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