Fróðskaparrit - 01.01.1995, Page 99

PARASTENOCARIS GLACIALIS IN THE FAROE ISLANDS
103
crawling over the sand grains, not by swim-
ming. In northem Sweden it appears to
have one generation per year. It reproduces
in June-July in Lake Tometrásk (northem
Sweden) and the nauplii mature in about
two months (Enckell, 1969). The condi-
tions seem to be similar in the Faroes, since
both nauplii, metanauplii and adults were
found during the sampling in July, 1995. In
Fennoscandia live animals may be found in
ice-covered beaches during the winter,
which indicates a certain cold resistance.
Methods
Interstitial water was filtered from small
stretches of sandy/gravelly beaches accor-
ding to the method of Chappuis (1942). A
plankton net with mesh size of 25 pm was
used. Samples were sorted in the laborato-
ry under a magnification of 20-25X. The
occurrence of other animal groups was no-
ted (see Results).
Results
Sandy or sandy/gravelly beaches are not
common in Faroese lakes or brooks. Very
often a thin layer of sand/gravel overlies a
compact layer of peat, which completely
shuts out any transport of subsoil water to
the sand. Altogether 12 sites were sampled,
and P. glacialis was found in seven of these
(Leynarvatn and Mjøvuvatn, 18 July 1995,
on Streymoy; Saksunarvatn and Dalsá, 20
July 1995, on Streymoy; Sørvágsvatn at
Ivarsheyggjur and Skjatlá, 26 July 1995, on
Vágar; and Lítluvatn, 27 July 1995, on
Sandoy - see Fig. 3). Samples from Tofta-
vatn (Eysturoy), Hovsvatn (Suðuroy, and
Stóravatn, Sandsvatn and Heimara Helsa-
Fig. 3. Sites in the Faroes containing Parastenocaris
glacialis. For names oflakes and brooks, see main
text.
vatn (Sandoy) did not yielđ any specimen
of P. glacialis, which of course does not
preclude the species’ occurrence in these
water bodies.
The accompanying fauna in the beaches
varied very much. All beaches contained
nematodes and oligochaetes, and most also
ciliates. Rotatoria, Ostracoda, Hydracarina,
Copepoda Cyclopoida and Copepoda
Harpacticoida occurred in a few beaches,
while only the samples from Sørvágsvatn,
Skjatlá and Leynarvatn contained Tardigra-
da. A large part of this fauna does most
probably not belong to the true interstitial