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28(5
SMÄRRE UPPSATSER OCII MEDDELANDEN
looked. As to bathymetrical distribution it is a littoral and sublittoral species
(Kjellman 1890, Kylin 1907). Thus, in British waters it occurs at low-water
mark and down to a depth of about four fathoms (Newton 1931). In the Belt
Sea and the Baltic it is recorded from greater depths, down to 15 ni in Blekinge
and Danish waters (Levring 1940, Rosenvinge 1935) and 20 ni NW of
Fehmarn (Lakowitz 1929).
Caligus curtus is common on several fishes, especially on gadids, on
which it is most often found creeping on the skin, more seldom on the gills.
Still more rare are records of free-swimming specimens. C. curtus has a very
wide geographical distribution, from Greenland to the east coast of North
America, western Europe, and the Mediterranean. In our waters it is known
from the Skagerrak as well as from the Kattegat and the Sound. The deepest
record is from 538 m (van Oorde-De Lint & Schuuhmans Stekiioven Jr
1936).
As mentioned above Leptonemn is recorded from several animals, e.g.
Eupagurus bernhardus. Thus the discovery of this alga on Caligus curtus is in
itself not remarkable. On the contrary it is astonishing that it is not found
more often and on other animals, too, for one must suppose that spores of
Leptonema fasten on every hard substratum found, be it dead or living,
animal or plant. Nevertheless I think that the new find is of interest, because,
especially if followed by others, it may give us possibilities to draw certain
conclusions concerning different problems.
Thus, if someone were to search systematically for Leptonema and other
small algae on wandering animals, it would certainly be possible to arrive at
an explanation of the vertical migrations of the host animals, for as mentioned
above Leptonema like other algae is restricted to the lighted water layers down
to about 20 m, whereas (’.aligns and many other animals are found at greater
depths too (cf. above). The cod wanders horizontally as well as vertically,
but it is known also as a bottom fish, living in the littoral and sublittoral
region» with a partly limited area for more or less isolated stocks (Anderson
1942, p. 153). As Caligus curtus rarely is found free, it normally follows its
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