Gammarus lacustris Sars, 1863

Description and illustrations: Sars 1890 -95, p. 507, pl. 10. Gammarus lacustris Sars, 1863 View in CoL 177-1; Kinne 1954, p. 419, figs 1-4pp; Lincoln 1979, pp 243, 245,

figs 111e, 112. Synonyms: Rivulogammarus lacustris auct.; Gammarus Ecology and habitat: Gammarus duebenii is a very pulex sensu Sars (1890 -95); non Cancer pulex Linnaeus, 1758 ; euryoecious species, and generally one can say that it occurs Rivulogammarus scandinavicus S. Karaman, 1931 . everywhere where other Gammarus and Marinogammarus Description and illustrations: Sars 1890 -95, p. 503, pl. species do not thrive (see e.g. Forsman 1951, Kinne 1953, den 177-2 (as G. pulex ); Økland 1969, p. 132, figs 16-23. Hartog 1964). In Norway the main biotope is supralittoral Ecology and habitat: Dealt with in detail by Økland rockpools, the mouth of small and medium large streamlets (1969). G. lacustris lives in lakes, ponds and slow moving rivers (here they can ascend quite a bit upstream and live at least at places where the water is not too acidic and too deficient in temporarily in pure freshwater), and intertidally, under stones calcium. and among algae in meso- and oligohaline brackish waters, as in Distribution: See Segerstråle (1954) and Økland (1969, the inner part of fjords ( Brattegard 1966, Vader 1977a). fig.2). This species occurs in most of Norway, but has not been Gammarus duebenii has also several times been found reported from Østfold and Agder, while there are no reports in ‘freshwater’ lakes and pools in Norway (see Økland 1970, from Lofoten-Vesterålen either. Around Bergen G. lacustris has Kjaerstad et al. 2016). As ‘marflo’ samples are often transported been recently discovered by Bjerknes (pers. comm.). Outside by fishermen between lakes and even from the shore to lakes, Norway, G. lacustris has a very wide holarctic distribution at some of these occurrences may be not quite natural. northerly latitudes. Distribution. Common along the whole coast of Norway,

but absent from Svalbard waters. A few freshwater occurrences.