7. IDENTIFICATION SHEETS FOR KEYSTONE SPECIES OF KONGSFJORDEN & HORNSUND
Benthos - Crustacea
genus Gammarus, family Gammaridae, order Amphipoda
Gammarus setosus, Dementieva, 1931
G. oceanicus, Segerstrale, 1947
G. wilkitzkii, Birula, 1897
Three sibling species of large (30-50 mm) amphipods. G. oceanicus and G. setosus are most numerous and common inhabitants of stony littoral, occur almost exclusively between 0-2 m depth, in densities up to 1000 ind./m2. G. oceanicus is a boreal species - bioindicator of Atlantic water inluence, G. setosus is local, arctic species. G. wilkitzkii is an ice associated species, typically connected with multiyear ice from Central Arctic basin, thus its presence indicates true arctic waters inflow.
For Svalbard distribution see the map (Weslawski 1994, Sarsia ).
How to recognize the species:
check the setation on the last abdominal segment (telson).
G.oceanicus - have few, short, smooth setae
G. setosus - have long, distinctly feathered setae
G. wilkitzkii - have numerous, long, smooth setae and often orange bands at joints of legs.
See also the photo in species gallery menu 6.6.4.
Crustacea - Decapoda - details of morphology specimens from Hornsund (drawings by JM Weslawski).