This group comprises:
Euphausia gibba
Euphausia pseudogibba
Euphausia paragibba
Euphausia hemigibba
These four species are very difficult to separate although with experience it is apparrently possible to differentiate them using subtle differences in the shape of the keels on both the rostrum and the third segment of the antennular peduncle. However, the easiest way of telling them apart is by reference to the petasmae and the thelyca. Points of difference to note here with respect to the petasma include the shape of the median lobe; the thickness of the base and the presence of armature on the lateral process; as well as the relative size and shape of the terminal and proximal processes (petasmae). Differences in the structure of the thelyca can be seen by reference to Eu table 4 and figures thorax of Euphausia hemigibba and ventral surface of thorax, but in essence, the points to look for are differences in the shape and structure of the coxal lobe on segment 6 and the sternal plate on segment 7.
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