Mouthpart Morphology of Three Sympatric Native and Nonnative Gammaridean Species: Gammarus pulex, G. fossarum, and Echinogammarus berilloni (Crustacea: Amphipoda)

Table 1

Main differences in morphology of mouthparts and other structures involved in food acquisition.

Structure	Gammarus pulex	Gammarus fossarum	Echinogammarus berilloni
Antennal flagellum	Annuli medio-laterally broadened; each with a row of 12 posteriorly directed setae together building a flag-like brush	Each annulus with a group of 2–5 simple setae on median and lateral side	Antero-posteriorly flattened and therefore broadened; setation sparse; setae short
Cuspidate setae on distal; margin of basipodal endites of maxillula	Lateral setae with three finger-like secondary spines	2-3 lateral setae distally flattened and broadened like chisels with three humps on distal edge	4 lateral setae with thickened shafts, distally flattened; distal margin blunt with 2-3 humps
Setation of carpus and propodus of 2nd gnathopod	Long and closely arranged setae with curled distal ends	Long and closely arranged setae with curled distal ends	Less numerous and shorter setae than in G. pulex and G. fossarum
Third uropod	Endopod 3/4 as long as exopod; plumose setae on medial and lateral margins of endopod and exopod	Endopod half as long as exopod, plumose setae on median margin of endopod and exopod; simple setae on lateral margin of exopod	Endopod very short; only simple setae on lateral and median margin of exopod