Can be distinguished from S. siberica by smaller body size and the following features:
- symmetrical genital segment and unknown genital flap
- the third segment of the exopodite of P2-P4 carries 2, not 3 external spines
- male P5 left endopodite with digiform process equal in length to the first exopodal segment
USA (Lake Michigan, Lake Superior), Canada (Tigamani Lake, Nipigon Lake)
Freshwater eurythermic species characteristic of open waters in deep-water lakes of North America. Specimens recorded for the coastal waters of Siberia may in fact belong to the species M. sibirica (Vyshkvartzeva, 1994). The only freshwater member of the family Aetideidae
Female:
Forehead broadly rounded from dorsal or lateral view. Rostrum absent. Posterior corners of the last thoracic segment broadly rounded, reach the front 1/3 of the genital segment. Abdomen 4-segmented. Genital segment about as long as the next 3 segments combined, symmetrical.
A1 25-segmented.
A2 with endopodite slightly shorter than the exopodite. First 2 exopodital segments with 1 and 3 setae, respectively.
Md palp base with 2 setae, 1st endopodal segment with 2 setae, 2nd with 9 setae.
Mx1 gnathobase with 9 terminal spines and 4 posterior spines, 2nd and 3rd lobes with 3(?) setae each. Protopodite with 5 setae, endopodite with 12 setae and exopodite with 10 setae.
Mx2 with 6 endites, last one with 1 long seta.
Mxp protopodite with 2 seta proximally and groups of 2, 3, 2 setae.
P1-P4 typical of Aetideidae. The third segment of the exopodite of P2-P4 carries 2 external spines.
P5 is absent.
Male:
A1 25-segmented. Right exopodite in P5 relatively short, 2-segmented, the first segment with 1 small spine distally. Distal segment with small seta distally and long terminal spine. Right endopodite 1-segmented, elongate. Left exopodite 2-segmented, distal segment with a short terminal spine. Left endopodite 1-segmented, process equal in length to the 1st exopodal segment.
