Mysidacea
Vertical distribution and migrations

Many species of deep-sea mysids have been found on and just above the ocean-floor at various depths, but our knowledge on these organisms is very poor, both taxonomically and ecologically. The deepest recorded abyssal mysids are Amblyops magna (from 7120-7260 m in the Kurile-Kamtchatka Trench; Birstein and Tchidonova, 1958), followed by Mysimenzies hadalis (from 6146-6354 m in the Peru Trench, B|cescu, 1971), and A. aequispina (from 5760 m in the Kurile-Kamtchatka Trench, Birstein and Tchidonova, 1958).

Most sand-burrowing and coastal mysids perform a diel vertical migration, ascending and dispersing into the water column during the night, and descending to deeper layers towards dawn. In meso- and bathypelagic species, however, it seems that clear evidence of migration is generally lacking (day+ night distribution), although a few reports on vertical migrations of deep-sea mysids have been published (Waterman et al., 1939; Murano, 1977).