Feeding appendages of the Euphausiacea (Crustacea)

The Euphausiacea comprises about 85 species and the structure of the feeding appendages of 68 of these species is discussed here. A considerable uniformity is apparent in the appendages throughout the order but generic, and even in some cases, specific differences are evident. It is concluded from the study of the morphology of the appendages and the analyses of stomach contents that the majority of species in the genera Bentheuphwsia, Thysanopoda, Meganyctiphanes, Nyctiphanes, Pseudeuphausia, Euphausia, Tessara-brachion and Thysanoessa are omnivorous; that is, they can feed by filtering material from the water and act as predators of small zooplankton, especially copepods. Species in the genera Nematoscelis, Nematobrachion and Stylocheiron can feed on bottom deposits and also by predation of zooplankton but the amount of filter-feeding which they do may be limited because their mouthparts are not so well adapted for filtering as those of the previous group of genera.
It is suggested, from the study of the appendages and several other features of the animals, that the genera Thysanopoda, Meganyctiphanes, and Euphausia are closely related to one another and that a similar relationship exists between the genera Nematoscelis, Nematobrachion and Stylocherion. The genera Nyctiphanes and Pseudeuphausia are probably more closely related to the Thysanopoda group of genera and the genera Tessarabrachion and Thysanoessa to the Nematoscelis group of genera.