Nauplius(redirected from nauplial)
Also found in: Dictionary, Medical.
the plankton larva of numerous species of the family Crustacea. The body is unsegmented and has three pairs of appendages. In front of the mouth there are uniramous sensory antennules; in back there are biramous antennae and mandibles for swimming. The nauplius has a median eye. Between the mandibles and the anal opening there is a growth zone, where, as development progresses, the postnauplial segments with appendages develop.