nauplius larva

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nauplius larva The first, free-swimming, planktonic larva of most marine and some freshwater crustaceans. It has no evident segmentation. There is a single, median, nauplius eye at the front of the head. There are only three pairs of appendages, the first and second antennae, and the mandibles. The second antennae and mandibles bear swimming setae. Additional trunk segments and appendages appear with successive moults, the increments proceeding from anterior to posterior. The late nauplius stages are often called metanauplii. The term ‘post-larva’ is applied to all immature crustaceans when the full complement of segments and appendages have developed. Some or all larval stages are absent in certain groups of Crustacea, and in others they may be considerably modified. (Nauplius was the son of Poseidon, god of the sea.)

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