Having hidden, concealed, or inconspicuous nervous system structures or nerve pathways.
From Greek 'kryptos' (hidden) + 'neuron' (nerve) + '-ous' (characterized by). This term appears in zoological descriptions of organisms whose nervous systems lack obvious external features.
Some simple animals like sponges are cryptoneurous—they respond to their environment without any brain or obvious nerves, which makes them seem like they're moving mysteriously on their own!
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