A crustacean was a type of arthropod typically native to oceans. Talaxians ate crustaceans.
Neelix recalled his mother telling stories about the various ingredients in the food they ate, as per Talaxian tradition. In 2373, he was just about to elaborate on his favorite story to Tuvok, about a crustacean, when his eggs began to burn. (VOY: "Flashback")
Tuscadian pyrosomes fed primarily on bioluminescent crustaceans, which they tracked by sensing their electromagnetic signatures (DIS: "All Is Possible")
According to the RPG sourcebook Creatures (citation needed • edit), the Alvanian spine mite is a tiny crustacean that lives inside the spinal columns of larger animals and feeds on neural energy.