Behavior of Juvenile Nerocila Acuminata (Isopoda, Cymothoidae) During Attack, Attachment and Feeding on Fish Prey

Juvenile Nerocila acuminata are blood and tissue feeders which, under laboratory conditions, show no prey specificity attaching to and feeding upon Menidia beryllina (silversides), Cyprinodon variegatus (sheepshead minnow), Mugil cephalus (mullet), Fundulus similis (killifish), Trachynotus carolinus (pompano), Lagodon rhomboides (pinfish), and Anchoa mitchilli (anchovy) from the Gulf of Mexico. Attacks occurred either in mid-water or from the bottom. In mid-water, isopods would swim in from the rear, on any compass setting, adjusting their dorso-ventral swimming orientation to land with outstretched pereopods. Speed adjustments were precise since, in over 50 attacks, overshooting did not occur. From the bottom, isopods which were lying on their backs with the first three pairs of pereopods extended, either hooked a slowly passing fish or flipped their pleopods and propelled themselves onto a fish. Thus, juvenile N. acuminata are behaviorally equipped to attack either pelagic or demersal fishes. Undamaged fish did not respond overtly either to the sight of or transient contact with the isopods; damaged fish took evasive action. If attachment occurred on the body rather than on the fins, the fish responded with a variety of dislodgment tactics the vigor of which diminished with additional attachments.