Location
Luzon Island, Philippines
Caption
This appears to be a sharp-nosed pufferfish (Canthigaster valentini) at first glance, but the long, broad dorsal and ventral fins of this small three-inch (7.6 cm) filefish betray its true identity as an imposter, the mimic filefish, false puffer, or blacksaddle filefish (Paraluteres prionurus). The "real" pufferfish has a much smaller dorsal fin, set further rearward along the spine. The filefish gains a survival advantage through mimicry, since sharp-nosed pufferfish are avoided by predators because of their poisonous flesh. This one even has the act perfected down to the way it behaves, carrying its caudal fin closed most of the time and seen resting on the reef. Unfortunately it appears to have a parasitic fish louse attached.
