The Polka-dot Batfish (Ogcocephalus radiatus) is a bottom dwelling fish, usually found partially covered in sand or mud, on the bottom substrate near coral reefs. It is native to the Atlantic coast of the United States, ranging from North Carolina all the way to the Bahamas, in waters up to 60 metres deep.
Although it may not look like much, this little arrow-shaped, strange looking individual is jam packed with interesting adaptations to life on the seabed.
Warts or not
The Polka-dot Batfish got its name from the brown rimmed spots on its body. There are also many small nodules called tubercles on the upper surface of its body, making it appear wart-ridden. In fact, this breaks up the outline of the fish, providing it with ample camouflage from both predator and prey.
When a predator approaches the Batfish, it will bury itself partially beneath the surface of the sand. This, along with its polka-dots and tubercles, saves it from being eaten!
The Polka-dot Batfish has specially modified pectoral fins under its body that allows it to walk along the seabed – and sneak up on prey from behind!
When startled, it may panic and try to swim. Because it is more equipped to walk on the seabed, the Polka-dot Batfish is a notoriously bad swimmer. Its attempt at swimming is an awkward movement that has been described as “somewhere between humorous and just plain slow” (Source). See it for yourself:
The Polka-dot Batfish has a grisly hunting tool on its head. Called an esca, it is a moveable modified dorsal fin which can wiggle and twitch. Similar to the way fishermen place bait on their fishing lines, the Batfish uses its esca to lure prey near to its mouth. Check out the Batfish’s esca in action in this clip taken by Assistant Curator Jason Lim:
It is thought that the esca also secretes a chemical that aids in attracting prey. Once the unsuspecting victim is within range, the Batfish’s lips will propel forward, snapping the animal up!
Gills in “armpits”
While feeding the Polka-dot Batfish, our aquarists observed that their gills are located in an unconventional position. Unlike other fish whose gills are located under the gill cover (right behind their eyes), gills of the Batfish are located where their pectoral walking fins adjoin to their body – equivalent to armpits in humans! Aquarist Ng Boon Ping has a quirky description for this, “It looks just like an airplane exhaust nozzle!” Watch the gif below and see if you agree:
All images and videos by Boon Ping.