The Dusky Batfish (Pinnatus Batfish) – Facts and FAQs – Batesian Mimicry

Dusky Batfish (Pinnatus Batfish)

One of the most beautiful things about witnessing aquatic life is their movement. There is something incredibly soothing about the fluidic motion of an Eel, the slow swaying of a manta ray’s pectoral fins, and the rhythmic gliding of a beautiful flatworm. Add to that a dash of vibrant colors, and you get creatures that are pure bliss to witness. The Pinnatus Batfish is a gorgeous specimen of fish that combines both of the aforementioned aspects. Interestingly, its striking characteristics are a result of mimicking flatworms. This level of mimicry, combined with the Batfish’s ability to abandon it, is what makes it so special ultimately.

Why can’t we keep the Pinnatus Batfish in an aquarium?

The Pinnatus Batfish is a saltwater fish. It can survive only in a marine aquarium. And unlike a typical freshwater aquarium, a marine aquarium requires expert handling. The salinity and the temperature need to be at a certain level at all times to ensure the fish’s survival. The water has to be crystal clear. Moreover, since the Pinnatus Batfish can grow up to 18 inches, it needs at least 150 gallons of water.

Also, since it is a carnivore, the Pinnatus Batfish cannot be kept in a reef aquarium with other invertebrates and small fishes. It needs a carefully balanced diet of shrimp flesh, seaweed, and algae.

Where is the Pinnatus Batfish found?

The Juvenile Batfish is found in the coral reefs of Australia. They are also bred in captivity in Indonesia.

Why does the Batfish lose its color?

Juvenile Pinnatus Batfish
Juvenile Pinnatus Batfish
Adult Pinnatus Batfish - Dusky Batfish
Adult Pinnatus Batfish

The Pinnatus Batfish’s mesmerizing color is temporary. Only the juvenile members of the species possess it. As the fish grows older, it loses its fancy color. The dark black with orange stripes gives away to what will be a permanent yellow-gray skin. The juvenile fish’s vibrant color is a part of its adaptation to ensure a long life. Interestingly, the fish has adopted this pattern by mimicking flatworms in its ecosystem that are unpalatable. Consequently, the flatworms have earned a reputation as things-that-cannot-be-eaten among potential predators. By mimicking the flatworm, the Pinnatus Batfish ensure its longevity. This form of mimicry is known as Batesian Mimicry. However, as soon as the Batfish grows in size and can fend off predators based on its physical growth, it sheds the sexy color because it just doesn’t need it anymore.

What is Batesian Mimicry?

platyhelminth pseudoceros - Batesian Mimicry between Batfish and flatworm
Pinnatus Batfishes mimic the Platyhelminth Pseudoceros species of flatworm

It is a form of mimicry where the mimicking creature is palatable. So in order to avoid being hunted by predators, it takes on the appearance of a species in its ecosystem that is unappetizing. In this case, the Pinnatus Batfish mimics a flatworm species known as Psudeoceros Periaurantas. However, the flatworm species are invertebrates, and their motion is gliding across the seabed. To complete the illusion and truly mimic the flatworm, the Pinnatus Batfish, which is vertically flattened, may occasionally lie on its side and glide along the ground in a horizontal fashion.

What are the advantages of this fish?

Picture a rainwater forest. Imagine it teeming with life. A thriving ecosystem is at the crux of a rainforest. Similarly, corals are like forests of the ocean. They are incredibly scarce. But still, contain a vast diaspora of aquatic life. The ecosystems of coral reefs are very balanced, and hence they are an excellent habitat for marine life. The concentration of algae in a coral reef is very balanced too. However, overfishing has led to an increase in the algae content of reefs. This is where the Pinnatus Batfish comes in. It has been observed to reduce algal growth in simulation studies significantly.

Can I get one for my aquarium?

The Batfish is not an easy species to maintain. They are sensitive to the changes in their natural ecosystem. If you are looking to add these beautiful creatures to your aquarium, make sure of a couple of things. Your aquarium should be built to sustain marine life. It should have enough volume to allow the free movement of the Batfish. Buy them only after ensuring that they are bred in captivity. This would ensure that their ‘natural’ habitats can be replicated.


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