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Acanthuridae

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The Acanthuridae are a diverse family of ray-finned marine fishes. They include many well-known groups like surgeonfishes, tangs, and unicornfishes. These fishes live in tropical seas, mostly around coral reefs. There are approximately 86 different species currently living in our oceans. Because of their bright colors, many species are very popular in home aquaria.

Acanthurus MH-MCZArtwork ARC 209-030
Acanthurus MH-MCZArtwork ARC 209-030

The name of this family reveals a key physical feature. It comes from the Ancient Greek words "akantha," meaning spine, and "oura," meaning tail. This refers to the sharp, bony plates found on the caudal peduncle. The caudal peduncle is the narrow part of the body where the tail attaches. These plates are shaped like scalpels and are dangerously sharp. They can cause serious injury to anyone who handles the fish carelessly.

Acanthurus spine peduncle
Acanthurus spine peduncle

Surgeonfishes have specific body parts that help them survive. Their dorsal, anal, and caudal fins are quite large. These fins extend across most of the length of their bodies. They also have small mouths containing a single row of teeth. These teeth are specifically adapted for grazing on algae. While some fish feed alone, others travel in schools. This schooling behavior may help them overwhelm aggressive damselfishes. Damselfishes are small, territorial fish that guard patches of algae on reefs.

These fishes go through a very interesting life cycle. They begin life as larvae known as acronurus. An acronurus looks very different from the adult fish. These larvae are mostly transparent and live a pelagic lifestyle. This means they spend much of their time in the open ocean water. Eventually, they settle on the ocean bottom near the shore. Once they settle, they develop into juveniles and then into adults.

Post larval surgeonfish (Acanthurus sp.) (28822279247)
Post larval surgeonfish (Acanthurus sp.) (28822279247)

Digestion in surgeonfishes relies on a unique biological partnership. They are the only known hosts for bacteria in the genus Epulopiscium. These symbiotic bacteria live inside the fish and help with digestion. This process allows the surgeonfish to properly digest the algae in their diet. In the wild, they primarily graze on macroalgae. Common types include genera such as Caulerpa and Gracilaria.

We can learn about the history of these fish through fossils. Several extinct genera have been identified from the Eocene to the Miocene epochs. A large variety of fossil surgeonfish comes from the Monte Bolca lagerstatte in Italy. These fossils represent some of the earliest members of specific tribes. Scientists have identified many extinct genera, such as Acanthuroides and Metacanthurus. In the early 1900s, researchers actually referred to this family as Hepatidae.

Size varies greatly among the different species in this family. Most species remain fairly small as adults. However, certain genera like Acanthurus and Prionurus can grow larger. The genus Naso also contains many larger species. The largest member of the entire family is the whitemargin unicornfish, or Naso annulatus. This species can reach a total length of up to 45 centimeters.

Acanthurus MH-MCZArtwork ARC 209-030
Acanthurus MH-MCZArtwork ARC 209-030

Keeping these fish in aquariums requires careful planning. Many species, especially tangs, are very sensitive to diseases. Aquarists often use a technique called a refugium to help. They grow macroalgae in a separate area to absorb nitrates. This improves the water quality for the fish. Because many tangs are territorial, they may fight with other fish. Owners must ensure there is enough swimming room and many places to hide.

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🖼️ Images & Media (4)
File:Acanthurus spine peduncle.jpg
Acanthurus spine peduncle.jpg
File:Acanthurus MH-MCZArtwork ARC 209-030.jpg
Acanthurus MH-MCZArtwork ARC 209-030.jpg
File:Ctenochaetus striatus, Yamada, Onna, Kunigami, Okinawa 904-0416, Japan imported from iNaturalist photo 100256731 (cropped).jpg
Ctenochaetus striatus, Yamada, Onna,...
File:Post larval surgeonfish (Acanthurus sp.) (28822279247).jpg
Post larval surgeonfish (Acanthurus sp.)...
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