The Achilles Tang, scientifically known as Acanthurus achilles, is a highly valued surgeonfish in marine aquaristics and a popular food in Hawaii. Its impressive coloration and active behavior make it a jewel for any aquarium, but it is also known to be one of the most challenging fish to maintain due to its strict care requirements.
The Achilles Tang is a marine fish that is in high demand among marine aquarium enthusiasts; retail prices for a specimen range from €265.00 to €514.00 depending on size. In this article, we provide basic information about the Achilles Tang, its care, and feeding, to ensure the well-being of this fish.
Description and Characteristics
Taxonomy
- Domain: Eukaryota
- Kingdom: Animalia
- Phylum: Chordata
- Class: Actinopterygii
- Order: Perciformes
- Family: Acanthuridae
- Genus: Acanthurus
- Species: Acanthurus achilles (Shaw, 1803)
- Common names in Spanish: Cirujano encendido, Navajón de Aquiles, pez cirujano de Aquiles, cirujano de achilles
- Common names in English: Achilles Tang, Red-spotted Surgeonfish, Redspot Surgeonfish, Redtail Surgeonfish, Achilles Surgeonfish
The etymology of the scientific name of the genus Acanthurus comes from the Greek: akantha = spine + oura = tail.
Physical Characteristics
The Achilles Tang reaches a maximum size of approximately 23 cm (8.5 inches) and has the oval body shape typical of surgeonfish. These marine fish have a single foldable spine that tucks into a groove on the side of the tail base; a notched caudal fin; rough and very small scales; and a complete lateral line.
Randal (1956) described the Achilles Surgeonfish as follows: “A large elliptical area of pale yellowish color (bright orange in life) on the posterior part of the body, which encloses the caudal spine at its posterior part (this area is absent in specimens less than 65 to 70 mm in standard length); no white oval spot below the eye; a pure white elongated mark on the opercular membrane; a white line on the chin that does not extend above the rictus; pale area at the base of the dorsal and anal fins, narrow and almost uniformly wide; lunate caudal fin, caudal concavity 5.5 to 8.5 in standard length; soft dorsal rays 29 to 33 (usually 30 to 32); soft anal rays 26 to 29 (usually 27 to 29).”
On the other hand, Fishelson and Delarea (2014) investigated the unique characteristics within the mouths of surgeonfish (family Acanthuridae) and identified two key adaptations:
- Retention Plates: These are tough skin plates located at the front of the mouth, rich in collagen fibers. Researchers believe these plates help retain algae after the fish scrapes them with its sharp teeth.
- Abundant Taste Buds: The surgeonfish has a surprising number of taste buds, especially a type called Type I. These taste buds are arranged in species-specific patterns throughout the mouth, particularly on the roof, floor, and sides. The number of taste buds also increases with the size of the fish, concentrating in the back of the mouth.
Li et al. (2020) reported the complete mitochondrial genome sequence of A. achilles. The mitogenome has 16,537 base pairs and consists of a total of 37 genes and a putative control region.
Natural Habitat of the Achilles Tang
In the wild, the Achilles Tang is found on rocky coasts or coral reefs in the Indo-Pacific, at depths of up to 18 to 20 m, but they prefer 5 to 10 m (Grange and Singleton, 1985), especially in areas with strong wave action where there is abundant algae growth. According to Jones (1968), the Achilles Surgeonfish prefers upwelling areas.
Achilles Surgeonfish prefer clear, well-oxygenated waters, which must be replicated in the aquarium to maintain their health. They are often seen in pairs, swimming in parallel or in tight circles (Barlow, 1974).
Care Requirements for the Achilles Tang
Due to its demanding requirements, the Achilles Tang is recommended only for experienced aquarists. They need a carefully monitored and stable environment, with constant attention to water quality and diet.
Tank Size
To keep an Achilles Tang healthy, a tank of at least 180 gallons (700 liters) is recommended for a single specimen, although some experts suggest even larger tanks. If you want to keep a school of 4 Achilles Surgeonfish, you should have at least a 1000-liter tank.
Achilles Surgeonfish need plenty of swimming space and strong water flow to simulate their natural environment. You should also provide an appropriate environment with rocks or corals and cultivate marine algae to provide a more natural setting.
Water Parameters
In their natural habitat, the Achilles Tang lives in turbulent areas where dissolved oxygen concentrations in the water are high; thus, in captivity, to maintain the well-being of the fish, you must provide the following water quality conditions for their care:
Table 01. Water Quality Parameters for the Care of Achilles Tang
| Parameter | Range |
|---|---|
| Salinity | 1.020-1.025 |
| Water Temperature | 24-26°C (75-79°F) |
| Water pH | 8.1-8.4 |
| Water Hardness (dKH) | 8-12 |
| Ammonia | 0 ppm |
| Nitrates | <50 ppm |
Similarly, the breeding aquariums for the Achilles Tang should contain corals or rocks to mimic the natural habitat of these fish. The tank lighting must be intense. Maintaining these stable parameters is crucial, as Achilles Tangs are very sensitive to fluctuations in water quality.
Feeding Achilles Tang
The Achilles Tang is primarily herbivorous, feeding on algae in its natural habitat. The Achilles Tang grazes on a wide variety of benthic algae and also feeds on the films of microalgae that cover rocky substrates. Jones (1968) described that the Achilles Tang mainly feeds on filamentous microalgae. Therefore, it is important to have rocks or corals to promote the growth of algal films.
Clements (1991) studied the microbiota of surgeonfish and reported that Epulopiscium (a genus of Gram-positive bacteria) is the most characteristic element of the microbiota of herbivorous surgeonfish (family Acanthuridae). Additionally, Fishelson and Delarea (2014) reported that the Achilles Tang scrapes algae with its sharp teeth. The retention plates help keep the algae in place while the taste buds give the fish a good “taste” of its food, especially at the back of the mouth, allowing them to evaluate what they are about to swallow. This sophisticated system appears to be an adaptation to their plant-based diet.
In captivity, the Achilles Tang should be provided with a diet rich in marine algae to maintain its health and coloration. Commercial products like Sea Veggies, Seaweed Salad, and Ocean Nutrition are ideal and should be offered at least three times a week. However, it is also recommended to supplement with foods like mysis and Artemia, but the base of their diet should be plant-based.
Breeding in Captivity
Breeding Achilles Tangs in captivity is extremely rare and poorly documented. Generally, the fish available in the aquarium trade are wild-caught. This factor, along with their high sensitivity, makes their conservation and responsible management essential to avoid overexploitation of wild populations.
Randal (1956) reported that fish of the genus Acanthurus exhibit sexual dimorphism; large adult males develop a distinct convexity in the head profile above the mouth.
Like most surgeonfish, Achilles Tangs spawn in groups and produce small eggs that float in open water. The pelagic larvae, called Acronurus, develop in the plankton and then settle on the reef. Juvenile Achilles Tangs lack the orange spot. The size of the metamorphosis from postlarva to juvenile is around 6 cm.
It is important to note that the Achilles Tang is prone to natural hybridization with other surgeonfish species (A. japonicus, A. leucosternon, and A. nigricans). DiBattista et al. (2016) examined the evolutionary history of surgeonfish species in the Indo-Pacific, particularly those found near the borders of the Indian and Pacific Oceans, and reported that the meeting point of the Indian and Pacific Oceans appears to be a zone where hybridization is occurring between some species of surgeonfish; however, although there is evidence of hybridization, the vast majority of the fish (98%) still retained their distinctive physical characteristics and matched their expected genetic lineage.
Behavior and Compatibility
Achilles Tangs are known for being semi-aggressive, especially towards other surgeonfish. It is crucial to introduce them to the aquarium after other fish to reduce aggression. They are territorial and need an environment that allows them to establish their space without constant conflicts; in their natural habitat, the Achilles Tang occupies a territory ranging from 5 to 20 square meters (Barlow, 1974). In this sense, the presence of other surgeonfish can trigger aggressive behavior.
On the other hand, shrimp should not be kept with Achilles Tangs as they could become prey.
Conclusion
The Achilles Tang is an impressive and challenging addition to any well-established reef aquarium. With its dazzling coloration and active behavior, it can be a spectacular centerpiece, provided its strict care requirements are met. Proper maintenance not only ensures its well-being but also contributes to the conservation of this species in its natural habitat.
However, it is important to note that the retail trade of Achilles Tangs relies primarily on wild-caught specimens, making it necessary to promote the aquaculture of these marine fish to meet demand.
References
Barlow George. 1974. Contrasts in Social Behavior between Central American Cichlid Fishes and Coral-reef Surgeon Fishes. AMER. ZOOL., 14:9-34.
Clements, K. D. (1991). Gut microorganisms of surgeonfishes (family Acanthuridae) (Doctoral dissertation, James Cook University of North Queensland). 6 p.
DiBattista, J. D., Whitney, J., Craig, M. T., Hobbs, J. A., Rocha, L. A., Feldheim, K. A., Berumen, M. L., & Bowen, B. W. (2016). Surgeons and suture zones: Hybridization among four surgeonfish species in the Indo-Pacific with variable evolutionary outcomes. Molecular Phylogenetics and Evolution, 101, 203-215. https://doi.org/10.1016/j.ympev.2016.04.036
Fishelson, L., Delarea, Y. Comparison of the oral cavity architecture in surgeonfishes (Acanthuridae, Teleostei), with emphasis on the taste buds and jaw “retention plates”. Environ Biol Fish 97, 173–185 (2014). https://doi.org/10.1007/s10641-013-0139-1
Grange K. R. and R. J. Singleton. 1985. A Guide to the reef fishes of Palmerson and Suwarrov Atolls, Cook Islands. NZOI Oceanographic Field Report. 20 p.
Jones, R. S. (1968). Ecological relationships in Hawaiian and Johnston Island Acanthuridae (surgeonfishes). Micronesica, 4(2), 309-61.
Li, T., Yang, Y., Huang, X., Lin, H., Yu, W., Huang, Z., & Mu, X. (2020). The complete mitochondrial genome of Acanthurus achilles (Acanthuriformes, Acanthuridae). Mitochondrial DNA Part B, 5(1), 970–971. https://doi.org/10.1080/23802359.2020.1719921
Randal J. 1956. A Revision of the Surgeon Fish Genus Acanthurus. PACIFIC SCIENCE, Vol. X, April, 1956. 80 p.
