Scatophagus argus

Scatophagus argus, the spotted scat, butterfish, mia mia, spotted butterfish or tiger scat, is a species of fish in the scat family Scatophagidae. It occurs in two basic color morphs which are called green scat and ruby or red scat. This fish is generally distributed around the Indo-Pacific region, to Japan, New Guinea, and southeastern Australia. They live in coastal muddy areas, including estuaries, mangroves, harbours, and the lower courses of rivers. They are popular aquarium fish.

Taxonomy

Scatophagus argus was first formally described in 1766 as Chaetodon argus by Carl Linnaeus with the type locality given as India.[3] In 1831 Georges Cuvier described the genus Scatophagus and Linnaeus's C. argus was designated as its type species.[4] The specific name argus refers to the mythical hundred-eyed guardian of Io, Argus, who following his death had his eyes became the feathers of a peacock, a reference to the brown to reddish-brown spots on the body of this fish.[5]
Description

Scatophagus argus has a body which is rectangular and strongly compressed with the head having a steep dorsal profile. It has a moderately large eye which has a diameter noticeably smaller than the length of the rounded, snout. They have a small, horizontal mouth which is not protractile. There are a number of rows of small bristle like teeth in the jaws. The dorsal fin has 10-11 spines and 16-18 soft rays, while the anal fin has 4 spines and 13-15 soft rays.[2] Spines and rays of the dorsal fin are separated by a deep notch and the first spine in the dorsal fin lies flat. The rear margins of soft parts of the dorsal and anal fins is roughly vertical. The caudal fin is rounded in juveniles and truncate to weakly emarginate adults.[6] Small ctenoid scales cover the body. The body is greenish-brown to silvery with many brown to red-brown spots. Juveniles are a greenish-brown with either a few large, dark, rounded blotches, or five or six dark, vertical bars.[7] This species attains a maximum total length of 38 cm (15 in).[2]
Distribution and habitat

Scatophagus argus has a wide Indo-Pacific range. It is found from the Persian Gulf, along the south Asian coast into the western Pacific. It occurs as far north as Japan south to New South Wales, New Caledonia, and Fiji. It has also been recorded from French Polynesia.[1] It has become established in the Mediterranean Sea around Malta, probably as a result of released aquarium fishes.[8] This is a species of sheltered, shallow coastal waters such as estuaries, harbours, mangrove pools, and the lower parts of fresh water streams, particularly where there are high mineral concentrations. The very small juveniles float within the surface film of the water.[1]
Biology

Scatophagus argus is omnivorous and an indiscriminate eater. In 1992, biologists Barry and Fast reported adult scat from the Philippines were primarily herbivorous, while the juveniles preferred zooplankton.[7] Although scat were named for their purported habit of feeding on offal, the name of the genus Scatophagus means "dung eater".[5] it may be a misnomer as this behaviour has not been confirmed in diet studies.[7] Since spotted scats can live in relatively enclosed waterbodies, as well as quite far upstream in freshwater rivers, they can adapt to varying salinities. As fry, they live in freshwater environments, but as they mature, they move to saltwater environments. They do not live in temperate waters, as they require at least a little warmth between 21 and 28 °C (70 and 82 °F)[9] This species forms schools.[1]

The females attain sexual maturity at around 7-9 months of age and when the weigh 150 g (5.3 oz), whereas the males are sexually mature at a smaller size. In the Philippines, spawning is brought on by the monsoon rains that start in June and July and the increased rainfall brings cooler temperatures, increased river outflows and lower salinities. The eggs are about 0.7 mm (0.028 in) in diameter, they are transparent and have a spherical shape. The larvae take around 20 hours to hatch from fertilisation and on hatching are 1.8 mm (0.071 in) in length.[7] The juveniles pass through a pelagic tholichthys larval stage, like butterflyfishes.[6]
Utilisation

Scatophagus argus is fished for and eaten by some people from its original environment, and can sting with small spikes in its anterior parts, inflicting a venom that causes great pain and dizziness. Treatment of the wound is often done by soaking the site of invenomation in hot water.[10] It also appears in the aquarium trade.[1]
Parasites
The acanthocephalan worm Pararhadinorhynchus magnus

Scatophagus argus harbors parasites, like most fish. The acanthocephalan worm Pararhadinorhynchus magnus has been described from the intestine of this fish in waters off Vietnam.[11]
References

Collen, B.; Richman, N.; Beresford, A.; Chenery, A.; Ram, M.; et al. (Sampled Red List Index Coordinating Team) (2010). "Scatophagus argus". IUCN Red List of Threatened Species. 2010: e.T155268A4761779. doi:10.2305/IUCN.UK.2010-4.RLTS.T155268A4761779.en. Retrieved 19 November 2021.
Froese, Rainer; Pauly, Daniel (eds.) (2021). "Scatophagus argus" in FishBase. June 2021 version.
Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Species in the genus Scatophagus". Catalog of Fishes. California Academy of Sciences. Retrieved 19 August 2021.
Eschmeyer, William N.; Fricke, Ron & van der Laan, Richard (eds.). "Genera in the family Scatophagidae". Catalog of Fishes. California Academy of Sciences. Retrieved 19 August 2021.
Christopher Scharpf & Kenneth J. Lazara, eds. (12 January 2021). "Order Acanthuriformes (part 2): Families Ephippidae, Leiognathidae, Scatophagidae, Antigoniidae, Siganidae, Caproidae, Luvaridae, Zanclidae and Acanthuridae". The ETYFish Project Fish Name Etymology Database. Christopher Scharpf and Kenneth J. Lazara. Retrieved 19 August 2021.
Gomon, M.F. & Bray, D.J. (2021). "Scatophagus argus". Fishes of Australia. Museums Voictoria. Retrieved 20 August 2021.
Schofield, P.J. (2021). "Scatophagus argus (Linnaeus, 1766)". Nonindigenous Aquatic Species Database, Gainesville, FL. U.S. Geological Survey. Retrieved 18 August 2021.
Zammit, E. & Schembri, P. J. (2011). "An overlooked and unexpected introduction? Occurrence of the spotted scat Scatophagus argus (Linnaeus, 1766) (Osteichthyes: Scatophagidae) in the Maltese Islands". Aquatic Invasions. 6 (Supplement 1): S79–S83. doi:10.3391/ai.2011.6.S1.018.
"Scatophagus argus". Aquaticcommunity.com. Retrieved 2014-07-13.
Gisha Sivan; K. Venketesvaran; C.K. Radhakrishnan (15 September 2007). "Biological and biochemical properties of Scatophagus argus venom". Toxicon. Elsevier Ltd. 50 (4): 563–571. doi:10.1016/j.toxicon.2007.05.002. PMID 17599379.
Van Ha, Nguyen; Amin, Omar M.; Ngo, Ha Duy; Heckmann, Richard A. (2018). "Descriptions of acanthocephalans, Cathayacanthus spinitruncatus (Rhadinorhynchidae) male and Pararhadinorhynchus magnus n. sp. (Diplosentidae), from marine fish of Vietnam, with notes on Heterosentis holospinus (Arhythmacanthidae)". Parasite. 25: 35. doi:10.1051/parasite/2018032. ISSN 1776-1042. PMC 6057740. PMID 30040609. open access