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FACTSHEETS: September 2025 - no. 351

Erethistes filamentosus (Blyth 1860)

bit of history is called for, as in our September factsheet (2025). Ferraris (2007) moved Hara back to its original placement from Erithistidae to the Sisoridae family, which had been moved there by de Pinna in 1996, along with Conta, Erethistoides, Erithistes and Pseudolaguvia. Thompson & Page (2006) published a paper on the Genera of the Asian catfish families Sisoridae and Erethistidae. In part, they set forth their diagnosis and reasons for reclassifying or, more to the point, reassigning Hara species as Erethistes.

Erethistes filamentosus

Erethistes filamentosus is still listed as Hara filamentosa in Fishbase and a few other online sources but this name is treated as a synomyn in Eschmeyer's Catalog of Fishes.

Erethistes filamentosus - head view

Identifying the "Asian Moth cats" is no easy matter with at the the last count of about 11 (2025) described species of Erithestes. To go some way to identifying these species we have this months factsheet, Erithistes filamentosus which sports a long filament to the top ray of the caudal fin, E. jerdoni which has very long pectoral spines and is also very much smaller in size, E. horai which grows larger and has a larger adipose fin. These are the most common, along with E. hara for the "Moth Cats" seen in the aquarium trade today.

On another note, Talwar & Jhingran (1992), stated that both E. filamentosus (Blyth, 1860) and E. saharsai Datta Munshi & Srivastava, 1988 are synonyms of Erithistes hara, just confirming how alike and confusing the members of this genera are.

Distrbution: Asia, Ataran, Salween and Sitting river drainages: Myanmar and Thailand. Type locality: Tenasserim, Burma.

The Ataran, Salween, and Sittang (also known as Sittaung) river drainages are located in Myanmar (Burma) and Thailand. The Salween River is a major river in Southeast Asia, flowing from the Tibetan Plateau south into the Andaman Sea. The Ataran River is a tributary of the Salween, merging with the Gyaing River before joining the Salween near Mawlamyine. The Sittang River also flows through Myanmar, but it is separate from the Salween and Ataran systems.

Common Name

None

Synonyms

Erethistes maesotensis, Hara filamentosus, Hara filamentosa, Hara maesotensis

Family

Sisoridae

Subfamily

Sisorinae

Habitat

Found in fast flowing river with depth nowhere more than 80 cm and with bottom mainly consisting of stones and sand with numerous empty gastropod shells.

Distribution

Asia: Ataran, Salween and Sitting river drainages: Myanmar and Thailand. Type locality: Tenasserim, Burma.

Size

5.0cm. (2ins)

Temp.

20-24°C (66°-75°F)

p.H.

6.0-7.5.

Characteristics

Caudal peduncle length 14.9-17.8% SL, depth 6.1-7.2% SL (depth 2.1-2.9 times in its length); body depth 13.9-19.2% SL. No thoracic adhesive apparatus; robust (vs. slender) body; 8–12 anal rays; anterior margin of pectoral spine with serrations all pointing toward tip of spine, or arranged in divergent pairs, or outwardly directed and not divergent; smooth to granulate anterior margin on dorsal spine; papillate upper lip; 8–12 anal rays. Long filament extending from upper segment of caudal fin.

Colouration

Head and body dark chestnut brown to light chocolate brown, with a mottling caused by numerous smaller, irregular darker brown patches. Belly and ventral surfaces of head light brown. Two thin, irregular light brown bars on body: first chevron-shaped and located between dorsal and adipose fin bases, second thicker than first and located on caudal peduncle. Dorsal fin dark mottled brown, except for thin hyaline distal margin. Pectoral fin dark brown, with thin hyaline distal margin and either a small ovoid hyaline spot or a crescentic median hyaline band on middle third of fin. Pelvic and anal fins hyaline, with dark brown bases and subdistal stripes. Adipose fin brown as in body, with lighter coloured distal margin. Caudal fin hyaline, with irregular W-shaped band subdistally and with small dark brown flecks randomly distributed throughout fin. Two small light brown patches present at bases of caudal fin lobes in some individuals. Maxillary and mandibular barbels light brown, with dark brown annuli, (Ng, Heok Hee, & Kottelat, Maurice 2007).

Aquarium Care & Compatibility

A tank with a sandy bottom and rounded stones and pebbles with a good water flow as befits an asian hillstream setup. Good water quality is a must for this family. Keep the water temperature on the cool side of a tropical aquarium. Tank mates such as the zebra danio (Brachydanio rerio) and asian fish of the same small size will make good tankmates.

Reproduction

Unknown

Sexual differences

Females are deeper and wider bodied.

Diet

Prefers live foods such as bloodworm, grindle worm and daphnia.

Glossary of Terms

Anal fin: The median, unpaired, ventrally located fin that lies behind the anus, usually on the posterior half of the fish.
Caudal fin: The tail.
Caudal peduncle: The narrow part of a fish's body to which the caudal or tail fin is attached.
Dorsal fin: The primary rayed fin(s) on top of the body.
Hyaline: Transparent or clear without pigment.
Pectoral fin: The paired fins just behind the head.

Etymology

Erithistes: Etymology not explained, presumably erethizon, porcupine and–istes, adjectival suffix, i.e., porcupine-like, referring to strong and serrated dorsal and pectoral-fin spines.
filamentosus: Latin for filamentous, referring to long filament extending from upper segment of caudal fin.

IUCN Red List

Not evaluated.

References

Adrian Taylor: pers. comm.
Ferraris, C.J. Jr., 2007. Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types. Zootaxa 1418:1-628.
Ng, Heok Hee, & Kottelat, Maurice. (2007). A review of the catfish genus Hara, with the description of four new species (Siluriformes: Erethistidae). Revue suisse de zoologie, 114, 471--505.
Thomson, A.W. and L.M. Page 2006 Genera of the Asian catfish families Sisoridae and Erethistidae (Teleostei: Siluriformes). Zootaxa 1345:1-96.
Sisoridae Erethistes filamentosus" - Erethistes filamentosus (Blyth, 1860) collected in Thailand by Florida Museum of Natural History Ichthyology.
The ETYFish Project Fish Name Etymology Database © Christopher Scharpf.

Photo Credits

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ScotCat Sources

Etymology-genus name

Etymology-specific name

Other Sources

Fishbase

Wikipedia

Catalog of Fishes

GBIF

FishNet2

iNaturalist