Hemibagrus microphthalmus (DAY, 1877)

SynonymsTop ↑

Macrones microphthalmus Day, 1877; Mystus microphthalmus (Day, 1877)

Etymology

Hemibagrus: from the Greek hemi, meaning ‘half’ and the generic name Bagrus.

microphthalmus: from the Greek micro, meaning ‘small’, and ophthalmos, meaning ‘eye’.

Classification

Order: Siluriformes Family: Bagridae

Distribution

Type locality ‘s ‘Irrawaddy River valley, Myanmar’, and this species is currently known from the Salween, Irrawaddy (aka Ayeyarwady) and Sittaung (aka Sittang) river systems in Myanmar and western Thailand, plus the Manipur River drainage in northeastern India.

Maximum Standard Length

The largest specimen known to date measured 1500 mm.

Aquarium SizeTop ↑

Suitable only for public displays or the very largest home aquaria.

Diet

Probably a predator feeding on crustaceans and smaller fishes, although there should be no need to use such live foods in captivity.

Behaviour and CompatibilityTop ↑

Likely to prove aggressively territorial and incompatible with other fishes in all but the largest public installations.

NotesTop ↑

This species cannot be considered a suitable home aquarium‚ subject given its eventual size plus the fact it can live for‚ several decades.

It can be told apart from most other congeners by the diagnostic characters given in Ng and Kottelat (2013) for the H. wyckii species group (see below) and from other group members except H. wyckii by possessing grey (vs. red) fins in life, plus a number of biometric characters.

It differs from H. wyckii in having, a poorly-ossified dorsal spine which is thinner than the soft dorsal-fin rays (vs. a well-ossified spine at least as thick as the branched dorsal-fin rays) and lacking (vs. with 10–12) serrations on the posterior edge, absence (vs. presence) of pale principal rays in both the upper and lower caudal-fin lobes and a grey (vs. cream) cleithral region.

Hemibagrus has been divided into a number of putative species groups which may or may not represent monophyletic assemblages, and following a major review by Ng and Kottelat (2013) H. microphthalmus is included in the H.  wyckii group.

Members of this assemblage can be told apart from other congeners by possession of a broad, highly-depressed head, 50-54 vertebrae and light-coloured principal rays in both upper and lower caudal-fin lobes.

Currently valid members are H. maydelli, H. microphthalmus, H. wyckii, and H. wyckioides.

The genus Hemibagrus currently contains 40 nominal species which are distributed east of the Godavari River system in India and south of the Changjiang (Yangtze) drainage in China, with Southeast Asia a particular centre of diversity.

Many species are important food fishes and some are cultured for the purpose, or for sport angling.

Hemibagrus has previously been considered synonymous with Mystus but following Ng and Kottelat (2013) members can be diagnosed by their moderate to large adult size and strongly-depressed head shape with the interorbital region normally flat or slighly convex.

The grouping also shares a number of characters with the genera Sperata and Bagrus, and these three can be separated from other bagrids by the following: mesethmoid highly depressed (vs. not highly depressed), prominent (vs. reduced) dorsoposterior laminar extension of the mesethmoid, the first infraorbital with (vs. lacking) a posterolateral spine, enlarged (vs. moderate or small) premaxilla, and the metapterygoid with a long, free posterior margin (vs. contacting quadrate and hyomandibular).

Hemibagrus can be told apart from Sperata by possession of a a relatively short and slender (vs. enlarged and elongate) interneural and by absence (vs. presence) of a concave surface in the posterior portion of the posttemporal in which lies a portion of the swimbladder.

It’s distinguished from Bagrus by possession of 7, very rarely 8 (vs. 8-10) soft dorsal-fin rays.

References

1. Ferraris, C. J., Jr., 2007 - Zootaxa 1418: 1-628
   Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types.
2. Ng, H. H. and C. J., Jr. Ferraris, 2000 - Proceedings of the California Academy of Sciences 52(11): 125-142
   A review of the genus Hemibagrus in southern Asia, with descriptions of two new species.
3. Ng, H. H. and M. Kottelat, 2005 - The Raffles Bulletin of Zoology 61(1): 205-291
   Revision of the Asian catfish genus Hemibagrus Bleeker, 1862 (Teleostei: Siluriformes: Bagridae).