Discherodontus schroederi (SMITH, 1945)

SynonymsTop ↑

Acrossocheilus schroederi Smith, 1945

Etymology

Discherodontus: from the Ancient Greek δίς (dís), meaning ‘twice’, σειρά (seirá), meaning ‘series, line’, and ὀδών (odon), meaning ‘tooth’, since members of this genus possess two rows of pharyngeal teeth which sets them apart from related taxa.

schroederi: named for William C. Schroeder, associate curator of fishes in the Museum of Comparative Zoology (United States) at the time this species was described.

Classification

Order: Cypriniformes Family: Cyprinidae

Distribution

Native to the Mae Klong and Chao Phraya river basins in Thailand. According to Rainboth (1989) specimens from the two drainages vary in morphology with those from the Mae Klong possessing longer fins and greater body depth among other characters.

He surmises that this may be because it occurs sympatrically with D. halei in the Mae Klong and has thus evolved differently. Although D. halei has been recorded from the Chao Phraya it hasn’t been collected there for over 70 years.

Type locality is given as ‘the Mekang on Doi Angka, northern Thailand’, which corresponds to what is now referred to as Doi Inthanon National Park in Chiang Mai province, and thus the Mae Ping river basin, an upper tributary within the Chao Phraya watershed.

Habitat

Inhabits clear, fast-flowing minor rivers and forest streams. The latter tend to have thick marginal vegetation with dense rainforest canopy above. There are almost no true aquatic plants but submerged roots and other parts of emergent species are common. Leaf litter and fallen branches tend to accumulate in the stiller zones and this is where the fish are most often found.

It’s also been collected in more open areas but wherever it is found the substrate is composed of boulders, smaller stones, sand and/or gravel along with decomposing plant material. From images we’ve seen typical habitats are composed of short sections of rocky rapids interspersed by deeper pools with exposed bedrock.

Rainboth describes how he collected a large group of young specimens from a shaded, near stagnant side pool containing a deep layer of rotting vegetation next to a fast-flowing section of the Ping River.

Maximum Standard Length

90 – 100 mm.

Aquarium SizeTop ↑

An aquarium with base dimensions of 120 ∗ 30 cm or equivalent should be the smallest considered.

Maintenance

This species will do well in most larger, well-maintained tanks if plenty of hiding places are provided and should not harm softer-leaved plants. However we highly recommend keeping it in a set-up designed to resemble a flowing river with a substrate of variably-sized rocks and gravel and some large water-worn boulders. The tank can be further furnished with driftwood roots and branches arranged to form some shaded spots.

While the vast majority of plant species will fail to thrive in such surroundings hardy types such as Microsorum, Bolbitis or Anubias can be grown attached to the décor and bright lighting will promote the growth of algae upon which the fish will graze. In this kind of environment it will show more natural behaviour and can be kept alongside some other species that enjoy similar conditions.

Like many other fish that hail from running waters it’s intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive meaning  weekly water changes of 30-50% tank volume should be considered routine. Though torrent-like conditions are unnecessary it also does best if there is a high proportion of dissolved oxygen and moderate water movement.

Since it doesn’t cope well with fluctuating water conditions try to acclimatise it to the aquarium over a couple of hours if possible and never introduce it to a biologically immature system.

Water Conditions

Temperature: 23 – 26 °C

pH: 6.0 – 7.5

Hardness: 36 – 215 ppm

Diet

The natural diet of Discherodontus species is comprised largely of aquatic and terrestrial invertebrates. In the aquarium they should be offered regular meals of live and frozen foods such as bloodworm, Daphnia and Artemia along with good quality dried flakes and granules. In a river-style set-up as described above they will often be seen browsing the biofilm that tends to form on the rockwork.

Behaviour and CompatibilityTop ↑

Peaceful and an ideal resident of the larger, well-furnished community set-up where it will spend most of its time in the lower part of the tank. It will do best when kept alongside other non-aggressive species that require well-oxygenated water. There are plenty of suitable choices including many cyprinids, loaches, catfish and characins although substrate-dwelling cichlids are best omitted unless the tank is very large.

A community based around one of its native river basins would also make a worthwhile project with some interesting alternatives. Just a few of the species occuring in similar habitats of the Chao Phraya include Homaloptera smithi, Nemacheilus masyai, N. pallidus, Schistura menanensis, S. waltoni, Acantopsis choirorhynchos, Lepidocephalichthys berdmorei, L. hasselti, Yasuhikotakia morleti, Laubuca laubuca, Crossocheilus atrilimes, C. oblongus, C. reticulatus, Cyclocheilichthys repasson, Esomus metallicus, Garra cambodgiensis, G. fuliginosa, G. nasuta, Mystacoleucus obtusirostris, Rasbora argyrotaenia, R. paviana, R. rasbora and R. trilineata.

It’s a schooling species by nature and ideally should be maintained in a group of at least half a dozen specimens. Maintaining it in decent numbers will not only make the fish less nervous but will result in a more effective, natural-looking display. Males will also display their best colours as they compete with one other for female attention.

Sexual Dimorphism

Sexually mature females should be noticeably thicker-bodied and a little larger than males.

Reproduction

Unreported.

NotesTop ↑

Discherodontus species are poorly-documented in the hobby, partly as a result of their relatively limited natural ranges but also because most are notoriously delicate and difficult to ship. D. schroederi  is said to be the hardiest member of the genus but it is rarely collected for the aquatic trade and may not yet have been exported to Europe or the USA. Presumably this is because it is the least colourful of the Thai species as in other respects it would seem to have the makings of an excellent aquarium subject.

The genus was erected by Roberts in 1989 in order to group together a trio of species previously included in the genera Puntius or Acrossocheilus, and has since been expanded to include the Chinese species D. parvus. The primary basis for the separation is that members possess two rows of pharyngeal teeth rather than the three found in almost all other related species.

They’re most closely-related to members of the Indian genera Chagunius and Hypselobarbus and can be further defined by the following combination of characters: vent located relatively anteriorly on body, with additional scale rows between vent and anal-fin; dorsal–spine serrations smal or absent; absence of demarcation between the lower lip and jaw; tips of dorsal–fin and caudal-fin lobes with dark pigmentation.

Of its congeners D. schroederi is most similar to D. ashmeadi and when juvenile the two may be confused. However it is much the less colourful fish and as it grows the prominent dark dorsal blotch fades to a thin, dark distal band whereas in D. ashmeadi it is retained throughout life. It also has noticeably longer barbels than other members of the genus.

References

1. Smith, H. M., 1945 - Bulletin of the United States National Museum No. 188: i-xi + 1-622
   The fresh-water fishes of Siam, or Thailand.
2. Kottelat, M., 2013 - The Raffles Bulletin of Zoology Supplement 27: 1-663
   The fishes of the inland waters of southeast Asia: a catalogue and core bibiography of the fishes known to occur in freshwaters, mangroves and estuaries.
3. Rainboth, W. J., 1989 - Occasional Papers of the Museum of Zoology University of Michigan 718: 1–31
   Discherodontus, a new genus of cyprinid fishes from southeastern Asia.