Trichopsis schalleri LADIGES, 1962

Etymology

Trichopsis: from the Ancient Greek θρίξ (thriks), meaning ‘hair’, and ὄψις (opsis), meaning ‘aspect, appearance’.

schalleri: named for Dietrich Schaller, who first imported the species to Europe.

Classification

Order: Perciformes Family: Osphronemidae

Distribution

Known from the lower Mekong River basin in Laos, Thailand, Cambodia, and Vietnam, plus tributaries of the Chao Phraya watershed in central Thailand, and drainages between the Chao Phraya and Mekong in eastern Thailand.

Type locality is ‘Nam-Mun at Korat, 135 miles northeast of Bangkok, Thailand’.

Habitat

Found in all types of still to slow-moving, predominantly lowland habitat, including swamp forest, peat swamps, floodplains, river tributaries, irrigation canals, paddy fields, and roadside ditches. Displays a distinct preference for sluggish to still environments with dense growths of aquatic or riparian vegetation.

Maximum Standard Length

40 – 50 mm.

Aquarium SizeTop ↑

An  aquarium with base measurements of 60 ∗ 30 cm or equivalent is large enough to house a pair or small group.

Maintenance

This species fares best in a well-planted, shady aquarium with plenty of surface cover in the form of tall stem plants, floating varieties, or tropical lilies. Cryptocoryne spp. are also a good choice.

Driftwood can also be used and other plants such as Microsorum or Taxiphyllum spp. may be attached to it. Small clay plant pots, lengths of plastic piping or empty camera film cases can also be included to provide further shelter.

The addition of dried leaf litter offers additional cover and brings with it the growth of microbe colonies as decomposition occurs. These can provide a valuable secondary food source for fry, while tannins and other chemicals released by the decaying leaves are considered beneficial.

As it naturally inhabits sluggish environments strong water movement should be avoided, with an air-powered sponge filter set to turn over gently adequate. Keep the aquarium well-covered and do not fill it to the top since it requires occasional access to the layer of humid air that will form above the water surface, and is an excellent jumper.

Water Conditions

Temperature: 22 – 28 °C

pH: 5.0 – 7.5

Hardness: 18 – 215 ppm

Diet

Likely to feed on insects and other small invertebrates in the wild.

Captive fish will normally accept dried products once they are recognised as edible, but should be offered plenty of small live or frozen foods such as Daphnia, Artemia or chironomid larvae (bloodworm) to ensure development of optimal colour and condition.

Behaviour and CompatibilityTop ↑

This species is peaceful unless breeding. It can be maintained in a pair or group, and will display some interesting behavioural interactions under the latter circumstances.

Sexual Dimorphism

Males are larger than females and possess extended rays in the pelvic, dorsal, anal, and caudal fins. Sexually mature individuals can also be sexed by placing a strong light behind the fish, with the ovaries in females clearly visible below the swim bladder.

Reproduction

Bubble nester. Soft water with a slightly raised temperature is said to induce reproductive behaviour.

The aquarium should have the tightest-fitting cover possible (some breeders use clingfilm/plastic wrap) because the fry need access to a layer of warm, humid air, without which development of the labyrinth organ can be impaired.

The pair need not be separated prior to spawning. The male tends to construct his nest within a raft of surface vegetation, under an overhang or in a cavity.

Once the nest is complete, the male displays to potential mates using his elongated dorsal, anal, and caudal fins, and if receptive the female approaches in a vertical, head-up position, emitting a series of ‘purring’ sounds (see ‘Notes’). Spawning normally occurs beneath the nest in an ’embrace’ typical of osphronemids, with the male wrapped around the female.

At the point of climax milt and a few eggs are released in a cluster or ‘packet’, which the male collects and transports to the nest. The process is then repeated until the female is spent, with 1-200 eggs typically deposited.

Post-spawning the adults can normally be left in situ. The female is normally tolerated by the male and may even play an active role in defending the area around the nest from intruders.

The eggs normally hatch within 48 hours with the fry remaining in the nest for 3-4 additional days, until the yolk sac is fully-absorbed. When the fry begin to swim freely the male will lose interest, and adults or fry can then be removed.

They require an infusoria-grade food for the first few days, after which they can accept motile foods such as microworm and Artemia nauplii. Water changes should be small and regular rather than large and intermittent.

NotesTop ↑

This species is sometimes referred to as ‘Mekong croaking gourami’ or ‘three-stripe gourami’.

Among congeners it can be told apart from the similar-looking T. pumila by its larger adult size and presence of a single solid dark midlateral stripe on the body, above which is a second stripe that is variable depending on the mood of the fish, sometimes fading entirely. In T. pumila the upper stripe comprises a series of blotches, the appearance of which is not mood-dependant.

Trichopsis species are able to produce audible sounds via a specialised pectoral mechanism which is unique within the family Osphronemidae. The structure comprises modified pectoral-fin tendons and muscles which are stretched and plucked by the basal portion of the anterior fin rays in a similar way to guitar strings. The pectoral-fins beat alternately, each able to generate short or long bursts of sound. These sounds are produced by both sexes, predominantly during agnostic and nuptial interactions, and they differ in temporal parameters, frequency, and pressure between the species. Studies suggest that Trichopsis species are able to settle conflicts without damaging each other physically by assessing factors such as body weight and length, which are transmitted by both visual and acoustic ‘croaking’ signals. During courtship the female produces ‘purring’ sounds in order to initiate spawning, and they are the only fishes in which this is known to occur.

Following Rainboth (1996), the genus Trichopsis can be diagnosed as follows: dorsal-fin origin markedly posterior to pectoral-fin base; pelvic-fin with a single spinous ray with a filamentous extension, and 4 branched rays; 2-4 spinous dorsal-fin rays; 4-8 spinous anal-fin rays; lateral line absent. Its closest relatives are considered to be the genera Betta and Pseudosphromenus.

Like others in the suborder Anabantoidei this species possesses an accessory breathing organ known as the labyrinth, which permits the fish to breathe atmospheric air to a certain extent. Comprising paired suprabranchial organs formed via expansion of the epibranchial (upper) section of the first gill arch and housed in a chamber above the gills, it contains many highly-vascularised, folded flaps of skin which function as a large respiratory surface. Its structure varies in complexity between species, tending to be more developed in those inhabiting harsher environments.

References

1. Ladiges, W., 1962 - Aquarien und Terrarien-Zeitschrift 15(4): 101-103
   Trichopsis schalleri spec. nov., ein neuer Gurami aus Thailand.
2. Kottelat, M., 2013 - 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. Ladich, F., 1998 - Ethology 104: 517-529
   Sound Characteristics and Outcome of Contests in Male Croaking Gouramis (Teleostei).
4. Ladich, F. and G. Schleinzer, 2015 - Comparative Biochemistry and Physiology, Part A 182: 8-13
   Effect of temperature on acoustic communication: Sound production in the croaking gourami (labyrinth fishes).
5. Linke, H., 1991 - Tetra Press: 176 pp.
   Labyrinth Fish. The Bubble-Nest-Builders.
6. Rüber L., R. Britz and R. Zardoya, 2006 - Systematic Biology 55(3): 374-397
   Molecular phylogenetics and evolutionary diversification of labyrinth fishes (Perciformes: Anabantoidei).