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- Cyprinid Species (http://www.tropicalfishkeeping.com/cyprinid-species/)
- - Trigonostigma hengeli (http://www.tropicalfishkeeping.com/cyprinid-species/trigonostigma-hengeli-193809/)
Family: Cyprinidae, Subfamily Danioninae
Common Name: Hengel's Rasbora, Copper Rasbora
Origin and Habitat: Certain areas of the Greater Sundra Islands, Sumatra and Borneo, Indonesia. Occurs in slow-flowing streams thick with aquatic plants.
Compatibility/Temperament: Very peaceful, suitable for any aquarium of non-aggressive fishes. Must be kept in a group, minimum six but better with eight or more.
Hengels Rasbora Diet
In its habitat it feeds on insects, crustaceans, worms and zooplankton. It readily accepts prepared foods, but colouration will be best with some frozen or live foods and these will also aid in attempts at spawning the fish.
Slightly over 1 inch (3 cm).
Minimum Tank Suggestion
24 inches in length.
Water parameters for Hengels Rasbora
Soft to moderately hard (hardness to 10 dGH), acidic (pH 5.5 to 7.0) water, temperature 23-28C/73-82F.
This species is rarer in the hobby than its two close relatives the Harlequin Rasbora (T. heteromorpha) and Lambchop Rasbora (T. espei) and more demanding of specific water parameters. This fish does best in a thickly-planted and dimly lit aquarium with a dark substrate; some swimming room is essential. The fish occurs in very slow-moving streams and needs very minimal if any filter flow, otherwise it will struggle and not last.
It has a lifespan of 2-3 years. Females are rounder and deeper-bodied than males. Not easy to spawn; eggs are laid on the underside of plant leaves; parents will eat the eggs if not separated immediately after spawning.
This fish shares a very similar pattern with two other rasbora, Trigonostigma heteromorpha and T. espei. The subject species is smaller, the overall body colouration is rather colourless (sort of a gray and sometimes rather transparent) with a bright orange-copper colouration along the anterior and upper sides of the narrower dark mark that is "lambchop" in appearance. A fourth species in the genus, T. somphongsi, has a dark broad stripe [rather than a triangular mark] that runs laterally below an iridescent stripe; this species occurs in the basin and floodplain of the Menam River in Thailand and is very rare.
This fish is sometimes referred to as the Glowlight Rasbora, but this common name is confusing as another rasbora species is also seen under the same name.
This species was originally described in 1956 by H. Meinken and placed in the genus Rasbora. Rasbora has been a "catch-all" genus for 138 species of small minnow-type fish. Ichthyologists have (especially during the last two decades) questioned the relationships between many of these species, and Maurice Kottelat and others recognized that the genus was polyphyletic [Greek, "of many races"] which in this instance means it contains species whose last common ancestor is not included. Several species have been transferred out of Rasbora into Microrasbora [now considered a Danio], Boraras and Trignonstigma [these latter two are monophyletic, meaning that they include the ancestor and all descendants], and the species remaining in Rasbora were grouped into clades awaiting further study.
As a result of their study of some of the cyprinid fishes, Kottelat & Witte (1999) erected the new genus Trigonostigma for this and the three closely-related species. This name is from the Greek trigonon (=a triangle or hatchet) and stigma (=a spot or brand). T. heteromorpha is the type species for the genus. This separation was made on the basis not only of the striking similarity in colour and pattern, but more on the spawning method that differs from all other rasbora; in these four species, the female attaches the eggs to leaves, usually on the underside, and the male comes along to fertilize them. Other species of rasbora are egg scatterers. Subsequent studies (Liao et.al. 2010, and others) have confirmed this division on the basis of phylogenetics.
Fang, F., M. Norén, T.-Y. Liao, M. Källersjö and S. O. Kullander (2009), "Molecular phylogenetic interrelationships of the south Asian cyprinid genera Danio, Devario and Microrasbora (Teleostei, Cyprinidae, Danioninae)," Zoologica Scripta volume 38 (no. 3), pp. 237-156. [Published first online, 1 Jan. 2009, pp. 1-20.] Kottelat, Maurice & K.-E. Witte (1999), "Two new species of Microrasbora from Thailand and Myanmar, with two new generic names for small southeast Asian cyprinid fishes (Teleostei: Cyprinidae)," Journal of South Asian Natural History, volume 4 (no. 1), pp. 49-56.
Liao, Te Yu, Sven Kullander and Fang Fang (2010), "Phylogenetic analysis of the genus Rasbora (Teleostei: Cyprinidae)," Zoologica Scripta v. 39 (no. 2), pp. 155-176. [Electronic publication online 2 Oct. 2009.]
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