Family: Cyprinidae, Subfamily Danioninae
Common Name: Lambchop Rasbora, Espei Rasbora
Origin and Habitat: There are two separate populations in Thailand, one in the south and the other in the east that extends into Cambodia. The intensity of colouration differs between the two areas. Occurs in slow-flowing forest streams; the southern population inhabits basic (alkaline) water, important also as the only known habitat of Betta simplex.
Compatibility/Temperament: Very peaceful, suitable for any aquarium of non-aggressive fishes. Must be kept in a group, minimum six.
Lambchop 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 spawning the fish.
Can attain 1.6 inches though usually slightly smaller.
Minimum Tank Suggestion
24 inches in length.
Water parameters for Lambchop Rasbora
Soft to moderately hard (hardness to 10 dGH), acidic to basic (pH 5.5 to 7.5) water, temperature 23-28C/73-82F.
Like its close relative the Harlequin Rasbora (T. heteromorpha), this strikingly-similar fish is also a good choice for beginning aquarists. It adapts to varying water parameters that are not extreme, is colourful, extremely peaceful, and reasonably active. Although the two habitat locales are different, this fish seems to prefer a thickly-planted and dimly lit aquarium with a dark substrate; swimming room is essential. In such a setup, with soft, acidic water, and conditioned with live and/or frozen foods, the fish will readily spawn.
Females are rounder than males, while males are slightly more colourful. The "lambchop" mark is more pointed on males, more rounded on females. Eggs are laid on the underside of plant leaves; parents will eat the eggs if not separated immediately after spawning.
This fish shares a near-identical colour and pattern with two other rasbora, Trigonostigma heteromorpha and T. hengeli. The subject species has a thinner body, is a copper-reddish colouration somewhat variable as shown in the accompanying photos, and the dark side mark is narrow and "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 species was originally described in 1967 by H. Meinken and placed in the genus Rasbora as a sub-species of R. heteromorpha and thus named R. heteromorpha espei. Rainboth & Kottelat (1987) elevated it to distinct species status as Rasbora espei. The species epithet honours Heinrich Espe, who first imported these fish to Germany in 1967.
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 was online 2 Oct. 2009.]
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