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Last updated on April 25, 2014 at 1:22 EDT

Kribensis

Pelvicachromis pulcher is a freshwater fish of the cichlid family, endemic to Nigeria and Cameroon. The species is popular amongst aquarium hobbyists, and is most commonly sold under the name Kribensis, although the species has other common names, including various derivatives of Kribensis: Krib, Common Krib and Rainbow krib, along with rainbow cichlid and purple cichlid.

Appearance, size and coloration

In the wild, male P. pulcher grow to a maximum length of approximately 4.9 in (12.5 cm) and a maximum weight of 0.34 oz (9.5 g). Females are smaller and deeper bodied, growing to a maximum length of 3.2 in (8.1 cm) and a maximum weight of 0.33 oz (9.4 g). Both sexes have a dark longitudinal stripe that runs from the caudal fin to the mouth and pink to red abdomens, the intensity of which changes during courtship and breeding. The dorsal and caudal fins also may bear gold-ringed eye spots or ocelli. Males show color polymorphisms in some populations collected at single localities. Juveniles are monomorphic until approximately 6 months of age.

Distribution, habitat and predators

P. pulcher is native to southern Nigeria and to coastal areas of Cameroon, where it occurs in warm 75-79 °F (24″“26 °C), acidic to neutral (pH 5.6 – 6.2), soft water (12-22 mg L-1 [CaCO3]). The species inhabits both slow and fast-moving water, though it is only found where patches of dense vegetation are available. In the natural habitat, P. pulcher have been observed excavating, defending and sheltering in caves dug underneath plants, and these holes are also used for breeding. Not all P. pulcher, however, claim territories and many live in large, non-reproductive aggregates.

Feral populations

Populations of P. pulcher also occur outside its natural range in Hawaii, USA as a by-product of the ornamental fish trade.

Feeding

Despite the suggestion in some aquarium literature that the species feeds on worms, crustaceans and insects, analysis of the stomach contents of wild P. pulcher suggests this is incorrect. A study by Nwadiaro (1985) of 161 individuals showed that the main food items were diatoms, green algae, pieces of higher plants along with blue-green algae. Invertebrates, though consumed, were found by that study to be relatively uncommon food items for wild fish.

Sexual dimorphism and reproduction

Like other Pelvicachromis species, P. pulcher is sexually dimorphic. Males have a pointed pelvic fin, while the females’ pelvic fin appears more rounded. In addition, males are larger, lack the gold sheen to the dorsal fin and have a more elongated, spade-shaped caudal fin. The species are secretive biparental cave spawners (speleophils) but information on their reproductive biology in the wild is scarce. In captivity, however, the species is known to spawn in narrow-mouthed caves which are excavated prior to egg-laying. The eggs are adhesive and are frequently laid in rows of 10 on the upper surface of the cave and produce a clutch that ranges in size from 40-100. Both parents provide active brood care, typically lasting 21-28 days, which includes guarding, herding and feeding. It is noteworthy, however, that the female is predominantly responsible for fry care, while the male is primarily involved in territorial defense. As in all Pelvicachromis species, the gender ratio of female to male fry increases with pH. The ratio of males to females also is known to vary at different locales in the wild. Breeding pairs of P. pulcher have been known to adopt similarly aged fry from conspecifics in aquarium trials, and it has been suggested this may be an adaption to reduce predation on their own fry. Male color polymorphism may be indicative of behavioral differences. For example, red males obtained from a single site were found to be more aggressive and more polygamous than yellow males obtained from the same site. In addition, the species has been demonstrated to engage in cooperative territorial defense where multiple males defend a single territory.

Taxonomy

Pelvicachromis pulcher was originally described by George Boulenger in 1901, though subsequently a number of junior synonyms (Pelmatochromis aureocephalus, Pelmatochromis camerunensis) and misidentifications (Pelmatochromis kribensis, Pelmatochromis subocellatus var. kribensis and Pelmatochromis pulcher var. kribensis) were brought into use. Some of these synonyms are still in use by aquarium hobbyists which complicates identification of this species. Many of the common and trade names used for this species, such as Kribensis, Krib, Rainbow Krib are derived from the erroneous binomial, Pelmatochromis kribensis.

In the aquarium

P. pulcher is a popular cichlid for the aquarium. The species should be housed in minimum volumes of 21-25 gallons (80-90 liters). Fine gravel should be used as a substrate, as the species likes to burrow and to excavate caves. The aquarium should mimic the natural environment, and should be decorated with numerous caves, plants and hiding places. Dither fish are useful in reducing the innate shyness of the species. The species is an unfussy feeder and will accept a range of prepared foods. The species spawns readily in captivity and will accept artificial caves as substitutes for the holes used for spawning in the wild. Although tolerant of a range of water chemistries, the species has a preference for, and is more likely to breed when maintained in soft, acidic water.

Kribensis