Callochromis pleurospilus (Boulenger 1906): A beautiful beast

Description:

Callochromis pleurospilus was described by Boulenger in 1906, under the name of Pelmatochromis pleurospilus, but was moved to the new genus Callochromis, established by Regan in 1920, where it still remains today. Callochromis have some similarities in common with species in the genus Xenotilapia, but differ primarily by having only two lateral lines and the outer ray in the ventral fins being longer than inner ray, whereas Xenotilapia (sensu Poll 1986) have three lateral lines and the outer ray in the ventral fins are shorter than or equals the inner ray.

Callochromis pleurospilus is a maternal mouthbrooder with a distinct sexual dimorphism; while the males are gorgeously coloured, the females are much more anonymous dressed in silver. The body is elongated and the standard length is 10-11 cm for males and a little shorter for the females; the eyes are big and oval and placed high on the head. A very special feature linked with all Callochromis species are the unique egg-spot on the males’ anal fin, appearing as a orange-red band, which can’t be found in any other mouthbrooding cichlid in Lake Tanganyika.

The type specimen of Callochromis pleurospilus was caught in M’pala in Congo, but it has a like-wide distribution and several geographical variants are known. The variants from Burundi, Zambia and Kigoma in Tanzania are the most commonly exported to the aquarium hobby: The Burundi variant is known as the "red-dotted pleurospilus" and has a row of 6 horizontal red dots on the flank, the Zambian as the red one and last the variant from Kigoma, known under the trade names "Greshakei" or "Rainbow-pleurospilus" (Konings 1998). The latter has wide red margin to the dorsal fin and a beautiful bluish-green shimmering body.

Molecular phylogenies has confirmed the results of older morphological studies: The species in the genus Callochromis form a monophyletic entity, and constitute an independent clade within the Ectodini tribe (Koblmüller et al. 2004). In 1998 Takahashi & Nakaya made Callochromis stappersii a junior synonym of C. pleurospilus due to overlapping morphometric data between the two (Takahashi & Nakaya 1998), but recent molecular analyses have shown that C. stappersii may in fact be a valid taxa (Koblmüller et al. 2004). This topic will be discussed in a separate paper.

Callochromis pleurospilus in the wild…..

Callochromis pleurospilus are found in the sandy and sediment-rich shallows in the Lake, often located near river outlets or protected bays. Water plants are found in this habitat, the most commonly being Vallisneria spiralis, Ceratophyllum demersum, Myriophyllom spicatum and Hydrilla verticillata (Konings 1998). Out of the breeding season Callochromis pleurospilus form large foraging schools; they feed primarily on crustaceans, small snails, shrimps, insect larvae and other invertebrates and stomach investigations has even revealed remains of fish (Poll 1956); Callochromis pleurospilus can thus be regarded as a generalized carnivore.

Callochromis pleurospilus feeds by sifting the upper layer of sand, filtering it for food. In the Lake they leave the bottom strewn with small pits where they have been searching for food, and similar pits can be seen in the aquarium.

C. pleurospilus is a maternal mouthbrooder, where the males construct small sand-scrape nest, often near rocks or water plants; the nests are located in very shallow water, often less than two meters of depth. The small nests have a diameter of app. 15 cm with an elevated rim. Ripe females are often seen huddle together under the cover of the water plants or at the edge of a more rocky section of the habitat. Mouthbrooding females are often found solitary or in small groups and hide in the water plants as well (Konings 1998).

.....and in the aquarium

In the aquarium Callochromis pleurospilus turns out, in spite of its delicate appearance, to be a rather aggressive and rough sand-dweller, which is best kept in small groups consisting of a single male and at least three females. If more then one male is kept together, it nearly always ends up with one male being the strongest and most dominate, controlling more and more of the aquarium as time goes by; the result of this is at best a male hiding in the corner, or worse, a dead one.

A harem-group as the former can be kept in an aquarium with a length of 120 cm (app. 4 feet) if it’s provided with sufficient shelter for the females. Besides a sandy bottom the tank should have several caves built out of rock and some groups of water plants to offer the females some protection.

While the aggressiveness of Callochromis pleurospilus can be a drawback when trying to keep more males in the same aquarium, it can actually be an advantage when keeping them together with other lake Tanganyika cichlids, as they are much more robust and not so delicate as many of the species in the genus Xenotilapia tend to be. Callochromis pleurospilus can without problems be kept with some of the more rough free-swimming species like e.g. Cyprichromis sp. "leptosoma jumbo" and even Ophthalmotilapia ventralis, of course taken into consideration that the aquarium should be bigger than mentioned above. Callochromis pleurospilus will also do well with various small sized cave-dwelling species from the genus Neolamprologus, if the aquarium is decorated to fulfill the needs of all species, i.e. areas of open sand for Callochromis pleurospilus and piles of rock for the cave-dwellers.

The menu should consist of a replica of its natural diet so various forms of frozen food like artemia, cyclops, mysis and mosquito-larvae (not the red ones!) would be good, as well as chopped up krill and shrimps. I have often observed that Callochromis pleurospilus under their hunt for food stops up, swim a little backwards, looks at the sand and then suddenly trust themselves into the sand completely burying the head. To satisfy this feeding behavior I sometimes bury bits of frozen food in the sand; there is no need to worry about the food not getting eaten, the fish will quickly locate it in the sand – very interesting and good fun to watch!

Reproduction

Callochromis pleurospilus is like the rest of the three species in the genus Callochromis a lek-breeder. In their natural habitat the nests are placed a couple of meters apart and that is the reason why we cannot normally have more than one male in our tank; the males will constantly fight and the strongest male will try to chase the weaker male out of its territory. In a small tank the subdominant individual(s) cannot escape the wrath of the dominant male, which will get furious because of the never-ending intrusion on his territory; in time the story usually ends as described above, with only one male left in the aquarium.

But the most interesting has yet to come; the spawning. The male tries vigorously to lure the female into the nest and if he succeeds tries to cut her off in order to prevent her from escaping. The male then leads the female to the centre of the nest and shows where she should deposit her eggs; this is done by folding the anal fin so that the orange-red margin resembles an egg in three dimensions, while holding it in the centre of the nest; a very interesting play to watch! The female deposits some eggs in the centre of the nest and then turns around and picks them up. At the same time the male holds his folded anal fin in front of the female’s mouth and releases his semen. The female immediately tries to catch the moving "egg" and snaps at it, resulting in the fertilizing of the eggs inside the females mouth. This scenario is repeated until the females is empty of eggs

The clutch size of Callochromis pleurospilus ranges between 15 and 50 eggs. Young not fully grown females have smaller clutches and they often produce more eggs than can be taken into the mouth and they become eaten by the male. Being a maternal mouthbrooder, only the female holds the eggs and larvae in the mouthbrooding period which last for 18-21 days. The larvae are app. 10 mm upon release and no further brood care is being done by female. The newly released fry should immediately be fed with newly hatched artemia, frozen bosmins and cyclops. The fry grow relatively fast and reach 20-25 mm after a couple of months. After a year they reach a length of 6-7 cm and are ready to spawn; some individuals even become sexually mature at a length of only 4-5 cm.

Conclusion

Callochomis pleurospilus is an extremely beautiful sand-dweller, with a breeding behavior that is one of the most spectacular among the sand-dwellers, but in the same time a very aggressive one. Instead of seeing the aggression as an annoying drawback when keeping this species, it is much better to look at it on the bright side, and use the aggression to be able to have a sand-dweller element in a Lake Tanganyika community aquarium, where many other sand-dwelling species would be suppressed and stressed.