Amid the mouthbrooders of Lake Tanganyika one of the largest cichlids remains the supreme substrate brooder. But it only gets to breed once in its lifetime, explains Ad Konings.
Mouthbrooding among cichlids is a more advanced breeding technique than substrate brooding — and that’s probably down to the ages of Africa’s mighty Rift Valley lakes they inhabit.
Lake Tanganyika is between 12 to 20 million years old. Malawi is two to six million and Victoria is more or less 100,000 years.
Mouthbrooding in that oldest lake has likely evolved several independent times from substrate brooding ancestors and all mouthbrooding cichlids of the three lakes have likely had ancestors in Tanganyika.
Since it has been isolated from surrounding river drainage systems for most of its lifetime, the so-called less-advanced substrate brooders have had to find a way to endure life’s hardships and only the fittest survived…
Most feared of those survivors is Boulengerochromis microlepis — the Emperor cichlid — and a fish that truly rules the roost.
The reason for its survival could be down to the fact that the underwater environment has seen little change over millions of years and early substrate brooders have adapted so well to the lake’s habitats that they were never out-competed by evolving mouthbrooders.
Layer of lime
The structure of the rocky habitats in Lake Tanganyika is such that small hideouts, protecting millions of substrate brooders, are plentiful. Every object is covered with a layer of lime, a salt crust formed by the continuous precipitation of minerals from the water.
It’s therefore almost impossible to move a rock or stone. They are ‘glued’ together by the crust which provides pockets in which substrate-brooding lamprologines find shelter.
Nevertheless a few substrate brooders need neither cave nor shelter to propagate. These are large predatory cichlids that need no sympathy from the "advanced" mouthbrooders to survive.
Lepidiolamprologus profundicola and P. elongatus are both common predators of the rocky habitat and breed in the open. They are large enough to defend their offspring — although both parents are needed to effectively do so.
Even though these are large cichlids, and L. profundicola regularly exceeds 30 cm/12”, for their own protection they will find cover between the rocks. Large predators, such as Lates angustifrons, are common and will eat the predatory lamprologines if the opportunity arises.
However, Boulengerochromis microlepis has little to fear from any other fish in the lake. This is one of the largest cichlids known and can weigh more than 3 kilos/6.6 lb. Some are longer than 70cm/28”, but the average adult female is about 40cm/16” and males 50cm/20”.
B. microlepis occurs throughout the lake, but sports anglers head to the Zambian section for a real trophy species. They call it Yellow Belly, referring to the body colour of both male and female, but local fishermen call it Kuhe or Nkupe.
This giant is a piscivore when mature and juveniles of up to 20cm/8” may also feed on larger invertebrates such as crabs.
It seems most common in the deeper sandy habitats and adults are seen in shallow water only when breeding or fattening up to spawn. In deeper parts they pursue the herring-like Stolothrissa and Limnothrissa of the open water and other abundant fishes such as schooling Xenotilapia and Grammatotria on the sand.
This predator exhibits three dark blotches on a silvery-green body and one on the caudal peduncle, but, come breeding time, both male and female become golden yellow. Spawning takes place in the shallow intermediate habitat where most sightings occur. Frequently a pair can be seen together, either preparing to spawn or guarding offspring.
Fry guarders
B. microlepis is also the fastest-growing cichlid known, as males attain adult size in less than three years. It becomes sexually adult in its third year, which is when they arrive in shallow water to breed.
This is an open-substrate brooder in which both male and female guard the fry. The female, distinguished only by smaller size, keeps closer contact to the young while the male is more involved keeping intruders at bay.
A few days before the pair spawn, a suitable location is selected and defended. They may prefer sites that have few or no territorial species as neighbours. Most predation on eggs and wrigglers seems to come from roaming predators such as groups of ‘Lamprologus’ callipterus or nocturnal catfishes.
This cichlid does not always use flat rocks on which to deposit eggs. I have seen them on shells as well as on open sand. All nests, however, are close to rocks.
If spawning is taking place on sand, the female digs a shallow crater before mating. She initiates by starting to lay rows of eggs which are fertilised by the male after she leaves the nest. She then lays more rows in a different direction, again to be fertilised by the attendant male.
Although all intruders are chased from the immediate area of the nest, almost all aggression is directed towards conspecifics which are pursued up to 10m/39’ from it.
Kuwamura (1986) reported that spawning can take almost two hours and between 5,000 and 12,000 eggs are deposited!
While the eggs are still attached to the substrate, small pits are dug around the site. These are usually a single scoop of sand dug by one of the parents.
Pit transfers
It takes about three days before the eggs hatch and the larvae are immediately transferred by the female to a small pit nearby. The male does not initially help in this task, but both guard the wrigglers.
During the next five days, before the larvae become free swimming, they are transferred between pits as far as 10m/39’ apart, sometimes up to five times a day. This activity is performed by both parents to probably outsmart predators that find prey by smell, particularly catfishes at night.
When the smell of palatable young fish is spread out over 100 square metres it becomes more difficult to locate larvae huddled together in a pit with a diameter of about 15cm/6”.
Eight to nine days after spawning the fry become mobile and hover over the nest, feeding on plankton. This is the most vulnerable time as the parents cannot control the movements of more than 10,000 fry at the same time.
The fry will stay together in a dense cloud and are guarded by a parent on each side. Nevetheless, predators dart in from all sides and decimate numbers.
Most of these early-stage predators are rock-dwelling cichlids — many normally herbivorous species — and the pair have to lead their fry to even deeper regions, to habitats to avoid rocks that may hide fry predators.
In 1994 Fohrman found that captive female individuals ceased to eat about a week before spawning and continue to refrain during the period she has fry.
Poll in 1956 and Kuwamura in 1986 have examined breeding females and found they all had empty stomachs. Sometimes even males have empty stomachs.
Poll also noticed that the viscera of large sexually ripe specimens were almost completely absorbed and therefore non-functional. He suggested that this fish probably breeds just once in a lifetime...
Although we know that the viscera in other fish can regenerate after having been inactive, the semelparity (once a lifetime breeding) trait of B. microlepis is well established, having seen that parents remain with their offspring till they die from exhaustion.
Fry-guarding parents are far too occupied with fending off predators to hunt themselves. I have seen them defending offspring 10-15cm/4-6” long and therefore aged at least nine months!
It was clear that these parents had not been able to spawn again and since they were very emaciated I doubted if they ever would.
For giant tanks only
Young B. microlepis are occasionally offered for sale, but forget it if you don’t have an aquarium of at least 5,000 l/1,100 gal volume.
B. microlepis grows large in a matter of months and will eat any bite-size co-inhabitant of the aquarium. Needless to say, this predator needs a lot of food, preferably fish (frozen from a marine source) and frequent water changes in order to keep the nitrate level low.
This fish may be OK for a public aquarium where it can have sufficient space and compatible company, but with a lifespan of less than four years and quite a gregarious hunting behaviour, it may not be compatible for a Tanganyika community set-up.
The most suitable place to observe this beautiful beast is in its natural setting!
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.