BREEDING BEHAVIOUR: GETTING A PAIR
The greatest challenge in spawning cichlids in the home aquarium seems to be getting the pair to do their business and churn out the fry. Assuming one has a male and a female, which is not always easy to select in some species, the problem is to ensure that they mate and produce fry without killing each other. Aquarists often try to breed a pair of cichlids in an isolated tank. This may be necessary if the only available tanks are too small to sustain a community of fish. Given a large enough tank, however, it is known that it is often easier to breed cichlids if there are some dither fish with them.
Dither fish may be other cichlids of the same or different species, but need not be. They can be cyprinids or other speedy fish that distract the breeding pair’s aggression from each other and focus it outward against the dither fish. It was recently demonstrated with experiments on angelfish that pair bonding is maintained when there are intruders to defend the nest against . Monogamous marriages among angelfish are the result of a mutually defended territory, not an altruistic feeling.
Aquarists often have trouble selecting a male and a female of a cichlid species. The best method is to raise up six fry and let them do the selecting, but that is not always possible. Even for the fish themselves, they sometimes have trouble. This was shown with a study on three closely related Lake Malawi cichlids where males were isolated from various females by glass so they only had visual cues to go by. Pseudotropheus males in the study could identify females solely by sight in some species, but in other species the males were unable to correctly select females by sight alone . This suggests that olfactory cues, that is, the scent of the females in the water, may play a part in pair formation. Sound production was ruled out in this experiment, but it is known to be used by other cichlids. Given that even the males (who should know) have trouble identifying their own female conspecifics, it is not surprising that aquarists trying to do their own matchmaking have hybridized Pseudotropheus species unwittingly. All those bland females look alike but are not alike in the gene pool.
Courtship may involve sounds, although aquarists may not be able to hear the serenades. The males of two Malawi cichlids are known to produce pulsed sounds while courting females, those being Tramitichromis cf. intermedius and Copadichromis conophorus .
RAISING THE FRY
One peculiarity of some Tanganyikan cichlids is that juveniles will help older fish raise fry, such as assisting in mutual defence of territory. Neolamprologus brichardi is well known for this behaviour. A swarm of such fishes on a rock pile consist of parents, their young fry, older juveniles, and unrelated juveniles from elsewhere. Such altruism gives the brood care helpers experience in learning to raise children for when their own time comes. Aquarists should not be too hasty in breaking up hatches of such fish if all else is well. Indeed, what may contribute to cichlid mayhem and murder in aquaria, besides too-small tanks, is that many fry are siphoned out and raised separately. They never learn the social cues that enable fish to get along, much as the problem with most human juvenile delinquents is that they are from broken homes where they never learned proper behaviour. When they are sold off and placed in new homes, the isolated fry cause difficulties in breeding.
Sometimes altruism in habitat loses precedence to selfish DNA. Neolamprologus brichardi juveniles greater than 4.5 cm standard length are mature. Mature enough, in fact, to take an interest in the lady of the house, just as a human boarder may cuckold the landlord with his wife. Such fish will try to parasitize the spawning of the parents. Even if they only succeed in fertilizing a few eggs, that is better than nothing. The male of the pair does not take this lightly, anymore than a landlord would when he finds his wife in bed with the boarder, and the parasitic breeder will be driven out of the rock pile. The study that uncovered this determined that 4.5 cm is the boundary line before such a thing happens . From a practical point of view for the aquarist, it would therefore seem logical to start taking out juveniles at that length or perhaps even 3.5 cm, which is the length at which Neolamprologus brichardi is sexually mature.
Mixed schools of fry may not only contain fry from different parents but also different species. The Tanganyikan cichlids Lepidiolamprologus elongatus and Perissodus microlepis often have 20% to 40% foreign fry of other species in their schools . The parents are well aware of them but seem to tolerate them because the hassle of trying to evict foreign fry would attract the attention of predators. It would not be easy tracking and chasing one certain fry in a cloud of them and killing or evicting them.
WHY CAN’T WE ALL JUST GET ALONG?
A basic principle of ecology is that the more closely two species live in similar habitats, the more antagonistic they are to each other. An algae scraping cichlid does not worry about a mid-water feeder, and a cichlid that munches on snails is not upset to see an algae feeder nearby. (This assumes no breeding territorial functions are involved; if fry are being protected, then parental instincts override feeding behaviour.) For very dissimilar species, scientists have no trouble establishing this principle. Things get complicated when apparently similar species tolerate each other in the same territory. Is this because scientists haven’t identified the different behaviours (which have only micro-differences)? Or is it because the fish really use the same behaviour and the theory is wrong?
The Rift Lake cichlids have attracted scientific attention on this point because of similar species co-existing. One case study involved Lobochilotes labiatus, a Tanganyikan crevice feeder . These fish have large fleshy lips; they suck shrimp, mayfly, caddis fly, and midge larvae out of crevices. Feeding territories of similar-sized fish do not overlap, which is expected, since they would be competing for food. However, there was little aggression between large and small individuals. Analysis showed that the large fish worked large crevices and the small ones worked small crevices, thus separating their feeding microhabitats even though they overlapped on a larger scale. The difficulty in determining overlaps or not was seen in another study on a number of Lake Malawi cichlids . Many species apparently co-exist despite using the same feeding niches, although most differentiate their food sources. Further study will be required in habitat.
But further study can also be done by aquarists. Granted that a home aquarium is not a true representation of a Rift Lake; the biggest, most sophisticated aquarium can never fully duplicate wild conditions. But that is no reason not to study your fish and observe what they are doing. Professional ichthyologists will never be able to examine the behaviour of all the cichlids. Aquarists can fill in the gaps. Home research may not be as rigorous as professional research, but it can often suggest leads for others to follow. This does require communicating what you have learned in watching fish, the easiest way of which is to write up your observations for your club bulletin. Since most clubs exchange with others, your article will be read by more people than you imagine, and some of them are ichthyologists.
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