The Blue Sanddwellers

(This article was originally published in "Cichlids Yearbook Volume 1, Cichid press; 1990; pp. 29-32. It is here reproduced with the permission of Ad Konings, Cichlid Press).

Of all the different biotopes Lake Malawi has to offer, the rocky regions have brought forth the greatest variety of colorful aquarium fishes. The much less explored sandy areas may still hide many beautiful species. Due to the openness of the sandy habitats it is difficult, and sometimes impossible, to collect some specimens. Since on the sand there is no place to hide, almost all species living there have a light, silvery-yellow coloration which camouflages them. Furthermore, the sanddwellers often live in schools which gives them a protection against predators.

In contrast to most sanddwellers, there is a group of conspicuously colored cichlids which usually live solitarily or in very small groups. This group consists of at least five different species. These have no ancestor in common and do not belong to the same genus. However, they have an important and peculiar part of their feeding behavior in common (see later).

The five conspicuously colored sanddwellers are Cyrtocara moorii, Protomelas annectens, Otopharynx selenurus, Placidochromis electra, and Placidochromis phenochilus. The first three species have a lake-wide distribution. P. electra occurs around Likoma Island and probably all along the eastern shores, down to Fort Maguire. P. phenochilus, which seems to be closely related to P. electra, has been observed only in the north- western part of the lake. I found it near Mdoka, Chesese, Chirwa Island, and between Selewa and Kasinda.

phenochilus is characterized by its white lips and blue body. Even juveniles of 6 cm length have the typical dark blue coloration. Its inclusion in Placidochromis is based on its close resemblance to P. electra. Of the about 25 individuals I have seen at several locations, not a single one showed its basic coloration pattern. The vertical barring, which is faintly present in most individuals, is not a diagnostic feature since species from several other genera show vertical bars ­ especially courting males ­ as well.

The five species of the group have a particular feeding strategy. They are attracted to stirred-up material and usually follow a large sand-sifting species like Taeniolethrinops praeorbitalis. The food of most sanddwelling species consists of invertebrates which live and hide in the sand. There are several ways to obtain these. Lethrinops -like species dig in the sand and sift it through the gills. Species of the genus Aulonocara detect their prey by "listening to the sand." Other species blow away the upper layer in order to reveal the hiding invertebrates. The five blue sanddwellers let other species do the work. T. preaorbitalis is a large cichlid and its continuous digging efforts create a lot of stirred-up material. Although it seems that the blue sanddwellers select their food from the clouds of material spilled through the gills of the large sand-sifter, they are actually more interested in searching the ploughed sand for exposed invertebrates. These crawl back into the sand as soon as possible.

The intriguing question is, why are these sanddwelling species so conspicuously colored? Especially P. phenochilus, O. selenurus and to a somewhat lesser extent C. moorii, always show a distinct blue coloration. These three species seem to be mostly dependent on a large, sand-sifting host. The other two species are also found foraging on their own. It is therefore possible that their conspicuous colors might warn off other followers ­ especially other species ­ from joining their host. In sandy regions, cichlids commonly occur in groups or schools, often of mixed species and it would thus be normal for an individual to join such a group. The amount of food revealed by the ploughing activities of a large digger may not be sufficient for more than one adult follower. If the follower is highly dependent on the host, it may signal its position to the other species by taking on a territorial coloration. In particular individuals of the same species are wary of approaching an "occupied" host.

C. moorii and O. selenurus occur in very shallow water and are rarely found below depths of 10 meters. P. phenochilus and P. electra are usually observed in water deeper than 15 meters whereas P. annectens is found at any level.

The differences not only in the basic melanin patterns but also in breeding behavior point to different ancestral origins for these sanddwelling cichlids. The breeding behavior of C. moorii has been observed several times by different aquarists. They all noticed that as soon as the female had deposited some eggs they were fertilized by the male while they were still on the sand. The same sequence is also employed by P. annectens. Neither of the two species build a nest or any structure to indicate the spawning site. Although I have never observed any of these blue sanddwellers spawning in their natural environment, the courting behavior of the males indicates that spawning can take place at any site. Mouth-brooding and fry-guarding C. moorii and P. annectens have been observed on the open sand. P. electra is kept and bred by many hobbyists. Spawning in the aquarium has revealed that the eggs are fertilized inside the female's mouth, as is the case in most other Malawian cichlids. P. phenochilus has yet not been exported as an aquarium fish. Because P. phenochilus resembles P. electra to a great extent it may have a similar breeding behavior, i.e. that the eggs are fertilized inside the female's mouth.

O. selenurus is infrequently exported as Haplochromis Nussae. All specimens are collected in Senga Bay. It has been bred in captivity (Baasch, pers. comm.) but details of the spawning sequence are not known yet. The juveniles show the genus-specific blotch-pattern until they have reached a length of approximately 7 cm. O. selenurus is a very attractive and peaceful cichlid and makes a valuable addition to a Malawi community tank.

References

• Eccles, D.H. & Trewavas, 1989, Malawian cichlid fishes. The classification of some Haplochromine genera. Lake Fish Movics, Herten, Germany.
• Drummond, 1976, How I keep....Haplochromis annectens. Bunt. BulL (Am. Cichl. Ass.), Dec., pp. 29-30.
• Kocher, T.D. & Mckaye, KR. 1983, Defense of heterospecific cichlids by Cyrtocara moorii in Lake Malawi, Africa. Copeia (2), pp. 544-547.
• Konings, 1989, Malawi cichlids in their natural habitat. Verduijn Cichlids, Rotterdam, Netherlands.
• Seigars, D. & Berardo, 1979, Spawning the Deep- Water Haplochromis. TFH, Vol. 27; April, pp 412.