Above: Mylochromis labidodon is a little-known sandy shore "Hap" species with an oblique black stripe. The oblique stripe varies from quite thin and regular (as in the specimen designated as the lectotype of this species) to one having a "blotchy" appearance where the stripe is crossed by the vertical bars, as in the individuals shown here (variation is further discussed below). These aquarium photos of M. labidodon — a male (upper fish above) and a female (lower fish above), and the other photos of them below — were taken by Carsten K. Larsen, a Danish aquarist, who very kindly permitted me to use them here. (Carsten has a Web site, MalawiCarsten, with photos of several of Lake Malawi's invertebrates and other interesting features.)

As recently as 1989 (Eccles & Trewavas, 1989), M. labidodon was still known only from the five type specimens from northern Lake Malawi that Cuthbert Christy had collected in 1925-26.

Among the numerous Malawi cichlids with an oblique stripe, M. labidodon is best recognized by its distinctive jaw dentition (which, unfortunately, is difficult to observe in a living fish). Several anterior teeth in the lower jaw are abruptly enlarged

Lower jaw of a paralectotype of M. labidodon. Move the mouse over the photo to highlight the distinctive group of enlarged, forward-leaning teeth that are a characteristic specialization of this species. Photo adapted from Fig. 115 of Eccles & Trewavas (1989).

(instead of gradually becoming larger toward the front in the usual way), and are also markedly inclined forward. This diagnostic group of teeth is illustrated in the interactive photo at left. What could be the function of this specialized, forcepslike dentition? (Labidodon means forceps-teeth.) For more than 50 years after Ethelwynn Trewavas first described M. labidodon in 1935, the reason for this specialization remained unknown. The fish's diet, and indeed its entire ecology, were likewise undiscovered.

The mystery was finally solved by underwater observations made and reported by Konings (1995c), and the answer was a surprise. The feeding behavior of this species may be unique:

M. labidodon can be regarded as the Labidochromis analogue among the »haps«. Its teeth are pointed and considerably larger at the centre (front) of the jaws. The »Labidodon« is common over pebble beds where it turns over any small stone it can grasp with its mouth! When it finds something palatable beneath the stone, it quickly dives into the rubble to seize it. —Konings (1995c: 177)

The actual identity of the organisms eaten is not recorded, but presumably would include insect larvae, small crustaceans, worms, and other small animals. M. labidodon could be considered a crevice feeder, since these organisms hide in the spaces under pebbles; but these "crevices" are specifically exploited by few if any other cichlids, and this species is certainly the only one known to push or lift pebbles to exploit the food source hidden beneath them!

Konings also recorded his observations on coloration and on geographic variation in the color pattern:

The Labidodon has been exported for the aquarium trade on several occasions. Such specimens were caught in Senga Bay with beach seine nets dragged over pure sand. The species has a very silvery body with broad vertical bars and a very thin red edge to the dorsal fin. There is some geographical variation which seems to be restricted to the normal pigmentation pattern. Members of the genus Mylochromis

Male M. labidodon to show coloration of unpaired fins. Photo by Carsten K. Larsen, used by permission.

are characterised by a diagonal stripe on the flanks but such a stripe is rarely seen in M. labidodon; only the northern populations have a diagonal stripe but this is hardly ever a continuous line from the nape to the caudal peduncle. The southern populations have a very pronounced pattern of vertical bars. The juveniles of such barred individuals, however, have an incomplete diagonal line.

The snout profile is also variable, from straight or very slightly convex to distinctly concave (as illustrated by the individuals in the photos atop this page).

Of the known museum specimens of Mylochromis labidodon, the largest measures about 15 cm (6 inches) in standard length (not counting the caudal fin). Thus,

Female M. labidodon to show color pattern of body. Photo by Carsten K. Larsen, used by permission.

individuals to be kept in an aquarium should have a sufficiently large one, of at least 60 gallons (230 liters) and preferably larger. Although I know of no account of its behavior in captivity, it is probably safe to speculate that multiple adult males do not fraternize placidly in a confined space. As with most other "haps," a single male and several females would probably make the most stable group.
 

Last Update: 18 July 2005 Web Author: M. K. Oliver, Ph.D. Copyright © 1997-2008 by M. K. Oliver - ALL RIGHTS RESERVED