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!
Late in 2008,
Carsten K. Larsen (who provided the fish photos above and below) also recorded an excellent
underwater video sequence of M. labidodon feeding
at Chidunga Rocks. The clip shows two individuals flipping stones with their jaws.
The sequence also appears to show the fish turning stones by a second method, wedging
the snout under the edges of stones and flipping them over without holding them in the
jaws. The footage clearly documents the fish finding and ingesting a number of edible
items both on the substrate and on the undersides of the stones.
Konings 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.
