"Melanochromis" labrosus Trewavas, 1935 is a somewhat enigmatic Mbuna species,
a rarely encountered skulker on rocky shores. The subadult individual above was about
55 mm (2.2 inches) standard length (SL, excluding caudal fin) and 67 mm (2.7 inches)
total length. It was collected (part of collection field number MKO80-72) on 21 July 1980
by M.K. Oliver, K. McKaye, and T. Kocher using rotenone and SCUBA at Nkhata Bay, Malawi,
in the north bay along the peninsula, about 15 meters from its tip. We spread the
rotenone to a depth of 50 feet (15 m) on this rocky shore, which lacked any macrophytes
(higher plants). Photo copyright © by M.K. Oliver.
Below: A large adult male is shown in overall lateral view and in close-ups
of the underside of the laterally compressed head and of the anal fin with its remarkable
orange-red eggspots (all photos copyright © by M.K. Oliver). This fully grown individual
measured 119 mm (4.7 inches) SL, which must be close to
the maximum size this species attains in the wild. The fleshy median lobes of the lips
have been moved forward to show their length and fullness. This individual was collected
from trammel and experimental gill nets set overnight 24-25 July 1980 (MKO80-84),
by the same people, again in Nkhata Bay (this time off the southern shore of the south bay
near emergent offshore rocks, some 75 meters from shore). Capture depth ranged from 6 to 45
meters; unfortunately, the depth at which this fish was caught is unknown. This was a rocky
locality devoid of any macrophytes and exposed to wave action from easterly and
southeasterly winds. (Text continued below photo.)
Two other individuals (not photographed) were collected on 23 July 1980 (part of MKO80-79) by M.K. Oliver, K. McKaye, and T. Kocher. They were captured with SCUBA at Nkhata Bay, off the tip of the peninsula separating the north and south bays, using rotenone dispersed among rocks in a depth of 17-20 meters (55-65 feet). At this locality, the rocky shore dropped off rapidly, at an angle of 45°-75°. Higher plants were completely lacking; filamentous algae grew to a length of 5 mm (0.2 inches).
This species was at one time confused with the only distantly related Placidochromis milomo Oliver, which, among other differences, has larger thoracic scales, reaches a much larger size, and has only four vertical bars below the dorsal fin (vs. about seven in "M." labrosus).
"M." labrosus is rarely seen. The commercial aquarium collector and his staff handle only 5-10 per year, out of approximately 75,000 fish (S. Grant, in litt. 6/1999). I stated above that the species is enigmatic. Although it has remained in the genus Melanochromis since its description nearly 70 years ago, it bears little resemblance to its congeners, with its laterally compressed head bearing somewhat enlarged lateral line pores, a somber color pattern of muted vertical bars, and solitary, wandering habits. Matt Arnegard and I are actively re-examining its generic placement.
Ribbink et al. (1983) reported this species from shallower water than where I found it, less than 8 meters (26 feet) in depth. These authors note that "[i]t usually remains hidden among the rocks and appears to be rare. However, a rotenone sample at Maingano [Likoma Island] revealed that there are more M. labrosus among the rocks than indicated by transects and by observation." Ribbink et al. were able to observe its feeding behavior: "It moves from rock to rock placing its narrow mouth and large lips in cracks and grooves, which it seals, and then sucks the benthic Invertebrata and loose Aufwuchs from the sealed area."
Konings provides additional observations and speculation about this interesting species:
Two photos below:
The holotype of Melanochromis labrosus (BMNH 1935.6.14:321). Below the whole specimen
is a closeup of the holotype's head. As may be seen by comparing the preserved holotype with the
photos of even the smaller freshly collected specimen (above), the lips and their median lobes
have shriveled considerably in alcohol. Black and white photos copyright © by M.K. Oliver.
|Last Update: 5 April 2004
Web Author: M. K. Oliver, Ph.D.
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