subadult `Melanochromis` labrosus; photo © by M. K. Oliver
Above: "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.)

Adult male 'Melanochromis' labrosus; photo © by M. K. Oliver

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). `M.` labrosus, ventral head and anal fin; photos © by M. K. Oliver 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.

Melanochromis labrosus, holotype; photo © by M. K. Oliver
Melanochromis labrosus, head of holotype; photo © by M. K. Oliver


 

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The Cichlid Fishes of Lake Malawi, Africa:  MalawiCichlids.com

Last Update: 5 April 2004
Web Author: M. K. Oliver, Ph.D.
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