Metriaclima koningsi, Stauffer, 2018

Stauffer, Jay R., 2018, Description of Metriaclima koningsi, a new species (Teleostei: Cichlidae) from Lake Malaŵi, Malaŵi, Africa, Zootaxa 4370 (1), pp. 95-100 : 96-99

Metriaclima koningsi , new species

Fig. 1 .

Pseudotropheus ‘membe deep’ ( Ribbink et al. 1983) Metriaclima sp. “membe deep” ( Konings 1990)

Holotype. PSU 12891, adult male 56.8 mm SL, 12.058700° S, 34.752420° E, Membe Point, Likoma Island, Lake Malaŵi, Malaŵi, Africa, 5 August 2005, J. R. Stauffer, Jr.

Paratypes: PSU 12892, 16 (42.6–55.3 mm SL), data as for holotype; PSU 12893, 3 (40.3–49.0 mm SL), 12.046202° S, 34.759400° E, Maingano Island, Lake Malaŵi, Malaŵi, Africa, 18 February, 2002, A. F. Konings, J. R. Stauffer, Jr.

Diagnosis. The moderately-sloped vomer (43.1º in holotype) with a swollen rostral tip ( Fig. 2 ), bicuspid teeth in the anterior portion of the outer row of both upper and lower jaws, the lower jaw at a 45º angle to a line from the tip of the snout to the hypural plate, a lower jaw that is slightly longer than the upper, and its feeding at a 90º angle ( Konings 1990) to the substrate place this species in Metriaclima . The lack of conspicuous vertical bars on the flank and the dark submarginal band in the dorsal fin of male M. koningsi ( Fig. 3 ) distinguish it from all other species of Metriaclima , except Metriaclima usisyae Li, Konings , & Stauffer. Males of M. usisyae have a goldcoloured flank while this is blue in male M. koningsi . Females of M. koningsi are entirely brownish yellow and thus distinguished from those of most other species of Metriaclima except for females of M. flavifemina and M. phaeos . The snout of the latter species is relatively longer than that of M. koningsi (37.9–44.7% vs. 26.6–33.1% HL) but females of M. flavifemina cannot reliably be distinguished from those of M. koningsi apart from the fact that they have a larger size (maximum 79 mm SL vs. 49 mm SL for M. koningsi ).

Description. Morphometric and meristic data in Table 1. Dorsal fin with 17–18 spines and 7–9 rays. Anal fin with three spines (one specimen with two) and 7–8 rays. Lateral line with 30–32 ctenoid scales with 1–2 pored scales posterior to hypural plate. Caudal fin emarginate.

Head of males grey with two bright interorbital bars; cheek with gray markings; gular dark grey/black. Laterally light blue dorsally and dark blue/black ventrally. Dorsal fin light blue with dark submarginal band and light blue/white lappets. Caudal-fin membranes blue, rays pale orange. Anal fin black with 1–2 yellow ocelli; tips of rays light blue. Pelvic fins with blue leading edge; anterior membranes black fading to clear. Pectoral fins with black rays and clear membranes.

Head of females yellow/brown with 1 light brown/green interorbital bar. Cheek yellowish brown with yellow/ brown operculum with green highlights; dark grey opercle spot; gular yellow. Laterally yellow/brown ground colour with yellow scale margins; centre of scales pale blue/white; belly and breast white. Dorsal fin yellow/brown with yellow lappets; distal one-third of rayed membranes bright yellow/orange. Caudal-fin membranes yellowish brown with yellow rays. Proximal one-quarter of anal fin clear; distal three-quarters yellow orange. Pectoral fins with brown rays and clear membranes. Anterior three membranes and rays of pelvic fin bright yellow/orange; posterior membranes and rays clear.

Distribution. Metriaclima koningsi is a deep-water form and is usually found at depths greater than 15 m (Konings 2016). It is only known from Membe Point and Maingano Island along the northeastern shore of Likoma Island.

Etymology. Named after Adrianus Konings for his comprehensive knowledge and for teaching me most of what I know about the fishes of Lake Malaŵi.

Discussion. Metriaclima koningsi usually occurs over the sediment-rich habitat between 15–30 m (Konings 2016). Males have been observed feeding on the aufwuchs at a 90° angle, where they abduct their jaws to a near 180°; thus they can align their teeth of both the upper and lower jaws in the same plane. Both males and females will feed on zooplankton from the water column (Konings 2016, pers. obs.).

Metriaclima is a large genus of the endemic rock-dwelling cichlids in Lake Malaŵi. Stauffer et al. (2013) recognised 31 described species and subsequently Li et al. (2016) described two additional elongate species in the genus. Many authors ( Turner & Burrows1995, Van Doorn et al. 1998, Seehausen & Van Alphen 1999) have argued that sexual selection on male breeding coloration and behavior has driven speciation of these fishes. Thus, in many cases male coloration is the primary trait used to delimit species ( Ribbink et al. 1983, Stauffer et al. 1995, 1997). There are now 35 described Metriaclima spp., but Konings (2007) recognised at least 75 different forms within the genus; thus Metriaclima may be the most species-rich of the mbuna in Lake Malaŵi.

Figures

FIGURE 1. The holotype of Metriaclima koningsi (56.8 mm SL, male, PSU 12891).

FIGURE 2. Three-dimensional surface rendering of the cranium of the holotype of Metriaclima koningsi (PSU 12891), showing the position of the parashpenoid and the angle of the ethmo-vomerine bloc.

FIGURE 3. Metriaclima koningsi. A, Male from Mainango Island; B, Female from Membe Point, Likoma Island. Neither of the above were collected.