233 Ichthyol. Explor. Freshwaters, Vol. 17, No. 3, pp. 233-246, 11 fi gs., 2 tabs., September 2006 © 2006 by Verlag Dr. Friedrich Pfeil, München, Germany – ISSN 0936-9902 Revised diagnosis of Metriaclima with description of a new species (Teleostei: Cichlidae) from Lake Malawi National Park, Africa Adrianus F. Konings* and Jay R. Stauffer, Jr.** The diagnosis of Metriaclima is expanded to include several feeding behavioral characteristics. Species of Metria- clima feed at almost perpendicular angles to the substrate and are able to align the teeth of both upper and lower jaws in the same plane by abducting the jaws to a 180°-angle opening. While closing the mouth, the teeth comb through the algae anchored to the substrate and collect loose material. The bites to the substrate follow in rapid succession. We have further expanded the diagnosis of Metriaclima zebra to include a population without distinct vertical bars. Finally, we describe a new species, M. flavifemina, which inhabits the rock-sand interface in the southern part of the lake. Introduction a moderately-sloped ethmo-vomerine block with a swollen rostral tip. Morphological characteristics The small, rock-dwelling haplochromine cichlid of the feeding apparatus reflect the manner in fishes in Lake Malawi, Africa, are commonly which these fishes browse from the substrate and referred to as mbuna. The genus Pseudotropheus one of the purposes of this paper is to include – one of the dozen genera currently recognized characters of feeding behavior in the diagnosis of within the mbuna – originally included a widely Metriaclima. diverse group of cichlids and served as a catch-all When Stauffer et al. (1997) described Metria- genus for newly-discovered species. Several clima, the following species, hitherto in Pseudo- complexes have been recognized within the genus tropheus, were included: M. zebra (Boulenger), (Ribbink et al., 1983) and some of them have been M. heteropictus (Staeck), M. callainos (Stauffer & treated as distinct genera, e.g., Tropheops (Trewa- Hert), M. xanstomachus (Stauffer & Boltz), M. gre- vas, 1984) and Metriaclima (Stauffer et al., 1997). shakei (Meyer & Foerster), M. aurora (Burgess), The genus Metriaclima was diagnosed to accom- M. barlowi (McKaye & Stauffer), M. elegans (Tre- modate the Pseudotropheus zebra complex. The wavas), M. estherae (Konings), M. hajomaylandi main characters that delimit members of Metria- (Meyer & Schartl), M. lombardoi (Burgess), M. lani- clima from other complexes in Pseudotropheus are sticola (Burgess), M. livingstonii (Boulenger), and * Cichlid Press, P. O. Box 13608, El Paso, TX 79913, U.S.A. E-mail: [email protected] ** School of Forest Resources, Penn State University, University Park, PA 16802, U.S.A. E-mail: [email protected] Ichthyol. Explor. Freshwaters, Vol. 17, No. 3 234 had been withheld by its collector (P. Davies et al.) for commercial reasons (P. Davies, pers. comm.). Ribbink et al. (1983) and Stauffer et al. (1997) used the name P. heteropictus for a hitherto undescribed species of Metriaclima found at this island that phenotypically resembles P. heteropic- tus. In a continuing effort to better characterize the taxon M. zebra, the purposes of this paper are to 1) describe the populations of the Black Dorsal group from Nakantenga, Maleri, and Thumbi West islands and from Chidunga Rocks (Fig. 1); 2) compare these forms with type material of P. heteropictus; 3) compare blue-black barred in- dividuals from Namalenje Island to a neighboring population, at Maleri Island, that consists of light- blue individuals lacking black bars; and 4) com- pare the Namalenje and Maleri island populations to M. pyrsonotos, a blue-black barred form with a red dorsal fin from neighboring Nakantenga Is- land. Methods Fishes were collected by the authors in southern Lake Malawi (Fig. 1) by chasing them into a monofilament net while SCUBA diving. Fishes Fig. 1. Map of Lake Malawi with localities mentioned were anesthetized with clove oil, preserved in in the text. 10 % formalin, and placed in 70 % ethanol for permanent storage. All counts and measurements were made on the left side of the fish, with the M. pursus (Stauffer). In the same publication, these exception of gill-raker counts. Counts and meas- authors also described 10 more species in the new urement follow Barel et al. (1977) and Stauffer genus: M. melabranchion, M. chrysomallos, M. phae- (1991; 1994) with the following exceptions. Head os, M. cyneusmarginatus, M. benetos, M. pyrsonotos, depth was measured from the hyoid symphysis M. sandaracinos, M. emmiltos, M. mbenjii, and to the top of the head (jaws not extended) at a 90° M. thapsinogen. Several subgroups are recognized angle to the horizontal body axis (horizontal line within Metriaclima: 1. a so-called BB Zebra group drawn through the lower part of lateral line). (blue-black barred mbuna allied with M. zebra; Body depth was measured from the dorsal-fin see Stauffer et al., 1997); 2. an Aurora group (al- origin to the ventral outline of the fish at a 90° lied with M. aurora); 3. a Black Dorsal group allied angle to the horizontal body axis. The pre-orbital with an undescribed form called Pseudotropheus depth was measured as the length of the intersec- ‘zebra black dorsal’ by Ribbink et al. (1983) and tion of the lachrymal bone with a line continuing which is described herein. the radius of the orbit and parallel to the snout We recognize populations of the Black Dorsal profile, dissecting the lachrymal bone (Eccles & group at Nakantenga, Maleri, and Thumb West Trewavas, 1989). Institutional abbreviations fol- islands and at Chidunga Rocks. The population low Leviton et al. (1985), except UMBC, Univer- from Thumbi West Island had been confused sity of Malawi, Bunda College. repeatedly in scientific and popular literature Pigmentation pattern was recorded in the with P. heteropictus Staeck. Staeck (1980) states field, in territorial and non-territorial males, fe- that P. heteropictus was collected at Thumbi West males, and juveniles. The different patterns are Island, but its likely origin, Chizumulu Island, variable in all species examined and in the de- Konings & Stauffer: Revised diagnosis of Metriaclima 235 scriptions such variation is recorded by placing with a swollen rostral tip. 3. The lower jaw at 45° a slash between the two colors between which angle to a line from the tip of the snout to the the specific pattern varies, i.e. blue/white is used hypural plate. Additional morphological charac- to designate that the color ranges from blue to ters that define Metriaclima are as follows: 4. The white and includes intermediate shades in certain lower jaw is often slightly longer and thicker than individuals. The angle of the ethmo-vomerine the upper. 5. A large part of the upper dental block was assessed by measuring the angle be- arcade is normally exposed when the mouth is tween the horizontally-aligned parasphenoid and closed. 6. The tips of the teeth in the premaxilla a line bisecting the vomer (in lateral view) in two and dentary are in a V-shaped line with the an- equal halves. teriormost in upper and lower jaw furthest apart. Morphometric data were analyzed using 7. The placement of the bicuspid teeth in the sheared principal component analysis (SPCA), outer row along the side of the jaws does not with the covariance matrix factored (Humphries follow the contour of the jaw bone. The lateral et al., 1981; Bookstein et al., 1985). Meristic data teeth are rotated so that the plane of their two- were analyzed with principal component analy- pronged tips runs parallel with those in the an- sis (PCA), with the correlation matrix factored. terior part of the jaw. Differences among species were illustrated by Metiaclima is further diagnosed by the manner plotting the sheared second principal components it feeds from algae. It feeds at a perpendicular of the morphometric data against the first prin- angle to the substrate (Konings, 1995a; Stauffer cipal components of the meristic data (Stauffer & & Posner, 2006) and is able to align the teeth of Hert, 1992). both upper and lower jaws in the same plane by abducting its jaws to a near 180°-angle opening. The jaws are then pressed against the substrate Metriaclima Stauffer, Bowers, Kellogg and closed. While closing the mouth, the teeth & McKaye rake through the algae anchored to the substrate and collect loose material (Fryer, 1959). Numerous Type species. The type species of Metriaclima is bites to the substrate follow in rapid succession. M. zebra (Boulenger, 1899) and the holotype of During the process nothing is actually torn from this species comes from an unknown locality the substrate; only diatoms and loose algal strands within Lake Malawi. As currently used, the name are harvested. M. zebra includes a large number of populations In this respect, Metriaclima distinguishes itself of blue-black barred mbuna distributed all over from the species in Pseudotropheus, Tropheops, and Lake Malawi that include the holotype but which Melanochromis because these are not able to neither have not yet been resolved convincingly at the open their mouths to a 180° angle nor do these species level. Even though Stauffer et al. (1997) rake the loose algae from the substrate. Tropheops found that in a PCA plot the holotype is distinct feed from the algae by shearing the strands from from all other forms investigated, they decided the substrate. Cyathochromis obliquidens feeds in a to retain the name M. zebra for all these popula- manner very similar to that of Metriaclima, albeit tions because of a possibly extensive intraspe- from plant fronds; it is, however, distinguished cific variability, a lack of samples identifiable with because its specialized teeth consist of slender the holotype, and because of its wide usage in shafts and compressed, spoon-like crowns with scientific and popular literature.