Redescription of Pseudotropheus livingstonii and Pseudotropheus elegans from Lake Malaŵi, Africa

Abstract

Pseudotropheus livingstonii and P. elegans are two sand-dwelling cichlid species that belong to the so-called mbuna, a group of predominantly rock-dwelling haplochromines of Lake Malaŵi. The identity of these two species has confused taxonomists for almost a century until a recent rediscovery of representatives of P. elegans close to its type locality. New diagnoses for both species are provided.

Full text

Accepted by L. Page: 17 May 2016; published: 19 Aug. 2016
ZOOTAXA
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Copyright © 2016 Magnolia Press
Zootaxa 4154 (2): 169
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Article
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http://doi.org/10.11646/zootaxa.4154.2.4
http://zoobank.org/urn:lsid:zoobank.org:pub:B7D82FB6-A77A-49B3-AF05-87DB9B2F9A44
Redescription of Pseudotropheus livingstonii and Pseudotropheus elegans
from Lake Malaŵi, Africa
J.R. STAUFFER JR.
1
, A F. KONINGS
2
& T.M. RYAN
3
1
Ecosystem Science and Management, Penn State University, University Park, PA 16802 Honorary Research Associate, South African
Institute of Aquatic Biodiversity, Grahamstown, South Africa. E-mail: vc5@psu.edu
2
Cichlid Press, El Paso, TX 79913. E-mail: cichlidpress@gmail.com
3
Department of Anthropology, Penn State University, University Park, PA 16802, Center for Quantitative Imaging, EMS Energy Insti-
tute, Penn State University, University Park, PA 16802. E-mail: tmr21@psu.edu
Abstract
Pseudotropheus livingstonii and P. elegans are two sand-dwelling cichlid species that belong to the so-called mbuna, a
group of predominantly rock-dwelling haplochromines of Lake Malaŵi. The identity of these two species has confused
taxonomists for almost a century until a recent rediscovery of representatives of P. elegans close to its type locality. New
diagnoses for both species are provided.
Key words: Ethmo-vomerine bloc, mbuna, Metriaclima lanisticola
Introduction
In the lakes of East Africa, fishes of the family Cichlidae have undergone an extraordinarily rapid and extensive
radiation. Within Lake Malaŵi, over 450 species have been formally described, and many undescribed species
have been discovered from recently explored areas. It is estimated that in Lake Malaŵi alone, there may be as
many as 850 cichlid species (Konings 2007). Within this diverse assemblage of fishes the small and colorful rock-
dwelling cichlids are referred to as mbuna in the local vernacular. Although not formally described, the mbuna
share the following characters: 1) large number of small scales on the nape and chest region; 2) abrupt transition
from large flank scales to small chest scales; 3) reduction of the left ovary which is non-functional; and 4)
possession of true ocelli on the anal fin (Fryer 1959; Oliver 1984). The mbuna are mostly associated with rocky
habitats, but a small group of species occurs on sandy substrates (Fryer 1959; Fryer & Iles 1972; Ribbink et al.
1983; Stauffer 1991), including Pseudotropheus elegans Trewavas and P. livingstonii (Boulenger).
Discrimination among cichlid species of Lake Malaŵi can be difficult, because visual differences among
species may be very small (Konings 2007) and because morphological characters may be prone to convergence
(Kocher et al. 1993) and/or are phenotypically flexible (Stauffer & Gray 2004). In conjunction with their
morphological attributes, behavioral traits of these species are important diagnostic tools in distinguishing the
multitude of species (Barlow 2002; Stauffer et al. 2002). The taxonomic history of P. livingstonii and P. elegans
represents the difficulties researchers have in classifying Malaŵi cichlids.
In 1899, Boulenger described Tilapia livingstonii from a single specimen which was collected in Lake Malaŵi
about 40 years earlier by Livingstone during his Zambesi Expedition and which was since 1863 registered as Perca
vittata (a marine species) in the British Museum (BMNH 1863.11.12.22). In 1922, Regan synonymized T.
livingstonii with Pseudotropheus williamsi Günther 1893, but it was later reinstated as P. livingstonii by Trewavas
(1935). At the same time, Trewavas described P. elegans from a single specimen collected in Deep Bay (Chilumba
Bay), Lake Malaŵi, by Christy. Trewavas had examined the type of P. livingstonii and found that it was sufficiently
different from P. elegans to warrant the description of the latter. The type of P. livingstonii, even after more than
150 years of preservation, still exhibits a vague barring pattern (the drawing accompanying its description depicts

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distinct bars), but no such pattern is discernable on the type of P. elegans. Nevertheless, Trewavas (1935) did not
remark on this difference in melanin patterns, but instead distinguished P. elegans from P. livingstonii by its
slightly larger eye and narrower preorbital bone. In 1983, Ribbink et al. (1983) found that Pseudotropheus
lanisticola Burgess 1976, a shell-dwelling mbuna described from the southern part of the lake, was conspecific
with Boulenger’s P. livingstonii and regarded P. lanisticola as a junior synonym. Ribbink et al. (1983) further
reported on the presence of large numbers of P. elegans in the southern portion of the lake in schools over sandy
bottom. Stauffer et al. (1997) assigned P. l i v i n g s t o n i i and P. elegans to Metriaclima, but Konings (2007) reversed
this assignment.
Stauffer et al (1997) diagnosed Metriaclima, and this diagnosis was expanded by Konings & Stauffer (2006).
Condé & Géry (1999) claimed that Metriaclima should be regarded as a junior synonym of Maylandia Meyer &
Foerster (1984), however, Meyer & Foerster (1984) failed to supply a character in which their subgenus
Maylandia, defined by its type species M. greshakei, is distinct from Pseudotropheus. Characters were given for a
so-called zebra complex but M. greshakei was not considered part of that complex. The subgenus was thus not
diagnosed according to the requirements of Article 13.1.1 of the Code, and was therefore regarded a nomen nudum
by Stauffer et al. (1997) and subsequent authors (Konings & Geerts 1999, Geerts 2002, Stauffer & Kellogg 2002).
In 2007, Konings also synonymized P. elegans with P. l i v i ng s t o n i i and reinstated P. lanisticola as the shell-
dwelling species. The purpose of this paper is to redescribe P. livingstonii and P. elegans on the basis of
morphological examination of the type material and on behavioral differences obtained from field observations.
Our studies show that P. l i v i n gs t o ni i , P. elegans, and P. lanisticola are three species distinguishable by
morphological and behavioral differences.
Methods and materials
Fishes were collected in Lake Malaŵi by chasing them into a monofilament block net while SCUBA diving. Fishes
were collected and processed under approval of the Animal Use and Care Committee at Penn State University
(IACUC #24269). All fishes were anesthetized with clove oil, euthanized in 1% formalin, pinned in trays so that
the bodies were flat and the fins erect, preserved in 10% formalin, and placed in permanent storage in 70% ethanol.
Counts and measurements follow Stauffer (1994) and Stauffer & Konings (2006). All counts and measurements
were taken from the left side of the body with the exception of gill-raker counts, which were taken on the right side.
Morphometric data were analyzed using a sheared principal component analysis, which factors the covariance
matrix and restricts size variation to the first principal component (Humphries et al. 1981; Bookstein et al. 1985).
Meristic data were analyzed using a principal component analysis in which the correlation matrix was factored.
Differences among species were illustrated by plotting the sheared second principal components (SPC2) of the
morphometric data against the first principal components (PC1) of the meristic data (Stauffer & Hert 1992).
The holotypes of P. livingstonii (BMNH1863.11.12.22), P. elegans (BMNH1935.6.14.127) and Metriaclima
lanisticola (USNM 216266) were scanned on the high-resolution x-ray computed tomography (HRCT) system in
the Center for Quantitative X-Ray Imaging (CQI) at Penn State University. Specimens were mounted vertically, the
mandibles pinned together to create a standard position, and scanned with target pixel and slice resolutions of
approximately 20 µm. Scan data were reconstructed as 16-bit TIFF images with a 1024×1024 pixel grid. For each
individual, the entire head was scanned. The volumetric image datasets for each fish were used to create a three-
dimensional isosurface reconstruction (Fig. 1) in order to study bone tissue using the visualization software Avizo
6.1 (VSG, Burlington, MA). Because all of the fishes were HRCT scanned with the same energy settings and voxel
resolutions, a global threshold was used for all datasets to separate bone from non-bone for the three-dimensional
reconstructions.
Angles were measured on the ethmo-vomerine bloc of the parasphenoid in Avizo 8.0. The 3D reconstruction of
the parasphenoid was cut along a parasagittal plane, and a line was defined along the cranio-caudal axis of this
element using the ventral most extent of the juncture of the posterior parasphenoid processes and the ventral most
extent of the anterior portion of the parasphenoid at the top of the ethmo-vomerine bloc. The angle was measured
between this axis and the long axis of the ethmo-vomerine bloc drawn on this mid-line cross-section.

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FIGURE 1. Three-dimensional surface reconstructions of the skulls of the three holotypes, showing the position of the
parasphenoid and the angle of the ethmo-vomerine bloc. 1a, Metriaclima lanisticola (BMNH1976.7.29.2), angle 48.7°; 1b,
Pseudotropheus livingstonii (BMNH1863.11.12.22), angle 57°; 1c, P. e le g an s (BMNH1935.6.14.127), angle 58°.

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Results
Pseudotropheus livingstonii (Boulenger 1899)
(Fig. 2)
Tilapia livingstonii Boulenger 1899
Pseudotropheus williamsi (non-Günther).—Regan 1922
Pseudotropheus livingstonii, Trewavas 1935.—Konings 2007
Pseudotropheus elegans (non-Trewavas) .—Ribbink et al. 1983
Metriaclima livingstonii.—Stauffer et al. 1997
Material examined. Pseudotropheus livingstonii BMNH1863.11.12.22, holotype, 55.7 mm SL, Zambesi
Expedition, Lake Malaŵi; PSU4925, 19, 64.3–114.4 mm SL, Cape Maclear, 14º05’ S, 34º54’E, Lake Malaŵi .
Diagnosis. Pseudotropheus livingstonii is distinguished from all other members currently in Pseudotropheus
(Konings 2007), except P. crabro, P. demasoni, and P. saulosi, by the presence of five or fewer vertical bars below
the dorsal fin. Most Pseudotropheus species either have no bars or have greater than five below the dorsal fin.
Pseudotropheus livingstonii is distinguished from P. crabro, P. demasoni, and P. s au l o si by a pale yellow to hyaline
dorsal fin vs. dorsal fin heavily pigmented with black.
Description. Principal morphometric ratios and meristics for holotype and for specimens from population at
Cape Maclear in Table 1. Medium-sized to large mbuna, ovoid body (mean BD 31.4% SL) with greatest depth
between fourth to sixth dorsal spine. Dorsal body profile with gradual curve downward posteriorly, more
pronounced towards caudal peduncle; ventral body profile almost straight between pelvic fins and base of anal fin
with upward taper to caudal peduncle. Dorsal head profile rounded, with smooth curve between interorbital and
dorsal-fin origin; horizontal eye diameter (mean 32.0% HL) greater than preorbital depth (mean 19.6% HL); eye
(along horizontal axis) in center of head; snout straight to slightly concave in some individuals; isognathous jaws;
tooth bands with 4–5 rows in upper jaw and 3–5 rows in lower; rows continuous through symphyses; teeth in
anterior outer row bicuspid with posterior lateral teeth primarily unicuspid, teeth in inner rows tricuspid.
TABLE 1. Morphometric and meristic values of Pseudotropheus livingstonii, and P. elegans.
Variable P. livingstonii
(holotype)
BMNH1863.11.
12. 22
P. livingstonii
(PSU4925)
Cape Maclear (n=19)
P. elegans
(holotype)
BMNH1935.6.1
4.127
P. e le ga ns (PSU11394)
Chitande (n=12)
Mean Range Mean Range
Standard length, mm 55.7 82.7 64.3–114.4 85.4 55.9 43.4–63.1
Head length, mm 18.4 25.0 19.7–34.7 24.8 17.5 13.5–20.0
Percent standard length
Head length 33.0 30.3 28.2–32.5 29.3 31.3 29.4–33.1
Body depth 31.4 31.4 28–35 32.2 31.6 29–34
Snout to dorsal-fin origin 33.6 33.8 32.2–35.6 32.6 34.4 31.7–37.8
Snout to pelvic-fin origin 36.4 37.4 35.4–39.7 39.0 37.6 35.1–39.8
Dorsal-fin base length 64.0 59.2 56.9–61.8 61.1 60.7 57.6–64.9
Anterior dorsal to anterior anal 55.4 51.3 48.1–54.6 52.7 49.4 47.3–51.9
Anterior dorsal to posterior anal 63.7 62.4 58.7–65.4 64.6 61.1 57.1–64.7
Posterior dorsal to anterior anal 34.0 30.9 28.9–32.4 30.3 31.9 30.2–33.9
Posterior dorsal to posterior anal 18.2 15.2 14.3–16.2 15.4 15.8 14.5–16.9
Posterior dorsal to ventral caudal 20.6 18.0 16.0–20.0 19.5 18.4 16.8–21.1
Posterior anal to dorsal caudal 20.4 20.6 17.0–22.6 20.4 20.7 19.0–22.6
Anterior dorsal to pelvic-fin origin 33.3 33.1 30.2–36.7 34.3 32.2 29.1–35.4
......continued on the next page

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FIGURE 2. The holotype of Pseudotropheus livingstonii ((BMNH1863.11.12.22).
Dorsal fin XVII–XIX (mode XVIII) and 9–10 (mode 9). Anal fin III and 8–9 (mode 8). First 4–5 dorsal-fin
spines gradually longer posteriorly; fourth spine about 2 times length of first spine; last 13 spines slightly longer
posteriorly; last spine longest, about 3 times length of first spine; rayed portion of dorsal fin with subacuminate
TABLE 1. (Continued)
Variable P. livingstonii
(holotype)
BMNH1863.11.
12. 22
P. livingstonii
(PSU4925)
Cape Maclear (n=19)
P. elegans
(holotype)
BMNH1935.6.1
4.127
P. e le ga ns (PSU11394)
Chitande (n=12)
Mean Range Mean Range
Posterior dorsal to pelvic-fin origin 54.1 56.3 53.5–58.8 56.6 58.1 55.4–60.6
Caudal-peduncle length 17.2 16.0 14.1–17.9 15.6 15.8 14.6–17.0
Least caudal-peduncle depth 13.5 12.1 11.2–12.8 12.0 12.3 11.2–13.0
Percent head length
Snout length 32.7 34.6 31.7–40.4 31.3 28.9 26.4–31.9
Postorbital head length 45.8 37.3 35.2–40.8 36.7 40.8 37.4–47.3
Horizontal eye diameter 32.5 32.0 29.1–35.3 36.0 36.7 34.0–39.3
Vertical eye diameter 31.7 30.5 26.3–33.7 34.7 35.1 32.5–38.0
Preorbital depth 21.5 19.6 15.4–23.8 20.5 16.3 15.1–18.3
Cheek depth 24.0 22.9 20.8–25.9 27.5 20.9 19.3–22.7
Lower-jaw length 38.1 37.5 32.6–42.0 35.6 35.9 30.6–41.0
Head depth 85.8 84.6 74.9–98.7 97.0 84.5 77.2–89.2
Counts Mode Range Mode Range
Dorsal-fin spines 17 18 17–19 17 18 17–19
Dorsal-fin rays 9 9 9–10 9 9 8–9
Anal-fin spines 3 3 3 3 3 3
Anal-fin rays 8 8 8–9 8 8 8–9
Pectoral-fin rays 5 5 5 5 5 5
Pelvic-fin rays 14 14 13–14 14 13 12–14
Lateral-line scales 31 33 32–35 31 32 32–33
Pored scales posterior to lateral line 2 3 2–4 2 2 1–2
Scale rows on cheek. 4 4 3–4 4 3 3
Gill-rakers on first ceratobranchial 10 11 9–12 11 11 10–12
Teeth on outer row of left lower jaw 11 14 12–17 11 11 11–14
Teeth rows on upper jaw 5 5 4–5 5 4 4
Teeth rows on lower jaw 5 4 3–5 5 3 3–4

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(females) to pointed (males) tip, third or fourth ray longest, to approximately ¼ length of caudal fin in females and
approximately ¾ length of caudal fin in males. Anal-fin spines progressively longer posteriorly; third or fourth
anal-fin ray longest, ½ length caudal fin in both sexes; 0–3 small yellow spots on posterior part of anal fin in
females and 0–6 yellow spots on posterior part of anal fin in males. Caudal fin subtruncate to slightly emarginate.
Pelvic fin to first or second spine of anal fin. Pectoral fin moderately long and wing-shaped with upper pointed tip,
length to vertical line through base of 12th or 14th dorsal-fin spine. Flank scales ctenoid with abrupt transition to
small scales on breast; 32–35 lateral-line scales; cheek with 3–4 (mode 4) rows of small scales; caudal fin with tiny
scales to ¼ length; no scales on other fins. Gill rakers on first ceratobranchial 9–12 (mode 11).
Recently captured fish with dark brown head, white gular region with gray blotches; black spot on opercle with
reflected blue highlights. Laterally brown with 4 dark brown bars from dorsal fin to belly. Caudal fin with yellow
rays and clear membranes. Anal fin brown anteriorly to first or second ray, hyaline posteriorly; 0–6 yellow ocelli in
rayed portion. Pectoral fins with yellow rays and clear membranes. Pelvic fins black anteriorly, hyaline posteriorly.
Female coloration similar to male, not as vivid.
Pseudotropheus elegans Trewavas 1935
(Fig. 3)
Pseudotropheus elegans Trewavas 1935
Metriaclima elegans.—Stauffer et al. 1997
Pseudotropheus livingstonii (non-Boulenger).—Konings 2007
Pseudotropheus sp. ‘acei’.—Konings 2007
Material examined. Pseudotropheus elegans, BMNH1935.6.14.127, holotype, 85.4 mm SL, Chilumba Bay, Lake
Malaŵi; PSU11394, 12 specimens, 43.4–63.1 mm SL, Chitande Island, 12º 23.764'S 34º 15.275'E, Lake Malaŵi .
Diagnosis. Pseudotropheus elegans is distinguished from all other members currently in Pseudotropheus,
except P. williamsi, by a pale yellow to hyaline dorsal fin and by the absence of distinct vertical bars below the
dorsal fin. Most species of Pseudotropheus either have distinct bars below the dorsal fin or a dorsal fin with black
pigment. It is distinguished from P. williamsi by the absence of two horizontal lines of black dots on the flank.
Description. Principal morphometric ratios and meristics for holotype and population from Chitande Island in
Table 1. Medium-sized mbuna, ovoid body (mean BD 31.6% SL) with greatest depth at about 6–7th dorsal spine.
Dorsal body profile with gradual curve downward, more acute towards caudal peduncle; ventral body profile
slightly convex between pelvic fins and base of rays of anal fin with upward taper to caudal peduncle. Dorsal head
profile round, with continuous curve between interorbital and dorsal-fin origin; horizontal eye diameter (mean
36.7% HL) greater than preorbital depth (mean 16.3% HL); eye (along horizontal axis) in anterior half of head;
snout straight; jaws isognathus; tooth bands with 4 rows in upper jaw and 3–4 rows in lower; teeth in anterior outer
row bicuspid with posterior lateral teeth primarily unicuspid, and teeth in inner rows tricuspid
FIGURE 3. The holotype of Pseudotropheus elegans (BMNH1935.6.14.127).
Dorsal fin XVII–XIX (mode XVIII) and 8–9 (mode 9). Anal fin III and 8–9 (mode 8). First 4–5 dorsal-fin
spines gradually longer posteriorly with fourth spine about 1½ times length of first; last 13 dorsal-fin spines
increasingly longer posteriorly with last spine longest, about 2 times length of first; soft dorsal fin with
subacuminate tip, third or fourth ray longest, to approximately ¼ length of caudal fin. Anal-fin spines progressively

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longer posteriorly; 3
rd
or 4
th
ray longest, to base of caudal fin in both sexes; 1–3 small yellow spots on posterior part
of anal fin. Caudal fin subtruncate to slightly emarginate. Length of pelvic fin to first spine of anal fin. Pectoral fin
short and paddle-shaped, length to vertical line through base of 10–11
th
dorsal-fin spine. Flank scales ctenoid with
abrupt transition to small scales on breast; 32–33 lateral-line scales; cheek with 3 rows of small scales; caudal fin
with tiny scales to ¼ length; no scales on other fins. Gill rakers on first ceratobranchial 10–12 (mode 11).
Recently captured fish with gray head, white gular region, and black opercular spot. Laterally gray ground
coloration; scales with green outline; breast and belly gray. Dorsal fin pale yellow to hyaline. Caudal fin with two
ventral rays and membranes black; remainder clear with faint white spots. Anal fin black with white marginal band;
1–3 yellow ocelli in rayed portion. Pectoral-fin rays clear; pelvic-fin rays black anteriorly, remainder clear.
Coloration of female similar to male.
Remarks. The holotype of P. elegans and a population of this species collected from Chitande Island were
compared morphologically to the holotype of P. livingstonii and a population of P. livingstonii collected from Cape
Maclear. A plot of the sheared third principal components of the morphometric data against the first principal
components of the meristic data (Fig. 4) showed that the holotype of P. livingstonii grouped within the minimum
polygon clusters and the 95% confidence ellipses formed by the meristic and morphometric data from those
individuals collected at Cape Maclear. A plot of the sheared second principal components against the sheared third
principal components (Fig. 5) showed that the holotype of P. elegans grouped within the minimum polygon cluster
and the 95% confidence ellipses formed by the morphometric data from those individuals collected at Chitande
Island.
FIGURE 4. Sheared third principal components (morphometric data) plotted against the first principal components (meristic
data) of the holotype (x) and specimens of Pseudotropheus livingstonii from Cape Maclear (■) and the holotype (+) and
specimens of P. elegans from Chitande (o). The minimum polygon clusters are bounded by 95% confidence levels.

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FIGURE 5. Sheared second principal components (morphometric data) plotted against the sheared third principal components
(morphometric data) of the holotype (x) and specimens of Pseudotropheus livingstonii from Cape Maclear (■) and the holotype
(+) and specimens of P. elegans from Chitande (o). The minimum polygon clusters are bounded by 95% confidence levels.
The first principal component (size variable) of the morphometric data explained 96% of the observed
variance, the sheared second principal component explained 25% and the third sheared principal component
explained 15% of the remaining variance. Variables that had the highest loadings on the sheared second principal
components of the morphometric data were preorbital depth (-0.51), distance between the posterior insertion of the
anal fin and dorsal origin of the caudal fin (0.38), and the distance between the posterior insertion of the dorsal fin
and the ventral origin of the caudal fin (0.27). Variables that had the highest loadings on the sheared third principal
components of the morphometric data were snout length (-0.63), vertical eye diameter (0.43), and head depth
(0.31). The first principal component of the meristic data explained 39.8% of the variance. Variables with the
highest loadings on the first principal components of the meristic data were tooth rows on the upper jaw (0.40),
pored scales posterior to the lateral line (0.36), and anal-fin rays (0.38).
The HRCT scans permitted us to critically analyze the shape of the skull of the type specimens of P.
livingstonii, P. elegans, and M. lanisticola, a sand-dwelling species of Metriaclima. We found that the angle that the
ethmo-vomerine bloc makes with the parasphenoid is much more acute in Pseudotropheus than in Metriaclima.
The angle in the holotype of P. livingstonii is 57°, and in that of P. elegans is 58°. The ethmo-vomerine bloc/
parasphenoid angle in the holotype of M. lanisticola is 48°.
Discussion
Pseudotropheus livingstonii and P. elegans belong to a small group of sand-dwelling mbuna, while almost all other
members of the mbuna are found in rocky habitats. One of the characteristics that sets these sand-dwelling mbuna
apart from almost all rock-dwellers is the fact that there is no, or very little, sexual dimorphism.

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A third sand-dwelling mbuna, M. lanisticola, played a role in the taxonomic confusion as for a long time it was
thought to be a junior synonym of P. livingstonii (Ribbink et al. 1983). Both of these species exhibit a distinct
barring pattern, lacking in P. elegans, and are difficult to distinguish on the basis of external morphology.
Metriaclima lanisticola lives in empty shells of the snail Lanistes nyassanus and rarely attains a total length of
more than 6 cm while P. livingstonii can grow to a size of about 13 cm. All known populations of M. lanisticola are
characterized by a caudal fin that has a pattern consisting of irregular yellow and blue bands. The caudal fin of P.
livingstonii, however, is clear and usually has a white upper and lower edge. Other morphological differences
between P. livingstonii and M. lanisticola include: the latter rarely has more than four rows of teeth in the oral jaws
while P. livingstonii usually has five or six rows. The teeth of the inner rows in M. lanisticola are widely spaced
whereas they are close-packed in P. livingstonii. The holotype of P. livingstonii has six rows of closely packed
teeth.
In addition, M. lanisticola feeds on algae, which is raked from shells, shell fragments, or small pebbles lying
on the sand. Pseudotropheus livingstonii and P. elegans feed by picking or scooping algae from the sand or from
objects on the sand. Their feeding technique differs from the combing or raking technique displayed by M.
lanisticola (Konings 2007). Since the holotype of P. l i v i n g s t o n i i is a relatively small specimen (55.7 mm SL) it
could be confused with a large specimen of M. lanisticola. Our HRCT scans, however, revealed that the vomer-
parasphenoid angle in the holotype of P. livingstoni is 57° and that of P. elegans is 58º, well outside the range found
in Metriaclima (35–50°) (Konings 2007, Konings & Stauffer 2006). The vomer-parasphenoid angle in the holotype
of M. lanisticola is 48.7º, which is within the range found in Metriaclima spp.
It should be noted that we realize that Pseudotropheus is polyphyletic, and that P. livingstonii and P. elegans do
not form a monophyletic group with P. williamsi, the type species of the genus. We are in effect using
Pseudotropheus as a holding place, similar to the way in which Greenwood (1979) used Cyrtocara for many Lake
Malaŵi species when he removed them from Haplochromis. We currently lack sufficient data to diagnose a new
genus to accommodate these two and undoubtedly many other species that are still assigned to Pseudotropheus.
Acknowledgements
The authors wish to thank the government of Malaŵi for providing the necessary permits to collect fishes. Funding
was provided by the NSF/NIH joint program in ecology of infectious diseases (DEB0224958).
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