Metriaclima gallireyae, Miller & Konings & Stauffer, 2021

Miller, Torin A., Konings, Adrianus F. & Stauffer, Jay R., 2021, Descriptions of two new shell-dwelling species of Metriaclima (Cichlidae) from Lake Malaŵi, Africa, Zootaxa 5052 (3), pp. 419-432 : 425-429

Metriaclima gallireyae , new species

Figures 5 , 6 , 7 ; Tables 2

Pseudotropheus lanisticola (in part), Konings 1989

Pseudotropheus livingstonii (in part), Konings 1995

Metriaclima livingstonii (in part), Konings 2001

Metriaclima sp. ‘lanisticola north’ Konings 2007

Holotype. PSU 13370 , adult male, 54.4 mm SL, (10.500153 S, 34.233362 E), Gallireya Reef , Lake Malaŵi , Malaŵi, Africa, 15 Jan. 2008, A. F. Konings & J. R. Stauffer Jr.

Paratypes. PSU 13371 , 20, (36.4–54.4 mm SL), data as for holotype .

Diagnosis. The moderately sloped vomer (49.6º in holotype) with a swollen rostral tip ( Fig. 6 ) and bicuspid teeth in the anterior portion of the outer row of both upper and lower jaws place this species in Metriaclima . The presence of a black submarginal band in the dorsal and anal fin, and 4–5 bars below the dorsal distinguishes M. gallireyae from most other species in Metriaclima , except for M. ngarae . It differs from M. ngarae by a smaller interorbital width (30.7–37.4% vs. 23.6–29.7% HL) and by a smaller ratio of the snout length in the distance between snout tip and pelvic fin origin (20.6–27.8% vs. 28.7–32.8% SNP2). On average the ratio of premaxillary pedicel length in snout length is greater in M. gallireyae at 44.6% vs. 35.1 %SNL in M. ngarae (ranges 33.1–62.7 vs. 20.3–45.2 %SNL). Mature males of M. gallireyae have a dark brown to blue coloration on flank ( Fig. 7 ) on which no bar pattern is visible. Male M. ngarae resemble females and display 4–5 dark bars on a light-colored flank. Female M. gallireyae have a similar color pattern to those of M. ngarae but the bars on the flank are more prominent and extend to the abdomen.

Description. Morphometric and meristic data in Table 2. Small mbuna with ovoid body (mean BD 38.6% SL) with greatest depth between the 3 rd and 4 th dorsal spine. Dorsal body profile with gradual curve downward posteriorly (more pronounced than in M. ngarae ) with highest point between the 4 th and 5 th spine, less deep towards posterior end of dorsal fin and beginning of caudal peduncle; ventral body profile flat between pelvic fins and origin of anal fin with slight upward angle to caudal fin. Dorsal head profile round with continuous curve between interorbital and dorsal-fin origin; short snout with isognathous to slightly retrognathous jaws; teeth in upper and lower jaws in 3–4 rows (mode 3); teeth in outer row bicuspid, inner rows unicuspid or tricuspid.

Dorsal fin with XVI or XVIII (mode XVII) spines and 7–9 (mode 8) rays. Anal fin with III spines and 7–8 rays. First 5–6 dorsal-fin spines gradually longer posteriorly with sixth spine about twice as long as first spine; posterior 13 spines slightly longer posteriorly with last spine longest; soft dorsal fin with subacuminate tip, 2nd or 3rd ray longest, extending to approximately 1/3–1/2 length of caudal fin. Anal-fin spines progressively longer posteriorly; 3 rd or 4 th ray longest, extending to halfway caudal fin, equal to or slightly further posterior than tip of dorsal fin. Caudal fin subtruncate to emarginate. Pelvic fin reaching to first anal-fin spine. Pectoral fin rounded, paddle-shaped, short, reaching vertical through base of 10th or 11th dorsal-fin spine. Flank scales ctenoid with small scales on breast and belly; 29–32 (mode 30) lateral-line scales, cheek with 4–5 rows of small scales. Small scales over proximal ¼ of caudal fin.

Head of male brown with dark brown interorbital bar; cheek and preopercle with blue highlights; opercle with blue and green highlights and black spot; throat brown ( Fig. 7 ). Flank dark brown to blue (in territorial males), center of scales brown with blue outline; 4–5 brown bars, obscured in fully mature males; breast and belly black. Dorsal fin brown with black submarginal bar; orange and brown lappets, with orange pigmentation in membranes of rayed portion. Caudal fin with black dorsal and ventral margin; brown rays; blue membranes. Anal fin with proximal ¼ gray, distal ¾ black; one yellow ocellus. Pelvic fin black with white leading edge. Pectoral fin with clear membranes and gray rays.

Distribution. Metriaclima gallireyae is found on Gallireya Reef (10.500153 S, 34.233362 E), Youngs Bay and in Chitimba Bay (10.581122 S, 34.23692 Lake Malaŵi, Malaŵi ( Fig. 1 ).

Field observations. The population density of Metriaclima gallireyae is much higher than that of M. ngarae and is often seen in large groups of up to 20 individuals in the vicinity of empty shells of L. nyassanus . Both sites where this small species was observed contained either many football-sized (lava?) rocks (Gallireya Reef) or large slabs of sandstone (Chitimba Bay) that may provide additional shelter to individuals that were not able to secure an empty shell for protection. The depth range at Gallireya Reef is about 8–12 m while the reef (almost solely consisting of sandstone slabs) in Chitimba Bay is at a depth of about 20– 25 m. Pure sandy habitats in the area of these two reefs were not visited other than near shore (shallower than 5 m) where M. gallireyae was absent.

No stomach analyses were performed but individuals were observed picking from the rocks and slabs, particularly from patches that showed less sediment cover. Repeated application of the fully opened mouth to a sediment-free spot on a rock suggests that it combs the algal matrix for loose strands of (blue-green) algae. Females and immatures were often seen in small foraging groups mainly feeding from plankton in the water column close (<20cm) to the sandy bottom.

Mature males protect an empty shell as their territory but mouth-brooding females at Gallireya Reef were frequently encountered among the rocks of the habitat. Mouth-brooding females in Chitimba Bay were mostly seen near their shell.

Etymology. The specific epithet gallireyae is a genitive of Gallireya Reef, the local name for a reef in Youngs Bay, Lake Malaŵi.

Remarks. There was complete separation of the minimum polygon clusters when the sheared second principal components (SPCA2) of the morphometric data were plotted against the first principal components (PC1) of the meristic data for M. ngarae and M. gallireyae ( Fig. 8 ). The first principal component (size variable) of the morphometric data explained 87.8% of the observed variance and SPCA2 explained 5.4%. Variables that had the highest loadings on SPCA2 were the premaxillary pedicel length (0.89), snout length (-0.24), and cheek depth (- 0.21). The first principal component of the meristic data explained 24.7% of the variance. Variables with the highest loadings on the first principal components of the meristic data were pored lateral-line scales posterior to the hypural plate (0.50), number of tooth rows on the upper jaw (0.44), and tooth rows on the lower jaw (0.28).

Figures

FIGURE 1. Map of Lake Malaŵi with the localities marked that are mentioned in the text.

FIGURE 5. Metriaclima gallireyae. Holotype, PSU 13370, adult male, 54.4 mm SL, Gallireya Reef, Lake Malaŵi.

FIGURE 6. CT scan of the cranium of Metriaclima gallireyae. Holotype, PSU 13370, adult male, 54.4 mm SL, Gallireya Reef, Lake Malaŵi; angle of ethmovomerine block is 49.6° with parasphenoid.

FIGURE 7. A male Metriaclima gallireyae at Gallireya Reef (10.500153 S, 34.233362 E), Lake Malaŵi.

FIGURE 8. Sheared second principal components (morphometric data) plotted against the first principal components (meristic data) of 14 specimens of Metriaclima ngarae from Ngara (x) and 20 specimens of Metriaclima gallireyae from Gallireya Reef (+).

Tables

TABLE 2. Morphological and meristic data for Metriaclima gallireyae from Gallireya Reef, Lake Malaŵi, PSU 13370, 13371, n=20. Ranges include holotype.

Variable	Holotype	Mean	Std Dev	Range
Standard length (mm)	54.4	45.8	5.0	36.4–54.4
Head length (mm)	17.7	15.1	1.4	12.4–17.7
Percent head length (%)
Snout length	28.3	31.0	2.3	26.2–35.0
Postorbital head length	41.9	42.7	1.8	39.0–46.0
Horizontal eye diameter	32.3	31.1	1.6	28.5–34.2
Vertical eye diameter	30.8	29.0	1.8	25.1–32.4
Preorbital depth	17.9	16.3	1.5	14.1–18.9
Cheek depth	31.1	26.3	3.6	21.1–33.5
Lower jaw length	26.9	26.0	3.0	21.6–33.5
Head depth	104.8	100.1	5.4	91.3–109.7
Inter-orbital width	26.2	27.3	1.5	23.6–29.7
Premaxillary pedicel length	15.7	13.7	1.7	10.9–16.4
Percent standard length (%)
Head length	32.7	33.0	0.8	31.5–34.4
Body depth	43.3	38.6	1.8	34.9–43.3
Snout to dorsal fin origin	39.5	35.7	1.3	32.6–39.5
Snout to pelvic fin origin	38.9	40.6	1.5	37.4–42.5
Dorsal fin base length	60.2	57.2	2.2	52.4–60.2
Anterior dorsal to anterior anal	55.3	51.8	1.7	48.6–55.3
Anterior dorsal to posterior anal	65.3	62.5	1.8	58.0–65.3
Posterior dorsal to anterior anal	34.9	33.0	1.4	30.2–35.0
Posterior dorsal to posterior anal	19.9	18.6	1.0	17.0–19.9
Posterior dorsal to ventral caudal	20.9	19.3	0.9	17.5–20.9
Posterior anal to dorsal caudal	23.2	22.0	0.9	21.0–23.8
Anterior dorsal to pelvic-fin origin	42.7	38.5	1.8	35.0–42.7
Posterior dorsal to pelvic-fin origin	61.1	57.5	1.7	54.7–61.1
Caudal peduncle length	13.6	13.3	1.0	11.5–14.8
Least caudal peduncle depth	15.8	15.6	0.7	14.4–16.3
Meristics		Mode	Frequency (%)	Range
Dorsal-fin spines	17	17	80.0	16–18
Dorsal-fin rays	8	8	80.0	7–9
Anal-fin spines	3	3	100.0	3–3
Anal-fin rays	7	8	75.0	7–8
Pectoral-fin rays	14	14	45.0	12–15
Pelvic-fin rays	6	6	90.0	6–7
Lateral line scales	30	30	40.0	29–32
Pored scales caudal	2	1	40.0	0–3
Cheek scale rows	4	4	85.0	4–5
Gill rakers 1st ceratobranchial	10	10	70.0	9–11
Gill rakers 1st epibranchial	5	4	85.0	3–5
Teeth outer left lower jaw	12	10	25.0	6–17
Tooth rows upper jaw	4	3	70.0	3–4
Tooth rows lower jaw	4	3	90.0.	3–4