Metriaclima ngarae, 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 : 422-425

Metriaclima ngarae , new species

Figures 2 , 3 , 4 ; Table 1

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 13365, adult male, 59.1 mm SL, (10.233397 S, 34.106592 E) Ngara , Lake Malaŵi, Malaŵi, Africa, Jan. 2000, S. Grant’s crew.

Paratypes. PSU 13366, 14 , (49.6 mm – 62.4 mm SL), data as for holotype .

Diagnosis. The moderately sloped vomer (45.4º in holotype) with a swollen rostral tip ( Fig. 3 ) 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 ( Fig. 4 ) in the dorsal and anal fin distinguishes M. ngarae from most other species in Metriaclima , except for M. phaeos (Stauffer, Bowers, Kellogg, & McKaye) , M. lundoense Stauffer, Black, & Konings , M. nigrodorsalis Stauffer, Black, & Konings , M. koningsi Stauffer , M. gallireyae n. sp., and from some populations of M. zebra (Boulenger) , M. pulpican Tawil , and M. usisyae Li, Konings, & Stauffer. It differs from all of these except M. gallireyae by the number of vertical bars below the dorsal fin which is 4-5 for M. ngarae and 6-10 for the other species or none at all for M. koningsi . It differs from M. gallireyae by a greater interorbital width (30.7–37.4% vs. 23.6–29.7% HL) and by a greater ratio of the snout length in the distance between snout tip and pelvic fin origin (28.7–32.8% vs. 20.6–27.8% SNP2). On average, the ratio of premaxillary pedicel length in snout length is smaller in M. ngarae at 35.1% vs. 44.6 %SNL in M. gallireyae (ranges 20.3–45.2 vs. 33.1–62.7 %SNL). Males of M. ngarae have a color pattern similar to that of females but males of M. gallireyae are dark brown to blue without visible bar pattern. Female M. ngarae have a similar color pattern to those of M. gallireyae but the bars on the flank are less prominent and do not extend to the abdomen.

Description. Morphometric and meristic data in Table 1 . Small-sized mbuna, ovoid body (mean BD 38.7% SL) with greatest body depth at about 3 rd and 4 th dorsal-fin spine. Dorsal body profile with gradual curve downward posteriorly with highest point at 6 th or 7 th dorsal-fin spine, more pronounced towards posterior end of dorsal fin and beginning caudal peduncle; ventral body profile nearly straight between pelvic fins and base of anal fin with slight upward curve to caudal fin. Dorsal head profile round with continuous curve between interorbital and dorsal-fin origin; short snout with isognathous jaws; teeth in upper and lower jaws in 2–3 rows (mode 3); teeth in outer row bicuspid, inner rows unicuspid or tricuspid.

Dorsal fin with XVI or XVII (mode XVII) spines and 7–8 (mode 8) rays. Anal fin with III spines and 8 rays. First 5–6 dorsal-fin spines gradually longer posteriorly with 6 th spine about twice as long as first; last 11 spines only slightly greater in length posteriorly with last spine longest; soft dorsal fin with rounded to subacuminate tip, second or third ray longest, to approximately ¼ length caudal fin. Anal-fin spines progressively longer posteriorly; 5th or 6th anal-fin ray longest, tip to base of caudal fin in females and to ½ length of caudal fin in males, equal to or slightly further posterior than tip dorsal fin. Caudal fin subtruncate to emarginate. Pectoral fin rounded, paddle-shaped, short, extending to vertical through base of 8th or 9th dorsal-fin spine. Flank scales ctenoid with abrupt change to small scales on breast and belly; 30–32 (mode 31) lateral-line scales, cheek with 4 rows of small scales. Tiny scales over proximal ¼ of caudal fin.

Head of males gray with two light gray interorbital bars; black opercular spot; throat yellow. Flank gray with light blue spots; 4–6 light bars below lateral line; ventrally white. Dorsal fin clear with orange markings, black submarginal band and white lappets. Caudal-fin rays orange with blue membranes. Anal fin with black marginal band encompassing all spines and through rays over 2/3 of distal portion fin; proximal portion of rays light blue; one yellow ocellus. Pelvic fin with spine and first two rays black; remaining clear. Pectoral fin clear.

Head of females dark gray with two faint green interorbital bars; ventral half pale yellow; black opercular spot; pale yellow throat. Flank yellowish, white below lateral line with light gray bars above lateral line. Fin coloration same as males, not as intense.

Distribution. Metriaclima ngarae is found on submerged reefs near Ngara (10.233397 S, 34.106592 E) and Mdoka (10.280608 S, 34.179156 E), and has also been reported from Chesese (10.280608 S, 34.179756 E) and Kaporo (9.731972 S, 33.94415 E), Malaŵi ( Fig. 1 ).

Field observations. Metriaclima ngarae is most often encountered near empty shells of the gastropod Lanistes nyassanus Dohrn that lie scattered on the sandy bottom at a depth ranging between 10–25 m ( Fig. 4 ). Most observations occurred near rocky habitats, but it was also found at a depth of about 20 m near the outflow of the Songwe River that forms the border between Malawi and Tanzania, with no known rocky reefs within 30 km. No stomach analyses were performed but individuals were observed picking at targeted sites on the sand as well as combing the algal matrix covering the empty shells, small rocks, and other objects that lie on the open sand. Most individuals encountered were solitary and always in association with an empty shell of Lanistes nyassanus into which it would retreat when threatened. Mouth-brooding females stay near their shell and probably release their offspring inside such shells as well.

Etymology. The specific epithet ngarae in the genitive of Ngara, Malawi, where the specimens were collected.

Figures

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

FIGURE 2. Metriaclima ngarae. Holotype, PSU 13365, adult male, 59.1 mm SL, Ngara, Lake Malaŵi.

FIGURE 3. CT scan of the cranium of Metriaclima ngarae Holotype, PSU 13365, adult male, 59.1 mm SL, Ngara, Lake Malaŵi; angle of ethmovomerine block is 46.4° with parasphenoid.

FIGURE 4. A male Metriaclima ngarae at a submerged reef near Ngara (10.233397 S, 34.106592 E).

Tables

TABLE 1. Morphological and meristic data for Metriaclima ngarae from Ngara, Lake Malaŵi, PSU 13365, 13366, n=14. Ranges include holotype.

Variable	Holotype	Mean	Std Dev	Range
Standard length (mm)	59.1	56.6	3.7	49.6–62.4
Head length (mm)	19.1	18.7	1.2	17.0–21.4
Percent head length (%)
Snout length	34.6	34.9	1.2	30.8–36.4
Postorbital head length	39.5	40.8	1.7	36.8–42.7
Horizontal eye diameter	30.6	30.1	1.6	26.7–32.3
Vertical eye diameter	28.9	28.0	1.5	24.4–29.9
Preorbital depth	18.7	19.3	1.1	17.9–21.2
Cheek depth	35.3	34.6	2.5	30.3–38.6
Lower jaw length	25.0	26.0	2.8	20.7–30.4
Head depth	109.9	104.1	4.6	98.5–113.0
Inter-orbital width	34.4	33.4	2.1	30.7–37.4
Premaxillary pedicel length	15.0	12.2	2.9	7.0–15.8
Percent standard length (%)
Head length	32.3	33.1	0.9	32.0–34.5
Body depth	39.1	38.7	0.8	37.1–40.1
Snout to dorsal fin origin	34.9	35.7	1.3	33.9–37.7
Snout to pelvic fin origin	38.4	37.5	1.1	36.3–39.9
Dorsal fin base length	59.8	58.3	1.4	56.0–60.2
Anterior dorsal to anterior anal	50.1	50.1	0.8	48.8–51.5
Anterior dorsal to posterior anal	63.5	62.9	1.3	60.8–64.6
Posterior dorsal to anterior anal	36.6	36.0	1.2	34.2–37.7
Posterior dorsal to posterior anal	19.3	19.4	0.9	18.1–20.3
Posterior dorsal to ventral caudal	21.1	20.6	0.9	19.3–22.3
Posterior anal to dorsal caudal	25.1	23.2	1.1	20.6–25.1
Anterior dorsal to pelvic-fin origin	39.4	38.5	0.9	37.5–40.2
Posterior dorsal to pelvic-fin origin	65.2	61.5	1.4	58.7–65.2
Caudal peduncle length	14.9	14.0	1.0	11.8–15.4
Least caudal peduncle depth	16.3	16.2	0.6	15.5–17.3
Meristics		Mode	Frequency (%)	Range
Dorsal-fin spines	17	17	71.4	16–17
Dorsal-fin rays	8	8	71.4	7–8
Anal-fin spines	3	3	100.0	3–3
Anal-fin rays	8	8	100.0	8–8
Pectoral-fin rays	12	14	85.7	12–15
Pelvic-fin rays	7	7	85.7	6–7
Lateral line scales	32	31	57.1	30–32
Pored scales caudal	2	2	50.0	0–2
Cheek scale rows	4	4	100.0	4–4
Gill rakers 1st ceratobranchial	10	11	57.1	9–12
Gill rakers 1st epibranchial	5	5	50.0	4–5
Teeth outer left lower jaw	8	7	35.7	4–10
Tooth rows upper jaw	3	3	92.9	2–3
Tooth rows lower jaw	3	3	64.3	2–3