Neolamprologus devosi, Robert Schelly, Melanie L. J. Stiassny & Lothar Seegers, 2003

Robert Schelly, Melanie L. J. Stiassny & Lothar Seegers, 2003, Neolamprologus devosi sp. n., a new riverine lamprologine cichlid (Teleostei, Cichlidae) from the lower Malagarasi River, Tanzania., Zootaxa 373, pp. 1-11 : 2-9

Neolamprologus devosi , new species

(Fig. 1)

Holotype. AMNH 233614 , male, 56.9 mm SL, a few kilometers upstream from Ilgala, lower course of Malagarasi River , 5°11'59"S 29°49'59"E, Tanzania, L. Seegers, 02/07/94 .

Paratypes. Total of 24 specimens, 23.0-57.1 mm SL; AMNH 233615 , male, 57.1 mm SL, a few kilometers upstream from Ilgala, lower course of Malagarasi River , 5°11'59"S 29°49'59"E, Tanzania, L. Seegers, 02/07/94. - MRAC 93-152-P-1385-1394 , 23.0-35.6 mm SL, delta Malagarasi, right arm , Tanzania, 5°13’S 29°48’E, L. DeVos, 20/08/1993. - MRAC 96-031-P-0528-0537 , 28.1-53.3 mm SL (of which 2 specimens are cleared and double stained), delta Malagarasi, right arm , Tanzania, 5°13’S 29°48’E, L. De Vos, 20/08/ 1993 .

Differential diagnosis. Neolamprologus devosi is distinguished from the following congeners in having fewer than 40 scales in the longitudinal series: N. furcifer , N. christyi , N. prochilus , N. pleuromaculatus , N. hecqui , N. meeli , N. boulengeri , and N. bifasciatus . With 34-35 lateral line scales, N. devosi is further distinguished from N. variostigma , which has 39-40 lateral line scales. A low gill raker count (5-6) on the lower limb of the first arch distinguishes N. devosi from the following taxa that have 8 or more rakers: N. brevis , N. longicaudatus , N. moorii , N. sexfasciatus , N. toae , N. leleupi , and N. calliurus . The presence of 5-6 anal fin spines distinguishes N. devosi from both N. niger and N. fasciatus , which have 8 or more anal spines, and from N. tetracanthus , which has only 4 anal spines. The caudal fin of Neolamprologus devosi is enlarged, rounded, and paddle shaped, distinguishing it from the following species with emarginate caudal fins, often also with the outer caudal rays produced and filamentous: N. mondabu , N. leloupi , N. caudopunctatus , N. savoryi , N. falcicula , N. gracilis , N. crassus , N. marunguensis , N. pulcher , N. brichardi , N. buescheri , N. splendens , N. olivaceous , and N. helianthus . Lacking their striking coloration and large molariform lower pharyngeal jaw teeth, N. devosi is distinguished from N. tretocephalus and N. modestus ; similarly it lacks the numerous vertical bars of N. similis , N. cylindricus , and N. multifasciatus , the solid orange coloration of N. longior , and the solid black coloration of N. schreyeni . With a body depth of 22.5-25.9% SL, N. devosi is shallower-bodied than N. mustax (28.3-33.4% SL), N. wauthioni (28.6- 29.4% SL), N. petricola (30.3-35.7% SL), and N. obscurus (25.6-34.8% SL), which is further distinguished in having 7-8 anal spines compared to 5-6 in N. devosi . Neolamprologus devosi has fewer vertebrae (31-32) than N. nigriventris and N. pectoralis , which have 34 or more vertebrae, and finally, N. devosi lacks the extremely elongate pelvic fins characteristic of N. ventralis .

Description: Counts and measurements for the type series are given in Table 1. A relatively gracile, elongate species (BD 22.5-25.9, mean 23.9% SL), bearing a superficial resemblance to Lamprologus mocquardi from the Congo River, but differing from that taxon in the possession of a pelvic fin with the first ray longer than the second rather than vice versa as in L. mocquardi , and in the absence of tubular elements in the infraorbital series (see below). Greatest body depth at about base of second or third dorsal spine. Head length 32.5-35.0, mean 33.8% SL. Dorsal head profile slightly interrupted by prominent premaxillary pedicel then smoothly rounded to the dorsal fin origin. Dorsal body profile convex, curving gently downward along the length of the dorsal fin base to the caudal peduncle; ventral body profile somewhat rounded and posteriorly curving gently upward just anterior to caudal peduncle.

Fins. Dorsal fin with XVII -XIX (mode XIX) spines and 8-9 (mode 8) soft rays. Anal fin with V -VI (mode VI) spines and 6-7 (mode 7) soft rays. Spines in both fins gradually increase in length posteriorly. Dorsal and anal fins with tapering filamentous extensions reaching to about the middle of the caudal fin in larger individuals, and just beyond the caudal fin base in juveniles. Caudal fin enlarged, rounded, and paddle-shaped, with 14 branched rays. Pectoral fins short, not reaching a vertical through the anus, with 13 rays reaching to fin margin. First ray is the longest in the pelvic fin, and this is produced in larger specimens and reaches just beyond the second anal fin spine, and to the level of the anus in juveniles.

Teeth (Fig.2). Lower jaw slightly prognathous, with both outer and inner row teeth pointed unicuspids in both jaws. A series of 4-8 enlarged, recurved, procumbent canines situated anteriorly in the jaws with the largest teeth furthest from the symphysis. Posterior to the enlarged procumbent canines is a single row of slightly enlarged canines extending almost the entire length of the dentigerous arm of the dentary and premaxilla. Inner teeth in 3 rows of tightly-packed, small, recurved caniniform teeth tapering by mid-jaw into a single row.

Gill rakers (Fig. 3c). Relatively short, blunt and non-denticulate. 8-11 (mode 9) gill rakers along the outer row of the first gill arch. No rakers present on the hypobranchial, 5- 6 (mode 5) along the ceratobranchial, one raker in the angle of the arch, and 2-4 (mode 3) epibranchial rakers.

Lower pharyngeal jaw (Fig. 4). Lower pharyngeal jaw wider than long, with straight, or very slightly interdigitating, ventral suture. Usually 20-24 teeth in the posterior tooth row. Median row teeth slightly enlarged and with a robust hook, lateral teeth slender and either beveled or bluntly hooked.

Scales. Flank scales large, ctenoid and regularly imbricating. Pored lateral line scales 34-35. Upper branch of lateral line never overlapping lower branch, which is short, consisting of only 4-6 pored scales. Cheek and chest naked, belly with small scales. Nape naked to level of 6th dorsal spine. A few scattered scales on the opercle. Dorsal and anal fins scaleless. Small scales over proximal half of caudal fin.

Vertebrae. Vertebral count 31-32; 14+18 (13), 14+17 (2).

Additional osteology. Infraorbital series composed of a broad plate-like lachrymal which is perforated by five large pores of the sensory canal system (Fig. 3b), there are no tubular infraorbitals adjacent to the lachrymal, and no dermosphenotic is present. Supraneural usually absent (Fig. 3a), but in four individuals a very small weakly ossified supraneural is present. Neurocranium is somewhat dorsoventrally compressed and the supraoccipital crest is low, as is the frontal ridge, which extends anteriorly to the median coronal pore (Fig 3a).

Coloration (Fig. 5). In life, base body coloration light beige brown fading to pale yellow on the belly and along the dorsum, and with a bright yellow patch under the eye. Four or five dusky vertical bars are often present along the body from nape to caudal peduncle. Individual body scales have dark pigment around the free scale margins, creating a reticulate pattern of thin, oblique bands of pigment that present the appearance of “chain mail” or a “chain link fence”. A broad lachrymal stripe more-or-less covers the lachrymal bone, and a dark horizontal band runs from the eye over the dorsal cheek and merges with a scaleless opercular spot. The lower lip and opercle are suffused with a pale blue flush. Dorsal fin with a yellow marginal band and a black submarginal band. The interspinous and soft ray membranes of the dorsal and anal fins with a strong pattern of yellow banding and merging spotting. Caudal fin also banded and spotted. Caudal fin with a yellow marginal band and black submargin; ventral portion of fin has a bluish flush. Preserved coloration, beige brown with banding and scale pigmentation usually visible.

Viscera and diet. Gut short and straight, intestinal length 60-70% SL. Contents included some detritus, freshwater shrimps, ostracods, and the soft-bodies of snails. As no crushed snail shells were found in the stomach or intestines this perhaps indicates that N. devosi is “picking” the snails from shells rather than crushing the shells to obtain the flesh.

Reproductive biology. Nothing is currently known of the reproductive biology of this species.

Distribution and habitat. Currently N. devosi is known only from two localities in the Malagarasi River basin: from the delta and in the river a few kilometers upstream from Ilgala, which itself is situated some kilometers to the east of the Malagarasi delta on the northern bank of the Malagarasi River (Fig. 6).

It is noteworthy that when one of us (L.S.) collected in the Malagarasi delta (12/1991) at the same locality from where most paratypes were collected by L. De Vos (8/1993), no specimens of N. devosi were seen. This might be due to the fact that there is a small rainy season in December-January with relatively high water stands whereas in July the dry season is ongoing and water levels are low. However, the possibility that N. devosi undergoes seasonal migration is raised.

Water parameters taken in December 1991 in the delta were: air temperature, 28.5°C, water temperature, 26.0°C, 7.8 mg/l O2, conductivity, 185 microsiemens/cm-1, pH 8.33, German hardness, 5° DH. The visibility of the water was very low. These measures differ markedly from those taken in December 1991 near Kigoma on Lake Tanganyika where conductivity was 450 microsiemens/cm-1, pH, 9.17 and German hardness was 12° DH. The lower conductivity, pH and German hardness clearly indicate the riverine conditions that prevail in the delta as opposed to the lake proper.

Etymology. Named in memory of our friend and colleague Luc (Tuur) De Vos who dedicated so much of his career to expanding our knowledge of the fishes of East and Central Africa. His sudden and untimely death is a great loss to our community.

Remarks. De Vos et al. (2001) suggest that the presence of a lamprologine cichlid in the lower Malagarasi River with close phylogenetic affinities with certain of the Congolese Lamprologus casts doubt on the hypothesis, advanced by Sturmbauer et al. (1994), that the Congolese riverine lamprologines (or at least some of them) are phylogenetically nested within the Lake Tanganyika flock and represent a secondary invasion of the Congo River system. They reason that given such a scenario, it is highly unlikely that one would find two closely related riverine species both to the west and to the east of the lake. Ongoing studies, however, indicate that the resemblance between Neolamprologus devosi and Lamprologus mocquardi is superficial, and that no close phylogenetic relationship exists between them (Schelly & Stiassny, submitted) and the question of the origin/s of the riverine Lamprologus radiation remains an outstanding issue.