Engraulicypris ngalala Riddin, Villet & Bills

Riddin, Megan A., Bills, I. Roger & Villet, Martin H., 2016, Phylogeographic, morphometric and taxonomic re-evaluation of the river sardine, Mesobolabrevianalis (Boulenger, 1908) (Teleostei, Cyprinidae, Chedrini), ZooKeys 641, pp. 121-150 : 138-140

Engraulicypris ngalala Riddin, Villet & Bills sp. n.

Holotype.

SAIAB 74087 A, GenBank KX788909, unsexed, SL 40 mm. "Lucheringo River, Singa Hunting Camp, Mozambique, 11°48'56"S 36°13'15"E, 25 August 2003, I.R. Bills, seine net". In 70% ethanol [SAIAB].

Paratypes.

SAIAB 193064, 2 unsexed, SL 42-45 mm, collected with holotype; SAIAB 73944, 29 unsexed, 2 cleared & stained, SL 18-29 mm, Rovuma River below Chamba, Mozambique, 12°35'47"S 36°56'8"E, 19 August 2003, I.R. Bills; SAIAB 39269, 11 unsexed, 1 cleared and stained, SL 42-53 mm. Lake Chiuta at Mthubula Beach, Malawi, 14°78'33"S 35°83'33"E, 13 July 1992, P. Skelton & D. Tweddle [SAIAB].

Diagnosis.

Operculum shiny only on ventral posterior edge and small area at posterior edge of orbit (not entire area); body midline black (not silver); head with tubercles along lower jaw and lower head in breeding males; snout rounded (not pointed); iris white to light grey (not dark grey) with a few melanophores; pelvic fin melanophores present, dark and widely dispersed.

Morphology.

(Figs 6-8; Table 8). Maximum SL 51 mm. Body elongated; somewhat fusiform; laterally compressed. Maximum body depth midway along body. Pre-dorsal profile straight or slightly convex behind head. Head length 18% of SL; with tubercles along lower jaw and lower head. Snout rounded; short; 33% of head length. Mouth terminal; slightly crescent-shaped with long anterior side. Nostrils large; level with dorsal margin of eye; separated from orbit by less than one orbit radius. Tubular anterior naris short; adjacent to open posterior naris. Eye lateral; visible from above and below (more prominent); diameter 43% of head length. First gill arch with 13+3 gill rakers on cerato- and epibranchial arms, respectively. Gill rakers long; pointed; widely-spaced. Pharyngeal bones in four rows. Pharyngeal teeth 5,3,2,1-1,2,3,5; slender and long; falcate.

Modal fin formulae in Table 8. Fins large in relation to body size. Dorsal fin closer to caudal fin than tip of snout; more or less above origin of anal fin; length 14% of SL; posterior margin straight; rays soft; anterior-most branched fin ray longest. Dorsal and anal fin point parallel. Pectoral fins largest; reaching 1/2 to 3/4 distance to base of pelvic fin; fin lacking lobe at base. Pelvic fins reaching 2/3 distance to base of anal fin; relatively small; pointed; fin lacking a basal lobe. Anal fin moderately long; extending 2/3 length of caudal peduncle; last unbranched ray longest. Ano-genital opening at anterior of base of anal fin. Caudal peduncle moderately long; depth half of length. Caudal fin forked; lobes slightly concave interior lobe into point; upper lobe shorter.

Scales small to medium relative to body size; in regular rows; cycloid; radially striate; rounded, slightly elongate. Base of anal fin lacking sheath of enlarged, elongate scales. Lateral line present; complete; dipping sharply towards ventral at tip of pectoral fin; joins midline at posterior of caudal peduncle; scale count 51-52 (n = 2) along lateral line, 14-16 (n = 3) around caudal peduncle.

Live colouration.

(Fig. 6). Body and head white ventrally with pale brown dorsal surface. Body midline black; colouration without vertical bars or bands. Dorsal surface with ubiquitous melanophores. Snout with dense dark spotting on tip. Operculum shiny only on ventral posterior edge and small area at posterior edge of orbit. Iris white to light grey with a few melanophores. Dorsal fin membrane clear; rays clear with dark melanophores. Caudal fin membrane clear to pale orange towards midline; rays dark brown to black, lighter towards edge; melanophores abundant and fading towards tips. Anal fin rays clear; membrane clear; pale orange spotting above origin; melanophores dark brown fading towards tips. Pectoral fin membranes clear; rays clear; first ray with abundant dark melanophores. Pelvic fin rays clear; membrane clear.

Preserved colouration.

(Fig. 7). Body and head pale yellow with dark brown spotting on dorsal surface and midline. Scales on dorsal surface lightly pigmented. Ventral scale pigmentation less intense than dorsal. Dorsal surface of head lightly pigmented. Melanophores small, dark; grouped on rear of head, below orbit, and on lips and snout; along midline, increasing in intensity to caudal fin; browner on dorsal surface, darkening between origin of pectoral and dorsal fin; forming small dark line above anal fin. Operculum and posterior base on orbit with silver sheen. Membranes between fin rays white to clear towards end. Pelvic fin clear membranes with melanophores on first ray. Dorsal, caudal and pectoral fin rays with melanophores small, widely-spaced, fading towards edges; pale brown to clear.

Etymology.

In the Cyao language spoken in the Niassa region of northern Mozambique, the name ‘ngalala’ denotes any, small, compressed, silvery fish, including Mesobola and species of Brycinus Valenciennes, 1850 and Hemigrammopetersius Pellegrin, 1926. The epithet is treated as a nominative singular noun in apposition.

Distribution.

Mozambique, Malawi: Rovuma River system and Lake Chiuta.

Type locality.

Lucheringo River below rapids at Singa hunting camp (11°48'56"S 36°13'15"E), Mozambique.

Biology.

This species is found in ecological conditions very similar to those characteristic of Engraulicypris gariepinus ( Bills 2004). It favours big rivers, gathering in slack, turbid and shallow regions with sandy, rocky or muddy substrates. In Lake Chiuta specimens were caught in reed beds along the margins. The Lake Chiuta and Rovuma River stocks may differ ecologically because Lake Chiuta offers a lacustrine pelagic and benthic prey community (copepods, etc.) that is not found in the Rovuma River channel, where fish would predominantly have access to invertebrate drift.