Aphyosemion cryptum, Van Der Zee & Walsh & Boukaka Mikembi & Jonker & Alexandre & Sonnenberg, 2018

Van Der Zee, Jouke R., Walsh, Gina, Boukaka Mikembi, Valdie N., Jonker, Michiel N., Alexandre, Marco P. & Sonnenberg, Rainer, 2018, Three new endemic Aphyosemion species (Cyprinodontiformes: Nothobranchiidae) from the Massif du Chaillu in the upper Louessé River system, Republic of the Congo, Zootaxa 4369 (1), pp. 63-92 : 80-82

Aphyosemion cryptum , new species

( Figs 12–13 ; Table 7)

Aphyosemion coeleste non Huber & Radda, 1977: Wildekamp, 1993: p. 129, fig. of specimen from Mbinda, western Congo.

Holotype. AMNH 263407 , male, 39.5 mm SL, Republic of the Congo, tributary of the Mandoro River, tributary of the Louessé River, Niari River drainage (2°21'57" S, 12°46’16" E), field code OS43, field label M331, collected by G. Walsh, M. Alexandre & V. Boukaka Mikembi, November 2013.

Paratypes. AMNH 262594, 4 males (field label 306, 329, 330, 332), 34.0– 41.2 mm, 1 female (field label 308) 39.4 mm SL, collected with the holotype; AMNH 262593, 1 male (field label 304), 34.6 mm SL, 1 female (field label 305), 31.1 mm SL, Republic of the Congo, tributary of Mandoro River ; field code M21 S, G. Walsh, V. Mamonekene, M. Jonker & V. Boukaka Mikembi, January 2012 ; AMNH 258825 , 7 specimens, Republic of the Congo, Lipia River , tributary of Louessé River , field code L8 S, G. Walsh, V. Mamonekene, M. Jonker & V. Boukaka Mikembi, January 2012 ; AMNH 258849 , 10 specimens, Republic of the Congo, Tributary of Leala River , tributary of Louessé River , field code L15 S, G. Walsh, V. Mamonekene, M. Jonker & V. Boukaka Mikembi, January 2012 ; AMNH 258498 , 10 specimens, Republic of the Congo, tributary of Leala River , tributary of Louessé River , field code L5 S, G. Walsh, V. Mamonekene, M. Jonker & V. Boukaka Mikembi, 10 January 2012 ; AMNH 258888 , 10 specimens, Republic of the Congo, Tributary of Mandoro River , field code M21 S, G. Walsh, V. Mamonekene, M. Jonker & V. Boukaka Mikembi, January 2012 .

Diagnosis. Males of ‘ Aphyosemion ’ cryptum ( Figs 12–13 , Table 7) are distinguished from all other Aphyosemion s.l. except for ‘ A ’. coeleste by its unique combination of colouration characters in males: a light blue body with a few red markings on flanks and caudal peduncle; yellow to orange on distal part of unpaired fins; base of dorsal and anal fins blue, distally followed by a red band, two parallel or converging red lines along the blue centre of caudal fin. At least in anal and ventral part of caudal fin between red band and yellow to orange distal parts a narrow white line. By mitochondrial DNA results and male colour pattern it clearly belongs to the ‘ A ’. coeleste group. It differs from ‘ A ’. coeleste by the lack of a green or yellow iridescent blotch posterior to the operculum. In ‘ A ’. coeleste three to four less regular rows of red spots on anterior part of side within the green or yellow blotch versus rows of red spots absent or reduced to a few irregular spots in ‘ A ’. cryptum .

Description. See Figures 12–13 for general appearance and colour pattern and Table 7 for morphometric data of type series. Largest observed specimen in type series 39.5 mm standard length. Strong sexual dimorphism, adult males more colourful than females and have larger unpaired fins.

Dorsal profile slightly convex, greatest body depth at base of pelvic fin, ventral profile slightly convex, caudal peduncle dorsally and ventrally concave. Snout rounded, mouth directed upwards, lower jaw longer then upper jaw, posterior end of rictus at level of dorsal third of eye.

Frontal neuromasts in two separate grooves, pre-opercular, pre- and post-orbital system with tubular canals. Two supra-orbital grooves (12.1–13.1 % of inter-orbital width, Table 5) with three neuromasts each. Teeth on jaws unicuspid, outer row large and inward curved, inner teeth smaller and more irregularly placed. Scales cycloid, body completely scaled except ventral head surface. Frontal squamation of G-type. No scales on dorsal and anal fin base; two to three scale rows on caudal fin base; scales on mid longitudinal series 30–32; transverse series of scales before dorsal fin nine; circumpeduncular scale row 14.

All unpaired fins rounded in males, adult males have no elongated rays at caudal fin edges. Number of dorsalfin rays 9–12, anal fin rays 14–16; first dorsal fin ray above anal fin ray seven to eight. Pectoral fin not reaching pelvic fin, pelvic fin not reaching anal fin.

Colouration. Live specimens. Males ( Figs 12–13 ). Body on side blue, only anteriorly some irregular red spots, in some populations these spots are completely absent. Ventrally light blue to greyish, dorsally brown. Snout yellow. Up to three red streaks on operculum in an approximate 45° angle, however, in most populations reduced or completely absent. Anal, dorsal, and pelvic fin distally yellow to orange, with red band above narrow blue base, sometimes with light blue narrow edge. Caudal fin dorsally and ventrally yellow to orange, separated from the blue fin centre by two parallel or converging red bands. Red band in fins distally often followed by narrow white line. Pectoral fin yellow to orange.

Females. Body light brown to grey-brownish, dorsally darker and ventrally light brown. Scales on sides, especially on dorsal part and on caudal peduncle, with dark border, forming reticulated pattern. Most scales on dorsal half of sides with small red dot at transition of two scales. Dorsal fin hyaline with inter-radial red streaks, sometimes spotted at base, anal fin hyaline with inter-radial reddish-grey streaks, caudal fin hyaline, unspotted, pelvic and pectoral fins hyaline, unspotted.

After 3 months in 70 % ethanol. Males. Body dark grey, ventrally lighter from pelvic fins to ventral part of head and throat. Chin and lips light grey. Dorsal, anal, and pelvic fin whitish with red band at the base. Caudal fin whitish with dark grey central part, edged with red bands. Pectoral fin whitish.

Females. Dorsal part of flanks grey-brown with gradual transition to lighter ventral side. All scales with dark border, especially on the caudal peduncle. Pelvic and pectoral fin grey. Dorsal fin with inter-radial red streaks, anal and caudal fin grey with inter-radial dark grey pigmentation.

Distribution and habitat. ‘ Aphyosemion ’ cryptum is known from shallow parts of small tributaries of the upper Louessé and Mandoro Rivers in the southern Massif du Chaillu within the Republic of the Congo. It can sometimes be found syntopic with ‘ A ’. coeleste or ‘ A ’. mandoroense . However, sites characterised by sand and clay substrate associated with higher average velocity, higher elevation and relatively higher pH values were more likely to yield ‘ A ’. cryptum than ‘ A ’. coeleste or ‘ A ’. mandoroense .

Etymology. The name cryptum (an adjective from the Greek krypton, meaning "hidden") refers to the fact that the species was first thought to represent just a colour variation of ‘ A ’. coeleste and not a species of its own.

Figures

FIGURE 12. Males of ‘Aphyosemion’ cryptum, holotype (AMNH 263407) indicated by the letter H, syntopic paratypes (AMNH 262594), and syntopic ‘A’. coeleste (indicated by the letter C, AMNH 262596).

FIGURE 13. ‘Aphyosemion’ cryptum, male, 34.6 mm SL, paratype, AMNH 262593.