Pachypanchax sparksorum, Paul V. Loiselle, 2006

Paul V. Loiselle, 2006, A review of the Malagasy Pachypanchax (Teleostei: Cyprinodontiformes, Aplocheilidae), with descriptions of four new species., Zootaxa 1366, pp. 1-44 : 30-34

Pachypanchax sparksorum sp. nov.

Holotype: AMNH 235770 (male, 53.6 mm SL), Bentainkilotra Creek (14°52'20”S, 48°14'52”E), (Ankofia River drainage), collected by P. V. Loiselle and J. Rasoloariniainina, 16 Oct. 2004.

Paratypes: AMNH 235771 (9, 39.7-49.7 mm SL), paratopotypes, collected with holotype . AMNH 215504 (1 male, 55.0 mm SL), Anjingo River (Ankofia drainage), at km 40 on the Antsohihy-Bealanana road , P. de Rham, Oct. 1992. UMMZ 240104 (8, 26.7-55.3 mm SL), Behmamavony Creek, in Bora Special Nature Reserve (14°52'20”S, 48°14'52”E) (Ankofia drainage), J. S. Sparks and K. Riseng, 31 July 1994. UMMZ 240415 (5, 26.4-37.8 mm SL), Behmamavony Creek, at same locality as preceding series , J. S. Sparks and K. Riseng, 15 Nov. 1994.

Diagnosis

The absence of raised dorsolateral scales in males and of an ocellated black basal spot in the dorsal fin of females preclude confusion of this species with P. playfairii . The reduced size of its pectoral scales sets it apart from all Malagasy congeners save P. sakaramyi , from which it differs in its unscaled dorsal and anal fin bases, its longer dorsalfin base (12.8 ± 1.8% vs 10.3 ± 1.9% SL), the presence of discrete red spots and faint reddish-brown spots on the flanks of males and females, respectively, and the presence of a narrow black anal-fin margin in males.

Description

Morphometric characters appear in Table 7. A Pachypanchax of moderate size with a distinctly pointed snout. Mouth wide, cleft directed upward. A single row of slightly recurved, conical teeth present in each jaw. Ten to 11 (mode=11) branchiospines on first gill arch. Two scale rows present on cheeks. In the largest male and in two smaller individuals from UMMZ 240104, the frontal squamation is of the G-type, without H scales. In all other specimens examined, the frontal squamation is of the E-type. H scales are absent in five of the 24 specimen examined, and present in the remainder. Cephalic neuromast pattern closed in two individuals from AMNH 235771, open in the remaining specimens examined. Scales cycloid, 32-33 (mode=33) along midlateral line. Fourteen transverse scale rows immediately anterior to origin of the anal fin; 18-20 (mode=18) scale rows around caudal peduncle. Scales on chest half the size as those on flanks. Vertebrae 14 pre-caudal + 17 caudal.

Dorsal-fin origin above midpoint between origins of eighth and ninth anal-fin rays. Dorsal-fin rays iii,8 (1); iv,8 (1); iii,9 (1); iv,9 (3); ii,10 (3); iii,10 (3); iii,11 (3). Eighth or ninth dorsal ray longest in males, seventh or eighth longest in females. Anal-fin rays iii,14 (1); ii,15 (2); iii,15 (1); ii,16 (7); iii,16 (1); ii,17 (1); iii,18 (1). Fourteenth or fifteenth anal ray longest in males, ninth or tenth longest in females. Base of dorsal and anal fins unscaled. Caudal fin rounded truncate, basal half to three quarters heavily scaled. Pelvicfin rays i,5. Pectoral-fin rays 14-16 (mode=16).

Coloration

Living specimens: Figures 15 and 16 depict an adult male and female P. sparksorum .

Preserved specimens (Males): Dorsum, top of head, and lips reddish brown, shading to off-white on cheeks, operculum, lower third of flanks and venter. No dark longitudinal stripe present on flanks, but scales on posterior two-thirds of body with dark centers. Posterior third of body marked with indistinct narrow vertical lines. Dorsal and anal fins clear gray, with a narrow black margin and a complex pattern of dark interradial streaks and dots. Basal two thirds of caudal fin clear gray, with a pattern of fine dark interradial dots. Distal third of caudal fin hyaline. A fine black distal margin present along the lower leading edge in some specimens. Pelvic fins clear gray with a darker leading edge. Pectoral fins hyaline. (Females): Similar to males, but without dark-centered scales or vertical markings on flanks. All fins uniformly hyaline.

Etymology

The species name honors John S. and Karen Riseng Sparks, who first documented the presence of a distinctive Pachypanchax in the Ankofia drainage and collected much of the type series.

Range

This species has, to date, only been collected from streams flowing into the Ankofia River and from its principal tributary, the Anjingo (Figure 6). The Ankofia empties into the drowned estuary of the Loza River at 14°40'00”S, 48°03'20”E. The presence of P. sparksorum in the Maevarano, the next drainage to the north, remains to be confirmed. It is replaced in the Loza basin proper by an undescribed congener.

Natural history

This species inhabits both the main channel of the Anjingo and Ankofia rivers (de Rham, 2000a) and their small tributary streams flowing through more or less degraded deciduous forest (Sparks, 2002). During the dry season, these streams are shallow, with a moderate current. Their water is clear, with a pH of 6.8-7.0, soft (total hardness 34.2-40.0 ppm), and deficient in dissolved substances (electrical conductivity 28-31 μS/cm2). Stream bottoms are bedrock interspersed with cobble and patches of sand/gravel. The banks of the Ankofia and Anjingo rivers are overgrown with dense overhanging riparian vegetation, but neither filamentous algae nor vascular aquatic plants are present. Here, Pachypanchax sparksorum is restricted to the shallows, where it finds shelter along the banks or among rocks, and occurs syntopically with Arius festinus , Teramulus waterloti , Ambassis natalensis , Scatophagus tetracanthus , Ptychochromis inornatus , Paretroplus damii , and unidentified representatives of the families Mugilidae , Eleotridae and Gobiidae . In tributary streams it coexists with T. waterloti and A. natalensis .

Feces of freshly captured specimens contained recognizable remains of the imagos of terrestrial insects, the nymphs and larvae of aquatic insects, and small freshwater shrimps. The most important predators of this species appear to be predatory aquatic insects and fish-eating birds.

Based upon observations of the growth rate of juveniles in captivity, the size distribution of the type series suggests that P. sparksorum breeds throughout the austral summer. While courtship behavior and the mechanics of spawning are similar to what have been observed in other Pachypanchax , this species differs from its congeners in that, at least under aquarium conditions, individual eggs may remain attached to the female ’s vent after fertilization, eventually forming a cluster that falls off several hours later (J. S. Sparks, pers. com.). Such post-fertilization retention of the eggs has been reported from only one other cyprinodontiform species, the Neotropical Cubanichthys cubensis (Innes, 1959; Wildekamp, 1995), although it is the norm in the beloniform families Oryziatidae and Adrianichthyidae (Kottelat et al., 1993).

Conservation status

Pachypanchax sparksorum is present in substantial numbers throughout its range and to date must contend with neither exotic predators nor competitors. However, because of its circumscribed distribution, it is classified as endangered following the criteria established by the World Conservation Union (Raminosoa et al., 2002).