Pachypanchax varatraza, 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 : 20-25

Pachypanchax varatraza sp. nov.

Holotype: AMNH 235858 (male, 63.3 mm SL), Mahazava Creek at village of same name (13°52'97”S, 49°56'22”E), 30 m a.s.l. (Ampanobe drainage), P. V. Loiselle and J. Miandrizava, 9 Oct. 2000.

Paratypes: AMNH 231244 (8, 29.9-53.5 mm SL), paratopotypes, collected with holotype . AMNH 235519 (1, 64.2 mm SL), Andampy Creek, at Ampizametana Village (13°31'15”S, 49°49'73”E), 70 m a.s.l. (Menambery drainage), P. V. Loiselle and J. Miandrizava, 8 Nov. 2000. AMNH 211333 (7, 24.0-40.1 mm SL), Antafiabe Creek, at Antsahandrero Village (13°39'05”S, 49°39'00”E) (Fanambana drainage), C. J. Raxworthy, 24 April 2002.

Diagnosis

Pachypanchax varatraza differs from P. playfairii in lacking raised dorsolateral squamation, and in details of its color pattern. Males lack rows of discrete red dots on the flanks and red edging to the vertical fins. Females lack any sort of black markings on the dorsal fin. Pachypanchax varatraza has the shortest pectoral fins (13.4 ± 1.6% SL) of any Malagasy Pachypanchax . The absence of pectoral scales of reduced size distinguishes both sexes from P. sakaramyi and P. sparksorum sp. nov. The rounded dorsal and anal fins of males and their lack of discrete metallic gold spangling on the flanks set them apart from P. omalonotus , whereas the absence of iridescent white edging to, or darker submarginal banding on, the vertical fins distinguishes it from the remaining Malagasy congeners.

Description

Morphometric characters appear in Table 5. A robust Pachypanchax , capable of reaching 80.0 mm SL in nature, with a distinctly pointed snout. Mouth wide, with cleft directed upward. A single row of slightly recurved, conical teeth present in each jaw. Ten (5), 11(10) or 12 (2) branchiospines on first gill arch. Two scale rows present on cheeks. Frontal squamation of E-type, with H scales present. Cephalic neuromast pattern open in all specimens examined. Scales cycloid, 30-32 (modes=31, 32) along midlateral line. Fourteen transverse scale rows immediately anterior to origin of anal fin; 20 scale rows around caudal peduncle. Scales on chest same size as those on flanks. Vertebrae 14 precaudal + 16 caudal.

Dorsal fin origin above midpoint between origins of ninth and tenth anal fin rays. Dorsal fin rays iii,8 (3); iv,8 (1); iii,9 (6); iii,10 (6); ii,11 (1). Seventh or eighth dorsal ray longest in both sexes. Anal-fin rays iii,14 (1); iii,15 (6); ii,16 (8); iii,16 (1); ii,17 (2). Fifteenth or sixteenth anal ray longest in males, seventh or eighth longest in females. Bases of both dorsal and anal fins scaled. Caudal fin rounded truncate, with basal half heavily scaled. Pelvic-fin rays i,5. Pectoral-fin rays 14-16 (mode=16).

Coloration

Living specimens: This species is characterized by male color polymorphism. Figure 8 depicts the red morph and Figure 9 the green morph of P. varatraza . Rusty brown to maroon edging is present on the scales of the posterior half of the body in all individuals of the green morph, but its extent and intensity varies among populations. Males of the Ampanobe basin population have redder unpaired fins and the maroon scale edging on the flanks is more intense. Figure 10 depicts an adult female.

Preserved specimens: Males: Dorsum and top of the head reddish brown, shading to off-white on lower third of flanks and venter. A faint dark midlateral stripe, one scale row deep, extends along flanks from posterior margin of orbit to base of caudal peduncle. Cheeks, opercula and throat off-white. Dorsal fin clear gray, with a well-developed pattern or darker interradial dots present in its posterior third. Anal fin clear gray basally, with traces of a narrow darker submarginal band. Caudal fin clear gray, with a pattern of fine dark interradial dots on basal two-thirds. Pelvic fins clear gray, pectorals hyaline. Females: Similar to males, but longitudinal stripe fainter and all vertical fins hyaline, with interradial dots less evident.

Etymology

Varatraza is the Malagasy word for the east wind. The name acknowledges the unanticipated presence of a Pachypanchax species in rivers draining the eastern slope of the Tsaratanana Massif, and is to be treated as a noun in apposition.

Range

Pachypanchax varatraza is native to the basins of the Menambery, Fanambana and Ampanobe rivers in northeastern Madagascar (Figure 5). South of the Ampanobe, Pachypanchax is replaced by representatives of the ecologically analogous endemic atheriniform family Bedotiidae .

Natural history

Pachypanchax varatraza inhabits a wide range of habitats. The Menambery population was collected from the Andampy, a small stream flowing under relatively intact forest cover at an altitude of 70 m above sea level. At this point, the stream consists of a series of quiet pools with clay/sand bottoms, interspersed with short stretches of flowing water over sand/gravel bottoms. The water was very turbid, with ca. 20.0 cm visibility, slightly acidic (pH: 6.5), soft (general hardness <18.0 ppm, carbonate hardness 36.0 pp), with a conductivity of 49.0 μS/cm2. Extensive stands of Marsilea sp. were present in the shallows of flowing stretches of the stream. Neither filamentous algae nor other aquatic macrophytes were observed. No other fish were captured, but a small atyid shrimp and a variety of aquatic insects, including dragonfly nymphs and the adults of a number of aquatic Coeleoptera and Hemiptera, were present. According to local informants, P. varatraza is relatively rare at this altitude, but becomes more abundant as one moves upstream towards the headwaters of the Andampy.

Representatives of the Ampanobe basin population were collected from the Mahazava, a small stream flowing through modified low-altitude rain forest at an altitude of 30 m above sea level. The bottom was clay/sand, interspersed with patches of bedrock. The water was clear and the current moderate. No aquatic macrophytes or attached algae were observed. Gambusia holbrooki and fry of Oreochromis mossambicus were also collected. According to local informants, large gobies of the genera Awaous and Glossogobius , atyid shrimps, and freshwater crabs also occur in the Mahazava.

Feces of freshly captured specimens contained recognizable remains of both the imagos of terrestrial and the nymphs and larvae of aquatic insects. This suggests that, like its congeners, P. varatraza feeds both at the surface and from the bottom. The most likely predators of adults of this species in both the Menambery and Ampanobe basins are Glossogobius giuris and the Malagasy malachite kingfisher.

Specimens from both localities collected in early October began spawning within three weeks after their arrival in the United States in early November. Based upon observations of the growth rate of juveniles in captivity, the size distribution of specimens from the Andampy suggests a protracted breeding season lasting through the austral summer, which coincides with the rainy season in northeastern Madagascar.

Conservation status

This species has been extirpated from the lower reaches of the Menambery, Fanambana and Ampanobe rivers by an exotic predator, Channa maculata . It persists in one high-gradient tributary of the upper Menambery, whose watershed lies in a surviving patch of forest. As a result of deforestation, the remaining headwater s tributaries of this river are devoid of water during the dry season, and thus are no longer viable Pachypanchax habitats. The basin of the Fanambana is subject to the same sharply seasonal pattern of precipitation, but as its watershed is not deforested to the same degree as that of the Menambery, habitat loss has not affected P. varatraza as seriously. The Ampanobe River marks the transition between the rain forest of the east coast and deciduous forest of Madagascar’s extreme north (Gautier and Goodman, 2003). Its watershed benefits from a less seasonal pattern of rainfall and retains most of its forest cover. While the presence of G. holbrooki in the middle and upper reaches of the Ampanobe is cause for concern, the dominance of vanilla culture in the local economy strongly discourages extensive deforestation. This should prevent the large-scale habitat loss that has negatively impacted P. varatraza in the Fanambana drainage and threatens its survival in the Menambery.

Following the criteria established by the World Conservation Union (Raminosoa et al., 2002), P. varatraza is thus classified as a species of special concern, whose status needs to be monitored on a regular basis.