Pachypanchax patriciae, 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 : 25-30

Pachypanchax patriciae sp. nov.

Holotype: AMNH 232450 (male, 43.8 mm SL), Ampandra River ca. 2 km upstream of village of the same name (13°24'90”S, 48°50'20”E), altitude of 44 m a.s.l., P. V. Loiselle and J. Miandrizava, 27 Oct. 2001.

Paratypes: AMNH 235860 (11, 28.1-51.8 mm SL), paratopotypes, collected at same time as holotype . AMNH 232426 (8, 26.9-37.5 mm SL), oxbow lake of Ifasy River at Ambodipont (13°22'13”S, 48°52'38”E), altitude 6 m a.s.l., P. V. Loiselle and J. Miandrizava, 24- 25 Oct. 2001. AMNH 232452 (5, 29.8-45.6 mm SL), unnamed creek below bridge on RN-5A, flowing into main channel of Mahavavy du Nord River (13°12'46”S, 49°04'38”E), altitude 57 m a.s.l., P. V. Loiselle and J. Miandrizava, 28 Oct. 2001. MNHN 1931 0198 (4, 20.9-40.5 mm SL), Antikotazo Creek, near town of Ambilobe (Mahavavy du Nord drainage) , E. G. Waterlot.

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 scales on the chest are the same size as those on the flanks in Pachypanchax patriciae , which clearly differentiates that species from both P. sakaramyi and P. sparksorum sp. nov. The presence of iridescent white edging in the caudal fin of males, as well as a longer caudal peduncle (16.1 ± 1.9 % SL vs. 14.7 ± 1.6 % SL) and wider orbital diameter (9.8 ± 1.0 % SL vs. 7.8 ±.07 % SL) differentiate P. patriciae from P. omalonotus . The dorsal and anal fins of males come to a sharp point in P. patriciae , in contrast to the more rounded vertical fins of P. varatraza sp. nov. and P. arnoulti sp. nov. It differs further from P. varatraza in its longer pectoral fins and from P. arnoulti in its shorter head and presence of broad iridescent white caudal and anal-fin margins.

Description

Morphometric characters are given in Table 6. A Pachypanchax of moderate size, with a distinctly pointed snout. The mouth is wide, its cleft directed upward. A single row of slightly recurved, conical teeth present in each jaw. Nine (1), 10 (22) or 11 (10) 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 (mode=32) along midlateral line. Fourteen transverse scale rows immediately anterior to origin of anal fin; 18-20 (mode=18) scale rows around caudal peduncle. Scales on chest same size as those on flanks. Vertebrae 14 precaudal + 17 caudal.

Dorsal-fin origin above midpoint between origins of either the ninth and tenth, or tenth and eleventh anal-fin rays. Dorsal-fin rays iii,8 (2); iv,8 (1); ii,9 (4); iii,9 (3), iv,9 (1), ii,10 (11), iii,10 (10), iv,10(1) ii,11 (2). Seventh or eighth dorsal ray longest in females, eighth or ninth longest in males. Anal-fin rays iii,14 (6); ii,15 (9); iii,15 (2); ii,16 (10); iii,16 (7), iii,17 (2). Fourteenth or fifteenth anal ray longest in males, seventh or eighth longest in females. Bases of both dorsal and anal fins scaled. Caudal fin rounded truncate, basal third to half heavily scaled. Pelvic-fin rays i,5. Pectoral-fin rays 13-15 (mode=14).

Coloration

Living specimens: This species is characterized by male color polymorphism. Figures 11 and 12 depict males of the red and blue morphs, respectively, while Figure 13 depicts an adult female. The percentage of each color form varies between populations, with red males disappearing completely as one moves from south to north. Figure 14 represents the frequency of occurrence of each color form in populations sampled in 2001.

Preserved specimens: Males: Dorsum and top of the head reddish brown, shading to off-white on lower third of flanks and on venter. Dark longitudinal stripe, ca. one scale row deep, extending from posterior margin of eye to origin of pectorals. A faint dark midlateral stripe, two scale rows deep, extending along flanks from edge of operculum to base of caudal peduncle. Lower jaw narrowly edged in dark gray. Cheeks, opercula and throat offwhite. Dorsal clear gray, with a broad dark gray distal margin. Anal fin clear gray basally, darker gray distally, with a narrow clear distal margin present anteriorly. A narrow dark gray submarginal band variably present. Caudal fin clear gray, with a pattern of fine dark inter-radial dots in its median portion and a narrow dark gray distal margin along upper and lower leading edges. Pelvic fins clear gray, pectoral fins hyaline. Females: Similar to males, but longitudinal stripe less evident and all fins uniformly hyaline.

Etymology

The species name honors Patricia Yazgi, and recognizes her support of ongoing efforts to document and conserve the Malagasy freshwater ichthyofauna.

Range

Pachypanchax patriciae is native to the basins of the Mananjeba, Mahavavy du Nord, Ifasy, Manehoko and Ampandra rivers in northwestern Madagascar (Figure 5).

Natural history

The range of P. patriciae spans two distinct biomes, the monsoon or Sambirano forest of the northwest, and the deciduous forest of the extreme north of Madagascar, with the Ifasy River marking the transition between the two. The Ampandra and Manehoko are small rivers flowing through the somewhat degraded Sambirano forest. Limnologically, they resemble the streams draining the eastern versant of Madagascar. Their waters are tannin stained, acidic (pH: 5.0-6.0), very soft (GH and KH <18.0 ppm), and deficient in dissolved substances (conductivity: 19-24 μS/cm2). Their bottoms are compacted clay/ sand, overlain with organic detritus. Extensive stands of the emergent aroid Typhonodorum lindleyanum and both blue and white-flowered Nymphaea are present in their shallows, but neither filamentous algae nor other aquatic macrophytes were observed. Juvenile Oreochromis mossambicus , small atyid shrimps, and a wide variety of aquatic insects were collected syntopically with P. patriciae . Local residents interrogated about the presence of other fish species recognized photographs of Paratilapia polleni , Ptychochromis oligacanthus and Glossogobius giuris , and indicated that, together with Anguilla bicolor , all three inhabited deeper water.

The Ifasy, Mahavavy du Nord and Mananjeba are larger rivers more typical of streams draining the western versant of Madagascar. They are characterized by a markedly seasonal hydrological regime and substantial flood plains, which contain numerous matsabory (shallow lakes). Their waters range from clear to turbid, but are never tanninstained, are less acidic (pH: 6.5-7.2), harder (total and carbonate hardness 36.0-71.6 ppm), and carry a greater concentrations of dissolved minerals (conductivity: 38-74 μS/ cm2).

According to local informants, Pachypanchax are restricted to such lakes and to small tributary streams of these three rivers. Matsabory Faregniny, in the flood plain of the Mananjeba, was characterized by turbid water, a compacted clay bottom, the presence of much waterlogged wood and the absence of aquatic macrophytes or filamentous algae. Juvenile Tilapia zillii and O. mossambicus were the only other fish captured there. The water of the unnamed lake in the Ifasy basin where P. patriciae was found had clear water and a clay/sand bottom overlain with a thin layer of organic detritus. It was bordered by an extensive marshy zone dominated by emergent sedges that gave way to a white-flowered Nymphaea species in deeper water. Neither filamentous algae nor other aquatic macrophytes were observed. In addition to P. patriciae , Paratilapia polleni , atyid shrimps and a wide variety of aquatic insects were collected there.

A small unnamed creek flowing into the main channel of the Mahavavy du Nord was the final site from which this species was collected. The water was clear, with minimal flow evident. The bottom consisted of sand/clay, heavily overlain with organic detritus. Stands of a Marsilea species and clumps of filamentous green algae were present. Pachypanchax patriciae was the only fish caught, although dragonfly nymphs and an assortment of aquatic Coleoptera and Hemiptera was also present.

Feces of freshly captured specimens contained recognizable remains of both the imagos of terrestrial and the nymphs and larvae of aquatic insects. While this species is at risk from both predatory aquatic insects and such piscivorous fishes as P. polleni and G. giuris , its most important predators in most habitats appear to be fish-eating birds and dragonfly nymphs.

Specimens collected in early October began spawning within a week 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 Ampandra and Manehoko Rivers and from the Matsabory Farengniny suggests a protracted breeding season lasting through the austral summer.

Conservation status

This widely distributed species presently faces no threats from introduced predators or competitors. However, habitat loss caused by deforestation of the watersheds of the Mananjeba, Mahavavy du Nord and Ifasy rivers threatens the survival of the northern populations of P. patriciae . This species is thus classified as vulnerable following the criteria established by the World Conservation Union (Raminosoa et al., 2002).