Ptychochromis mainty, Martinez, Christopher M., Arroyave, Jairo & Sparks, John S., 2015

Martinez, Christopher M., Arroyave, Jairo & Sparks, John S., 2015, A new species of Ptychochromis from southeastern Madagascar (Teleostei: Cichlidae), Zootaxa 4044 (1), pp. 79-92 : 81-87

Ptychochromis mainty , new species

Figures 1–10 ; Tables 1–2

Holotype. AMNH 238825, 140.4 mm SL, Fort Dauphin region, Taolagnaro, Madagascar, coll. P.V. Loiselle, 13 September 2006.

Paratypes. AMNH 265944, 1 ex., 148.8 mm SL, data as for holotype. AMNH 241978, 1 ex., 101.3 mm SL, Fort Dauphin region, Taolagnaro, Madagascar, coll. A. Saunders et al., 2007. AMNH 241979, 1 ex., partial C&S, 100.5 mm SL, Fort Dauphin region, Taolagnaro, Madagascar, coll. A. Saunders et al., 2007.

Diagnosis. A Ptychochromis with palatine morphology typical of species on Madagascar’s east coast (i.e., “eastern-type palatine” of Stiassny & Sparks, 2006). Distinguished from all congeners by uniform dark brownish to black coloration in preservation and in life by expansive, continuous (or nearly so), longitudinal black blotch on midlateral flank extending from posterior margin of opercle to caudal peduncle (versus absent in P. inornatus , P. onilahy , P. curvi dens , P. loisellei , P. insolitus , or comprising multiple distinct midlateral blotches or bars in P. ernestmagnusi , P. m ak i r a, P. grandidieri , and P. oligacanthus ). Ptychochromis mainty displays little or no overlap of anterior supraneural relative to supraoccipital crest, versus marked overlap in some eastern congeners ( P. makira and P. ernestmagnusi ). In comparison to P. grandidieri , body depth as a percentage of SL in P. mainty considerably less for similarly sized individuals and slope of head in profile less steep. New species further distinguished from P. grandidieri by fewer and more sparsely arranged teeth on second pharyngobranchial toothplate (Pb2) of upper pharyngeal jaw (vs. numerous, densely arranged teeth).

Description. Morphometric and meristic data presented in Table 1. Shallow bodied, with elongated caudal peduncle ( Fig. 2 ). Body overall convex in shape, most notably in dorsal profile. Ventral margin between pelvic fin and vent nearly flat to slightly convex. Prominent point along ventral margin at first anal spine due to moderate ventral sloping between vent and first anal spine and strong dorsal sloping along anal fin toward the caudal peduncle. Profile of head flat and rising at roughly 40 degrees from midline. Slight hump visible from supraoccipital crest in larger specimens.

Vertebral count 27 in all examined specimens, with 14 pre-caudal and 13 caudal vertebrae.

Oral jaws isognathous with dentition present across most of premaxillary arcade and covering about 2/3 of dentary. Dentition distally expanded and bicuspid anteriorly. Posterior teeth weakly bicuspid or flat, and rarely unicusped with pointed distal end. Outer row of teeth larger than inner rows. Three inner rows of teeth on anteriormost portion of dentary, reducing to single row of outer teeth posteriorly. Up to four inner rows of teeth on anterior portion of premaxilla, reducing to single row of outer teeth posteriorly.

P. mainty

Character N Holotype Range Mean SD Standard length (mm) 4 140.4 100.5−148.8 122.7

Percentage of HL

Snout length 4 44.8 39.8−44.8 42.9 2.24 Orbit diameter 4 33.4 31.1−34.8 33.0 1.54 Upper-jaw length 4 37.1 34.7−38.3 36.4 1.62 Lower-jaw length 4 42.0 38.5−42.0 40.8 1.58 Interorbital width 4 29.5 27.7−31.9 29.5 1.74 Preorbital depth 4 27.8 24.1−27.8 26.5 1.70 Caudal peduncle length/depth 4 1.0 0.9−1.0 1.0 0.04 Caudal peduncle length/width 4 4.2 2.5−4.2 3.4 0.80 FIGURE 3. Lower pharyngeal jaw (LPJ) in dorsal view, representing fused 5th ceratobranchials in Ptychochromis mainty . Tooth-bearing rakers on 4th gill arch are also visible (lateral to LPJ). AMNH 241979, paratype, 100.5 mm SL.

Robust lower pharyngeal jaw (LPJ), consisting of medially fused 5th ceratobranchials, with interdigitating suture uniting both halves. Posteromedially, both LPJ and upper pharyngeal jaw (UPJ) with enlarged molariform dentition (Fig. 3). Remaining dentition on LPJ and UPJ comparatively small and biscuspid, with well-developed posterior cusp and poorly developed anterior cusp. Second pharyngobranchial toothplate (Pb2) with three to four rows of elongate, sparsely arranged hooked and biscupid teeth ( Fig. 4 ). Presence of free second epibranchial toothplate. Teeth on second epibranchial toothplate bicuspid, with one cusp strongly hooked and other cusp very poorly developed. Non-molariform teeth on third pharyngobranchial toothplate, decreasing in size laterally, but increasing in intensity of hooked appearance. Fourth upper toothplate with sparsely arranged hooked and bicuspid teeth that decrease in size and development toward plate’s outer margin.

Gill rakers number 10 on lower limb of first gill arch, not including raker in angle of arch. Tooth-bearing rakers present on lower limb of first gill arch. Raker dentition conical with occasional weak curvature. Seven to eight elongate epibranchial gill rakers. Rakers increasingly robust and with more numerous teeth from second gill arch to fourth.

Flank squamation comprised of large, regularly imbricate, weakly ctenoid scales. Anteriormost occurrence of ctenii near first dorsal spine and just posterior to pectoral fin base, and continuing posteriorly to origin of caudal fin. Chest scales in larger specimens reduced in size and weakly embedded. Embedded cycloid scales present on nape and head. Cycloid scales present on opercle. Preopercle asquamate. Cheek scales cycloid, comprising up to four rows. Anterior half of interorbital area, snout, anterior cheek and lachrymal asquamate. Scales on caudal fin ctenoid at base, and become increasingly smaller, cycloid and embedded posteriorly. Lateral line scales with welldeveloped pores and numbering 28, 30 (mode) and 31. Four scales between pectoral and pelvic fin bases. Five (mode) or six scales diagonally between dorsal-fin origin and upper lateral line. No scales extending onto dorsal- or anal-fin membranes.

Dorsal fin with XIII spines and 11 to 13 soft rays. Anal fin with III spines and eight or nine soft rays. First anal spine much shorter in length than the second and third. Soft rays of dorsal and anal fins elongate, producing tapered appearance in both. Anal-fin rays extend approximately to origin of caudal fin, although in one smaller specimen (AMNH 241978) first three soft rays extend well posterior of caudal base. Pectoral fin elongate, with rays increasing in length dorsally and extending posteriorly to anterior origin of lower lateral line. Pelvic fin long and extending approximately to first anal-fin spine when adpressed, but more elongate in AMNH 242978, extending to middle of anal fin. Caudal fin emarginate, with somewhat rounded and equally sized upper and lower lobes.

Miscellaneous osteology and anatomy. Infraorbital series comprising seven elements. Lachrymal with four pores; fourth pore directly adjacent to anterior pore of second infraorbital. Second infraorbital expanded. Second infraorbital excluded from margin of orbit by third infraorbital. First supraneural flattened dorsally and with little or no overlap with posterior portion of supraoccipital crest. Second supraneural smaller than first or absent ( Fig. 5 C), and more varied in shape, with forms either having anterior extension with flattened dorsal surface ( Fig 5 D) or no anterior projection. Less developed or absent second supraneurals present in larger specimens (AMNH 238825, 140.4 mm SL and AMNH 265944, 148.8 mm SL). Laterosenory canals on dentary and preopercle well developed with large pores.

Taxon Voucher Specimen/Tissue # GenBank Accession #

16S COI H3 Tmo-4C4 Coloration in life ( Fig. 6 ). No images available from type series illustrating live coloration. Photos of live P. mainty , collected from Fort Dauphin region of southeastern Madagascar, provided by A. Saunders. Ground coloration light to dark olive green. One expansive longitudinal black blotch present on midlateral flank, and sometimes one or two smaller blotches also on caudal peduncle. Primary blotch starting just posterior to opercle and continuous to caudal peduncle, but sometimes with break approximately at a vertical through anterior insertion of anal fin. This pattern contrasts with that of conspecifics, including P. ernestmagnusi , P. m a k i r a, P. grandidieri and P. oligacanthus , where several distinct midlateral blotches or bars are present. In individuals with darker ground coloration, ventral half of body has non-uniform yellow to greenish-yellow coloration. Base color of fins same as body. Yellow coloration present on margin of dorsal fin, associated with distal portion of spines and sometimes also present on tips of soft rays. Small patches of yellow coloration also present near distal ends of dorsal and ventral caudal fin rays. Head color uniform and same as base body coloration. Additional images of specimens from Lake Taransty ( Ptychochromis n. sp. “Tarantsy”) and of an unidentified Ptychochromis from west of Fort Dauphin region show fishes with expansive, but less continuous midlateral blotches (de Rham and Nourissat 2004, pp. 47–49), which could potentially represent color variants of P. mainty .

Coloration in preservation ( Fig. 2 ). Base color of body dark brown, with ventral half just slightly lighter than dorsal. In smaller individuals (AMNH 241978, 101.3 mm SL and AMNH 241979, 100.5 mm SL), ventral half of body pale brown and markedly lighter than dorsal half. Darkest pigment (i.e., black) occurs midlaterally and is most prominent directly posterior of opercle, although it does not contrast greatly with ground coloration of body. This darkened area corresponds to large, black midlateral blotch present in life. Posterior half of lower jaw cream to light brown in color. Pectoral fin radials dark, but membrane cream colored, giving fin a light overall appearance. Some fading of pelvic fin at medial base, becoming light brown to nearly white in color. Anal fin slightly (holotype) to mostly cream colored near base posteriorly. Vent clearly stands out from ventral margin of body and is white to cream in color.

Distribution and habitat ( Fig. 1 ). Known only from Fort Dauphin region near Taolagnaro in extreme southeastern Madagascar. Another, presumably distinct, population of Ptychochromis , referred to as P. sp. “Tarantsy”, is known from Lake Tarantsy, roughly 45 km southwest of Fort Dauphin, but its relationship to P. mainty and other members of the genus is currently unknown (de Rham & Nourissat, 2004).

Diet. Diet is largely unknown, although a radiograph of a P. mainty paratype (AMNH 241978) reveals that the stomach contains gastropod shells ( Fig. 7 ).

Conservation Status. Madagascar’s freshwater biotas are severely threatened due to widespread habitat destruction, overfishing, and the introduction of numerous exotic species. This situation is exacerbated by high levels of endemicity and greatly restricted ranges (often comprising a single river system or lake) for most of the island’s freshwater fishes (Sparks & Stiassny, 2003; Sparks & Smith, 2004b; Sparks, 2008). In fact, over half of Madagascar’s native freshwater fish species are categorized as endangered, critically endangered or extinct ( Benstead et al., 2003; Sparks & Stiassny, 2008; Irwin et al., 2010), and the situation has become far more dire in recent years (JSS, pers. obs.). The region from which the type series of P. mainty was collected has been poorly surveyed for freshwater fishes, and the conservation status of the new species remains unknown. We attempted to survey the region from which the type series was collected during an expedition to Madagascar in April of 2014, but were unable to gain access to forested regions in the area with suitable habitat due to permitting issues.

Etymology. Named after the Malagasy word for black, mainty , referring to the species’ uniform dark pigmentation pattern in preservation and large black midlateral blotch in life.

Figures

FIGURE 1. Map of Madagascar, showing known geographic ranges of Ptychochromis species.

FIGURE 2. Ptychochromis mainty, AMNH 238825, holotype, 140.4 mm SL (scale bar = 1 cm). Photo taken on right side due to specimen bending.

FIGURE 4. Ventral view of upper pharyngeal jaw (UPJ) in (A) Ptychochromis mainty (AMNH 241979, paratype) and (B) Ptychochromis grandidieri (AMNH 88018). Jaw elements pictured are the pharyngobranchial toothplates (Pb 2 & Pb 3), the second epibranchial toothplate (Ep 2 - tp) and the fourth upper toothplate (Up 4 - tp).

FIGURE 5. Variation in supraneural morphology for (A) Ptychochromis ernestmagnusi (AMNH 249489, paratype), (B) Ptychochromis grandidieri (UMMZ 237312), (C) Ptychochromis mainty (AMNH 238825, holotype) and (D) Ptychochromis mainty (AMNH 241979, paratype).

FIGURE 6. Ptychochromis mainty. Live specimen collected from the Fort Dauphin region of Madagascar and photographed by Alex Saunders.

FIGURE 7. Radiograph of Ptychochromis mainty, AMNH 241978, paratype, showing gastropod shells in the gut. Scale bar = 1 cm.

FIGURE 8. Maximum likelihood phylogeny for all available species of Ptychochromis, including P. mainty, new species. Bootstrap support values are shown at the nodes.

FIGURE 9. Body depth / SL for Ptychochromis species, with error bars showing standard error. Individuals included in analysis were of a similar size range to the new species, with no small juveniles.

FIGURE 10. (A) Principle components (PC) 1 and 2, displaying variation in body shape for east coast Ptychochromis species. Visualization of shape variation is provided as warped grids of (B) the largest and (C) the smallest PC 1 values relative to mean shape. The largest PC 1 values are set by the shallow-bodied P. mainty and the smallest by the deep-bodied P. curvidens. Fixed landmarks are shown in gray and sliding semilandmarks are in black.