Microphilypnus acangaquara, Caires, Rodrigo A. & Figueiredo, José Lima De, 2011

Caires, Rodrigo A. & Figueiredo, José Lima De, 2011, Review of the genus Microphilypnus Myers, 1927 (Teleostei: Gobioidei: Eleotridae) from the lower Amazon basin, with description of one new species, Zootaxa 3036, pp. 39-57 : 53-55

Microphilypnus acangaquara sp. nov.

( Figs. 1 , 10–12 ; Table 3 )

Type material. Holotype, MZUSP 108204, 15.1 mm SL, collected by the Permanent Expedition to the Amazon (EPA) in Brazil, Amazonas: rio Tapajós basin, São Luís, 0 5 November 1970. Paratypes, MCP 15317, 3, 14.4–16.8 mm SL, collected by C.A. Lucena et al. in Brazil, Pará, Tapajós river basin, rio Itapacurá, 0 8 December 1991; MZUSP 27015, 43732, 40, 12.9–18.5 mm SL, same data as the holotype, MZUSP 92677, 25, 11.3–15.2 mm SL, collected by J.L. Birindelli and L.M. Souza in Brazil, Amazonas, rio Tapajós, between Itaituba and Pimental waterfalls 04º21’34” S 56º10’03” W, 0 8 August 2006.

Etymology. The specific epithet acangaquara is derived from the Tupi words akang, which means “head”, and quara, which means “hole”, in allusion of the sensory pores on the head that are exclusively present in this species. To be used as a noun in apposition.

Diagnosis. Microphilypnus acangaquara can be recognized by the following set of characters: snout short, blunt; upper jaw not reaching vertical through middle of the eye; D. V–VII + 6–8; A. 6–9; P. 12–15; 27–32 scales in longitudinal series (usually 28 or more); opercle covered with ctenoid scales; predorsal region partial to fully covered with 4–11 cycloid scales; head with paired anterior supraocular (SOT) and preopercular (POP) pores; 7 transverse rows of sensory papillae below the eye; two to three predorsal longitudinal rows of sensory papillae (rows g, h and m)

Description. Morphometric data in Table 3 . Body thin, elongated, moderately compressed, caudal peduncle long, slender; head long, snout short with blunt tip, anterior naris small, tubular, posterior naris a small circular slit; eye larger than snout, placed higher on head; interorbital region narrow. Upper jaw inclined, barely surpassing anterior border of eye; lower jaw inclined, slightly protruded; lower lip stiffened. Tongue short, emarginated; gill opening large, anterior margin on vertical through anterior eye border; gill rakers 1+7–8 (3 specimens examined).

Three head pores on each side of head, one supraotic (SOT) and two on preopercular channel (POP); head with 6–7 transverse rows of sensory papillae below eyes, last two rows usually the shortest; two long horizontal rows of papillae below eye, one below the transverse rows (row d), other behind the sixth transverse row (row b). Three rows of papillae on opercle: one vertical (row ot), one short, joined to row ot (row oi), and other diagonal or curved (row os). Preorbital region with longitudinal row on each side (r) and a short transverse row (s 1); interorbital region with two (rarely three) short rows of papillae (p rows), with 2–6 elements; postorbital transverse row n and tra present, short; oculoscapular longitudinal rows x 1 and x 2 long, transverse oculoscapular row trp short, between x 1 and x 2; anterior dorsal longitudinal rows g, m and h present ( Figs. 11–12 ).

Dorsal fin elements: VI + 6 (1), VI + 7 (6), VI + 8 (36*), VI + 9 (10) or VII + 8 (1); anal fin rays 6 (3), 7 (7), 8 (40*) or 9 (7). Pectoral fin rhomboid, medial rays the longest, rays: 12 (3), 13 (18), 14 (33) or 15 (2*); pelvic fins long, separate from base; first pelvic ray the shortest, second and third the largest; caudal fin with convex margin; vertebrae 12+14–15=26–27 (5 specimens examined).

Trunk covered with ctenoid scales; scales absent on snout, interorbital region, belly, and pectoral fin base; trunk scales on longitudinal series 27 (1), 28 (9), 29 (10*), 30 (11), 31 (2) or 32 (1); scales on transverse rows 7 (28), 8 (22*), or 9 (1); circumpeduncular scales 11 (1), 12 (34*), or 13 (6); 4–5 transverse rows of ctenoid scales on opercle. Predorsal region partial to fully covered with cycloid scales: 4 (5), 5 (6), 6 (11), 7 (9), 8 (5*), 9 (4), 10 (1), or 11 (2).

Coloration in alcohol ( Fig. 10 ): ground color yellowish, with chromatophores on posterior margin of the scales forming three irregular series of spots along the flanks; row of slender dark brown markings along belly, a vertical row of small dark spots from hind border of eye to chin and other from anterior margin of eye to upper jaw; small black dots on opercle; fins with inconspicuous series of dark brown spots along the rays; eyeball black or silvery on lower half and dark on the upper one; iris black.

Remarks. This species is unique in the genus in having sensory head pores. Neither Myers (1927) nor Thacker et al. (2006) paid much attention to the morphology of this system in Microphilypnus , although in the last paper the head sensory system of M. ternetzi has been represented ( Thacker et al., 2006, Fig. 2 D). In fact, we searched this feature in hundreds of specimens of Microphilypnus ternetzi , but we were unable to see any external openings in the head canals of these individuals.

Distribution. Microphilypnus acangaquara is known to date in the Tapajós river basin ( Fig. 1 ).

Holotype Paratypes (N=36) Mínimum Máximum

Figures

FIGURE 1. Map of the rivers of South America with geographic distribution of the species of Microphilypnus. Legends: black circles: Microphilypnus macrostoma; red triangles: M. ternetzi; pink circles: M. acangaquara.

FIGURE 2. Microphilypnus macrostoma. a) holotype, CAS 76820, Brazil: Amazonas, Manaus, igarapé da Mãe Joana, 15.5 mm SL. b) MZUSP 74234, Brazil: Amazonas, igarapé in Tapurucuara, 18.1 mm SL. c) INPA 26256, rio Negro basin, Igarapé Tarumã-Mirim, 17.0 mm SL. Photographs: CAS Dept. of Ichthyology (a) and R. A. Caires (b, c).

FIGURE 10. Microphilypnus acangaquara sp. nov. a) MZUSP 108204, holotype, Brazil: Pará, rio Tapajós basin, São Luís 15.1 mm SL. b) MZUSP 27015, paratype, same data as the holotype, 14.1 mm SL. c) MCP 15317, paratype, Brazil: Pará, rio Tapajós basin, rio Itapacurá, 16.8 mm SL. Photographs by R. A. Caires (a, b) and André da Silva Casas (c).

FIGURE 11. Microphilypnus acangaquara sp. nov., MZUSP 27015, paratype, Brazil: Amazonas, rio Tapajós basin, São Luís, 14.1 mm SL. Head in lateral view, pectoral fin not represented. Scale: 1.0 mm.

FIGURE 12. Microphilypnus acangaquara sp. nov., MZUSP 27015, paratype, Brazil: Amazonas, rio Tapajós basin, São Luís, 14.1 mm SL. Head in dorsal view. Scale: 1.0 mm.