Apteronotus caudimaculosus

description

Body elongated and compressed; greatest depth contained 4.8 to 6.0 times in TL; head length 5.1 to 5.9, anal-fin base length 1.2 to 1.4, caudal-peduncle length 5.4 to 6.8, preanal distance 3.9 to 5.0 and prepectoral distance 7.0 to 7.9 in LEA; snout length 2.7 to 4.7, horizontal orbital diameter 9.0 to 16.7 and least interorbital width 3.9 to 4.7 in HL. Mouth terminal. Pectoral fin with 15 - 16, anal fin with 157 - 170 and caudal fin with 18 - 22 rays (Santana, 2003). Transversal series above lateral line with 11 to 14 scale rows. Ground color dark-brown, with brownish-white middorsal stripe from tip of lower jaw to nape, continuing as narrower line until about middle of body (occasionally faded or discontinuous); region around branchial aperture, including isthmus, brownishwhite; wide brownish-white transverse bar across tail and posterior portion of anal fin, with irregular, dark-brown spots; narrower brownish-white transverse bar across posterior portion of caudal peduncle and caudal-fin base. Distal portion of caudal fin brownish white; fins otherwise dark-brown (Graça, Pavanelli, 2007). Maximum total length. 280.0 mm (Graça, Pavanelli, 2007).

Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated

biology_ecology

Following Strussmann et al. (2000), the type-locality showed the following characteristics: it is a small channel in a swamp, with turbid water, mud and sand at the bottom and moderate current. The borders of the channel are covered by thick aquatic vegetation extending across the rest of the marsh. The Middle Rio Negro swamp was characterized by abundant water hyacinths and other rooted and floating aquatic plants (Willink et al., 2000). The water characteristics in August and September of 1998 were: temperature 23.2 - 23.5 ° C; pH 5.85 - 5.82; conductivity 53.8 - 55.0 µS / cm; dissolved oxygen 7.67 - 7.93 mg / cm. The specimens of A. caudimaculosus (cited as A. albifrons) were captured among water hyacinths (Eichornia sp.), which included also the following gymnotiforms: Eigenmannia trilineata, E. virescens, “ A ”. bonapartii; Rhamphichthys sp., Brachyhypopomus sp. and Gymnotus sp. (Willink et al., 2000). The following fish genera were caught in the same locality: Apistogramma, Crenicichla, Cichlasoma and Bujurquina (Cichlidae); Hypostomus, Loricariichthys, Rineloricaria and Farlowella (Loricariidae); Pimelodella (Pimelodidae).

Apteronotus caudimaculosus n. sp. (Gymnotiformes: Apteronotidae), a sexually dimorphic black ghost knifefish from the Pantanal, Western Brazil, with a note on the monophyly of the A. albifrons species complex.

description

Description- Morphometrics for holotype and paratypes are presented in Table 1. Body laterally compressed, with greatest body depth at abdominal cavity or a little posterior to this region. Dorsal profile straight. Lateral line extending to tail, absent in caudal fin. First perforated scale above pectoral fin origin. Head laterally compressed, widest at opercular region and deepest at dorsal region; profile straight in males and slightly convex in females. Snout long in males, shorter in females and immature specimens. Eyes small, located laterally on head, completely covered by a thin membrane. Mesethmoid short and narrow, its anterior tip reduced, flexed ventrally, and concave. Lateral ethmoid present, ossified, small and slender, shaped as a tube. Premaxilla of moderate size, with two irregular rows of teeth. Maxilla crescentshaped, with an ossified anterodorsal head and anteroventral shelf, the ventral margin of its descending blade curved. Dentary longer than deep, bearing two rows of teeth. Anguloarticular elongated. Mouth large, terminal, rictus passing a vertical through posterior border of eyes in both sexes. Endopterygoid narrow, without teeth, with ascending process conn

Apteronotus caudimaculosus n. sp. (Gymnotiformes: Apteronotidae), a sexually dimorphic black ghost knifefish from the Pantanal, Western Brazil, with a note on the monophyly of the A. albifrons species complex.

diagnosis

Diagnosis- A. caudimaculosus is included in the Apteronotidae by the presence of a dorsal-thong and caudal fin (Mago-Leccia, 1994; Albert & Campos-da-Paz, 1998; Albert, 2001). The new species shares the following diagnostic features within the Apteronotinae (Albert & Campos-da-Paz, 1998; Albert, 2001): gape of mouth large, extending to the edge of the eyes; maxilla rhomboid in lateral view; anterior surface of mesethmoid concave and lateral process of ventral ethmoid robust. It was included in the genus Apteronotus by the presence of three of the five synapomorphies proposed by Albert (2001): body surface deep brown or black with a white mid-dorsal stripe and white mental and caudal patches; elongated posterior limb of the anguloarticular; and surface of cranial bones solid, not pitted. A. caudimaculosus was included in A. albifrons species-group by the presence of a pale pigment patch on the caudal peduncle and a highly contrasting pale or white mid-dorsal stripe and mental patch. The new species can by recognized within the genus by the following derived characters: (1) two clear bands encircling the caudal peduncle (vs. one clear band encircling the base of caudal fin, except A.

Apteronotus caudimaculosus n. sp. (Gymnotiformes: Apteronotidae), a sexually dimorphic black ghost knifefish from the Pantanal, Western Brazil, with a note on the monophyly of the A. albifrons species complex.