Gladioglanis anacanthus, Rocha & Oliveira & Rapp Py-Daniel, 2008

Rocha, Marcelo Salles, Oliveira, Renildo Ribeiro de & Rapp Py-Daniel, Lúcia H., 2008, A new species of Gladioglanis Ferraris & Mago-Leccia from rio Aripuanã, Amazonas, Brazil (Siluriformes: Heptapteridae), Neotropical Ichthyology 6 (3), pp. 433-438 : 434-436

Gladioglanis anacanthus , new species Fig. 1-2

Holotype. INPA 28446 (26.3 mm SL), Brazil, Amazonas , Novo Aripuanã , rio Aripuanã, lake on Mamão Island, 06°08’48”S 60°11’50”W, 29 Apr 2005, L. Rapp Py-Daniel et al.

Paratype. INPA 28447 (21.5 mm SL, cs), same data as holotype .

Diagnosis. Gladioglanis anacanthus n. sp. can be distinguished from its congeners by the following features: dorsalfin spine and spinelet absent (vs. both structures present); first dorsal-fin ray (homologous to spine) flexible, unbranched, followed by five branched dorsal-fin rays (vs. spinelet, spine and six branched dorsal-fin rays in congeneric species); pectoral-fin spine 5.8-6.1% of SL (vs. 9.2% in G. conquistador and 8.2% in G. machadoi ); dentations on pectoral spine 5 on anterior side and 4 on posterior (vs. 5-8 on anterior and 6-8 on posterior side in G. conquistador , and 10 on anterior and 7 on posterior in G. machadoi ); anal-fin rays 22-25 (vs. 15-21 in G. conquistador and 15-19 in G. machadoi ); round profile of the head in dorsal view (vs. triangular shaped in dorsal view in congeners); first pterygiophore of dorsal fin in contact with neural spine of eighth vertebra (vs. seventh vertebra in G. conquistador and sixth vertebra in G. machadoi ); both caudal-fin lobes with 13 rays, (vs. upper and lower lobes with 13- 18 and 9-13 rays respectively in G. conquistador and 20-24 and 12-15 in G. machadoi ), 60 total vertebrae (vs. 48-51 in G. conquistador and 45-48 in G. machadoi )

Description. Morphometric data is presented in Table 1. Body slender and elongate. Head depressed; dorsal profile of head rounded. Body compressed from pectoral-fin origin to caudal peduncle. Skin of head thin and semi-transparent, open cranial fontanels externally visible. Mouth terminal, lower jaw projecting. Premaxillary and dentary tooth small, villiform, in bands.

Barbels ovoid in transversal section. Maxillary barbel inserted above upper lip, posterolateral to anterior nostril and anterior to pore of infraorbital sensory canal; reaching origin of pectoral fin but not exceeding tip of adpressed pectoral fin. Inner mental barbel reaching to or just beyond margin of branchiostegal membrane. Outer mental barbel reaching to or just beyond pectoral-fin insertion. Branchiostegal membranes free and overlapping.

Anterior nostril tubular, located above margin of upper lip; nostril immediately lateral to anterior supraorbital pore and anteromedial to anterior infraorbital pore. Posterior nostril circular and lacking raised rim, located closer to eye than to anterior nostril. Eye small and without free orbital rim; centered on anterior third of head. Sensory canals of head with simple (non-dendritic) tubes leading to large pores.

Dorsal fin without spine and spinelet; six soft fin rays, first ray (homologous to spine) unbranched and articulating with second pterygiophore; five branched rays. First and second pterygiophores inserted between neural spines of vertebrae 8 and 9. Bifid neural spines of vertebra 6 surrounding small, horizontally elongate bone, interpreted as a supraneural. Adipose fin elongate, united to caudal fin; its origin posterior of vertical through origin of anal fin.Anal fin elongate, bearing 22-25 rays. Caudal fin deeply lobed with lower lobe longer; 13 rays in upper lobe and 13 in lower. Pectoral fin with heavy and sharp spine and four slender soft rays. Spine covered with thick layer of skin. Spine with 5 large and sharp dentations on anterior side and 4 on posterior. Posterior cleithral process slender and sharp. Pelvic fin with six rays, first simple, five branched; not reaching anal-fin origin. Urogenital papilla in a depression. Six pleural ribs. Total vertebrae 60.

Color in alcohol. Body color brownish. Small dark chromatophores scattered over dorsal surfaces of head and body, imparting to body a darker pigmentation. Chromatophores smaller than nares. Ventral portion of body less pigmented. All fins hyaline.

Distribution. Gladioglanis anacanthus was found only at the type locality, lago do Mamão, rio Aripuanã basin, Amazonas state, Brazil ( Fig. 3).

Ecological notes. The type locality of G. anacanthus is a large lake, lago do Mamão, inside an island ( Ilha do Mamão), located in the middle portion of rio Aripuanã ( Fig. 3). The new species was first collected during field work on rio Madeira basin (PROBIO project). It was collected together with many specimens of G. conquistador during high water season. The specimens were collected in the flooded forest (igapó) on the border of the lake, in a shallow (up to 0.5 m) marginal area on a deep mat of leaf litter as substrate.

A second field trip sponsored by the “All Catfish Species Inventory” Project was conducted during the dry season and, as the water receded, the area around the lake was not flooded. The collection was conducted on leaf litter along the shore of the lake. We found more specimens of G. conquistador but no additional specimens of the new species.

Etymology. The specific name anacanthus is derived from the Latin an (absence) and canthus (spine) in allusion to the absence of its dorsal-fin spine.