Description of a new species of Microglanis ( Siluriformes : Pseudopimelodidae ) from the Amazon basin , Amazonas State , Brazil

Microglanis Eigenmann, 1912 is the most species-rich genus of Pseudopimelodidae, with 21 described species (Ottoni et al., 2010; Ruiz & Shibatta, 2010), besides other possible new species (Shibatta, 2003). The genus was considered monophyletic by Shibatta (1998) and differs from other pseudopimelodids especially by the sharing of three characters: small size, rarely reaching 80 mm standard length; incomplete lateral line; and premaxillary tooth patch with rounded margin, without posterior projection (Schultz, 1944; Gomes, 1946; Mees, 1974, 1978). The species have a body color pattern consisting of orange-brown with large dark-brown spots, which justify their vernacular name: bumble-bee catfish. Species of Microglanis are widely distributed in South America, from northern Venezuela to Uruguay, and also west of Andes (Shibatta, 2003). However, a more scrutinous evaluation on the distribution of these species reveals a large gap in the brazilian Amazon region, where no new species had been registered to date. Species of Microglanis described from the Amazon basin were so far restricted to the upper region, in Peru and Ecuador: Microglanis zonatus Eigenmann & Allen, 1942, from río Morona, Peru and M. pellopterigius Mees, 1978, from río Araguarico, Ecuador. Microglanis poecilus Eigenmann, 1912 and M. secundus Mess, 1974 are also recorded to the Amazon basin (Mees, 1974; Shibatta, 2007), however they were originally described from coastal areas of the Guiana shield. During the field expeditions for fish collection in rio Amazonas during the Calhamazon project between 1994 and 1996, first specimens of a new species of Microglanis were caught near the mouth of some major tributaries. Subsequent effort provided additional material and this species is herein described.

Species of Microglanis are widely distributed in South America, from northern Venezuela to Uruguay, and also west of Andes (Shibatta, 2003).However, a more scrutinous evaluation on the distribution of these species reveals a large gap in the brazilian Amazon region, where no new species had been registered to date.Species of Microglanis described from the Amazon basin were so far restricted to the upper region, in Peru and Ecuador: Microglanis zonatus Eigenmann & Allen, 1942, from río Morona, Peru and M. pellopterigius Mees, 1978, from río Araguarico, Ecuador. Microglanis poecilus Eigenmann, 1912and M. secundus Mess, 1974 are also recorded to the Amazon basin (Mees, 1974;Shibatta, 2007), however they were originally described from coastal areas of the Guiana shield.
During the field expeditions for fish collection in rio Amazonas during the Calhamazon project between 1994 and 1996, first specimens of a new species of Microglanis were caught near the mouth of some major tributaries.Subsequent effort provided additional material and this species is herein described.

Material and Methods
Body measurements were taken point-to-point with a digital caliper with accuracy of 0.1 mm.Twenty morphometric characters and counts were taken preferably on the left side of the fish, under stereomicroscope, according to Mori & Shibatta (2006).Meristic data included counts of dorsal, pectoral, pelvic, anal and caudal-fin rays; gill rakers; serrations of pectoral-fin spine; and pores of lateral line of trunk.Counts of vertebrae, ribs, branchiostegal rays, proximal pterygiophores and procurrent caudal-fin rays, along with osteological observations, were made on one cleared and stained specimen prepared according to Dingerkus & Uhler (1977).Vertebral counts included only free centra (anterior elements of complex centrum were not counted), and the compound caudal centra (preural 1 + ural 1) counted as a single element.Specimens of all other described species of Microglanis were examined for comparison with the new species, except M. ater Ahl, 1936, M. zonatus Eigenmann & Allen, 1942and M. minutus Ottoni, Mattos & Barbosa, 2010.For those species comparisons were through characters obtained from pictures and data available in the literature.The new species and congeners were compared by size-free canonical variate analysis with the program PAST (Hammer et al., 2001).
The examined material belongs to the following institutions: Academy of Natural

Microglanis lundbergi new species
Figs Head slightly depressed, anteriorly rounded in dorsal view.Eye small, closer to mouth than to distal margin of operculum, more dorsal than lateral, inserted after first third of head length, completely covered by skin without free orbital margin.Snout short.Anterior nostril tubular, closer to upper lip than to eye; posterior nostril near anterior margin of eye, with anterior membrane.Gill membrane free from isthmus; nine branchiostegal rays.Gill rakers spiniform, usually small; first branchial arch with 1, 1, 4 gill rakers.
Mouth wide, terminal.Premaxillary tooth patch with rounded margin, no posterior projection.Dentary tooth patch semicircular, larger and wider than premaxillary patch.Tooth villiform, curved backwards.
All barbels thin, flattened in cross section.One maxillary pair, two mental pairs.Outer mental barbel surpassing pectoral-fin spine base; inner mental barbel shorter, reaching almost half length of outer mental barbel.Maxillary barbel short, not reaching pectoral-fin base.Dorsal fin I,6, located anteriorly to half of body length, posterior margin rounded; spinelet present.Dorsal-fin spine straight, shorter than branched rays.
Adipose fin relatively small.Caudal fin forked with deep notch, lower lobe slightly longer than upper lobe.Principal caudal rays 15, dorsal procurrent rays 15, ventral procurrent rays 10.Anal fin short and rounded, iv,7.Pectoral fin I,5.Pectoral spine strong, slightly flattened, with developed serrations on both margins, completely covered by thin skin.Anterior margin of pectoral spine with 10-14 hooks; hooks on distal portion antrorse or straight.Posterior margin of pectoral spine with 7-9 retrorse serrations greater than anterior margin, increasing in size from proximal to distal portion (Fig. 2).Tip of pectoral spine ossified, very strong and sharp.Pelvic fin rounded, with i,5 rays.Vertebrae 27.Ribs 6.
Posterior cleithral process short, narrow and pointed, spiniform.Proximal pterygiophores 9. Swim bladder relatively Color in alcohol.Ground color orange-brown.Head darkbrown with two elliptical and juxtaposed pale spots in supraoccipital region, confluent or not with a pale band in post-opercular region, reaching pectoral-fin base.Two small, semilunar, pale stripes in anterior region of head in dorsal view, between edge of snout and anterior orbital margin.Barbels pale, scattered by dark-brown chromatophores.
Ventral region light-brown.Trunk with large dark-brown blotch, saddle shaped, horizontally divided by pale lateral line.Caudal region with two dark-brown blotches of irregular shape.First one at dorsolateral position, beginning below anterior portion of adipose fin, extending up to half of caudal length.Second one at caudal peduncle, as dark brown spot approximately rectangular with irregular margins.
Pectoral and pelvic fins with scattered dark chromatophores.Dorsal fin with dark band covering distal half, with hyaline margin on all rays.Adipose fin with dark spot on anterior portion, confluent to caudal dark-brown blotch.Anal fin with thin dark band approximately median.Caudal fin with thin vertical "3-shaped"dark band.
Habitat notes.The individuals were collected in the main channel of the rio Amazonas (white waters), bottom rich in organic matter and pieces of wood (data obtained from lots' labels).
Etymology.The specific name is homage to the North American ichthyologist John G. Lundberg, coordinator of the Calhamazon project, who kindly provided specimens of the new species, and for his great contribution to the Systematics of Neotropical catfishes.

Discussion
All the characters proposed by Shibatta (1998), supporting the monophyly of Microglanis, are present in M. lundbergi.The morphological characters that sustain the hypothesis that the species is new are discussed as follows.
In Microglanis, a forked caudal fin with pointed lobes is a unique condition only found in M. lundbergi.Microglanis iheringi Gomes, 1946, from río Turmero, Venezuela, is the only congener whose caudal-fin shape -slightly forked with caudal lobes with the same size -roughly resembles the condition present in M. lundbergi, which may differ by a deeper notch in the caudal fin.Among the remaining species of Microglanis the most generalized caudal-fin shape is the emarginated, found in several species such as M. carlae from río Salado, río Paraguay basin, M. cibelae from coastal basins of Santa Catarina and Rio Grande do Sul, and M. garavelloi from the upper rio Paraná.Less frequently forms are: bilobed caudal fin, present in M. nigripinnis from coastal basins of the Rio de Janeiro State and M. secundus from coastal regions of Guiana Shield; and rounded, as in M. zonatus from río Morona, Peru.Among other Pseudopimelodidae   only Pseudopimelodus pulcher has a forked caudal fin, which is certainly a case of convergence or secondary reversion in the evolutionary history of the family due to frequent occurrence of non-forked caudal fins in the group.Another peculiar characteristic of M. lundbergi is the presence of two elliptical light spots in the supraoccipital region, distinguishing it from the other species that in general present a pale band in this region, which can be narrow, like in M. leptostriatus from the middle rio São Francisco, wide in M. cottoides from drainages of Laguna dos Patos and the río Uruguay basin, and M. parahybae from the rio Paraíba do Sul basin, or cordiform in M. robustus from the lower rio Tocantins basin.
Among all species of the genus, the coloration pattern of M. lundbergi is similar to species of the M. cottoides complex, whose members are distributed on southern and southeastern Brazil.This complex includes M. cibelae, M. cottoides, M. malabarbai, and M. nigripinnis, which are grouped by the following combination of characters: long subdorsal dark band, reaching the pectoral fin, with a clear spot located below the dorsal spine; caudal lobes practically of the same size; dark blotch on adipose fin; and dark stripe of caudal fin roughly number three shaped.However, the results of the canonical variables evidenced that M. lundbergi has morphometric differences from the species of M. cottoides complex, and it is morphologically more similar to the Amazonian M. poecilus (Fig. 4).The species of M. cottoides complex were morphologically distinct from other species of northern Brazil by the first and second axes (Table 2), whose morphological variables with greater weights were the length of the head, interorbital distance, mouth width, dorsal-spine length, and adipose-fin base length.Regarding the delimitation of groups based on similarities of morphology and coloration among the species of Microglanis, Mori & Shibatta (2006) and Alcaraz et al. (2008) suggest that they are merely artificial, and call attention to the need of further phylogenetic analysis encompassing all species to determine natural lineages within the genus.

. 1-2
It also differs from other species on the following morphometric characters: length of the head 27.4-30.0%of;eye diameter 8.0-9.9% of Diagnosis.Microglanis lundbergi is distinguished from all congeners by the presence of a forked caudal fin with a deep notch between upper and lower lobes (vs.rounded, emarginated, or slightly forked), two pale juxtaposed and elliptical spots in the supraoccipital region (vs.wide, or narrow, or absent supraoccipital pale band), and shorter length of the adipose-fin base (13.1-16.6% of SL; except for M. carlae 14.7-19.1%,M. secundus 12.2-18.2%and M. iheringi 14.7-19.0%).