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Abstract

Two new species of Ancistrus are described from Amazon basin: A. krenakarore from rio Itapacura, a tributary of the right margin of the lower rio Tapajós drainage; and A. karajas from small headwater streams of rio Parauape- bas, a tributary of left margin of lower rio Tocantins drainage, both from Para State, Brazil. The two new species differ from all congeners except A. jataiensis, A. parecis, A. reisi, A. tolima, A. tombador, A. verecundus and A. veri- caucanus by the absense or vestigial adipose fin (vs. presence of a fully-developed fin). The new species differ from all congeners without adipose fin by the presence of only one preadipose plate and by a combination of morphometric characters; and differ from each other by color pattern.

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This study aims to provide an annotated list of the type-material housed in the fish collection of the Núcleo de Pesquisas em Limnologia, Ictiologia e Aquicultura (NUP), Universidade Estadual de Maringá, Paraná, Brazil. NUP’s fish type collection hosts type-material of 157 species, distributed in 503 lots (11 holotypes and 492 lots of paratypes) totalling 2,915 specimens. For each species, catalog numbers of all available lots are provided, and for each lot, total number of specimens, range of variation of standard length, number of cleared and stained specimens (when any), locality data, collectors, and date of collection, are provided.
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Neoplecostomus paranensis was the only Neoplecostomus species known from the upper Rio Paraná basin, and it was diagnosed from its congeners mainly by the absence or reduction of the adipose fin. In this study we describe three new Neoplecostomus species. All of them are promptly differentiated from N. paranensis by having a well-developed adipose fin. Furthermore, the new species are differentiated from congeners by morphometric and meristic traits, in addition to color pattern. Neoplecostomus paranensis is redescribed. We also provide an identification key to all Neoplecostomus species.
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The genus Otocinclus Cope (1872) of the siluriform family Loricariidae is diagnosed as monophyletic on the basis of shared derived characters of the cranial and hyobranchial skeleton, dorsal gill arch musculature, and gut. Otocinclus are relatively small herbivorous catfishes restricted to small streams and quiet slow-flowing margins of larger rivers, most frequently living in close association with aquatic macrophytes and terrestrial marginal grasses extending into the water column. Otocinclus species share a novel modification of the distal esophageal wall which is developed into an accessory blind diverticulum that may function in aerial respiration and for providing additional modulatory positive buoyancy for remaining in the upper water column at stream margins. Otocinclus has no junior synonyms, however several nominal species originally described in Otocinclus are here formally re-assigned to other genera in the subfamily Hypoptopomatinae. Otocinclus cephalacanthus Ribeiro 1911, O. depressicauda Ribeiro 1918, O. francirochai Ihering 1928, O. laevior Cope 1894, O. leptochilus Cope 1894, O. maculipinnis Regan 1904, O. nigricauda Boulenger 1891, and O. paulinus Regan 1908 are all placed in the genus Microlepidogaster Eigenmann & Eigenmann 1889; O. obtusos Ribeiro 1911 was placed in Pseudotothyris Britski & Garavello 1984; the genus Nannoptopoma Schaefer 1996 was erected for O. spectabilis Eigenmann 1914 in the tribe Hypoptopomatini; O. gibbosus Ribeiro 1908 is removed from Otocinclus, yet remains of undetermined generic status. Thirteen species are recognized in Otocinclus: O. affinis Steindachner 1877 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. bororo n. sp. of the upper Río Paraguay; O. caxarari n. sp. of the middle Río Guaporé/Mamoré system; O. flexilis Cope 1894 of the lower Paraná/Paraguay and Uruguay basins and coastal streams of southeastern Brazil; O. hasemani Steindachner 1915 of northern Brazil; O. hoppei Ribeiro 1939 of the upper Amazon, Tocantins and Paraguay basins and coastal streams of northeastern Brazil; O. huaorani n. sp. of the upper Amazon and Orinoco basins; O. macrospilus Eigenmann & Allen 1942 of the upper Amazon basin of Colombia, Ecuador, and Peru; O. mariae Fowler 1940 of the lower Amazon, upper Madeira and Paraguay basins; O. mura n. sp. of the middle Amazon River; O. vestitus Cope 1872 of the upper Amazon and lower Paraná basins; O. vittatus Regan 1904 of the Amazon, Orinoco, Paraná/Paraguay, and Tocantins basins; and O. xakriaba n. sp. of the rio São Fransisco basin. Two species are placed in synonymy: Otocinclus arnoldi Regan 1909 and O. fimbriatus Cope 1894 are junior synonyms of O. flexilis. Keys to the species of Otocinclus and genera of the Hypoptopomatinae are provided. A descriptive treatment of the osteology and cranial myology is provided for O. vittatus. Detailed analysis of meristic and morphometric variation based on geometric morphometric procedures is provided for the phenetically similar species pairs O. mariae and O. vittatus, O. bororo and O. huaorani in an a posteriori evaluation of separate species status. The phylogenetic relationships among Otocinclus species, and the phylogenetic position of Otocinclus among genera of the Hypoptopomatinae, are determined based on analysis of 27 morphological features using cladistic parsimony. Monophyly of Otocinclus was confirmed; within Otocinclus, a clade comprised of O. affinis and O. flexilis is the sister-group to the remainder of the genus. Within that latter clade, O. hasemani and O. xakriaba are the first and second-level sister-groups to the remainder of the genus, within which relationships among species are not fully resolved with available data. The phylogenetic biogeography of Otocinclus is informative regarding the historical relationships among major river drainage basins, particularly of those river systems of the Brazilian Shield. A biogeographic hypothesis is proposed based on the area cladogram derived from the species-level phylogenetic relationships, which suggests successive vicariance and speciation in the non-Amazonian regions of endemism of southeastern and eastern South America, followed by speciation and dispersal within the Amazon, Orinoco and upper Paraguay basins. The pattern of vicariance revealed by the Otocinclus species-level phylogeny is congruent with the geologic history of the major river drainage basins of the Brazilian Shield. This result suggests that, for Otocinclus and perhaps other loricariid catfishes, much of their generic and species-level diversification occurred prior to the formation of the Amazon basin.
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Ancistrus maximus, new species, is described from the igarapé Macoari, rio Branco drainage, Roraima State, Brazilian Amazon. It is distinguished from all congeners, except A. dolichopterus, A. fulvus and A. latifrons, by having more branched rays in the dorsal fin (8 vs. 7). Ancistrus maximus is distinguished from A. dolichopterus, A. fulvus and A. latifrons by color pattern and by the combination of various characters. Ancistrus maximus is remarkable in its very large body size, attaining 200 mm SL, an uncommon size for species of the genus reached otherwise only by A. chagresi and A. centrolepis.
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Armored catfish (Loricariidae) are the major grazers of attached algae in pools of the Rio Frijoles, Panama (9@?9' N, 79@?44' W). In the dry season, sunny pools were inhabited by @?6 individuals loricariids per square metre of grazeable substratum. At these densities, armored catfish depleted algae and cleared sediment from bedrock substrata, leaving sparse standing crops of small, adnate diatoms (primarily Achnanthes spp.). To study the effects of armored catfish at 1/6 their natural density, I stocked four 6-7 cm (SL), 10-g Ancistrus (the most common size class of the most common species in stream pools) in each of five stream pens. Pens enclosed 4 m^2 of bedrock substratum, and were alternately stocked or left empty during three consecutive periods of 29, 11, and 11 d. At the end of each period, standing crops of sediment and attached algae, and rates of photosynthesis by attached algae, were measured. The attached algae that developed with sparse Ancistrus had higher standing corps with larger cells or colonies, and higher primary productivity, than did periphyton subjected to heavy grazing by unconfined armored catfish. Even heavy grazing, however, was less deleterious to attached algae than prolonged sedimentation on substrata in enclosures left empty for 11 or 29 d. The net effect of Ancistrus on their algal food changed from depletion at high grazer densities to enhancement at low grazer densities, as sedimentation became more limiting to algae than grazing.
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The adipose fin on fishes is a highly conserved and enigmatic, small, non-rayed fin that has persisted from the Mesozoic on some basal teleosts such as salmonids. Using juvenile steelhead, Oncorhynchus mykiss (Walbaum, 1792), ranging from 5 to 18 cm standard length, we experimentally test the effects of adipose fin removal on swimming performance in a variable velocity flow chamber and quantify, with seven independent trials, amplitude and frequency of caudal fin movement at multiple flow velocities (range 10-39 cm.s(-1)). Results demonstrate that adipose fin removal on smolts produces an average 8% (range -3% to 23%) increase in caudal fin amplitude relative to unclipped fish across all velocities. However, we observed no effects in trials with smaller fish (<7 cm) or larger fish (>12 cm). Consistent with speculations in the literature, our results show that the adipose fin may function to control vortices enveloping the caudal fin during swimming or, alternatively, function as a passive precaudal sensor of turbulent flow. Phylogenetic persistence of this trait among multiple groups of early bony fishes is probably due to its hydrodynamic attributes rather than developmental constraints, and the current widespread practice in fisheries of removing the adipose fin as a marking technique may have significant biological costs.
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Based on recent evidence suggesting a hydrodynamic function of the small adipose fin in salmonids to turbulent flow conditions, we test for associations between presence and absence of the adipose fin and flow regime in Siluriformes, one of the largest freshwater groups of fish with variable expression of this fin. Among 1906 species from multiple families, those living in habitats with flow (streams or rivers) exhibited an adipose fin significantly more frequently than expected relative to no-flow habitats (lakes, marine, parasitic). These trends were robust and occurred on different continents and among multiple paired comparisons within sister groups. Exceptions to these trends generally had atypical body shape or occupied divergent habitat types. These results are concordant with the hydrodynamic function of this small fin.
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Armored catfish, Ancistrus spinosus, graze substrates in a central Panamanian stream. They ingest both attached algae and sediment that settles onto substrates. During the dry season, this sediment is organic-rich (18–24% ash-free dry weight), and is derived from decomposing periphyton and vegetation from the surrounding, largely deciduous forest. This sediment, however, is not a food for Ancistrus, and in fact imposes energetic costs. These costs were estimated to be 15–22% of the daily energy budgets of 10 g individuals held under experimental conditions. In the stream, the presence of thick sediment on substrates increases the tendency for small Ancistrus to seek out larger individuals or areas cleared by them. Clearing of substrates by larger individuals may be particularly important to smaller Ancistrus during the dry season, when sediment-free substrate in stream pools is in short supply.
Article
Ancistrus is the most speciose genus of the tribe Ancistrini, with 58 valid species and many yet to be described. Cytogenetic studies were conducted on five apparently undescribed species from the Amazon basin, which showed different diploid numbers: Ancistrus sp. Purus (2n = 34); Ancistrus sp. Macoari (2n = 46); Ancistrus sp. Dimona (2n = 52); Ancistrus sp. Vermelho (2n = 42) and Ancistrus sp. Trombetas (2n = 38). All species possessed only one pair of NOR-carrying chromosomes, but with extensive variation in both the location on the chromosome as well as in the position of the ribosomal sites on the karyotype. The karyotypic evolution of Ancistrus species seems to be based on chromosomal rearrangements, with a tendency to a reduction of the diploid number. Two new instances of XX/XY sex chromosomes for Ancistrus species, based on the heteromorphism in the male karyotype, were also recorded. The large karyotypic diversity among Ancistrus species may be related to biological and behavioural characteristics of these fish that include microhabitat preferences, territoriality and specialized reproductive tactics. These characteristics may lead to a fast rate of fixation of chromosomal mutations and eventually speciation across the basin.
Nekton. Junk, The Hague
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Aleyev, Y. G. 1977. Nekton. Junk, The Hague, vi + 435 pp.
Subfamily Ancistrinae (armored catfishes)
  • S Fisch-Muller
Fisch-Muller, S. 2003. Subfamily Ancistrinae (armored catfishes). Pp. 373-400 in: R. E. Reis, S. O. Kullander & C. J. Ferraris (eds.), Check list of the freshwater fishes of South and Central America. Edipucrs, Porto Alegre.
Die Hypostomiden. Zweite Hauptgruppe der Familie der Panzerfische (Loricata vel Goniodontes)
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Kner, R. 1854. Die Hypostomiden. Zweite Hauptgruppe der Familie der Panzerfische (Loricata vel Goniodontes). Denkschriften der Kaiserlichen Akademie der Wissenschaften, 7: 251-286.