RESUMO

Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.(AU)

Parodontidae é um grupo relativamente pequeno de peixes caraciformes neotropicais que consiste em três gêneros (Apareiodon, Parodon e Saccodon) com 32 espécies válidas. Uma vasta literatura citogenética está disponível sobre Apareiodon e Parodon, mas até o momento não há dados citogenéticos sobre Saccodon, um gênero que contém apenas três espécies com distribuição transandina. No presente estudo foi descrito o cariótipo de S. wagneri, baseado em métodos convencionais (coloração de Giemsa, Ag-NOR, bandas C) e moleculares (mapeamento de DNA repetitivo por hibridização fluorescente in situ). Um número cromossômico diplóide de 2n = 54 foi observado, e a presença de cromossomos sexuais heteromórficos do tipo ZZ/ZW foi revelada. O cromossomo W possui uma banda terminal heterocromática que ocupa aproximadamente metade do braço longo, sendo esta banda aproximadamente a metade do tamanho do cromossomo Z. O ensaio FISH mostrou uma sintenia dos genes 18S-rDNA e 5S-rDNA no par de cromossomos 14, e a ausência de sítios teloméricos intersticiais. Nossos dados reforçam a hipótese de uma estrutura cariotípica conservadora em Parodontidae e sugerem uma origem ancestral dos cromossomos sexuais nos peixes desta família.(AU)

Assuntos

RESUMO

Parodontidae is a relatively small group of Neotropical characiform fishes consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid species. A vast cytogenetic literature is available on Apareiodon and Parodon, but to date, there is no cytogenetic data about Saccodon, a genus that contains only three species with a trans-Andean distribution. In the present study the karyotype of S. wagneri was described, based on both conventional (Giemsa staining, Ag-NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ hybridization) methods. A diploid chromosome number of 2n = 54 was observed in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/ZW type was detected. The W chromosome has a terminal heterochromatin band that occupies approximately half of the long arm, being this band approximately half the size of the Z chromosome. The FISH assay showed a synteny of the 18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative karyotype structure in Parodontidae and suggest an ancient origin of the sex chromosomes in the fishes of this family.(AU)

Parodontidae é um grupo relativamente pequeno de peixes caraciformes neotropicais que consiste em três gêneros (Apareiodon, Parodon e Saccodon) com 32 espécies válidas. Uma vasta literatura citogenética está disponível sobre Apareiodon e Parodon, mas até o momento não há dados citogenéticos sobre Saccodon, um gênero que contém apenas três espécies com distribuição transandina. No presente estudo foi descrito o cariótipo de S. wagneri, baseado em métodos convencionais (coloração de Giemsa, Ag-NOR, bandas C) e moleculares (mapeamento de DNA repetitivo por hibridização fluorescente in situ). Um número cromossômico diplóide de 2n = 54 foi observado, e a presença de cromossomos sexuais heteromórficos do tipo ZZ/ZW foi revelada. O cromossomo W possui uma banda terminal heterocromática que ocupa aproximadamente metade do braço longo, sendo esta banda aproximadamente a metade do tamanho do cromossomo Z. O ensaio FISH mostrou uma sintenia dos genes 18S-rDNA e 5S-rDNA no par de cromossomos 14, e a ausência de sítios teloméricos intersticiais. Nossos dados reforçam a hipótese de uma estrutura cariotípica conservadora em Parodontidae e sugerem uma origem ancestral dos cromossomos sexuais nos peixes desta família.(AU)

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BACKGROUND: Management and conservation of biodiversity requires adequate species inventories. The Yasuní National Park is one of the most diverse regions on Earth and recent studies of terrestrial vertebrates, based on genetic evidence, have shown high levels of cryptic and undescribed diversity. Few genetic studies have been carried out in freshwater fishes from western Amazonia. Thus, in contrast with terrestrial vertebrates, their content of cryptic diversity remains unknown. In this study, we carried out genetic and morphological analyses on characin fishes at Yasuní National Park, in eastern Ecuador. Our goal was to identify cryptic diversity among one of the most speciose fish families in the Amazon region. This is the first time that genetic evidence has been used to assess the species content of the Napo Basin, one of the richest regions in vertebrate diversity. RESULTS: Phylogenetic analyses of partial mitochondrial 16S ribosomal RNA gene (∼600 pb) DNA sequences from 232 specimens of the family Characidae and its closest groups revealed eight candidate new species among 33 species sampled, representing a 24% increase in species number. Analyses of external morphology allowed us to confirm the species status of six of the candidate species. CONCLUSIONS: Our results show high levels of cryptic diversity in Amazonian characins. If this group is representative of other Amazonian fish, our results would imply that the species richness of the Amazonian ichthyofauna is highly underestimated. Molecular methods are a necessary tool to obtain more realistic inventories of Neotropical freshwater fishes.

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Small-scale gold mining in Portovelo-Zaruma, Southern Equador, performed by mercury amalgamation and cyanidation, yields 9-10 t of gold/annum, resulting in annual releases of around 0.65 t of inorganic mercury and 6000 t of sodium cyanide in the local river system. The release of sediments, cyanide, mercury, and other metals present in the ore such as lead, manganese and arsenic significantly reduces biodiversity downstream the processing plants and enriches metals in bottom sediments and biota. However, methylmercury concentrations in sediments downstream the mining area were recently found to be one order of magnitude lower than upstream or in small tributaries. In this study we investigated cyanide, bacterial activity in water and sediment and mercury methylation potentials in sediments along the Puyango river watershed, measured respectively by in-situ spectrophotometry and incubation with (3)H-leucine and (203)Hg(2+). Free cyanide was undetectable (<1 µg·L(-1)) upstream mining activities, reached 280 µg·L(-1) a few km downstream the processing plants area and was still detectable about 100 km downstream. At stations with detectable free cyanide in unfiltered water, 50% of it was dissolved and 50% associated to suspended particles. Bacterial activity and mercury methylation in sediment showed a similar spatial pattern, inverse to the one found for free cyanide in water, i.e. with significant values in pristine upstream sampling points (respectively 6.4 to 22 µgC·mg wet weight(-1)·h(-1) and 1.2 to 19% of total (203) Hg·gdry weight(-1)·day(-1)) and undetectable downstream the processing plants, returning to upstream values only in the most distant downstream stations. The data suggest that free cyanide oxidation was slower than would be expected from the high water turbulence, resulting in a long-range inhibition of bacterial activity and hence mercury methylation. The important mercury fluxes resultant from mining activities raise concerns about its biomethylation in coastal areas where many mangrove areas have been converted to shrimp farming.

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Hemibrycon pautensis (Characiformes, Characidae), a new fish species from Paute River, eastern Ecuador is described. Diagnostic characteristics: eight to nine branched rays in the dorsal fin (vs.six to seven), and 27 –28 in the anal fin (vs.16 –26, except in H. dariensis which presents 22 –27, in H. metae 26 –31 and H. jabonero 23 –28); a no occurrence of dorsal pharyngeal plate (vs. occurrence); a cartilaginous and divided-in-two basihial (vs. an osseous base and a cartilaginous upper part). Hemibrycon pautensis resembles H. metae by its oblique external edge of the pelvic fins. They can be distinguished by the position of the pectoral fins in relation to the snout (38.24-41.6% in H. pautensis vs. 21. 21-25.87) and by the position of the pectoral fins in relation to the origin of the dorsal fin (20.95-24.30 in Hemibrycon pautensis vs. 35. 89-42.63), and by the number of proximate radials in the pectoral girdle (five in Hemibrycon pautensis vs. three to four). In addition, the geographic distribution of H. metae is restricted to the upper part of the Meta River in Colombia and can be distinguished of H. boquiae by: the number of scales between the lateral-line and the origin of the dorsal fin (eight in H. pautensis vs. 5-7); the distance between the snout and the pelvic fins (38.00-42.90% in H. pautensis vs. 42.9-46.19%); the pelvic fins length (13.77-17.96% in H. pautensis vs. 10.72-13.21%); and the snout length (21.34-27.88 in H.pautensis vs.26.92-33.66%).

Se describe Hemibrycon pautensis (Characiformes: Characidae), una especie nueva de pez del río Paute al oriente de Ecuador. El nuevo taxón se distingue de las demás especies por las siguientes caracteristicas: ocho a nueve radios ramificados enaleta dorsal (vs. seis a siete), y 27 –28 en la aleta anal (vs.16 –26, excepto en H. dariensis la cual presenta 22 –27, en H. metae 26 –31 y H. jabonero 23 –28); no presenta placa faringea dorsal (vs. presenta); basihial dividido en dos y cartilaginoso (vs. óseo y cartilaginoso en la parte superior). Hemibrycon pautensis es parecida a H. metae es parecida a H. metae por el borde externo de las aletas pélvicas oblicuo. Se distinguen por la posición de las aletas pectorales con relación al extremo del hocico (38.24- 41.6 en H. pautensis vs. 21.21-25.87) y por la posición de las aletas pectorales con relación al origen de la aleta dorsal (20.95-24.30 en Hemibrycon pautensis vs. 35.89-42.63), y por el número de radiales proximales en la cintura pectoral (cinco en Hemibrycon pautensis vs. tres a cuatro). Además, la distribución geográfica de H. metae está restringida a la cuenca alta del río Meta en Colombia. Se distingue de H. boquiae por el número de escamas entre la línea lateral y el origen de la aleta dorsal (ocho en H. pautensis vs. 5-7), por la distancia entre el hocico y el origen de las aletas pélvicas (38.00-42.90% en H. pautensis vs.42.9-46.19%), por la longitud de las aletas pélvicas (13.77-17.96% en H. pautensis vs. 10.72-13.21%), y por la longitud del hocico (21.34-27.88 en H. pautensis vs. 26.92-33.66%).

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Hemibrycon pautensis (Characiformes, Characidae), a new fish species from Paute River, eastern Ecuador is described. Diagnostic characteristics: eight to nine branched rays in the dorsal fin (vs. six to seven), and 27 - 28 in the anal fin (vs. 16 - 26, except in H. dariensis which presents 22 - 27, in H. metae 26 - 31 and H. jabonero 23 - 28); a no occurrence of dorsal pharyngeal plate (vs. occurrence); a cartilaginous and divided-in-two basihial (vs. an osseous base and a cartilaginous upper part). Hemibrycon pautensis resembles H. metae by its oblique external edge of the pelvic fins. They can be distinguished by the position of the pectoral fins in relation to the snout (38.24-41.6% in H. pautensis vs. 21.21-25.87) and by the position of the pectoral fins in relation to the origin of the dorsal fin (20.95-24.30 in Hemibrycon pautensis vs. 35.89-42.63), and by the number of proximate radials in the pectoral girdle (five in Hemibrycon pautensis vs. three to four). In addition, the geographic distribution of H. metae is restricted to the upper part of the Meta River in Colombia and can be distinguished of H. boquiae by: the number of scales between the lateral-line and the origin of the dorsal fin (eight in H. pautensis vs. 5-7); the distance between the snout and the pelvic fins (38.00-42.90 % in H. pautensis vs. 42.9-46.19%); the pelvic fins length (13.77-17.96% in H. pautensis vs. 10.72-13.21%); and the snout length (21.34-27.88 in H. pautensis vs. 26.92-33.66%).

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The new species Grundulus quitoensis is described from El Voladero Lake, El Angel Biological Reserve, Northern Ecuador. The new taxon can be distinguished from all congeners by the following characters, respectively: a low number of unbranched rays in the anal fin (three vs. four-five) and in pectoral fins (on vs. two - three), a higher number of dentary teeth (12-14 vs. 8-10), a second infraorbital about three times larger than the first (vs. about two times larger), a third infraorbital which is not in contact with the preopercle (vs. in contact with preopercle), the presence of four small fenestrae in the infero-lateral bone dentary (vs. one - two); and a premaxilla which presents a long lateral process (vs. short), a maxilla with two notches in the infero-lateral surface (vs. one notch in the infero-lateral surface)

Se describe Grundulus quitoensis nueva especie (Characiformes, Characidae) proveniente de las Lagunas El Voladero reserva biológica El Angel al norte de Ecuador. El nuevo taxon se distingue de las demás especies por el menor número de radios simples en la aleta anal (tres vs. cuatro a cinco) y en las aletas pectorales (uno vs. dos a tres), por el mayor número de dientes en cada dentario (12- 14 vs. 8-10), perfil ventral posterior a la cintura pectoral hasta el origen de la aleta anal plano (vs. curvo), el segundo infraorbital es tres veces más grande que el primero (vs. dos veces más grande), el tercer infraorbital está separado del preopérculo (vs. en contacto con la superficie del preopérculo), dentario presenta cuatro pequeñas fenestras en el margen infero-lateral (vs. uno a dos), el premaxilar presenta un proceso lateral largo (vs. corto), maxilar con dos muescas en la superficie infero-lateral (vs. maxilar con una muesca en la superficie inferolateral)

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RESUMO

The new species Grundulus quitoensis is described from El Voladero Lake, El Angel Biological Reserve, Northern Ecuador. The new taxon can be distinguished from all congeners by the following characters, respectively: a low number of unbranched rays in the anal fin (three vs. four-five) and in pectoral fins (on vs. two - three), a higher number of dentary teeth (12-14 vs. 8-10), a second infraorbital about three times larger than the first (vs. about two times larger), a third infraorbital which is not in contact with the preopercle (vs. in contact with preopercle), the presence of four small fenestrae in the infero-lateral bone dentary (vs. one - two); and a premaxilla which presents a long lateral process (vs. short), a maxilla with two notches in the infero-lateral surface (vs. one notch in the infero-lateral surface).

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