Cytogenetic characterization of F1, F2 and backcross hybrids of the Neotropical catfish species Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum (Pimelodidae, Siluriformes)

The cytogenetic characteristics of Pseudoplatystoma corruscans and Pseudoplatystoma reticulatum and their F1, F2 and backcross hybrids were assessed by using chromosome banding techniques. The diploid number of 56 chromosomes was constant in all species and lineages, with a karyotypic formula containing 20 metacentric, 12 submetacentric, 12 subtelocentric and 12 acrocentric chromosomes. Nucleolar organizer regions (NORs) were identified in two subtelocentric chromosomes in the parents and hybrids, with partial nucleolar dominance in F1 and F2 specimens. Heterochromatic blocks were detected in the terminal and centromeric regions of some chromosomes in all individuals. For parental and hybrid lineages, 18S ribosomal clusters corresponding to NORs and 5S ribosomal genes were identified in distinct pairs of chromosomes. The striking conservation in the chromosomal macrostructure of the parental species may account for the fertility of their F1 hybrids. Similarly, the lack of marked alterations in the chromosomal structure of the F1 hybrids could account for the maintenance of these features in post-F1 lineages

Cytogenetic markers as diagnoses in the identification of the hybrid between Piauçu (Leporinus macrocephalus) and Piapara (Leporinus elongatus)

The genetic monitoring of interspecific hybrids involves the application of methodologies able to provide an easy and indubitable genetic characterization of both parental and hybrid individuals. In the present work, cytogenetic techniques were used to identify a hybrid lineage of Piaupara in order to caracterize them in relation to the parental species, Leporinus macrocephalus (piauçu) and L. elongatus (piapara). The cytogenetic analysis revealed that L. macrocephalus presented 2n = 54 chromosomes and a nucleolar organizer regions (NOR) at the telomere of the long arm of the submetacentric chromosome pair 2. Analysis of constitutive heterochromatin (C-banding) revealed a conspicuous block at the pericentromeric region on the long arm of a submetacentric chromosome pair. L. elongatus presented the same diploid number, 2n = 54, and a karyotypic formula similar to that of L. macrocephalus. The NORs were also at the telomere of the long arm of the submetacentric pair 2, which was morphologically different from that of L. macrocephalus. Heterochromatic blocks were observed at both telomeres of a submetacentric chromosome pair. The hybrid Piaupara presented the same diploid number (2n = 54) and karyotypic formula as the parental species and there were no visible differences between parental and hybrid individuals. Differently from the Giemsa staining, NOR- and C-banding analysis showed marked differences which allowed the identification of the hybrids by the different morphology and/or size of the chromosomes carrying the NORs and patterns of heterochromatin distribution in their chromosomes. Such genetic studies are important for fish culture since they can provide tools for monitoring natural and artificial hybridization. They are also useful in biological conservation programmes and in the proper management of natural and reared fish stocks.195202Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Intraspecific crosses resulting in the first occurrence of eight and nine B chromosomes in Prochilodus lineatus (Characiformes, Prochilodontidae)

B chromosomes are supernumerary elements present in about 15% of eukaryotic species and are most frequently heterochromatic, behave parasitically, show a transmission rate higher than standard (A) chromosomes, and can provoke harmful effects on carriers. In the current work, Prochilodus lineatus individuals carrying eight and nine B chromosomes were obtained by induced crossing performed involving breeders with different B chromosome numbers in their cells. The high B chromosome numbers found in the offspring were recorded for the first time in this species. The use of cytogenetic techniques applied in the present study revealed that regardless of the increase in number of B chromosomes in the genome of these individuals, those elements did not presented active genes, and showed their normal heterochromatic characteristic

Variação periódica da triiodotironina (T3) plasmática e sua ação na reprodução induzida do matrinxã, Brycon cephalus (Günther, 1869) em cativeiro

O matrinxã, Brycon cephalus, espécie nativa oriunda da Bacia Amazônica, apresenta características adequadas para a piscicultura. Entretanto, trata-se de peixe reofílico, sendo necessário manejo adequado para induzir à reprodução. O objetivo deste trabalho foi caracterizar o perfil da triiodotironina (T3) plasmática no matrinxã, durante 16 meses (outubro/97 a janeiro/99), relacionando-o com a maturação sexual, além de testar a ação do T3 associado ao extrato pituitário de carpa na reprodução induzida da espécie. O experimento foi conduzido no Centro Nacional de Pesquisa de Peixes Tropicais - CEPTA, Pirassununga, SP, e no Departamento de Morfologia e Fisiologia Animal, da Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal - UNESP. Foram amostrados, mensalmente, 8 a 12 peixes, de ambos os sexos, totalizando 173 animais, de onde retirou-se sangue para dosagem do T3 plasmático. As gônadas foram removidas para análise histológica com identificação do sexo e determinação do estádio de maturação. Analisaram-se testículos e ovários de 161 peixes em corte transversal, tendo predominado machos (63,35%) e o estádio sexual imaturo entre ambos. A concentração plasmática de T3 foi maior de dezembro a janeiro, para machos e fêmeas, coincidindo com o período de maior atividade reprodutiva da espécie e maiores temperaturas da água. em janeiro/99, reprodutores de matrinxã foram induzidos com extrato de pituitária de carpa (EPC) associado à administração de T3 (20 mg/kg em 0,1 mL de suspensão oleosa). Os resultados sugeriram que o T3 atuou sinergicamente à gonadotropina do extrato hipofisário e que o tratamento agudo de triiodotironina com o EPC pode estimular o eixo hipotálamo-hipófise-ovário. O tempo de eclosão das larvas provenientes das fêmeas tratadas com o T3 foi menor e o crescimento inicial e a sobrevivência dessas larvas, maiores.The matrinxã, Brycon cephalus, native specie from the Amazonian Basin, shows good characteristics for farming. It is a migrating fish, being necessary an appropriate handling to induce its spawning. The objective of this work was to characterize the profile of plasma triiodotironina (T3) in matrinxã, during 16 months (October/97 to January/99), associated to the sexual maturation, besides testing T3 action associated to the carp pituitary extract in the induced reproduction. The experiment was carried out at the National Center of Research of Tropical Fish, CEPTA, Pirassununga, SP, and at the Animal Morphology and Physiology Department, of the University of São Paulo State, UNESP, Jaboticabal, SP. A total of 173 one and half year old matrinxã were sampled. Monthly, from eight to twelve fish, of both sexes, were bled for plasma T3 determination. The gonads were collected for histological identification of the sex and maturation stage. Testes and ovaries of 161 fish were observed, prevailing males (63.35%) and immature sexual stage. The concentration of plasma T3 was higher from December to January, both in males and in females, coinciding with the period of higher reproductive activity of the species and higher temperatures of the water. on January/99, breeders were induced with extract of carp pituitary (ECP), associated to the administration of T3 (20mg kg-1 in 0.1 ml oil solution). Results suggest that T3 played a synergistic role to the gonadotropin of the ECP, and a short-term treatment of ECP associated to triiodothyronine can stimulate the hipothalamus-hypophysis-ovary axis. The hatching time of the larvae from females treated with T3 was lower than the control ones. The initial growth and percent survival that larvae were better

Seminal analysis, cryogenic preservation, and fertility in matrinxã fish, Brycon cephalus (Günther, 1869)

Visando o desenvolvimento das técnicas de reprodução em peixes, foi realizada a caracterização e a criopreservação do sêmen de Brycon cephalus. As características seminais observadas foram: sêmen de coloração leitosa quase transparente, com um volume médio de 4mL e concentração espermática de 9.617±1.630 x 10(6) espermatozóides/mm³. Os espermatozóides (comprimento = 31,288±4,47 µm) são do tipo aquasperm, apresentando uma pequena cabeça arredondada (comprimento= 1,752±0,18 µm; largura = 1,752±0,17 µm) sem vesícula acrosomal, com um núcleo com cromatina altamente compactada, formando grumos grosseiros e um complexo centriolar localizado na fossa nuclear; uma peça intermediária (comprimento = 2,561±0,44 µm) que se estreita no sentido antero-posterior, um canal citoplasmático e um flagelo (comprimento = 29,521±4,37 µm). Os testes de fertilização com sêmen descongelado demonstraram um efeito significante (alfa = 0,05) no aumento da fertilidade quando utilizado o diluente tipo B, para ambos os tipos de palhetas, 0,5mL e 4,0mL. Não foi constatado efeito significativo (alfa = 0,05) entre a utilização de palhetas de 0,5mL ou de 4,0mL em relação à porcentagem de eclosão.Aiming to improve fish reproduction techniques, the characterization and cryopreservation of semen of Brycon cephalus were performed. The seminal characteristics observed were: an almost transparent, milky semen with a mean volume of 4mL, and sperm concentration of 9.617±1.630 x 10(6) spermatozoa/mm³. Spermatozoa (length = 31.288 ±4.47µm) were of the aquasperm type and displayed a small, round head (length = 1.727 ±0.18 µm; width = 1.752 ±0.17µm) without acrosomal vesicle, nucleus with highly condensed chromatin forming coarse clots and centriolar complex located in the nuclear fossa; a midpiece (length = 2.561±0.44µm), narrowed rearward, with a cytoplasmic canal; and a flagellum (length = 29.521 ±4.37µm). Fertilization tests with thawed semen demonstrated a significant effect (alpha= 0.05) on the increase of thawed semen fertility with diluent type B in both 0.5mL and 4.0 mL straws. No significant effect (alpha= 0.05) on hatching rate was observed in both straw sizes used.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

<b>Crescimento de juvenis de pacu em tanques com aeração noturna</b> - DOI: 10.4025/actascianimsci.v25i1.2122 <b>Growth of pacu juveniles in nightly aerated system</b> - DOI: 10.4025/actascianimsci.v25i1.2122

O presente estudo avalia o efeito de duas densidades de estocagem (20 e 40 peixes/m²) e da aeração noturna da água dos tanques de cultivo do pacu<em> Piaractus mesopotamicus</em> (Holmberg, 1887). Um total de 12 tanques com fundo de terra e paredes de alvenaria foram utilizados em 4 tratamentos com 3 repetições cada. Foram utilizados alevinos com 30 dias de idade, pesando em média 1,93 &plusmn; 1,70g, e o experimento foi conduzido durante 60 dias. A aeração noturna possibilitou a obtenção de valores médios de oxigênio de 5,6 &plusmn; 0,5 e 5,8 &plusmn; 0,5mg O₂/l para as densidades de 20 e 40 peixes/m², enquanto nos tanques sem a aeração os valores de oxigênio foram de 4,3 &plusmn; 0,7 e 3,4 &plusmn; 0,7mg O₂/l, respectivamente. A biomassa foi o único parâmetro que aumentou com a aeração noturna, enquanto que a sobrevivência e o crescimento apresentaram efeitos discretos.<br>The present study evaluated the effects of two stocking densities (20 and 40 fish/m²) and nightly aeration on water quality and growth of pacu, <em>Piaractus mesopotamicus</em> (Holmberg, 1887). Twelve ponds with concrete walls and earthen bottom were used to set 4 treatments with 3 repetitions each. 30-day old fish with average weight (mean standard &plusmn; deviation) of 1.93 &plusmn; 1.70g in the beginning of the experiment were observed for 60 days. Nightly aeration promoted 5.6 &plusmn; 0.5 and 5.8 &plusmn; 0.5mg O₂/l at dawn in the population densities of 20 and 40 fish/m², while the unaerated ponds allowed 4.3 &plusmn; 0.7 and 3.4 &plusmn; 0.7mg O₂/l for these densities, respectively. Fish biomass was the only biological parameter increased by nightly aeration, while discrete effects were observed in growth and survival