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

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Origin and molecular organization of supernumerary chromosomes of Prochilodus lineatus (Characiformes, Prochilodontidae) obtained by DNA probes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

B-chromosome frequency stability in Prochilodus lineatus (Characiformes, Prochilodontidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic Markers in Wild Population of Curimbata (Prochilodus lineatus) from Mogi-Guacu River

Within the genus Prochilodus, the species Prochilodus lineatus is certainly the most studied one from a cytogenetic point of view. In this study, a cytogenetic characterization of specimens of P. lineatus from Mogi-Guacu River was performed in the period from 2003 to 2007, through utilization of cytogenetic markers, such as Giemsa, Ag-NOR, C-banding and cytogenetical-molecular markers (FISH) to detect both 5S and 18S ribosomal genes. All analyzed individuals presented 2n=54 meta/submetacentric chromosomes, besides bearing up to 7 supernumerary Microchromosomes. Polymorphic NORs were detected on a single chromosomal pair. The constitutive heterochromatin was distributed at centromeric region of all chromosomes in the A complement, while the microchromosomes were totally heterochromatic. A syntenic distribution of 5S and 18S ribosomal genes was detected, comprising the NOR-bearing chromosomal pair. No additional ribosomal clusters in other chromosomes were observed. Although the karyotype features are commonly conserved within the genus Prochilodus, the few differences on the distribution of both ribosomal genes and heterochromatin when compared to specimens of P lineatus from other localities can be associated to the evolutionary changes that these repetitive sequences have undergone through the years.

Supernumerary chromosome inheritance in the curimbata (Prochilodus lineatus) of the Mogi-Guacu River

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cryogenic preservation of embryos of Prochilodus lineatus (Valenciennes, 1836) (Characiforme; Prochilodontidae)

While the freezing techniques of mammal embryos have been providing promising results, the cryopreservation of teleostean eggs and embryos have remained unsuccessful up to now. Therefore, this work aimed to develop a procedure of cryogenic preservation of embryos of Prochilodus lineatus and to observe, at both structural and ultrastructural levels, the morphological alterations that took place after the application of freezing/thawing techniques. The embryos at the morula stage could not tolerate exposure to the cryoprotectants ethylene glycol monomethyl ether, propylene glycol monomethyl ether, methanol, dimethyl sulphoxide and propylene glycol, presenting 100% of mortality. Embryos at the 4- to 6-somites stage tolerated exposure to propylene glycol and dimethyl sulphoxide, and the results revealed no significant differences (alpha = 0.05) regarding survival from both treatments. None of the freezing, thawing and hydration protocols was effective on preserving embryo viability. The ultrastructural analyses of frozen and thawed embryos showed that cells from ectoderm, somites, notochord and endoderm were structurally intact, with well preserved nuclei and mitochondria. The yolk globules were able to tolerate the freezing process, but the yolk syncytial layer was unorganized, displaying an electron-dense and compacted appearance, collapsed reticules, nuclei with modified chromatin and ruptures on the plasmatic membrane at the contact zone with endoderm. It might be concluded that the procedures tested for freezing were unable to avoid the formation of intracellular ice crystals, leading to drastic morphological modifications and making P. lineatus embryos unviable.

Histology, histochemistry and stereology of the adipose fin of Prochilodus lineatus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of exposition to polluted environments on blood cells of the fish Prochilodus lineatus

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Migration of the curimbatá Prochilodus lineatus (Valenciennes, 1836) (Pisces, Prochilodontidae) at the waterfall Cachoeira de Emas of the Mogi-Guaçu river - São Paulo, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chemical modulation on heterogeneous growth in Prochilodus lineatus (Valenciennes, 1847) (Pisces; Characiformes)

No presente trabalho, testou-se o efeito de fatores químicos liberados por coespecíficos sobre o crescimento e sua variabilidade no grupo (crescimento heterogêneo, CHet), numa espécie gregária, o curimbatá, Prochilodus lineatus. O CHet foi avaliado pelo coeficiente de variação do peso dos animais, em dois períodos consecutivos de 21 dias. Os peixes foram agrupados em aquários (4 peixes cada) que receberam água corrente, com vazão constante, de tanques contendo (C) ou não (N) coespecíficos. Quatro condições foram delineadas de acordo com a água que abastecia os aquários: a) água com contato prévio com coespecíficos durante todo o experimento (CC); b) água sem contato prévio com coespecíficos durante todo o experimento (NN); c) água com contato prévio com coespecíficos apenas no primeiro período, 0 a 21 dias (CN); e d) apenas no período de 21 a 42 dias (NC). Ao término dos experimentos, verificou-se que ocorre modulação química sobre a variabilidade de crescimento em P. lineatus: os peixes que receberam água com contato prévio com coespecífico (C) apresentaram exacerbação do CHet. Fato que corrobora a idéia de que o mecanismo predominante da determinação da variação intra-específica do crescimento, em espécies gregárias, está associado à ação de fatores químicos liberados por coespecíficos.

Structural and ultrastructural analysis of embryonic development of Prochilodus lineatus (Valenciennes, 1836) (Characiforme ; Prochilodontidae)

This survey was performed to characterize the embryogenesis of Prochilodus lineatus. Seven stages of embryo development were identified - zygote, cleavage, blastula, gastrula, segmentation, larval and hatching - after a period of incubation of 22h (24 degrees C) or 14h (28 degrees C). The following cleavage pattern was identified: the first plane was vertical (2 blastomeres); the second was vertical and perpendicular to the first (4 blastorneres); the third was vertical and parallel to the first (4 x 2); the fourth cleavage was vertical and parallel to the second (4 x 4); the fifth was vertical and parallel to the first (4 x 8); and the sixth cleavage was horizontal (64 blastomeres). At the blastula stage (3.0-4.0 h (24 degrees C); 1.66-2.0h (28 degrees C) irregular spaces were detected and periblast structuring was initiated. At the gastrula stage (4.0-8.0 h (24 degrees C); 3.0-6.0 h (28 degrees C) the epiboly, convergence and cell movements, as well as the formation of embryonic layers, had begun. The segmentation stage (10.0-15.0h (24 degrees C); 7.0-10.0h (28 degrees C)) was characterized by a rudimentary formation of organs and systems (somites, optic vesicle and intestinal delimitation). The embryo at the larval stage (16.0-21.0 h (24 degrees C); 11.0-13.0 h (28 degrees C)) showed a free tail, more than 25 somites, an optic vesicle and a ready-to-hatch larval shape. The blastomeres at cleavage stage had disorganized nuclei indicating high mitotic activity. At gastrula, the blastomeres and the periblast had euchromatic nuclei and a large number of mitochondria and vesicles. The yolk was organized into globose sacs, which were dispersed into small pieces prior to absorption.

Increased B chromosome frequency and absence of drive in the fish Prochilodus lineatus

The neotropical freshwater fish species Prochilodus lineatus (Pisces, Prochilodontidae) shows 2n = 54 chromosomes plus supernumerary microchromosomes ranging in number from zero to seven among different animals. The transmission rates of B chromosomes were studied by the analysis of the parental and F1 generations in 10 controlled crosses performed with specimens from a natural population. The mean transmission rate observed for B chromosomes (k(B) = 0.511) was consistent with that expected from a regular meiotic behaviour orbs in both sexes and with the theoretical value under a Mendelian mode of transmission (0.5). Possible explanations for the dramatic increase in B frequency observed in this population during the last 10 years are discussed, bearing in mind the current absence of drive.

Synapsis in supernumerary chromosomes of Prochilodus lineatus (Teleostei: Prochilodontidae)

Meiotic analysis performed on a sample of 10 specimens of Prochilodus lineatus revealed continuous filaments of different sizes stained by AgNO3, corresponding to the bivalent of the normal complement. Small supernumerary chromosomes were observed as isolated and well stained bodies, scattered among the other elements. Synaptonemal complex studies have shown that the beginning of chromosome pairing process in P. lineatus usually occurs from the telomeres to the pericentromeric region. At the end of the pachytene 27 bivalents are perfectly paired and the small supernumerary chromosomes of this species are seen as bivalents, trivalents, or tetravalents. The central region of these small chromosomes show a trick staining when they formed bivalents or tetravalents. This portion seems to correspond to the pericentromeric region of the regular chromosomes with the heterochromatic characteristic of B chromosomes.

Molecular characterization and chromosomal localization of two families of satellite DNA in Prochilodus lineatus (Pisces, Prochilodontidae), a species with B chromosomes

Prochilodus lineatus, an abundant species in the Mogi-Guaçu river basin, represents a large part of the region's fishing potential. Karyotypic analyses based on classic cytogenetic techniques have revealed the presence of 54 metasubmetacentric type chromosomes, together with the occurrence of small supernumerary chromosomes with intra and interindividual variations. This paper describes the genomic organization of two families of satellite DNA in the P. lineatus genome. The chromosomal localization these two repetitive DNA families through fluorescence in situ hybridization (FISH) demonstrated that the SATH1 satellite DNA family, composed of approximately 900 bp, was located in the pericentromeric region of a group of chromosomes of the standard complement, as well as on all the B chromosomes. The SATH2 satellite family has a monomeric unit of 441 bp and was located in the pericentromeric regions of some chromosomes of the standard complement, but was absent in the B chromosomes. Double FISH analyses showed that these two families participate jointly in the pericentromeric organization of several chromosomes of this species. The data obtained in this study support the hypothesis that the B chromosomes derive from chromosomes of the standard complement, which are carriers of the SATH1 satellite DNA.