Chromosome banding and 18S rDNA in situ hybridization analysis of seven species of the family Achiridae (Teleostei : Pleuronectiformes)

Achiridae is an important family of the order Pleuronectiformes widely distributed in North, Central, and South America with freshwater and marine species. In the present study cytogenetic analyses comprising conventional and molecular techniques were carried out in seven species of this family. The following diploid numbers (2n) and fundamental numbers (FN) were obtained: Achirus declivis 2n = 34, FN = 52; Achirus lineatus 2n = 40, FN = 66; Catathyridium jenynsi 2n = 40 and FN = 50; Gymnachirus nudus 2n = 36 and FN = 50; Hypoclinemus mentalis 2n = 38 and FN = 54; Trinectes paulistanus 2n = 42 and FN = 52; and Trinectes sp. 2n = 38 and FN = 54. All species presented a single nucleolar organizer region (NOR) bearing chromosome pair and C-band positive segments mainly distributed at the pericentromeric position. The wide variation observed in chromosome number and FN suggests the occurrence of larger chromosome rearrangements in the family Achiridae if compared with other families of the same order.

Localization of 5-methylcytosine in metaphase chromosomes of diploid and triploid pacu fish, Piaractus mesopotamicus (Pisces, Characiformes)

The distribution of 5-methylcytosine (5-MeC) was investigated in fish chromosomes by indirect immunofluorescence using a highly specific 5-MeC monoclonal antibody. Diploid and artificially produced triploid specimens of the pacu fish, Piaractus mesopotamicus, were analyzed. The strong immunofluorescent signals were coincident with the heterochromatic regions of both diploids and triploids in a pattern that matched the C-banding pattern. In the euchromatin, heterogeneous labeling was observed along the chromatids. The weakness of this labeling hindered comparison of the fluorescence labeling of homologous chromosomes from diploid and triploid individuals. However, no striking differences were observed. The possibility that the euchromatin labeling by the 5-MeC antibody is related to the occurrence of mildly repetitive sequences in the genome of Piaractus is discussed.

Cytogenetic analysis of three species of the genus Haemulon (Teleostei : Haemulinae) from Margarita Island, Venezuela

This paper describes the karyotype analysis of Haemulon aurolineatum, Haemulon bonariensis and Haemulon plumierii, by Giemsa staining, C-banding, Ag-staining and fluorescent in situ hybridization (FISH), to locate the 18S and 5S rRNA genes. Diploid modal count in the three species was 2n = 48 acrocentric elements. Except for pair 24, which exhibited an unmistakable secondary constriction in all three species, it was not possible to classify them as homologous to each other because differences in chromosome size were too slight between adjacent pairs within a size-graded series. Ag-NOR clusters were located in pair 24 in the three species with signal located on the secondary constriction of these chromosomes. C-banding demonstrated that the three species share the same distribution pattern of the constitutive heterochromatin with centromeric heterochromatic blocks in the 23 chromosome pairs and a pericentromeric block in pair 24 which is coincident with the NORs. FISH experiments showed that 18S rDNA sequences were located coincident with the Ag-NOR site in the three species; however, differences in both the number and chromosome distribution of 5S-rDNA cluster were detected among them. Our data suggest that chromosome evolution of Haemulon has been preserved from major changes in the karyotypic macrostructure, whereas microstructural changes have occurred.

Cytogenetic studies in three species of Lutjanus (Perciformes: Lutjanidae: Lutjaninae) from the Isla Margarita, Venezuela

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Occurrence of ZZ/ZW sex chromosomes in Thoracocharax stellatus fish (Characiformes, Gasteropelecidae) from the Araguaia River, south America

The karyotypic and chromosomal characteristics of the hatchetfish Thoracocharax stellatus from the Araguaia River, Brazil (Araguaia-Tocantins basin) were analyzed using Giemsa, AgNO3, and CMA(3) fluorescent staining, and C-banding. The diploid chromosome number was 54 and the karyotypes of females and males were composed of six metacentrics, six submetacentrics, six subtelocentrics and 36 acrocentrics. Two impaired acrocentric chromosomes were detected in the female karyotype. C-banding showed heterochromatic blocks at several chromosomes and an entirely heterochromatic acrocentric chromosome in females that was lacking in the male karyotype. This discovery indicated a heteromorphic sex chromosome system of the ZZ/ZW type. Ag-staining and CMA(3) fluorescence revealed one major chromosome pair bearing the NORs with the presence of additional signals in some metaphases. Both heterochromatic segments associated with Ag-NORs and the W chromosome were positively stained by CMA(3). Considering the present data and previous findings it is hypothesized that the occurrence of ZW sex chromosome system is widespread in the genus Thoracocharax.

Comparative Cytogenetic Analysis of the Genus Symphysodon (Discus Fishes, Cichlidae): Chromosomal Characteristics of Retrotransposons and Minor Ribosomal DNA

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evolutionary dynamics of rRNA gene clusters in cichlid fish

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

Three sympatric karyomorphs in the fish Astyanax fasciatus (Teleostei, Characidae) do not seem to hybridize in natural populations

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

Cytogenetic analysis of B chromosomes in one population of the fish Moenkhausia sanctaefilomenae (Steindachner, 1907) (Teleostei, Characiformes)

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

Differences in the number of some antennal sensilla of four honey bee (Apis mellifera) types and comparisons with the defensive behaviour

The number of sensilla coeloconica, ampullacea and campaniformia of flagellomeres 3 to 10 of the antennae of workers of four honey bee types (Italian, Caucasian, African and Africanized) was studied by scanning electron microscopy. Comparisons of the four bee types showed that only African and Africanized honey bees did not differ from one another with respect to the number of sensilla coeloconica and ampullacea of flagellomere 10. African and Africanized honey bees and Caucasian and Italian honey bees also did not differ from one another in terms of flagellomere 9. In the other flagellomeres there were no differences among bee types. Italian and Caucasian honey bees differed from Africanized honey bees in terms of number of sensilla campaniformia on flagellomere 6, and Caucasian honey bees differed from African and Africanized honey bees in terms of flagellomere 3. Five significant but random correlation values were obtained between number of antennal sensilla and defensive behaviour in Africanized honey bees. Thus,there is no relationship between antennal structures and defence behaviour.

Chromosomal organization of the 18S and 5S rRNAs and histone H3 genes in Scarabaeinae coleopterans: insights into the evolutionary dynamics of multigene families and heterochromatin

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

Relationship between number of ovipositions of Cotesia flavipes (Cam.) and number of descendants emerged from its host Diatraea saccharalis (Fabr.)

Fêmeas de Cotesia flavipes (Cam.) foram introduzidas, individualmente, em placas de Petri contendo uma larva de seu hospedeiro Diatraea saccharalis (Fabr.). Permitiu-se que cada fêmea de C. flavipes realizasse posturas uma ou duas vezes em uma mesma larva. O período de emergência das larvas e dos adultos, a razão sexual, o número de larvas e pupas inviáveis e a longevidade dos adultos de C. flavipes registrados nas duas condições experimentais (uma ou duas posturas) foram comparados. Os resultados revelaram que duas oviposições sucessivas no hospedeiro não alteraram a razão sexual na descendência, mas aumentaram o número de parasitóides e também o número de larvas e pupas inviáveis.

Chromosomal differentiation of populations of Lysapsus limellus limellus, L. l. bolivianus, and of Lysapsus caraya (Hylinae, Hylidae)

Cytogenetic analysis were done on specimens from two populations of Lysapsus limellus limellus. three of L. l. bolivianus and of one of Lysapsus caraya. All animals showed a diploid chromosomal number of 2n=24. The karyotypes of the two L. limellus subspecies were very similar, differing only by the larger amount of telomeric heterochromatin and a small pericentromeric C-band on the short arms of pair 2 in L. l. limellus specimens. The karyotype of L. caraya differed from those of the two L. limellus subspecies in terms of chromosomal morphology, C-banding pattern and location of the main NOR on chromosomes 7 and 6. respectively. The karyotype of the L. l. bolivianus population from Guajara-Mirim/RO differed from those of the other populations of the same subspecies in morphology and heterochromatin pattern of chromosomes 7 and 8. Additional NORs were detected by silver staining and confirmed by FISH in one of the homologues of pairs 1 and 8 in L. l. bolivianus and in pair 7 in L. caraya. These results suggest that a reassessment of the taxonomic status of L. limellus subspecies, especially of the L. l. bolivianus populations, may be necessary. (c) 2005 Elsevier Ltd. All rights reserved.

Molecular phylogeny and karyotype differentiation in Paratelmatobius and Scythrophrys (Anura, Leptodactylidae)

Paratelmatobius and Scythrophrys are leptodactylid frogs endemic to the Brazilian Atlantic forest and their close phylogenetic relationship was recently inferred in an analysis that included Paratelmatobius sp. and S. sawayae. To investigate the interspecific relationships among Paratelmatobius and Scythrophrys species, we analyzed a mitochondrial region (approximately 2.4 kb) that included the ribosomal genes 12S and 16S and the tRNAval in representatives of all known localities of these genera and in 54 other species. Maximum parsimony inferences were done using PAUP* and support for the clades was evaluated by bootstrapping. A cytogenetic analysis using Giemsa staining, C-banding and silver staining was also done for those populations of Paratelmatobius not included in previous cytogenetic studies of this genus in order to assess their karyotype differentiation. Our results suggested Paratelmatobius and Scythrophrys formed a clade strongly supported by bootstrapping, which corroborated their very close phylogenetic relationship. Among the Paratelmatobius species, two clades were identified and corroborated the groups P. mantiqueira and P. cardosoi previously proposed based on morphological characters. The karyotypes of Paratelmatobius sp. 2 and Paratelmatobius sp. 3 described here had diploid chromosome number 2n = 24 and showed many similarities with karyotypes of other Paratelmatobius representatives. The cytogenetic data and the phylogenetic analysis allowed the proposal/corroboration of several hypotheses for the karyotype differentiation within Paratelmatobius and Scythrophrys. Namely the telocentric pair No. 4 represented a synapomorphy of P. cardosoi and Paratelmatobius sp. 2, while chromosome pair No. 5 with interstitial C-bands could be interpreted as a synapomorphy of the P. cardosoi group. The NOR-bearing chromosome No. 10 in the karyotype of P. poecilogaster was considered homeologous to chromosome No. 10 in the karyotype of Scythrophrys sp., chromosome No. 9 in the karyotype of Paratelmatobius sp. 1, chromosome No. 8 in the karyotypes of Paratelmatobius sp. 2 and of Paratelmatobius sp. 3, and chromosome No. 7 in the karyotype of P. cardosoi. A hypothesis for the evolutionary divergence of these NOR-bearing chromosomes, which probably involved events like gain in heteochromatin, was proposed.

Copy number of P elements, KP/full-sized P element ratio and their relationships with environmental factors in Brazilian Drosophila melanogaster populations

The P transposable element copy numbers and the KP/full-sized P element ratios were determined in eight Brazilian strains of Drosophila melanogaster. Strains from tropical regions showed lower overall P element copy numbers than did strains from temperate regions. Variable numbers of full-sized and defective elements were detected, but the full-sized P and KP elements were the predominant classes of elements in all strains. The full-sized P and KP element ratios were calculated and compared with latitude. The northernmost and southernmost Brazilian strains showed fewer full-sized elements than KP elements per genome, and the strains from less extreme latitudes had many more full-sized P than KP elements. However, no clinal variation was observed. Strains from different localities, previously classified as having P cytotype, displayed a higher or a lower proportion of KP elements than of full-sized P elements, as well as an equal number of the two element types, showing that the same phenotype may be produced by different underlying genomic components of the P-M system.