Karyotype, constitutive heterochromatin and nucleolar organizer regions (NORs) in Belosacris coccineipes (Acrididae-Leptysminae)

Abstract

Several techniques including C-banding, fluorochromes and silver staining were used to obtain information about heterochromatin patterns in the grasshopper B. coccineipes. Conventional staining showed a karyotype with 2n = 23 chromosomes in males and 2n = 24 in females, as well as XO:XX sex determination and acrotelocentric chromosomes. The medium-sized X chromosome was heteropycnotic positive at the beginning of prophase I and negative in metaphase I. C-banding revealed heterochromatic blocks in the pericentromeric regions of all chromosomes. Silver nitrate staining in this species showed three small bivalents (S9-S11) as nucleolar organizers with NORs located in the pericentromeric regions. CMA3-positive blocks were seen in pericentromeric regions of pairs M6, S9, S10 and S11. Sequential staining with CMA3/AgNO3 revealed homology between the CMA3-positive bands and NORs of the bivalents S9, S10 and S11. The CMA3-positive block of the bivalent M6 could represent a latent secondary NOR. The results obtained permit us to distinguish two categories of the constitutive heterochromatin in B. coccineipes.<br>Algumas técnicas incluindo bandeamento C, fluorocromos e coloração com nitrato de prata foram utilizadas visando obter informações sobre os padrões de heterocromatina no gafanhoto B. coccineipes. A análise convencional mostrou um cariótipo com 2n = 23 cromossomos nos machos e 2n = 24 nas fêmeas, sistema XO de determinação do sexo e cromossomos acro-telocêntricos. O cromossomo X de tamanho médio mostrou-se heteropicnótico positivo no início da prófase I e negativo em metáfase I. O bandeamento C revelou blocos positivos nas regiões pericentroméricas de todos os cromossomos. A coloração com nitrato de prata nesta espécie evidenciou 3 bivalentes pequenos (S9-S11) portadores de nucléolos com as NORs localizadas nas regiões pericentroméricas. Blocos CMA3-positivos foram visualizados nas regiões pericentroméricas dos pares M6, S9, S10 e S11. Pela coloração seqüencial CMA3/AgNO3 observamos homologia entre as bandas CMA3-positivas e as NORs dos bivalentes S9, S10 e S11. A marcação CMA3-positiva do bivalente M6 poderia representar uma NOR secundária latente. Os resultados obtidos permitiram distinguir duas categorias de heterocromatina constitutiva em B. coccineipes

Cytogenetic analysis of the neotropical spider Nephilengys cruentata (Araneomorphae, tetragnathidae): standard staining, NORs, C-bands and base-specific fluorochromes

“…Thus, these results have shown that the NORs in N. cruentata possess DNA rich in GC base sequences and poor in AT base sequences. NORs are known to possess GC-rich DNA in several plants (Schweizer, 1976), invertebrates (Schweizer et al, 1983;LopezFernandez et al, 1989;Loreto & Souza, 2000), and vertebrates species (Schmid, 1980).…”

Cytogenetic variability among Bradyporinae species (Orthoptera: Tettigoniidae)

“…CMA3+ bands and NORs are quite often associated with each other in insects, especially grasshoppers (e.g. Loreto & Souza, 2010) and katydids (Warchałowska-Śliwa et al, 2009). In comparison with Ephippigerini, heterochromatin in Bradyporini shows a different composition; in this case, the C-blocks were CMA3+/DAPI+, carrying both AT-and CG-rich segments.…”

Karyotypic analysis, constitutive heterochromatin and NOR distribution in five grasshopper species of the subfamily Leptysminae (Acrididae)

“…Leptysminae, in turn, occurs only in the neotropical region and chromosomal studies of this subfamily are scarce, most of them involving standard staining (MESA et al 1982). Among the 22 Leptysminae species studied, 19 showed basic 2n=23,XO karyotypes (MESA et al 1982;MESA and FONTANETTI 1983;BIDAU and HASSON 1984;CONFALONIERI and BIDAU 1986;COLOMBO 1989;LORETO and SOUZA 2000). However, Stenopola pallida, Leptysma argentina (21,XO) and Tetrataenia surinama (19,XO) presented karyotypic reductions due to centric autosomal fusions (MESA et al 1982;BIDAU and HASSON 1984).…”

“…The Tetrataeniini tribe, in turn, comprises 14 genera and occurs from the south of Mexico to the south of the temperate zone in Uruguay and Argentina (ROBERTS 1978;ROBERTS and CARBONELL 1980). Literature data show that most Leptysminae species have a basic karyotype of the 23,XO type in males (MESA et al 1982;MESA and FONTANETTI 1983;BIDAU and HASSON 1984;CONFALONIERI and BIDAU 1986;COLOMBO 1997;LORETO and SOUZA 2000). On the other hand, the occurrence of derived karyotypes is not frequent in this subfamily.…”

“…Neotropical representatives, however, have been less investigated with techniques of chromosomal differentiation. In the particular case of subfamily Leptysminae, chromosome analysis by these techniques are limited to Leptysma argentina (BIDAU and HASSON 1984) and Belosacris coccineipes (LORETO and SOUZA 2000). In the present study, C-banding, basespecific fluorochromes and silver nitrate staining were used for a comparative analysis of the distribution and structure of heterochromatin regions and NORs in five species of grasshoppers of the Leptysminae.…”