Abstract
The grasshopper species Orthoscapheus rufipes and Eujivarus fusiformis were analyzed using several cytogenetic techniques. The karyotype of O. rufipes, described here for the first time, had a diploid number of 2n = 23, whereas E. fusiformis had a karyotype with 2n = 21. The two species showed the same mechanism of sex determination (XO type) but differed in chromosome morphology. Pericentromeric blocks of constitutive heterochromatin (CH) were detected in the chromosome complement of both species. CMA3/DA/DAPI staining revealed CMA3-positive blocks in CH regions in four autosomal bivalents of O. rufipes and in two of E. fusiformis. The location of active NORs differed between the two species, occurring in bivalents M6 and S9 of O. rufipes and M6 and M7 of E. fusiformsi. The rDNA sites revealed by FISH coincided with the number and position of the active NORs detected by AgNO3 staining. The variability in chromosomal markers accounted for the karyotype differentiation observed in the tribe Abracrini.
Highlights
The grasshopper subfamily Ommatolampinae (Acrididae) comprises nine tribes and more than 50 genera that have a wide geographic distribution, with most of them being found in North, Central and South America (Amedgnato, 1974; Carbonell, 1977)
The use of base-specific fluorochromes has contributed to the characterization of Constitutive heterochromatin (CH) (King and John, 1980; Santos et al, 1983; John et al, 1985), for Neotropical grasshoppers the data obtained with such probes are limited to a few species of the families Acrididae and Romaleidae (Souza et al, 1998; Loreto and Souza, 2000; Pereira and Souza, 2000; Souza et al, 2003; Rocha et al, 2004; Loreto et al, 2005; Souza and Melo, 2007)
Among the ten Neotropical Acrididae subfamilies studied cytogenetically by Mesa et al (1982), the Copiocerinae, Melanoplinae and Ommatolampinae were characterized by derived karyotypes (81.8%, 48.4% and 42.9%, respectively) that resulted mainly from centric fusions and inversions
Summary
The grasshopper subfamily Ommatolampinae (Acrididae) comprises nine tribes and more than 50 genera that have a wide geographic distribution, with most of them being found in North, Central and South America (Amedgnato, 1974; Carbonell, 1977). The use of base-specific fluorochromes has contributed to the characterization of CH (King and John, 1980; Santos et al, 1983; John et al, 1985), for Neotropical grasshoppers the data obtained with such probes are limited to a few species of the families Acrididae and Romaleidae (Souza et al, 1998; Loreto and Souza, 2000; Pereira and Souza, 2000; Souza et al, 2003; Rocha et al, 2004; Loreto et al, 2005; Souza and Melo, 2007) Other techniques, such as fluorescent in situ hybridization (FISH), have identified important differences in the composition of CH that involve variable quantities of repetitive DNA sequences in these regions, including satellite or ribosomal DNA (rDNA) (Rodríguez Iñigo et al, 1993, 1996; Loreto et al, 2008). In contrast to silver nitrate (AgNO3) staining, FISH does not depend on the presence of a transcription product it permits the identification of active or inactive rDNA sequences in the genome (López-León et al, 1999)
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