The comparative mitogenomics and phylogenetics of the two grouse-grasshoppers (Insecta, Orthoptera, Tetrigoidea)

OBJECTIVE: This study aimed to reveal the mitochondrial genomes (mtgenomes) of Tetrix japonica and Alulatettix yunnanensis, and the phylogenetics of Orthoptera species. METHODS: The mtgenomes of A. yunnanensis and T. japonica were firstly sequenced and assembled through partial sequences amplification, and then the genome organization and gene arrangement were analyzed. Based on nucleotide/amino acid sequences of 13 protein-coding genes and whole mtgenomes, phylogenetic trees were established on 37 Orthoptera species and 5 outgroups, respectively. RESULTS: Except for a regulation region (A+T rich region), a total of 37 genes were found in mtgenomes of T. japonicaand A. yunnanensis, including 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes, which exhibited similar characters with other Orthoptera species. Phylogenetic tree based on 13 concatenated protein-coding nucleotide sequences were considered to be more suitable for phylogenetic reconstruction of Orthoptera species than amino acid sequences and mtgenomes. The phylogenetic relationships of Caelifera species were Acridoidea and Pamphagoidea > Pyrgomorphoidea > Pneumoroidea > Eumastacoidea > Tetrigoidea > Tridactyloidea. Besides, a sister-group relationship between Tettigonioidea and Rhaphidophoroidea was revealed in Ensifera. CONCLUSION: Concatenated protein-coding nucleotide sequences of 13 genes were suitable for reconstruction of phylogenetic relationship in orthopteroid species. Tridactyloidea was a sister group of Tetrigoidea in Caelifera, and Rhaphidophoroidea was a sister group of Tettigonioidea in Ensifera.

Metaphase I orientation of Robertsonian trivalents in the water-hyacinth grasshopper, Cornops aquaticum (Acrididae, Orthoptera)

Trivalents resulting from polymorphic Robertsonian rearrangements must have a regular orientation in metaphase I if the polymorphisms are to be maintained. It has been argued that redistribution of proximal and interstitial chiasmata to more distal positions is necessary for a convergent orientation, the only one that produces viable gametes. Cornops aquaticum is a South-American grasshopper that lives and feeds on water-hyacinths, and has three polymorphic Robertsonian rearrangements in its southernmost distribution area in Central Argentina and Uruguay. The orientation of trivalents in metaphase I, the formation of abnormal spermatids and the frequency and position of chiasmata in the trivalents, was analysed in a polymorphic population of C. aquaticus. In this study we observed a correlation between the number of trivalents with the frequency of abnormal spermatids; additionally, the number of chiasmata, especially proximal and interstitial ones, was strongly correlated with the frequency of the linear orientation. Therefore we confirmed our previous assumption, based on other evidence, that the chiasmata redistribution in fusion carriers is essential to the maintenance of the polymorphisms.

Chromosome polymorphisms in natural populations of the South American grasshopper Sinipta dalmani

Six populations of Sinipta dalmani from the provinces of Buenos Aires and Entre Rios (Argentina) were analyzed. The populations of "El Palmar" National Park (Entre Rios) were polymorphic for pericentric inversions in pairs M4 and M7 and for a centric fusion involving pair M5 and the X chromosome. The M4 inversion remained similar over time and the karyomorphic frequencies did not depart from those expected according to the Hardy-Weinberg equilibrium. The analysis of chiasma frequency and distribution showed clear intra- and interchromosome effects of the different chromosome rearrangements. Both inversions and centric fusions were related with total or partial crossing over restriction in heterozygous condition, leading to a genetic differentiation between rearranged and non-rearranged chromosomes. The chromosome polymorphisms analyzed herein were associated with an increase in the number of terminal chiasmata both in the rearranged chromosomes (heterozygous centric fusion and homozygous M4 inversion) and in the other chromosomes (M4 inversion). Our results showed that the chromosome polymorphisms in S. dalmani may be associated with a significant decrease in genetic recombination, which may explain in part their maintenance in some areas of its geographical distribution.

Localization of HSP single-copy genes by inexpensive, permanent non-fluorescent in situ hybridization on meiotic chromosomes of the grasshopper Schistocerca pallens (Acrididae)

There have been many studies on Schistocerca gregaria and Locusta migratoria, which are important grasshopper pests in many parts of the world. However, the main pest grasshopper species in Brazil, S. pallens, Rhammatocerus schistocercoides and Stiphra robusta, are very poorly characterized genetically. We adapted a permanent in situ hybridization method to extend the genetic characterization of S. pallens by mapping the single-copy genes Hsp70, Hsp83, Hsp27, and Ubi on meiotic chromosomes. Hsp70 was mapped on the L2 chromosome, in which 82% of the signals were observed. Hsp83 was mapped on a medium-sized chromosome, on which 81% of the signals were observed, tentatively identified as M7. The hybridization signals for the Hsp27 gene were detected on the L1 chromosome at a frequency of 58%. The main hybridization site of the Ubi probe was on the L2 chromosome, with 73% of the signals. All mapped genes also presented secondary hybridization signals, always at frequencies below 30%. These are the first single-copy genes mapped for S. pallens and also for the Acrididae family. Since the Acrididae generally present very similar karyotypes, these data are useful as new landmarks for chromosome identification and as a tool for phylogenetic studies on the genus Schistocerca and for comparison with other insects.

Ronderosia ommexechoides: a new species of Brazilian Dichroplini (Orthoptera: Acrididae, Melanoplinae)

A new species of the genus Ronderosia Cigliano 1997 is described. Color illustrations of the female and male, drawings of female and male external genitalia as well as drawings of its phallic structures and photographs of the chromosomes are included.

Uma nova espécie do gênero Ronderosia Cigliano, 1997 é descrita. Ilustrações em cor de fêmea e macho, desenhos de fêmea e genitália externa do macho, assim como desenhos da estrutura fálica e fotografias de seus cromossomos são incluídos.

Micro-and macrospermatid production induce by meiotically unstable B-chromosomes in two species of grasshoppers (Acrididae)

Os efeitos dos cromossomos B na formaçäo de esperma anormal (no haplóide) foram investigados em duas espécies de gafanhotos, Dichroplus pseudopunctulatus e Sinipta dalmani. Um pequeno cromossomo B telocéntrico foi estudado em machos da primeira espécie. Quando o B se encontrava em dose simples, ele apresentava um comportamento muito irregular que incluia retardo nas primeira e segunda divisöes meióticas. Como resultado, foram observados grandes números de microespermátides portadoras do B atrasado nos machos B. Um macho que possui dois cromossomos B näo mostrou um aumento significativo na produçäo de microespermátides, fato este que está correlacionado com o comportamento meiótico regular do bivalente B. Näo foi observado aumento na produçäo de macroespermátides nos machos portadores do B, e é evidente que um mecanismo de eliminaçäo age sobre o cromossomo B desta espécie. Em S.dalmani foram encontrados dois pequenos cromossomos B; um deles induzia divisäo celular defeituosa, provavelmente através do seu comportamento meiótico falho, resultando em grande proporçäo de espermátides diplóides (cerca de 50%), com consequente reduçäo de fertilidade. Os efeitos dos cromossomos B na freqüência de quiasmas foram também registrados. Os efeito do B de D.pseudopunctulatus aumentava significativamente a freqüência média de quiasmas por célula, enquanto que, inesperadamente, os cromossomos B de S.dalmani pareciam diminuir a freqüência de quiasmas significativamente. A conseqüência da produçäo incrementada de esperma anormal e a modificaçäo das freqüências de quiasmas através da presença de cromossomos B säo avaliadas em termos de seus resultados evolutivos e citológicos