ABSTRACT
Abstract Borellia bruneri, a common grasshopper in much of the grasslands of Argentina and Uruguay, is considered, according to the categories widely accepted for defining the pest status of grasshopper species, a "Frequent plague of importance". In order to determine fundamental aspects of its biology and reproduction, three cohorts of B. bruneri were monitored under controlled conditions (30º C, 14L: 10D, 40% RH). The total duration of nymphal development was 50.6 days, both males and females having five nymphal instars. There was a significant difference in the duration of the different stages within each cohort. In the three cohorts, the first instar duration (12.87 days) was longer than the rest, approximately 5.6 days more than the second that was the shortest (7.26 days). The average longevity of female adults was 56.6 days, and in males, 54.4 days. The number of egg-pods per female was 3.5 and the amount of eggs per egg-pod was 10.8. Mean fecundity was 37.9 eggs per female with an oviposition rate of 1.20 eggs/female/day. Finally, knowing the life cycle of B. bruneri is relevant in order to optimize the control measures for this species.
ABSTRACT
In Argentina, the grasslands of Pampas region comprise approximately 15% of the country. As in other grasslands of the world, grasshoppers are among the most important native herbivores. Their economic importance has been recognized in Argentina since the mid to late nineteenth century, since outbreaks of different species have become recurrent phenomena. Therefore, the main objective of this work was to study their diversity and distribution in grasslands of the Southern Pampas region (Laprida county, Buenos Aires province), as one of the most affected areas. The study was conducted during five seasons (2005-10). Sampling sites were represented by the most common plant communities in this area, classified in four categories: native grasslands, disturbed grasslands, implanted pastures and halophilous grasslands. The samplings were conducted from mid-spring to early autumn, with five or six samples per season. We estimated the following population descriptors: species richness (S), eveness (E), dominance (J), and diversity index (H´). In order to evaluate the similitude of the grasshopper communities present in the different plant communities, we used qualitative and quantitative coefficients of similitude. A total of 22 species of grasshoppers were collected, of which 21 belong to the family Acrididae. The subfamily Melanoplinae was the most diverse with eight species. The largest species richness was recorded in native grasslands (18). The different communities of grasshoppers had similar indices of evenness and dominance (p>0.05). Considering all plant communities, the average value of Shannon-Wiener index was 1.58±0.075. There was a positive correlation between evenness index and species richness (p<0.05). The diversity index H’ was different between plants communities (p<0.05), and it was higher in the disturbed grassland (1.75±0.096, p<0.05) than in the halophilous grasslands (1.34±0.12). Native and disturbed grasslands had a higher plant richness than halophilous grasslands and implanted pastures (p<0.05). There was a positive relationship between plant richness and grasshoppers species richness, and diversity of grasshoppers. According to the qualitative indices applied, the similitude between different grasshopper communities was higher than 60%. In general, the species that had a higher frequency of occurrence showed greater abundance and distribution. Covasacris pallidinota, Dichroplus elongatus, D. maculipennis, Borellia bruneri and B. pallid were the most widely distributed species, most of them (12) showed a restricted distribution and few (five) an intermediate distribution.
Los acridios son componentes nativos de los pastizales, dichos sistemas han sido modificados debido a la intensificación de las actividades agrícola-ganaderas y por lo tanto se considera importante estudiar las comunidades de acridios asociadas. Se estudió la diversidad y distribución de acridios en el Sur de la región pampeana a través de muestreos realizados en las comunidades vegetales más representativas del partido de Laprida, provincia de Buenos Aires, durante cinco temporadas (2005-2010). Se recolectaron 22 especies. La subfamilia Melanoplinae fue la más diversa (ocho especies). La mayor cantidad de especies se observó en los pastizales nativos (18). La diversidad en los pastizales alterados (1.75±0.096) fue superior (p<0.05) a la de los pastizales halófilos (1.34±0.12). La riqueza de plantas en los pastizales nativos y los pastizales alterados fue superior (p<0.05) a la de las demás comunidades. Se registro una relación positiva entre la riqueza de plantas y las variables riqueza y diversidad de acridios. La similitud entre las comunidades de acridios estimada por los índices cualitativos fue superior al 60%. En general, las especies que tuvieron una mayor frecuencia de aparición, mostraron una mayor abundancia y distribución. Covasacris pallidinota, Dichroplus elongatus, D. maculipennis, Borellia bruneri y B. pallida fueron las de mayor distribución, cinco especies tuvieron una distribución intermedia y la mayoría (12) una distribución restringida.
Subject(s)
Animals , Biodiversity , Grasshoppers/classification , Poaceae , Argentina , Population Density , Population DynamicsABSTRACT
Variação do peso fresco em Cornops aquaticum (Bruner) (Orthoptera, Acrididae) associado a Eichhornia azurea (Sw) Kunth (Pontederiaceae) em uma baía no Pantanal de Poconé, Mato Grosso. Cornops aquaticum (Bruner, 1906) (Orthoptera, Acrididae) desenvolve seu ciclo de vida sobre macrófitas aquáticas da família Pontederiaceae. Como os gafanhotos são capazes de responder às mudanças sazonais, a alternância de períodos que ocorre no Pantanal pode refletir em sua biologia. Este estudo foi desenvolvido no Pantanal de Poconé - MT, com o objetivo de avaliar possíveis variações no peso fresco dos adultos e ninfas de C. aquaticum. Durante o período de março/2006 a fevereiro/2007 coletaram-se mensalmente, 50 indivíduos de C. aquaticum. Um total de 600 indivíduos foi avaliado, sendo 43,5 por cento adultos e 56,5 por cento ninfas. Os maiores valores de peso fresco total ocorreram nos meses de setembro (9,106g; 0,182g/indivíduo) e outubro/2006 (8,865g; 0,177g/indivíduo) e os menores em março/2006 (3,413g; 0,068g/indivíduo). Nos indivíduos adultos os maiores pesos frescos foram registrados em setembro/2006 (8,680g; 0,223g/indivíduo) e outubro/2006 (8,654g; 0,234g/indivíduo), no final do período de seca, e o menor em março/2006 (1,792g; 0,138g/indivíduo), durante o período de cheia. As ninfas tiveram o maior peso fresco em abril/2006 (2,913g; 0,076g/indivíduo) início da vazante, enquanto o menor peso fresco ocorreu em outubro/2006 (0,211g; 0,016g/indivíduo) início da enchente. Apenas a variação no peso fresco médio das fêmeas foi significativa (f = 6,43; p = 0,001), com os maiores registros durante o período de enchente, o que pode evidenciar uma estratégia reprodutiva.
Cornops aquaticum (Bruner, 1906) (Orthoptera, Acrididae) develops its life cycle on aquatic macrophyte of the Pontederiaceae family. As grasshoppers are able to respond to the seasonal changes, the alternation of periods that occurs in the Pantanal may reflect in their biology. This study was carried out in the Pantanal of Poconé- MT, with the aim of evaluating possible variations in the fresh weight of the adults and nymphs of C. aquaticum. From March/2006 to February/2007, 50 individuals of C. aquaticum were collected each month. A total of 600 individuals was assessed, 43.5 percent of which were adults and 56.5 percent nymphs. The highest values of total fresh weight occurred in September (9.106g; 0.182g/individual) and October/2006 (8.865g; 0.177g/individual) and the lowest in March/2006 (3.413g; 0.068g/individual). Among the adult individuals the highest fresh weight was registered in September/2006 (8.680g; 0.223g/individual) and October/2006 (8.654g; 0.234g/individual), at the end of the dry period, and the lowest in March/2006 (1.792g; 0.138g/individual) during the flood period. The nymphs had the highest fresh weight in April/2006 (2.913g; 0.076g/individual) at the beginning of the draining period, whereas the lowest fresh weight occurred in October/2006 (0.211g; 0.016g/individual) at the beginning of the flood period. Only the variation in the average fresh weight of females was significant (f = 6.43; p = 0.001) with the highest recordings occurring during the flood period, what may show a reproductive strategy.