Canibalismo no predador Podisus distinctus (Heteroptera: Pentatomidae): aspectos populacionais e comportamentais

• Autor(a) principal: Sá, Veríssimo Gibran Mendes de
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/914
• topic: Controle biológico; Canibalismo; Predação intra-específica; Competição; Podisus distinctus; Biological control; Cannibalism; Intraspecific predation; Competition; Podisus distinctus; CNPQ::CIENCIAS BIOLOGICAS::ZOOLOGIA::COMPORTAMENTO ANIMAL

Pentatomidae predators are important in pest control in forest systems and Podisus distinctus (Stal) (Heteroptera: Pentatomidae) has potential for application in biological control of Lepidoptera, however, high rates of cannibalism observed in the mass rearing of the predator inhibit the production of a large number individuals. The causes of cannibalism in P. distinctus are still poorly studied. In spite of population factors such as density, age and sex of individuals be appointed as the main motivators of intraspecific predation on insects, complex behaviors such as zoophytophagy, opportunism, kin recognition and parental care may alter the frequency of cannibalism. And besides, the life and fertility tables with different preys and conspecifics may help in understanding the cannibalism and the costs and benefits of this habit. The objectives of this paper were to test the influence of population density, age and sex of individuals in cannibalism in P. distinctus; observe behaviors that affect cannibalism in this specie; and evaluate the development and life and fertility tables of P. distinctus fed with alternative prey Tenebrio molitor (Coleoptera: Tenebrionidae) and conspecifics. Population density raises cannibalism in nymphs until about ten individuals per Petri dish, when going to be a stability and posterior reduction of cannibalism. However, adult P. distinctus showed a linear increase of intraspecific predation. Second instar nymphs showed less intraspecific predation (6.00 ± 3.05%) than third (22.00 ± 2.00%), fourth (22.00 ± 3.60%) and fifth (20.00 ± 5.16%) instar. Nymphs of third to fifth instar showed higher predation on conspecifics than adults. The sex of individuals affected intraspecific predation in P. distinctus and females (16.67 ± 2.05%) cannibalized more than males (6.67 ± 1.40%). Feeding on plants decreased cannibalism on nymphs. The deaths caused by attacks decreased from 20.00 ± 4.22% in absence to 8.00 ± 3.27% in presence of plants, representing a reduction of approximately 60% in mortality. The opportunistic behavior increases the success of the attacks and reduce the chances of reciprocal predation. The number of successful attacks was higher in amputees (1.50 ± 0.33), smaller (0.88 ± 0.40) or in molt (ecdysis) insects (1.38 ± 0.26) compared to control (0.12 ± 0.12), where all individuals were in the same condition. The biological kinship recognition in nymphs decreased predation among sibs, and had not been described previously for Asopinae predators. The deaths caused by attacks decreased from 26.00 ± 4.27% in unrelated nymphs to 10.00 ± 3.33% in sibs, which represents a reduction of approximately 61.5% in mortality. Another inedited observation described in this paper was the behavior of P. distinctus of using conspecifics as sites of oviposition. This habit can decrease the frequency of egg cannibalism and increase the fitness of the parents. The results of the nymphal stage development and life and fertility tables showed that conspecifics are low quality preys. Eating conspecifics not allowed nymphs to survive beyond the third stage. Feeding on conspecifics caused an increase in nymphal development time and decreased nymphs survival by 40%; reduced the number of eggs per female, number of eggs per clutch, number of nymphs per female and adult weight of P. distinctus. This predator showed higher decline in adult survival rate and lower peak production of eggs and nymphs when individuals feed on conspecifics. Besides, this habit has reduced the reproductive and population growth rates. Females fed only on T. molitor showed greater fecundity (92%) than those with mixed diet (60%). Although P. distinctus not get the nutritional benefits of feeding on conspecifics, the cannibalism is important for P. distinctus and acts controlling the population density and preventing resource competition. The maintenance of a low number of predators in the rearing cages can reduce cannibalism rate and increase the mass rearing efficiency, especially among the nymphs, which had a more pronounced cannibalistic behaviour. The use of tactics such as age stratification, and proper management, avoiding overpopulation, can promote the success of biological control programs.