ABSTRACT
Background & objectives: Indigenous larvivorous fishes bear potential for regulating vector mosquitoes through trophic interactions. The mosquito prey preference of five indigenous larvivorous fishes in the presence of alternative food items was assessed to highlight their use in mosquito vector management. Methods: Laboratory experiments were carried out using the larvivorous fishes Ambassis (=Chanda) nama, Parambassis (=Chanda) ranga, Colisa fasciatus, Esomus danricus and Aplocheilus panchax, as predators and IV instar Culex quinquefasciatus larvae as target prey. Mosquito prey preference of these fishes in the presence of chironomid larvae, tubificid worms and artificial fish foods, in varied proportions, were assessed using preference index. Results: The fishes consumed considerable amount of mosquito larvae both in absence and presence of alternative food items. However, the positive selectivity for mosquito larvae at all densities were significantly (p <0.05) affected by the alternative foods. The chironomid larvae and tubificid worms were consumed proportionately higher than expected (p <0.05), while the artificial fish food was consumed at lower than expected proportions (p <0.05). The niche overlap was significantly similar among the fish species suggesting likeliness in predation pattern and prey preference. Interpretation & conclusion: The results reflect that the alternative food items influence the mosquito prey selectivity and thus the efficacy of indigenous larvivorous fishes. While use of these fishes in the wetlands and allied mosquito larval habitats in different parts of the country is suggested, impact of the alternative prey may affect the successful regulation of mosquitoes. Assessment of appropriate predator-prey ratio under natural habitat conditions is recommended to enhance successful mosquito control by these fishes.
ABSTRACT
Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.
Redes tróficas apresentam geralmente uma variada rede de interações onde múltiplas presas são comuns. Neste contexto, a onivoria vem sendo objeto de intensas análises à luz da estabilidade e estrutura do sistema. A modelagem do termo de preferência pelo predador de topo sobre suas presas pode exercer uma forte influência sobre as dinâmicas transiente e de longo prazo em uma rede trófica onívora composta por três espécies. Claramente, isto tem implicações sobre a estrutura e estabilidade do sistema sob distúrbios tais como o enriquecimento por nutrientes.
Subject(s)
Animals , Ecosystem , Food Chain , Models, Biological , Predatory Behavior , Food PreferencesABSTRACT
The spider Misumenops pallidus (Thomisidae) is commonly found in alfalfa crops. We studied its predatory preferences on potential insect prey, particularly regarding agroecosystems pests. Two kinds of tests were done under normal laboratory conditions: simultaneous presentation of prey (n = 215) and alternative prey test (n = 45). The spiders preferred insects that were mobile, small, without defensive glands and with thin exoskeletons. According to the amount of prey consumed, we established four predation levels: high (> 55%, on adult Drosophila melanogaster flies); intermediate (30%-55% on the defoliator larvae of Rachiplusia nu and adult heteropterans: Horciasinus argentinus and Halticus spegazzinii); and low (10%-30% on the chrysomelids Colapsis sp. and Diabrotica speciosa). The pentatomid Piezodorus guildinii, the curculionid Naupactus sp. and the aphid Acyrthosiphom pisum were not accepted as food. Once the spider captured a prey item it did not accept another, independently of prey item species (82% of trials).
Se analizó la preferencia alimentaria de la araña Misumenops pallidus frente a diferentes potenciales insectos presas, algunos de los cuales son plaga en cultivos agrícolas. Se efectuaron pruebas de presentación simultánea de presas (n= 215) y de presa alternativa (n= 45), en condiciones normales de laboratorio. M. pallidus mostró predilección por insectos móviles, pequeños, de exoesqueleto delgado y sin glándulas repelentes. Se establecieron cuatro niveles de depredación. El grado máximo (> 55%) correspondió a las moscas adultas Drosophila melanogaster. Hubo depredación intermedia (30%-55%) de larvas desfoliadoras (Rachiplusia nu) y heterópteros adultos (Horciasinus argentinus y Halticus spegazzinii); y depredación mínima (10%-30%) de los crisomélidos Colaspis sp. y Diabrotica speciosa. Los pentatómidos Piezodorus guildinii, los curculiónidos Naupactus sp. y los áfidos Acyrthosiphom pisum, no fueron depredados. En el 82% de los casos, una vez que M. pallidus logra cazar su presa, no la cambia por otra (independientemente del tipo de presa considerada).