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Resumo -O objetivo deste trabalho foi avaliar genótipos de capim-elefante (Pennisetum purpureum Schum.) quanto à resistência à cigarrinha-das-pastagens (Mahanarva spectabilis). Para avaliação da antibiose, aos trinta dias após o plantio, cada planta foi infestada com seis ovos próximos à eclosão, em delineamento inteiramente casualizado, com 30 genótipos e dez repetições. Quarenta e cinco dias após a eclosão das ninfas, avaliou-se a porcentagem de sobrevivência do inseto-praga nos diferentes genótipos. Para avaliação da não-preferência, foram quantificados, quinzenalmente, o número e tamanho de ninfas por vaso, em plantas mantidas em casa de vegetação, onde adultos de M. spectabilis eram periodicamente liberados, em delineamento inteiramente casualizado, com três repetições por genótipo, em dois períodos de amostragem. Os genótipos Cameroon de Piracicaba, Pioneiro, Cuba 169, Santa Rita, Mineiro Ipeaco, Mercker Comum de Pinda e CNPGL 96-27-3 foram selecionados quanto à resistência, pelo mecanismo de antibiose. O número e o tamanho médio das ninfas variaram significativamente em razão do genótipo de capim-elefante, no estudo da não-preferência. Os genótipos Roxo de Botucatu e Pioneiro são candidatos à testemunha suscetível e resistente, respectivamente, pelo mecanismo de antibiose, e os genótipos Cameroon e Cameroon Piracicaba são promissores pelo mecanismo de não-preferência.Termos para indexação: Pennisetum purpureum, Mahanarva spectabilis, resistência a pragas, forrageiras, antibiose, não-preferência. Selection of elephant grass genotypes for resistance to spittlebugAbstract -The objective of this work was to evaluate genotypes of elephant grass (Pennisetum purpureum Schum.) regarding resistance to the spittlebug Mahanarva spectabilis. For antibiosis evaluation, each plant was infested with six eggs near hatching, thirty days after planting, in a completely randomized design with 30 genotypes and ten repetitions. Forty-five days after the nymphs hatched, the insect survival rate was evaluated on the different genotypes. For nonpreference mechanism evaluation, the size and number of the nymphs per pot were assessed every 15 days, in plants kept at greenhouse, where adults of M. spectabilis were periodically released, in a completely randomized design, with three repetitions per genotype in two sampling periods. Cameroon de Piracicaba, Pioneiro, Cuba 169, Santa Rita, Mineiro Ipeaco, Mercker Comum de Pinda and CNPGL 96-27-3 genotypes were selected for resistance, by antibiosis mechanism. In the study of the nonpreference mechanism, the number and average size of the nymphs varied significantly as a function of the elephant grass genotype. Roxo de Botucatu and Pioneiro genotypes are, respectively, susceptible and resistant check candidates by the antibiosis mechanism, and Cameroon and Cameroon Piracicaba genotypes are promising by the nonpreference mechanism.

The present study evaluated spermatozoal capacitation in Farfantepenaeus paulensis. This process has direct applications in aquaculture, and it consists of the ionic, biochemical and morphological changes during the period that the spermatophore is stored or adhered to the thelycum. These changes make the spermatozoa capable of fertilization. The morphological changes of spermatozoal capacitation have been previously investigated only in sicyoniids and open-thelycum penaeids. Thus, this study is the first morphological account of a closedthelycum penaeid. F. paulensis broodstock were captured offshore in southern Brazil, and spermatophores were collected from the terminal ampoule and from the thelycum of sexually mature females that had naturally copulated. The ultrastructure of the spermatozoal capacitation was investigated via transmission electron microscopy. Spermatozoa of F. paulensis show the following changes related to capacitation: (1) the chromatin became less condensed; (2) the acrosomal region became more electron-dense (3) the acrosomal cap became less concave; and (4) the subacrosomal region became much more electron-dense. These results demonstrate that the morphological changes in capacitated spermatozoa of F. paulensis are similar to those previously reported for open-thelycum penaeids, i.e., Litopenaeus species. Further studies on the capacitation process are required, especially to evaluate the interaction between biochemical and morphological changes. Such research could be useful for developing biotechnologies that will allow spermatozoal induction without storing the spermatophore in the thelycum and therefore allow in vitro larval production.

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