Estudo da herbivoria, com ênfase no ataque da mariposa Hyblaea puera Cramer (Lepidoptera: Hyblaeiidae) em árvores de siriúba (Avicenia germinans L. Verbenaceae) em manguezais do estado do Pará, Brasil

Abstract

The moth Hyblaea puera Cramer is a herbivore of economic importance mainly for its defoliating attack. The attack of this moth has been observed on siriuba trees (Aviceniagerminans L.,Verbenaceae), one of the dominant plants in Brazilian mangroves. This work intends to contribute to the knowledge of coastal ecosystems by studying herbivory attacks, with emphasis on the seasonal fluctuation of H.puera associated with A. germinans plants and at the same time with the seasonal fluctuation of shrimp species in the mangroves of the Pará coast. An attempt is made to prove the trophic relationship by the shrimps' utilization of the large drop in biomass of the trees (leaves, larval remains, pupae, droppings, etc.) during the attack of the moths. Traditional artisanal fishing communities observe an increase in the shrimp population, precisely at times of increased defoliation caused by H. puera. The study is being carried out in the municipality of São Caetano de Odivelas, on Rato Island. The attack of herbivores on A. germinans trees is being studied periodically, calculating the leaves attacked on young and adult trees, in the basal, median and apical portions of the trees. For shrimp sampling a collection methodology is being tested using a 0.5 cm mesh net. Suspended traps are also being used to sample the population of moths and other insects in the area. Data has been obtained on the periodic attack of various herbivores. The leaves of A. germinans are being attacked in greater proportions on adult plants than on young plants and the most frequent attacks are: leaves gnawed from behind, gnawed from above, leaves with galls, eaten leaves, leaves with mines, chewed leaves, and leaves gnawed internally. An attempt is made to relate the types of leaf attacks to the respective herbivore species. It is suspected, that the attacks "leaves eaten, gnawed from behind and gnawed from above" are caused by different types of larval stages of the moth H. puera. During the period studied (January 2000 to May 2001) only in March 20010 was an attack of H. puera detected. We collected 11 larvae attacking young siriuba leaves, from which we obtained the adults reared in the laboratory. The shrimp collection experiment did not show satisfactory results due to the difficulties encountered in the execution of the methodology and the period in which, according to some fishermen, the shrimp population is low at this time of the year.