The latex of Euphorbia splendens var. hispolii in 12 ppm concentration (12 mg/l) caused 100% mortality for a Biomphalaria tenagophila population in a lotic habitat after 9 hr of dripfeed application. For sentinel snails, in cages placed at the water surface and buried under 0.10 m, the mortality rates varied with the distance from the application point and were: 100% (0 m); 92.6% (50 m) and 94.7% (100). No lethal effects were observed for the other living species in this habitat (Pomacea haustrum and Poecilia reticulata).

Aqueous solutions of the molluscicidal latex of Euphorbia splendens are irritant to the rabbit eye in concentrations higher than 0.35% and to the rabbit skin in concentrations higher than 0.5%. Although this irritant potential does not proclude its use as a molluscicide, special precautions are recommended for hanbdling and application of the product and the hazard of skin tumor-promoting potencial should be carefully investigated before its use for schistosomiasis vector control.

Com finalidade de conhecer melhor o processod e orientação pela luz do caramujo Biomphalaria glabrata foi utilizada a técnica de situação de escolha num labirinto en Y sob esquemas de iluminação vertical ou horizontal. Foram tomadas como medidas de comportamento a distância percorrida (cm) por hora, a direção da locomoção e a localização do animal no labirinto. Procurou-se comparar a ação do estímulo sobre animais jovens e adultos provenientes de populações albina de Santa Luzia (MG) e melânica de Touros (RN), estudados em grupo e isolados. Os resultados mostraram um efeito atrativo da luz sobre todos os grupos estudados. A análise dos dados sugere a existência de dois mecanismos de orientação em relação à luz neste animal como alta foto-ortotaxia e fototaxia positiva, os quais devem influenciar seus deslocamentos no meio. Tais evidências permitem discutir aspectos da dinâmica da distribuição desse molusco no ambiente e de seu relacionamento com as fases larvais do Schistosoma mansoni, do qual é hospedeiro intermediário.

The process of light orientation by the snail Biomphalaria glabrata was studied using the selection technique in a Y-shaped aquarium under vertical or horizontal lighting schemes. Snail behavior was measured on the basis of distance (cm) covered per hour, direction of locomotion, and localization of the animal in the aquarium. A comparison was made of the action of the light stimulus on young and adult animals of albino populations from Santa Luzia (State of Minas Gerais, Brazil) and of a melanic population from Touros (State of Rio Grande do Norte) studied in groups and separately. All groups studied were attracted to light. Analysis of the data suggests the exitence of two orientation mechanisms with respect to light in these animals, i.e. high photo-orthokinesia and positive phototaxis, which influence their motion in the environment. This evidence permitted us to discuss features of the distribution dynamics of these mollusks in the environment and their relationship with the larval phases of Schistosoma mansoni, for which they act as intermediated hosts.