RESUMEN
In tropical freshwaters, different species of water bugs (Heteroptera) constitute a guild sharing similar prey resources including chironomid and mosquito larvae. Assuming possibilities of intraguild predation (IGP) among the constituent members, an attempt was made to evaluate the effects of prey and predator density on the mortality of mosquito and chironomid larvae (shared prey), using Laccotrephes griseus Guérin-Méneville (Hemiptera: Nepidae) and Ranatra filiformis Fabricius (Hemiptera: Nepidae) as IG predators and Anisops bouvieri Kirkaldy (Hemiptera: Notonectidae) as IG prey. The predation on mosquito and chironomid larvae varied with the density and combinations of the predators. When present as conspecific IG predators, L. griseus exhibited greater effect on the prey mortality than R. filiformis. The effects on shared prey suggest that the two predators are not substitutable in terms of the effect on the shared prey mortality. The mortality of A. bouvieri (IG prey) at low shared prey density was significantly different (p < 0.05) from high shared prey density. In view of predatory effect of the heteropteran predators on the dipteran larvae, the results suggest possible interference by the presence of A. bouvieri as an intermediate predator. It seems that the presence of heteropteran predators including A. bouvieri as IG prey may benefit the dipteran prey under situations when the density is low in tropical waters. The intensity of the predatory effect may differ based on the species composition at IG predator level. For mosquito biological control, the interactions between the predators may not be substitutable and are independent in their effects.
Asunto(s)
Heterópteros/fisiología , Conducta Predatoria , Animales , Culicidae , Larva , Densidad de PoblaciónRESUMEN
The ontogeny of lactate dehydrogenase (LDH) isozymes in developing Mexican axolotl, Ambystoma mexicanum was investigated by thin-layer isoelectric focusing in polyacrylamide gel. The isoelectric points (pI values) of the isozymes were determined. The minor components generally remained masked during conventional electrophoresis, but became sharp as isofocusing progressed. We identified in developing eggs and embryos five major LDH isozymes, which could also be traced in the ovarian eggs. All these isozymes, except LDH-1, consisted of one major and one minor component. Heterogeneity in axolotl LDH is reported for the first time. The separated isozymes had pI values from 5.24-6.60. Contrary to observations made by others, it was found that the anodal forms of LDH (PIs 5.24-5.80) were prominent throughout, while the remainder (pIs 6.16-6.60) gradually lost their stainability. It thus appears that isoelectric focusing is a possible method for the analysis of protein mixtures and can be successfully applied to problems of differentiation.