Electrical responses and K+ activity changes to light in the ocellus of the planarian Dugesia japonica

Digestion of starch granules from maize, potato and wheat by larvae of the the yellow mealworm, Tenebrio molitor and the Mexican bean weevil, Zabrotes subfasciatus

Scanning electron microscopy images were taken of starch granules from different sources following exposure in vivo and in vitro to gut alpha-amylases isolated from Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Zabrotes subfasciatus Boheman (Coleoptera: Bruchidae). One alpha-amylase was isolated from whole larval midguts of T. molitor using non-denaturing SDS-PAGE, while two other alpha-amylase fractions were isolated from whole larval midguts of Z. subfasciatus using hydrophobic interaction chromatography., Digested starch granules from larvae fed on maize, potato or wheat were isolated from midgut contents. Combinations of starch granules with isolated alpha-amylases from both species showed similar patterns of granule degradation. In vitro enzymatic degradation of maize starch granules by the three different alpha-amylase fractions began by creating small holes and crater-like areas on the surface of the granules. Over time, these holes increased in number and area resulting in extensive degradation of the granule structure. Granules from potato did not show formation of pits and craters on their surface, but presented extensive erosion in their interior. For all types of starch, as soon as the interior of the starch granule was reached, the inner layers of amylose and amylopectin were differentially hydrolyzed, resulting in a striated pattern. These data support the hypothesis that the pattern of starch degradation depends more on the granule type than on the alpha-amylase involved.

Mechanisms of hopperburn: an overview of insect taxonomy, behavior, and physiology

Hopperburn is a non-contagious disease of plants caused by the direct feeding damage of certain leafhoppers and planthoppers. Although long studied, especially with Empoasca spp. leafhoppers (Cicadellidae: Typhlocybinae), the mechanisms underlying hopperburn have only recently been elucidated. Hopperburn is caused by a dynamic interaction between complex insect feeding stimuli (termed hopperburn initiation) and complex plant responses (termed the hopperburn cascade). Herein we review the nature of the feeding stimuli in hopperburn initiation, especially for Empoasca spp., which we also compare with the planthopper Nilaparvata lugens. Contrary to previous reports, Empoasca hopperburn is not caused solely by toxic saliva. Instead, it is caused by a plant wound response triggered by a unique type of stylet movement, which is then exacerbated by saliva. Electrical penetration graph monitoring has revealed that all Empoasca spp. are cell rupture feeders, not sheath feeders, and that certain tactics of that feeding strategy are more damaging than others. Measuring the proportions of the most damaging feeding led to development of a resistance index, the Stylet Penetration Index, which can predict hopperburn severity in different plants or under different environmental conditions and can supplement or replace traditional, field-based resistance indices.

Photonegative response in brown planaria (Dugesia tigrina) following regeneration

The photonegative response was investigated in regenerated brown planaria (Dugesia tigrina). Old, middle, and young animals were tested, bisected into heads and tails, and allowed to regenerate. Different regeneration times affected function, with generally older planaria achieving full functionality of the photonegative response before younger planaria. Counterintuitively, the heads of the middle and young lost this function initially (despite only needing to regenerate their tails) and regained it over time. The size of the animal was not a factor in the photonegativity response. The biological basis for the photonegative response is complex, requiring nervous and locomotive system function and integration. Using the heads from young planaria may serve as a model in aging, degenerative diseases, or environmental toxins.