Localization of photoreceptors in the cercariae of Proterometra macrostoma (Trematoda: Azygiidae).

The swimming behavior of the cercaria of the digenetic trematode Proterometra macrostoma changes in response to light. However, this cercaria does not possess obvious eyes or eyespots. Using behavioral assays, we were able to show that both intact and distome-removed cercariae swim significantly greater vertical distances under dim, red light than under brighter, white light. Electrophysiological experiments confirmed this result and further showed that the transverse band of the tail, known to control cercariae swimming behavior, was necessary and sufficient for the display of the light-dependent swimming behavior. Together, these data show that the distome is not required for light-dependent swimming behavior in P. macrostoma cercariae and indirectly demonstrates the presence of photoreceptors in the transverse band of the cercaria tail.

Image analysis of small animal feeding behavior: an update.

Recently we published a design for an automated feeding behavior system (Rowley, Stitt, & Hanson, 2003). One disadvantage of this system is that it relied on expensive, custom hardware. Here we present a modified version that replaces the custom hardware with a simple, commercially available webcam and modified the MATLAB analysis software as well. The new system is much less expensive and easier to implement, while still providing for bias-free collection of consumption data in a feeding behavior trial.

Humidity detection and hygropreference behavior in larvae of the tobacco hornworm, Manduca sexta.

Water is a critical resource for any terrestrial animal, especially for a soft-bodied insect such as larvae of the tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae). Strategies for coping with a dry environment might include seeking out regions of high relative humidity that reduce desiccative stress, or to find and imbibe liquid water. Desiccated larvae placed in a linear arena with a humidity gradient preferred the humid end, whereas un-desiccated larvae did not. This behavior was not affected by temperature. Ablation or occlusion of the antennae showed that they are required to mediate this behavior. A series of experiments showed that control larvae oriented towards and imbibed liquid water whereas those whose antennae had been occluded with wax did not. Electrophysiological recordings from the lateral basiconic sensillum of the second antennal segment revealed the presence of at least one hygroreceptive unit that greatly increased its firing rate in response to moist air, decreased firing rates in response to dry air, and showed mild post-stimulatory inhibition.

Image analysis of small animal feeding behavior.

The optimal design of behavioral experiments includes measures to minimize observer bias while maximizing researcher efficiency. To this end, we have developed a reliable, autonomous monitor of animal feeding behavior. Previous studies of caterpillar (Manduca sexta) feeding have relied on human observation for visual evaluation of food consumption at specific time points over the course of several hours. This method is eliminated by our new behavior rig, which collects data automatically. Individual animals are monitored via CCD cameras activated in sequence by a computer. Images are obtained at preset time intervals using a frame grabber to capture still pictures from the cameras. Subsequently, images are analyzed using software written in MatLab to determine food selection and quantify consumption.