Hydra vulgaris are some of the simplest animals with neurons. They only have two thin, near transparent layers of tissue: myo-endodermal and myo-ectodermal layers. Interspersed in each layer is a network of neurons known as the nerve net. All cells in the animal are constantly renewed, which allows Hydra to regenerate after being cut in pieces or dissociated into single cells, though how the nerve net regenerates has not been well studied. Each cell in the animal can be examined simultaneously due to the animals’ small size and simple, translucent body pattern. Hydra also exhibit stereotypical (regular and defined) behaviors. This makes Hydra great models for examining simple signaling pathways from which the complex pathways in vertebrates derive. The Hydra nerve net is composed of circuits that coordinate the behavior of the animal. The most obvious are the contractile burst (CB) and rhythmic potential (RP) circuits. I selectively blocked these circuits to understand how they drive behavior. It has been found that N-[1-(2-phenylethyl)-3-piperidinyl]-1-benzofuran-2-carboxamide (E9), affects Hydra behavior, appearing to block the CB circuit but leaving others, including the RP circuit, uninhibited (unpublished data, Woods Hole MA). I worked to understand the affinity and response rate of this molecule to Hydra by establishing a dose response curve for E9 on Hydra. To determine effective concentrations of E9, I imaged animals in serial concentrations ranging from 3uM-300uM. I then identified the response of neural circuit firing patterns to varying concentrations of E9 by applying this technique to animals that express GCaMP, a protein that fluoresces when bound to calcium, in neurons. I found that 30uM is the lowest concentration of E9 sufficient to block the CB circuit. This research provides a tool for studying the link between circuits and behavior, and allows us to characterize how behaviors depend on identified circuits.

Throughout history, human-induced habitat loss, pollution, and hunting have pressured mammals to adapt to lifestyles that limit human interaction. When humans threaten wildlife, a fitness advantage is provided to animals who avoid human interaction. But what about in protected regions where these threats are limited? Cocha Cashu Biological Station, located in Manu National Park, is an example of one of these regions. While native communities continue to hunt within the research station, overall levels of hunting, deforestation, and pollution, are significantly lower than in the surrounding unprotected areas. Our research team chose to design a study in Cocha Cashu to analyze terrestrial mammal distribution in relation to human habitation in areas where human threats have historically been limited. Our hypothesis was that mammal abundance would increase with distance from human habitation. Our study design involved a northern and eastern transect with a near (N), medium-distanced (M), and far (F) trap location. Each trap location had both a sand and camera trap, and data was collected from the traps morning and night for four consecutive days. On the eastern transect, there was a positive linear relationship between distance from human habitation and number of mammals observed (N: 2 mammals, M: 4 mammals, F: 8 mammals). On the northern route, the highest number of mammals was observed at the medium-distanced location (N: 1 mammal, M: 7 mammals, F: 3 mammals). Overall, our data did not support our hypothesis that mammal abundance increases with distance from human habitation in protected areas. Our results do, however, provide a platform for further research on resource accessibility and its potentially larger influence on mammal distribution patterns than the influence of human habitation.