Neural basis of interactive behaviors in invertebrate animal model systems; impact of anthropogenic environmental changes on nervous system function of local river fauna
We are interested in understanding the neural basis of aggressive/submissive behavior and the establishment of dominance hierarchies, and the manner in which the underlying mechanisms may be modulated. We use as an experimental animal model freshwater prawns of the Macrobrachium genus (primarily rosenbergii and carcinus). Besides providing the well known benefits of other invertebrate model systems (e.g., simpler nervous systems, large identifiable neurons, stereotyped behaviors, etc.), the rosenbergii prawn has the added advantage of establishing dominance hierarchies on the basis of claw morphotype, a fixed characteristic, rather than only the basis of body size. Adult prawns progress through three claw morphotypes (small, yellow and blue) each corresponding to a higher level of dominance within a group.

Our research project integrates a variety of experimental approaches, including immunohistochemistry, confocal microscopy, in situ hybridization, western blot analysis, electrophysiology, and video recorded behavioral observation. We also collaborate with labs that work with proteomics and molecular biology (cloning, RT-PCR, expression). Rotating students can become involved in any of the ongoing projects and get exposed to any or all of these techniques.

We have characterized the location and distribution of various neurotransmitters/modulators (e.g., serotonin, octapamine, dopamine, GABA, glutamate, FMRF, proctolin, etc.) in the central nervous systems (CNS) of all three male and female morphotypes, as well as colocalizations and other forms of interactions among neurotransmitters systems, within each morphotype (e.g., dopamine and serotonin colocalization in single neurons, interactions between serotonin and dopamine neurons and octopamine and FMRF neurons, etc.).

We have used behavioral observation experiments to characterize interactive behaviors amongst morphotypes and have shown that the typical behavior of a morphotype can be manipulated to change into those of another morphotypes through systemic injections of neurotransmitters or agonists and antagonist of specific receptors.

Molecular biology techniques have been used to clone the fist crustacean aminergic receptors (two serotonergic and one octopaminergic). Antibodies and molecular probes have been raised against these cloned receptors and used to map their location and distribution in the prawn’s CNS, using immunohistochemistry, confocal microscopy and in situ hybridization techniques. Quantitative Western blot analysis, real-time RT-PCR, and proteomics techniques are being used to measure levels of expression of these receptors in different regions of the CNS of the three morphotypes of the prawn. [The latter two techniques, proteomics and molecular biology, are conducted in the labs of collaborators].

Other lines of experiments in progress include the expression and characterization of the cloned aminergic receptors, the cloning of other crustacean transmitter and neuropeptide receptors, the use of techniques of differential expression to isolate other target molecules that may be present in higher or lower amounts in each morphotype, and the isolation and identification of water-borne messenger molecules that communicate information on dominance status to animals with a group.

Another project is being developed to study the impact of anthropogenic changes in Puerto Rico urban rivers on behavior and underlying neural circuitry of crustacean species, soon to be expanded to also include other animals, such as insects, reptiles, and amphibians. This project compares the effects of urbanization on Puerto Rican rivers and its aquatic fauna. To do this, we first analyze three representative rivers in which we identify and quantify extraneous chemicals. The animal models, initially lab and local river prawns (rosenbergii and carcinus, respectively), are being exposed to pollutants found in the three rivers and are then being monitored to measure their locomotion and associated behaviors, along with assessment of the integrity of the underlying neural networks.