Collaborative Research: Mechanisms Underlying Circatidal Rhythms in Parhyale Hawaiensis

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The tides profoundly impact the behavior and physiology of marine organisms. In response, many species have evolved internal timers called circatidal clocks to anticipate tidal changes. These clocks control when animals living near the coastline forage, rest and reproduce, for example. Understanding the mechanisms underlying circatidal clocks has proven challenging because of the lack of model organisms that are amenable to gene-level manipulations. Parhyale hawaiensis is a coastal crustacean in which such manipulations are possible. We have established protocols to synchronize and observe circatidal behavioral rhythms in Parhyale. We are thus well-positioned to elucidate the fundamental mechanisms underlying circatidal timing. Our first goal is to elucidate the fundamental properties of circatidal clocks. In particular, we aim to reveal how Parhyale uses cues, such as water levels and turbulence, to synchronize its behavior with tides. Our second objective is to identify the genes that control the circatidal clock, and to determine which physiological processes are under its control. Our work should thus provide a much-improved understanding of how animals cope with the challenges associated with ever-changing water levels at the coastline. In this work, we will involve undergraduate underrepresented minority (URM) students through the “Biological Discovery in Woods Hole” REU program (NSF DBI 1659604). We will also engage high school URM students in Worcester through the creation of a “Chronobiology club” that will expose them to research in biological timing. Finally, we will introduce students at the Puerto Rico Center for Environmental Neuroscience to methods of gene editing in non-standard research organisms.Intertidal organisms use circatidal clocks to adapt their physiology and behavior to rhythmic tidal changes, in a similar fashion that circadian clocks allow organisms to anticipate daily environmental oscillations. Although the existence of circatidal clocks has long been established, little is known about how they operate. By contrast, the circadian clock is well understood and can therefore serve as a model for hypotheses regarding how the circatidal clock is constructed and functions. Parhyale hawaiensis is an intertidal crustacean amenable to genetic manipulations. We have developed methods to entrain Parhyale’s circatidal rhythms to artificial tides and observe circatidal swimming behavior. We aim to identify the environmental cues that entrain circatidal behavior and determine whether the Parhyale’s circatidal clock entrains to different natural tidal patterns. We also aim to elucidate the molecular mechanisms underlying circatidal rhythms. We will use CRISPR/Cas9-guided genome editing to determine whether core circadian clock genes also generate circatidal rhythms. We will profile gene expression across the tidal cycle to identify core circatidal genes and genes regulating organ-specific physiology. Our work should decisively advance our understanding of circatidal clocks, from their interactions with environmental inputs to the molecular mechanisms that generate them. URM students participating in the NSF-supported “Biological Discovery in Woods Hole” program will be involved in this work. A “Chronobiology club” will be created to expose high school URM students in Worcester to research in biological timing. Finally, students at the Puerto Rico Center for Environmental Neuroscience will be introduced to gene editing in non-standard research organisms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.