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BIOLOGICAL CLOCKS AND SYMBIOSIS OF CNIDARIANS

Circadian clocks are self-sustained endogenous timers that enable organisms to anticipate daily environmental rhythms and adjust their physiology and behavior accordingly. Species inhabiting coastal environments are challenged with particularly complex temporal patterns, dominated by tidal and lunar cycles and therefore, have evolved not only circadian clocks but circatidal clocks as well. We investigate natural rhythms and symbiotic complexity in three model cnidarian species: the symbiotic sea anemone, Aiptasia diaphana; the symbiotic coral, Euphyllia paradivisa; and the non-symbiotic sea anemone, Nematostella vectensis. We measure their behavior and physiology using different genomic and molecular toolkits, such as next-generation sequencing (NGS) and CRISPR, to define and characterize the circadian and circatidal clocks in these three cnidarian species. Understanding clock regulation in cnidarians will provide new insight into both the evolution of animal biological clocks and physiology of this important basal group of metazoans.

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MARINE ECOLOGICAL LIGHT POLLUTION

CORALS

Coral reefs are typically found in shallow waters where sunlight is abundant. Besides the role of light in photosynthesis and calcification, specific types of light can impact many aspects of coral biology. Corals are highly photosensitive – many species synchronize their spawning through detection of low light intensity from moonlight, such as the coral reef structure, which is strongly influenced by illumination. Blue light plays a key role in coral growth, algae density, chlorophyll-a content, and photosynthesis rates.

Light detection is likely mediated through photosensitive molecules such as photoreceptors - proteins that convert light into changes in intracellular levels of second messengers, typically cyclic nucleotides in mammals and calcium in invertebrates. On a global scale, the growth of the human population in coastal zones is occurring faster than human population growth in general. Due to this disproportionate growth, coastal habitats have become some of the most vulnerable to light pollution. The term “ecological light pollution” (ELP) has been coined to describe all types of photopollution that disrupt the natural patterns of light and dark experienced by organisms in ecosystems. In our lab, we aim to understand the physiology and molecular cell reaction of primary reef builders to natural light cycles changing daily, monthly, and yearly, as well as the reaction of corals to the ongoing threat caused by Artificial Light at Night (ALAN).

FISH

For most organisms, a variety of life processes are synchronized by the daily, lunar and seasonal light cycles. Animal behavior, from daily activity patterns to seasonal mating and migration, as well as diverse physiological clocks, are extensively driven by natural light. The advances in electricity and modern technology generated the phenomena known as ALAN, a major source of man-made environmental pollution influencing large-scales of both land and marine environments. One vital physiological mechanism greatly influenced by light is the sleep and wakefulness cycle, a critical metabolic state for all animals. Prolonged sleep deprivation and sleep disturbances are associated with various deficiencies from cancer to neurodegenerative disorders, aging, and even death. Recently, our collaborators in the Appelbaum Lab at Bar-Ilan University, revealed that sleep increases chromosome dynamics, which enables efficient repair of DNA damage that is accumulated during wakefulness in neurons of zebrafish larvae. We aim to characterize sleep and wakefulness states in the coral reef fish Chromis viridis, using behavioral criteria in the aquarium and on the reef. This will allow us to examine the effect of ALAN on sleep, DNA damage, repair during sleep, and wakefulness, in these common reef fish in the Gulf of Eilat/Aqaba, Red Sea.

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 CNIDARIAN EPIGENETICS 

"The branch of biology which studies the causal interactions between genes and their products, which bring the phenotype into being" - Waddington, 1942


The phenotype of an animal can't be explained fully by its genes. It is now clear that factors other than the genome contribute to the ecology and evolution of animals. Unlike the genes and regulatory regions of the genome, epigenetic factors such as chromatin spatial configuration can be rapidly modified, and may thus represent mechanisms for rapid acclimation to a changing environment. Until recent, researchers have focused on the balance of mutation and selection as the central explanation for the adaptation of populations to their environment and as the generator for phenotypic expression. These approaches have been central to determine how populations adapt to different environments. However, some organisms also have an incredible ability to acclimate to environmental change during their lifetime. The mechanisms for acclimation are generally assumed to be due to shifts in the regulation of gene expression. A focus on gene regulation alone is surely incomplete because the phenotype of an animal cannot be explained entirely by its genes. Epigenetic mechanisms that result from modifications of the genome without changes in the underlying nucleotide sequence can also have an important impact on the phenotype. For example, corals have a symbiotic relationship with symbiotic algae. It is known that in addition to the genome sequence, epigenetic regulations and symbionts are important factors contributing to the development and dynamic homeostasis of animals. Moreover, since symbionts and epigenetic modifications can be inherited, environmental induced changes could have transgenerational impacts for adaptation.

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CNIDARIAN SYMBIOSIS AND SLEEP

It is conserved as much as it is mysterious, sleep function is an exciting challenge for the scientific community. Indeed, even if this behavioral state makes predation easier, virtually all animals have to do it. Recently, cnidarians have come under the spotlight as it was discovered that Cassiopea spp. jellyfish exhibits sleep-like behavior, yet the molecular level remains mostly unknown. In the lab, we raise and study a variety of cnidarians including emerging marine tractable models such as Cassiopea spp. jellyfish, the non-symbiotic sea-anemone Nematostella vectensis, and the facultatively symbiotic Aiptasia Pellida. Examining the mechanisms of sleep in cnidarians, one of the first metazoan phyla to evolve tissue-level organization and differentiated cell types, can allow us to shed light on the reasons that made sleep evolve throughout evolution. We recently demonstrated that both Nematostella vectensis and Aiptasia Pellida, display a circadian behavioral activity suggesting a sleep-like state. How do neurons generate such behavioral state? How does symbiosis affect it? We combine video tracking behavior assisted by Artificial Intelligence, confocal live-imaging, molecular, pharmacological, and genetic approaches to explore sleep from cellular physiology to behavioral scale. We assume that studying sleep at the root of the animal kingdom will shed light on this fascinating question:

– Why do we sleep? –

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PALEO REEF RECONSTRUCTION AND PHYLOGENETICS

In this project, we aim to reconstruct the paleoecology and growth history of the unique coral reef environment of the Gulf of Eilat/Aqaba (GoE/A), Red Sea. Our goal is to better understand the rate of Red Sea coral recolonization following the termination of the Last Glacial Maximum, whether these reefs represent a true marginal reef-building environment, and how changes in climate during the Holocene and Anthropocene may have impacted coral growth and development in the GoE/A.

Our population genetics project aims to estimate population demographics and genetic connectivity of reef-building corals among reefs within and between Singapore and GoE/A using molecular phylogenetic tools. We focus, in particular, on the coral Pachyseris speciosa, which is common between the two localities in substantial abundance.

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CORAL REEF RESTORATION AND MONITORING

Coral reefs are critical ecosystems for abundant reasons: not only do they provide resources, coastal protection, and economy to millions of people, they also help consume approximately 29% of all CO2 absorbed by oceans. Small-scale coral reefs are often the most vulnerable to environmental and human impacts such as climate change, pollution, and overfishing, urgently requiring innovative restoration methods. Our goal is to use 3D printing technology to create unique, eco-friendly artificial reefs to support the recovery process for degraded reefs and exploited fisheries.
Our artificial reef structures are innovated to be mobile, freestanding ecosystems. By initially deploying structures at healthy reefs, allowing important reef organisms such as corals to grow, and later transporting these “living” structures to declining reefs. This new concept will bring healthy chemical cues to help recruit reef species and fish to repopulate degraded reefs. Mobilizing artificial reefs could improve the restoration process by encouraging settlement of juvenile species, enhancing biodiversity and water quality, and improving resilience of dying reefs. We plan to use a modernized, holistic approach to non-invasively monitor the restoration progress, using environmental DNA (eDNA) of species settling on artificial and degraded reefs. By upgrading restoration methods using 3D printing, mobility, and eDNA, we can provide communities with small-scale reefs, a tool that can be repeatedly reused to safeguard reefs for future generations.