Coral reefs are the most diverse and important marine ecosystems on the planet and
have dominated tropical oceans over the past 250 million years. Scleractinian (reef-building) corals are among the most efficient biomineralizing organisms in nature. Thus, the importance of scleractinian corals to global ocean chemistry, nutrient cycles, and the continental shelf-environment in particular, cannot be underestimated. Paradoxically, although there are some indications for rhythmic behavior, very little is known about the circadian clocks that control the biology of these symbiotic organisms.
The aim of our research group is to understand the dependency between environmental cues (e.g. light and temperature) that underlie circadian rhythms in reef-building corals, in regulating physiology and behaviour. Different species of symbiotic corals serve as a model system to find evidence of a molecular mechanism controlling the rhythmic processes of metabolism, photosynthesis, calcification and yearly reproduction cycles.
We are identifying and characterizing homologs of the known circadian clock genes in several coral and sea anemone species; sequencing transcriptomes using RNAseq and examination of their temporal expression patterns. We are further investigating the melatoninergic system in corals to try and understand the principal biological significance of melatonin in different rhythmic processes of Anthozoans. As melatonin is a key neuro hormone involved in governing the temporal activity of many animals, its role in a basal metazoan is of particular evolutionary significance. In addition, we are working toward a characterization of the circadian clock control of the calcification process in corals. Finally, we are conducting transcriptomic profiling of coral spawning in the Red-Sea, Okinawa and the Great Barrier Reef, in an attempt to elucidate the relative role of the solar and lunar environmental cycles governing the exact time of gamete release.
Cnidarian “macrobiome” symbiosis
We are interested in understanding the interaction and relative role of the macrobiome, including bacteria and algae, on the time keeping mechanism of cnidarians. This study is focused on representative cnidarians (Aiptasia anemone and Euphyllia coral, among others), maintained both under symbiotic and aposymbiotic states, in the field and laboratory, in conjuncture with Hi-Seq sequencing methods.
Tidal rhythms and clocks
Tidal rhythmicity has been documented and studied in a wide range of intertidal organisms. However, to date, little to nothing is known about the underlying molecular mechanisms governing the ‘tidal clock’. Also, it is under dispute whether the tidal and circadian clockworks share the same mechanisms and genes, or are entirely different. We are studying several different animal species (coral, sea anemones and molluscs), using a suite of behavioural, molecular and transcriptomic approaches, in order to deepen our knowledge in this enigmatic field.
Global change effects on cnidarian holobiont
Corals worldwide have been affected by global warming and the accompanying ocean acidification. We are studying coral host gene expression and the changes in coral’s bacterial community following environmental stress. Our aim is to shed light on the role of the symbiotic microbial community on coral resilience to environmental stress. In addition, we are conducting gene expression studies aimed at understanding the cellular mechanisms in various corals possessing different growth forms and corals from different ecosystems - sub tropical (Red Sea) and temperate corals (Mediterranean Sea). Mediterranean corals thrive in a wide annual fluctuation of sea surface temperatures and understanding the compensatory cellular mechanism of these corals could be crucial to forecast the overall fate of corals.
Developing marine model organisms
Cnidarians (corals, sea anemones, jellyfish and hydroids) form a diverse phylum (approximately 9000 species), which live in aquatic environment. There is a growing interest in the use of Cnidarians as model organisms due to several reasons: (1) in phylogenetic terms Cnidarian is a sister group to Bilateria (humans included). (2) Relatively simple body complexity enables to track changes following manipulations. (3) Advances in next generation sequencing (NGS) and the establishment of gene manipulating methods. We use a wide range of model organisms in the base of our research, ranging from the cnidarians, such as Nematostella, Aiptasia and Acropora to Molluscs (limpets).