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Mercier Lab -- Research Activities

Biology of deep-sea invertebrates

A first component of this research project is to increase our understanding of deep-sea echinoderms and other invertebrates, particularly in terms of reproductive ecology. It focuses on the gonadal development, spawning habits and larval development of species that dwell at bathyal depths and for which no or very few data have been collected to date. Another component is a special project designed to enhance our knowledge of the distribution and biodiversity of deep-sea corals in the Newfoundland & Labrador region. The general goal is to provide novel information on the biology and ecology of cold-water bathyal corals and associated species. Aspects to be investigated include gametogenesis, brooding vs. broadcasting, fecundity, control/timing of reproduction, larval development, growth and symbioses. This research is supported by NSERC and DFO. The main collaborators are J.-F. Hamel (SEVE), E. Edinger (Geography/Biology), K. Gilkinson (DFO), V. Wareham (DFO), S. Dufour (Biology), I. Eeckhaut (Univ. Mons-Hainaut, Belgium) and D. Pawson (Smithsonian Institution, USA).

Control of reproduction in marine invertebrates

Reproductive success in marine invertebrates depends on the synchronization of gamete synthesis and spawning. Mechanisms through which this is achieved involve a number of steps, including perception of environmental cues and interactions via chemical signals. My research has been aimed at determining the roles played by exogenous and endogenous factors in the reproductive success of boreal and tropical species. Initial work with sea cucumbers has revealed that inter-individual chemical communication acts together with environmental factors to ensure synchronous gametogenesis and mass-spawning and that perivisceral coelomic fluid becomes bioactive during spawning events. We also found that many echinoderms and molluscs display lunar and circadian rhythms of aggregation and reproduction. Due to a recent breakthrough in the holding of deep-sea invertebrates, a new segment of my work focuses on the factors underlying reproduction in bathyal species, which are presumably exposed to limited environmental fluctuations, yet may still exhibit seasonal breeding cycles. The short term goals of the present research program are to: 1) find evidence of chemical communication in other marine invertebrates using the techniques developed for sea cucumbers; 2) compare the importance of environmental and chemical cues in the reproductive processes of species from various depths with different breeding periodicities; 3) investigate the level of reproductive synchrony in deep-sea species and elucidate the factors involved in ensuring it; 4) refine knowledge of the bioactive properties of body components over the reproductive cycle using multilevel analyses and bioassays; and 5) investigate the concept of “sentinel” individuals (believed to be more receptive to environmental cues, and to use chemical signals to relay those to conspecifics). The long term goals are to clarify the respective roles played by external factors and interspecific exchanges and investigate how the former can perhaps be translocated via the latter. Better knowledge of biological rhythms and chemical communication in benthic animals could help devise new aquaculture techniques and improved ways to protect marine habitats from environmental disturbances. This project is funded by NSERC Discovery and Research Tools & Instruments grants, and by CFI.

Ecology and reproductive biology of commercially important holothurians

Holothurians, commonly known as sea cucumbers, have been harvested for over 1000 years to supply markets in Asia for beche-de-mer (e.g. the dried body wall of the animal). The demand for beche-de-mer has been growing, especially with the re-entry of China into world trade during the 1980s. However, inadequate management of the sea cucumber fishery has resulted in severe overfishing in many countries, so that natural stocks are depleted almost everywhere within their geographic distribution. Those wishing to restore depleted populations and to develop efficient aquaculture and stock enhancement programs quickly encountered a lack of knowledge of most aspects of the biology and ecology of holothurians. Our research focuses on assessing the complex factors that govern the spawning, settlement, recruitment, feeding and growth of holothurians. The study of larval settlement cues using multiple-choice experiments, together with the investigation of early juvenile ecology has been a major breakthrough in finding and characterizing nursery habitats. Prior to this work, juvenile sea cucumbers were only found accidentally and nursery habitats were in turn largely unidentified. Another goal of the research is to investigate the fundamental biology of boreal and tropical holothurians, including the daily feeding and activity cycles with respect to environmental factors, the symbiotic relationships and the prey-predator interactions. The main collaborators are J.-F. Hamel (SEVE), S. Uthicke (Australian Institute of Marine Science), I. Eckhaut (Univ. Mons-Hainaut, Belgium). Research on the Newfoundland populations of commercial sea cucumbers has been funded by DFA, DFO, CCFI, RDC and the fishing industry.

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