Mercier Lab -- Research Activities
Biology of deep-sea invertebratesA 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 1980’s. 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. This research focuses on assessing the complex
factors that govern the spawning, settlement, recruitment 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 and the fishing industry.
