Preprint volume - SIBM
Preprint volume - SIBM
Preprint volume - SIBM
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Pre-print Volume - Oral presentations<br />
Topic 2: MARINE ORGANISMS AND ECOSYSTEMS AS MODEL SYSTEMS<br />
Materials and methods – Experiments characterising physiological parameters were<br />
designed to examine individual tolerance, adaptive mechanisms and ecological<br />
relevance in the field. Tolerance: Cell burst assays recorded species survival following<br />
exposure to a severe (10‰ S) hypo-osmotic treatment throughout the first 48h of<br />
development. Species survival was assessed following a period of induced desiccation<br />
and re-immersion into natural seawater. Adaptive Mechanisms: Cell <strong>volume</strong><br />
measurements monitored <strong>volume</strong>tric changes occurring at within zygotes during and<br />
immediately after mild (15‰ S) hypo-osmotic exposure. Sub-lethal effects of hypoosmotic<br />
exposure were tested by exposing zygotes to several dilute salinity<br />
concentrations over varying lengths of exposure time, measuring the ratio between<br />
length/width growth over seven days. Field studies: involved both manipulative and<br />
descriptive experiments. Manipulative experiments transplanted laboratory released<br />
zygotes to high, mid and low shore levels for 24h. Descriptive sampling monitored the<br />
supply of propagules versus percentage recruitment. Wild fucoid embryos were<br />
identified to species level using a pioneered technique relying on auto-fluorescence<br />
using confocal microscopy and ratio image analysis identification.<br />
Results – Tolerance: Resistance to hypo-osmotic shock varied throughout<br />
development in all three fucoid species. Inter-specific differences in tolerance were<br />
also apparent. Embryos of the high shore alga, Fucus spiralis, as expected burst<br />
significantly less than the mid shore, F. vesiculosus, and low shore, F. serratus,<br />
embryos respectively when given the same hypo-osmotic treatment. Fucoid embryos<br />
also encountered hypo-osmotic stress after a period of desiccation followed by reimmersion<br />
to seawater. Bursting was highest among embryos from the low shore (F.<br />
serratus) with survival increasing respectively in F. vesiculosus and then F. spiralis.<br />
Adaptive Mechanisms: To examine mechanisms, we looked at <strong>volume</strong> control during<br />
mild stress exposure the high shore alga, F. spiralis, exerted considerable control over<br />
its internal <strong>volume</strong> preventing rhizoid apex swelling. However, when re-immersed in<br />
natural (32‰ S) seawater, F. spiralis expressed ion loss as a function of drastic rhizoid<br />
shrinking. The mid shore species, F. vesiculosus, demonstrated negligible fluctuations<br />
to its internal <strong>volume</strong> both during exposure and following re-immersion to seawater, no<br />
significant swelling or shrinking. The low shore species, F. serratus, possessed little<br />
internal <strong>volume</strong>tric control, swelling considerably during exposure and once reimmersed<br />
returned to a <strong>volume</strong> comparable prior to exposure. Burst characterisation<br />
indicated that the mid shore species, F. vesiculosus, possesses a high internal pressure<br />
despite not swelling prior to bursting, suggesting that cell walls may be reinforced in a<br />
thickening process. Assessing the sub-lethal effects following various exposure<br />
regimes, higher shore species (F. spiralis and F. vesiculosus) exhibited a negative<br />
response in terms of length/width growth compared to low shore species (F. serratus).<br />
Field studies: Manipulative field sampling showed survival to be highest among higher<br />
shore species, F. spiralis and F. vesiculosus, and lowest survival recorded among low<br />
shore species, F. serratus at all shore levels. Wild embryos of all three Fucus species<br />
could be identified on the basis of their autofluorescence properties. Descriptive field<br />
sampling indicated a significant export of low shore species’ (F. serratus) propagules<br />
to higher shore levels; similarly higher shore species’ (F. spiralis and F. vesiculosus)<br />
propagules were also being supplied to lower shore levels. Higher shore species exhibit<br />
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010<br />
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