Putting the year to rest..

And our final installment of highlights from the last year...

3) Anesthesia in mature oysters

In shellfish research, there are many situations in which tissues of individual animals need to be sampled multiple times, necessitating nonlethal sampling methods. In particular, an accurate way to effectively measure fecundity, one of the primary metrics of fitness in our project, would be highly beneficial.  We needed a nonlethal method to remove broods from female Olympia oysters to enable direct measurement of fecundity, and so we explored the possibility of oyster anesthesia.  Although relaxation methods have been developed for a number of oyster species, none were directly applicable or effective for the Olympia oyster, Ostrea lurida. We optimized an anesthetization method to induce gaping in the Olympia oyster.  We tested concentrations of 25-100 g/L MgSO4 and exposure durations of up to three hours on adult Olympia oysters, and measured response, recovery, and survival.  To stimulate opening of the valves to ensure exposure to the anesthetic, we also tested temperature increase and ambient air exposure as pre-treatments. We found the optimal concentration to be 85 g/L in 50% seawater, which resulted in 45% of the animals anaesthetized in two hours; the remaining oysters did not open their shells and were therefore not exposed. We also found pre-treatment with 30 minutes of air exposure and a temperature increase of 10°C to increase the proportion of oysters that opened their shells for exposure to the treatment.  We observed no adverse effects of treatment on subsequent recovery or survival. Future work will assess the influence of microalgae presence on the proportion of open oysters, efficiency of brood removal, and the effect of brood removal on survival. We are planning to use this method to measure fecundity and success in conservation efforts. In addition, this method can accommodate nonlethal tissue sampling.