Too sick to die? And some new ideas…

After returning from travels to Oregon and Seattle, Ian met with Elliot to discuss how the inoculation experiments had proceeded. As a bit of history, the team (and collaborators) had performed the exact same experiments a number of times, and only sometimes is it successful – most recently the experiments performed by Drew Harvell’s group (Morgan Eisenlord) and Colleen Burge in April 2014 at Marrowstone Labs, when nothing was frozen (think: In n Out Burger) – that experiment was reported in the 2014 PNAS paper. But before that in Winter 2014, Colleen, collaborator Ben Miner, and the Team Aquatic Virus has performed unsuccessful inoculation experiments (or ones producing inconsistent results). We’d assumed that the last experiment’s protocol, which uses fresh material (never frozen) and targeting epidermis and tube feet would be successful in a different species (then it was Pycnopodia, now it is Evasterias). After 10 days or incubation, there were no real disease symptoms in the inoculated stars – so Elliot made the decision to move the animals – which are now easily distinguishable – into shared holding tanks, and to start a new experiment with the other species we have in our lab, Solaster stimpsoni. We’ll keep an eye on the Evasterias, but usually by 10 days there are at least some disease signs – so perhaps these animals are too unhappy to die…

These observations of experimental success, along with discussions about the pattern of disease in the field (timing-wise) and size/shape of animals has led us to to a new hypothesis which we’re going to test moving forward. One must remember that animals inhabiting the ocean are not physiologically the same year-round, so they may react to pathogens in different ways at different times. Sometimes that is a clear relationship – for example, temperature can influence the growth of cellular pathogens. While in others, its related to nutrients and subsequent food availability. We’ll let you know how these experiments go.

Elliiot spent the day Friday setting up another inoculation experiment, this time using the Solasters we have. This time, though, we’re making the inoculum from a different part of the animal, which made it much easier to filter.

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Elliot preparing the inoculum

The Solasters used are looking healthy – it took a while for them to actually start feeding, since in the wild they normally eat Sea cucumbers and barnacles. Elliot finally had success with small chunks of sea cucumber we had in our freezer, and will wean them slowly onto bivalves we have from our local supermarket.

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Inoculated Solaster stimpsoni.

Based on our new hypothesis, there is probably a 10% chance of us seeing any disease during the incubation period. But watch out – the future holds many interesting possibilities…

Meanwhile the Evasterias that are infected from the Seattle Aquarium experienced a hiccup over the weekend when one of them decided to spawn – this in turn had a huge deleterious impact on the aquarium’s water quality. Basically the spawn drives bacterial production in tanks, draws down O2 concentration, and thus causes the rest of the stars to suffer from hypoxia.

Stay tuned!

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