After a highly successful and productive sabbatical in New Zealand (stay tuned for interesting results), we’re back in action investigating sea star wasting in North America. Reports from collaborators and citizen scientists from the west coast indicate that wasting continues at a low(ish) level in sea star populations this boreal spring at some sites, and at a few there has been a small resurgence in some species hard hit by wasting, like sunflower stars (Pycnopodia helianthoides). However, overall population density of this species remains far lower than pre-2013, and wasting hasn’t entirely disappeared. Coast-wide surveys are underway as part of a large monitoring program (see seastarwasting.org) and by citizen scientist divers in the Puget Sound and British Columbia.
The Cornell team’s current efforts now focus on wasting in the ochre star, Pisaster ochraceus in collaboration with Mike Dawson and Lauren Schiebelhut at UC Merced, John Wares at UGA, and Pete Raimondi at UC Santa Cruz. This new effort will investigate the relationship between wasting susceptibility and host population genetics and microbial ecology. We’re continuing to work on other species as well as we wrap our 4 year investigation of the microbial ecology of wasting – more on the latter soon. A big question in wasting, now that populations have seen a large die-off and consequently evolutionary selection for a resistant population, is whether the risk of wasting is also related to their microbial ecology.
To kick off our investigation, Ian and Chris (new lab manager) are working at the Long Marine Lab (UC Santa Cruz) to perform experiments designed to elicit wasting in ochre stars of variable genotype (they all look the same superficially, but they vary in terms of their DNA sequence in some genes which may confer the ability to cope better with wasting than others) and observe microbial dynamics on/in their tissues. So far we’ve been unable to actually make sea stars sick in our aquarium system in Ithaca, but we have some new leads and working in a flow-through system in Santa Cruz may bear fruit.
Ochre stars hanging out in the common garden
Yesterday we collected individuals at a site nearby and they’re now acclimating in a tank at the lab. We’ve taken samples to determine their ‘genetic identity’ and also determined their sex (which was 50/50 male:female). After an acclimation phase we’ll be hitting them with an environmental perturbation in individual tanks, but for now they’re in what’s called a ‘common garden’, which means they’re all in the same tank.
Now that we have info on their sex and size, how do we tell them apart? Well a cool thing about ochre stars is that they have white nodules all over their body, and what’s interesting is that the pattern of white nodules is unique to the individual (kind of a fingerprint). So we can tell them apart by looking at the pattern at a single place on their body. Ochre stars have a pentagon of these spikes on the very top of their central disc (the middle part of the animal), and within this pentagon there are various patterns of spike. Pretty cool eh?
See the difference in the white dots in the pentagon?
We’ll post more updates as we go along on these experiments, so stay tuned!