After events of the past week and harsh treatment (plus a lot of harsh language, too!), today we made the decision to see if our sea stars were SSaDV-positive or negative. Our objective in traveling to the Aleutians was to sample a ‘clean’ population in which neither SSWD nor SSaDV had been observed. In March we sampled over 80 stars and found that to be the case. We also didn’t observe any disease then. On this trip, Elliot and I observed at least a couple of stars which looked a bit suspect, although noted that these were all located near the boat ramp, and all appeared flattened or squished. So it’s quite possible they had been run over.
Step one in our friends’ viral status is to take samples of their tube feet, which is quite simple: we use sterilized forceps to yank off 4 – 5 of these feet and place them directly into DNA extraction tubes. Don’t worry, it doesn’t hurt the animals, they have several thousand and they regrow them rapidly.
Next, we extract DNA from the foot samples using a DNA extraction kit, then we run what’s called Quantitative PCR (qPCR) using a new probe which sensitively detects the presence and abundance of SSaDV. We switched over to a new probe earlier this year after we noted in working with museum specimens that sometimes while we detected one of the genes, we couldn’t detect the other, meaning that we were picking up on a related but not identical virus. So now we run this based on 2 genes and only count detection when we see both light up.
After 3 hrs (1 hr of DNA extraction + 2 hrs on the qPCR machine), the result was known. Drumroll…all our stars are negative. Which isn’t surprising, given they don’t exhibit any wasting disease symptoms, at least none that we couldn’t attribute to the horrid transport conditions, and none are dropping legs. So we have a green light to go with experiments!
The sea stars are happily munching away on mussel bits. Ru especially was seen sucking our several mussels throughout the day. Quite voracious!