Voyage Update 6: Thetys vagina – Giant of the salps and colossal pooper
13 November 2018. By Voyage Leader Dr Moira Decima.
We have been lucky to find a few specimens of the largest of all salp species: Thetys vagina.
T. vagina oozooid. You can see the muscle bands that allow these animals to pump large amounts of water through their bodies very clearly. To the left is the oral siphon (similar to the mouth), where water enters, and to the right, near the end, is the atrial siphon, where water comes out. [Photo: Mike Stukel]
The oozooid (solitary) of this particular species is known to be able to get up to 30cm long, but we measured some specimens that actually exceeded that! Our biggest critter came in at a whopping 33.5 cm (total length, Oral-to-Atrial siphon: 31.5), which is also about 3 times larger than our most abundant friend, Salpa thompsoni.
T. vagina oozooid up close. Can you see what is forming behind that orange part, which is the gut? It’s brown and it’s long… it’s a future poop pellet! Also notice the cell mass that will become a stolon and then a blastozooid chain. [Photo: Mike Stukel]
An interesting thing about the giant T. vagina—it’s poop pellets are huge! We measured a pellet that was about 2cm2, which is about 5-10 times the size of S. thompsoni poop. As part of our work, we are measuring how fast these different sized pellets sink, to estimate how quickly they can get from the surface to the deep ocean.
Not too surprisingly, these big pellets can sink fast!
S. thompsoni (left) and T. vagina (right) poop pellets from one of our experiments, for comparison. Could you guess without knowing which animal made each pellet? [Photos: Moira Decima, NIWA]
Unfortunately, the T. vagina salps are not around in large numbers. This means they are hard for us to study because we only catch one or two in some of our tows—as opposed to hundreds of S. thompsoni—but we are doing are best to find out as much as we can about these giant salps—so understudied and hard to come by but cool as!
Bucket of Thetys vagina blastozooids. Notice the green-blue colouring, particular to this species (the oozooid has it on the projections). We only get one or two of these animals, when we get any, but they are pretty! [Photo: Sadie Mills, NIWA]