This close-up view of salps, which have aggregated together into a long chain, have brilliant red guts from eating red plankton. They were observed by researchers with the Census of Marine Zooplankton in the Sargasso Sea.
Salps are sac-like, tubular organisms that spend part of their life as individual oozoids (a single, short tube with one red gut), reproducing asexually, and then link up in the aggregate phase, forming long chains. Once attached, the chain of individual oozoids swims and feeds together, and if they run into another chain, will reproduce sexually.
See more photos of cool zooplankton collected by the researchers in this zooplankton biodiversity slideshow.