Sea cucumbers are slippery tube-shaped echinoderms which inch along the ocean floor eating detritus, earning the affectionate title “vacuum cleaner of the sea.” These tubular creatures are one of my favorite marine invertebrates for many reasons, not least of which is their amazing ability to eject their digestive system and some other choice internal organs and regrow an entirely new set within a matter of weeks!
Cucumbers are a popular dissection specimen for biology labs, so it was not difficult to get my hands on one. The cucumber’s innards are pretty straightforward. The buccal tentacles capture food either by dusting the ocean floor or filtering tiny particles out of the water. These tentacles are brought to the mouth and licked, and then nutrients pass through a double looping tube gut to exit through the cloaca. Other than gut, the cucumber has a simple circulatory system (not shown for clarity), and a respiratory tree (sort of like gills) so the cucumber can “breath.” All these soft innards protected by five longitudinal muscle strips, and wrapping circular muscles which hold everything in and allow the cucumber a degree of freedom in body shape and hardness unknown to most creatures.
Spilling its guts
When a cucumber eviscerates, it may spew some or most of its guts. Tissue around the pharyngeal retractor muscles, and muscles around the introvert (sort of like a neck if it had one) and around the cloaca start to soften. The cucumber can accomplish this at will, and in a matter of minutes may have completely detached gut from the body. The mesentery (the thin membrane in which the gut tube is suspended) stays in place. This will serve as a roadmap as the new gut regenerates.