A transparent swimming polychaete carrying a pair of camera eyes as large as its head.
A pelagic polychaete, transparent along its whole length, with a row of paired paddle-like appendages down each side and a pair of very large dark red or black eyes at the head. The eyes are the striking part: they are spherical, carry a lens, and in some animals together take up more volume than the rest of the head. In a torch beam they read as two beads travelling through the water with a faint ribbon behind them.
The eyes are unusually well developed for an annelid and are built on the same general plan as a vertebrate or cephalopod eye, with a lens focusing an image onto a retina rather than simply registering light and shade. What the animals use them for is not settled; prey detection at low light and the location of bioluminescence are both suggested. Feeding is carnivorous, on small planktonic animals taken with an eversible pharynx.
Swimming is by undulation of the whole body with the paddles beating in sequence, and the animal moves faster than most of the other worms met on a blackwater dive. Several genera occur in the group and they are not separable in the water; records are normally kept at that level. Tomopterid worms, which are also transparent and also swim, have much smaller eyes and a more distinctly two-part body.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
