A small sponge-feeding bubble-shell relative that swims off with flapping parapodia.
A small gastropterid to about 2 cm — a bubble-shell relative rather than a true nudibranch, with a thin internal shell and a pair of broad parapodial flaps folded up over the back. The body is translucent white to grey, patterned with dark spots and finished with an orange to yellow border along the edge of the parapodia and the head shield, and there is a slender flagellum trailing from the rear. Two or three similar species occur across the region, Sagaminopteron nigropunctatum among them, and they are separated on the size and colour of the spots and on the width of the marginal band. That is finer work than most photographs of a 15 mm animal support, and a proportion of the region’s records are best left at genus.
Gastropterids feed on sponges and are found on or beside sponge-covered rubble, which is where to look rather than out on open sand. Disturbed, the animal lifts off and swims with the parapodia beating like wings — slowly, and only for a metre or two, but it is the behaviour that gets one noticed in the first place.
Recorded from about 5 to 25 m. Small, low-contrast and easily passed, and the records almost certainly understate it.
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.
