This is a tiny little sapsucker that I mistook for an aeolid nudibranch, the Green Ballon Nudibranch or Eubranchus rupium. . .  but sacoglossans (sapsuckers_ are a whole different entity — not nudibranchs at all, having no gills.  And since this is the ONLY sapsucker I have come across in British Columbia (they are much more rare in cold waters than they are in the tropics) here is a bit of an introduction: these animals come by their common name “sapsuckers” legitimately.  Nearly all of them use their radular tooth (they have more but they store used ones??) to puncture the cells of algae and suck out their contents — rather vampire-like, but innocent, and totally different in that many are diurnal, and most are herbivores.  Some are bright, brilliant — stunning actually. Others are more subtle, blending into the algae upon which they feed.  Some even have translucent cerata with visible digestive glands that look like coniferous trees, palms and even small hands.  The Brown-streaked Sapsucker documented here is indeed equipped with translucent cerata and visible, tree trunk-like digestive glands.  This little one was found on a clump of branching red algae that was caught in a back eddy  — approx. 8 mm. at a depth of 2 metres max.