Hawaii has many types of opisthobranchs,
better known as sea slugs, some
of which are undescribed species. Many species experience population
surges, abundant some years and absent others, or seasonal surges.
Most live less than a year and will be found near the specific food they eat
including seaweed and a wide assortment of small invertebrates
such as sponge, cnidarians, and
mollusks. Slugs that feed upon green
seaweed store ingested chloroplast cells within their mantle for photosynthesis.
Hares produce a purple ink from red algae when disturbed. Others may
produce toxic compounds from food or store stinging cells in the body as defense
against predators. Animals with somewhat transparent flesh will assume the
color of their prey. Opisthobranchs are found under stones, on
shaded walls, or within caverns. The pelagic Glaucus
atlanticus floats on the sea surface. As with many
invertebrates more may be seen at night.
& Fiene's Sea Slugs of Hawaii website