[5] This earns them the title of the "solar-powered sea slugs", and makes them unique among metazoan organisms, for otherwise kleptoplasty is known only among other euthyneurans and single-celled protists.

In photosynthetic members of the group, the wings, or parapodia, can be unfurled to maximise the area of the organism that is struck by sunlight.

The majority of sacoglossans are 1–3 cm in length; they are typically uniform in color because the chloroplasts they ingest end up installed in their own cells.

[9] This process is somewhat mystifying, as the upkeep of chloroplasts usually requires interaction with genes encoded in the plant cell nucleus.

[9] DNA amplification experiments on Elysia chlorotica adults and eggs using Vaucheria litorea derived primers revealed the presence of psbO, an algal nuclear gene.

The switch from active feeding to photosynthesis in sacoglossans is triggered by the shortage of food resources, and typically not preferred.

[14] Another unclear step in the process is how the chloroplasts are protected from digestion, and how they adapt to their new position in animal cells without the membranes that would control their environment in the algae.

[9] Sacoglossans can also use antiherbivory compounds produced by their algal foodstuffs to deter their own would-be predators, in a process termed kleptochemistry.

[citation needed] The majority of sacoglossans are shell-less, consequently, the Plakobranchoidea are commonly described using the vernacular term "sea slugs", which can lead to their confusion with the only very distantly related nudibranchs.

[17] Indeed, at least the Elysiidae, Limapontiidae, and Hermaeidae all bear larval shells, which are spiral, and possess between three-quarters and one complete whorl.

[1] The corresponding fossil record of algae points to an origin of the group deeper in time, perhaps as early as the Jurassic or Cretaceous.

[1] The suborder name comes from the Greek words σάκος sákos "shield" and γλώσσα glóssa "tongue" because the species have single toothed radulas.

Another possibility is that the slugs autotomized to escape predators, but when the researchers tried to mimic an enemy's attack by pinching and cutting the creatures, none cast off their bodies.

Mitoh and her colleagues suspect it may be tied to their ability to survive using the photosynthetic algae in their diet while other energy sources are unavailable.