(Nordman, 1845) (miniature aeolis)

Habitat: Coastal intertidal and shallow sublittoral zone, also found in estuaries; prefers small rock to sea grass bottom and man-made substrate as well; sheltered, low wave action waters.
Life History: Can reach 8 mm in length; color is generally pale yellow to light brown with black speckles; females produce up to 100 eggs; larvae are pelagic; sexually mature at 20 days old; life span is less than one year usually; T. adspersa is a carnivore feeding primarily on hydroids such as Cordylophora caspia; crawls along bottom for mobility.
Native Range: Northeastern Atlantic Ocean, Mediterranean Sea, Black Sea, Caspian Sea.
Nonindigenous Range: Chesapeake Bay, Virginia; Massachusetts (Also found in San Francisco Bay, Elkhorn Slough, and Long Beach, California; Coos Bay, Oregon).
Impacts: it is known to rapidly devour hydroid colonies.
Comments: In Britain this solitary species is referred to as the lagoon sea slug.

  Johnston, 1828 (lagoon sea slug)

Habitat: Marine, sublittoral zone to 129 mm.
Life History: Can reach up to 30 mm; primarily yellow with brown mottling; feeds on soft corals.
Native Range: Northeastern Atlantic from Norway to Portugal.
Nonindigenous Range: Coastal areas of Maine and Massachusetts.
Impacts: Although only present in the Gulf of Maine during the Mid-1980s, it had a severe impact on the soft coral, Alcyoniuum siderium.
Comments: Probable ballast water introduction.