Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that over evolutionary time have either completely lost their shells, or have seemingly lost their shells due to having a greatly reduced or internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.
Opisthobranchs is a now informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping.
The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine gastropod mollusks within the larger clade Euopisthobranchia. Bubble shells is another common name for these families of marine gastropods, some of which have thin bubble-like shells. This clade contains more than 600 species.
Aglajidae is a family of often colorful, medium-sized, sea slugs, marine opisthobranch gastropod mollusks. These are not nudibranchs; instead they are headshield slugs, in the clade Cephalaspidea.
Chelidonura varians is a species of small sea slug, a marine opisthobranch gastropod mollusc in the order Cephalaspidea, the headshield slugs.
Chelidonura hirundinina is a species of small and colorful aglajid sea slug, a shell-less opisthobranch gastropod mollusk in the family Aglajidae.
Chelidonura pallida is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.
Chelidonura is a genus of small, sometimes colorful, sea slugs. These are headshield slugs or cephalaspideans, marine opisthobranch gastropod mollusks in the family Aglajidae.
Mariaglaja inornata, also called the inornate headshield slug, is a species of sea slug or headshield slug, a marine opisthobranch gastropod mollusc in the family Aglajidae.
Chelidonura punctata is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.
Philine auriformis is a species of sea snail, a marine opisthobranch gastropod mollusk in the family Philinidae, the headshield slugs. Philine auriformis eats small clams and worms. This species can grow to be as big as 70 mm but are usually 35 mm in adult size. They live on muddy bottoms in the intertidal zone of bays and estuaries.
Chelidonura amoena is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.
Gastropteridae, the bat-winged slugs, is a family of sea slugs, gastropod molluscs in the superfamily Philinoidea of the clade Cephalaspidea, the headshield slugs and bubble snails. The greatest diversity of these colourful small slugs is in the tropical and sub-tropical Indo-Pacific region.
Chelidonura sandrana is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.
Chelidonura livida is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.
Chelidonura mariagordae is a species of sea slug or headshield slug, a marine opisthobranch gastropod mollusc in the family Aglajidae. It is chiefly found in the Bahamas. The species is also known as Chelidonura normani, a name it was given in 2011 by Dupont & Valdés.
Diaphorodoris papillata is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Calycidorididae.
Biuve fulvipunctata, the white-speckled headshield slug, is a species of sea slug or headshield slug, a marine opisthobranch gastropod mollusc in the family Aglajidae. This species is widespread in the Indian and Pacific Oceans but has invaded the Mediterranean Sea since 1961, despite apparently being absent from the Red Sea until recorded there in the 21st century. It is the only species in the monotypic genus Biuve.
Philinopsis speciosa, the blue-lined philinopsis, is a species of sea slug, a shell-less opisthobranch gastropod mollusc in the family Aglajidae. It is native to the Indo-Pacific region.
Tubulophilinopsis gardineri, the Gardiner’s philinopsis, or Gardiner's headshield slug is a species of sea slug, a shell-less opisthobranch gastropod mollusc in the family Aglajidae. It is native to the Indo-Pacific region.
