World’s Top 10 Most Amazing Sea Slugs

Sea slug is a common name which is applied to some marine invertebrates that more or less resemble terrestrial slugs. Most creatures known as sea slugs are actually slugs, i.e. they are sea snails (marine gastropod mollusks) that over evolutionary time have lost their shells, or have a greatly reduced shell or an 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.
The phrase "sea slug" is, however, also sometimes applied to taxa in other phyla, such as the sea cucumbers, which are not mollusks but echinoderms. Although the other animals sometimes called "sea slugs" are not gastropods, they are nonetheless soft-bodied, and their overall shape is slug-like. (source WIKI)

 The word ‘slug’ tends to conjure images of gross cabbage-eating creatures that leave slime trails in their wake; ugly drab-colored garden pests that wouldn’t be entered into even the lowliest of beauty contests. In the ocean, however, slugs can be quite the opposite… 

Below shows the World's Top 10 Most Amazing Sea Slugs

10 – Cyerce nigricans (source) Although most species of Cyerce, and the related genus, Polybranchia , are cryptically coloured, Cyerce nigricansbreaks the rule. It is one of the ‘icon’ species of the Great Barrier Reef, often being used in tourist posters and brochures. As with many brightly coloured sea slugs this species produces distasteful secretions, and the cerata are easily cast (autotomy)when the animal is disturbed.Distasteful secretions and autotomy are two common defensive strategies sea slugs use against predatory fish.

9 – Nudibranch (source) Nudibranchs live in oceans all over the world. These often brilliantly-colored animals are related to snails and slugs, and there are thousands of species of nudibranchs. There are two main types of nudibranchs – dorid nudibranchs, which have gills on their posterior (back) end, and eolid nudibranchs, which have obvious cerata (finger-like appendages) on their back.

8 – Nembrotha Kubaryana (source) This relatively large species, sometimes growing more than 5 inches long, seems to range in color. Essentially black with green pustules, or green longitudinal ridges, there is a bright orange border to the foot and around the oral lappets. In some specimens the rhinophores and gills have orange markings but in others, these are green. In Western Australia the black background region can have pinkinsh orange spots or elongate marks.

7 – Chromodoris lochi (source) Of these whitish species with three black lines, the most characteristic feature of Chromodoris lochi is the plain coloured gills and rhinophores which range in colour from a translucent straw colour to dull orange or pink.

6 – Chromodoris reticulata (source) The animals perform dual sexual roles during copulation. They give sperm to a mating partner while simultaneously receiving sperm, which they store for later insemination. Scientists observed sex between sea slugs that they had captured during scuba dives and held in a tank. After each coupling, which lasted between dozens of seconds and a few minutes, every slug discarded its penis – a thread-like organ that it projects from its side into a partner’s vagina.

5 – Nembrotha Cristata (source) Similar in size and colour to Nembrotha kubaryana, its main point of difference is the green border to its foot. It also feeds on a green compound ascidian which Willan & Coleman (1984) identify as Eudistoma olivaceum. Perhaps this is a biological difference from Nembrotha kubaryana, which is shown feeding on a blue solitary ascidian.

4 – Elysia crispata (source) Large elysiid, up to 50 mm long and 30 mm wide with prominent parapodia which are very folded at the edge, with both primary and secondary semipermanent folds. The parapodia on each side fuse just in front of the pericardial hump, to form a barrier between the head and the pericardium. The green colour in E. crispata is much more localised in certain areas of the body than in E. clarki. The dorsal surface between the parapodia of well-fed E. crispata is generally green, interspersed with much larger white spots which, unlike those of E.

3 – Hypselodoris apolegma (source) Hypselodoris apolegma differs from H. bullocki mainly in colour. The background colour is a rich pinkish purple with a white border to the mantle. At the edge of the mantle the border is solid white but inside this is a region of varying width in which the white forms a reticulate pattern gradually merging in to the pinkish purple. The rhinophore stalks and the base of the gills is an intense purple, the rhinophore clubs and the gills are orange yellow. I can find no anatomical grounds to place this ‘species’ in the genus Risbecia.

2 – Philinopsis gardineri (source) The Aglajidae are all carnivorous hunters, and species of Philinopsis are usually found burrowing in sand or sandy mud. There are two groups of species at present placed in the genus Philinopsis. The “typical” group, represented by Philinopsis cyanea , have a large partially eversible buccal bulb which is used to catch the bubble shells and other opisthobranchs which are their prey. Philinopsis gardineri represents the second “atypical” group which have a long muscular, tubular buccal bulb.

1 – Glaucus atlanticus (source) Glaucus atlanticus and its close relative,Glaucilla marginata, live in close association with what Sir Alistair Hardy described many years ago as “The Blue Fleet” – the siphonophores such as Physalia, Velella, Porpita and the other associated animals including the “Violet snails” of the genusJanthina. All these animals float on the surface of the ocean being carried by the currents and the winds. Most of us are only aware of their existence when days of onshore winds blow great fleets of them on to the beaches, causing pain and angst for swimmers.



  1. Absolutely beautiful.One of natures wonders

  2. Fascinating website. Thanks!


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