Secretly A Mermaid

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This spiky Mexichromis multituberculata is a dorid nudibranch found around Japan and (Southern) China. It usually is 3cm long. Although it is typically seen with purple spots around the mantle (like the one pictured above), it can be found with reddish, blue, or orange spots.

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This is the Irukandji jelly of Australia, and it’s sting can induce something called Irukandji syndrome, where one of the more unusual symptoms is an immense feeling of immediate impending doom, patients suffering from Irukandji syndrome have been reported to be so certain that they’re going to die that they beg doctors to kill them and get it over with. These symptoms generally abate in 4 to 30 hours, but all the same, that’s a truly incredible and terrifying ability.

The Lettuce Sea Slug (Elysia crispata) is a sacroglossan (not a nudibranch, but closely related) sea slug found in tropical areas of the Western Atlantic Ocean and in the Caribbean. It grows to be 5cm long, and participates in the same kleptoplasty shenanigans as most other sacroglossans- it retains the algae it eats and uses its photosythesis as a second food source! With frills pictured above and its ability to photosythesize, it’s no wonder it’s called the Lettuce Sea Slug (although additionally, many are coloured green)!

To post about the miniature melo (Micromelo undatus) may seem a bit odd, as it is not a nudibranch but a closely-related sea snail! Its thinly-calcified shell is easily seen covering half of its back and is patterned with dazzling brown-red lines, a stark contrast to the blue, white-spotted body below. It lives in many tropic waters, whether that be Japan or Florida, and reaches about 3cm in length. It eats polychaete worms, and uses their toxins as its own.

Hermissenda opalescens is a species of brightly coloured sea slug or nudibranch, a marine gastropod mollusc in the family Facelinidae.

Believe it or not, the animal pictured above is really a sea slug (although not a nudibranch)! It is a Sea Angel, a clade of sea slugs that is very small (ranging from 2cm to 5cm), mostly transparent, and lives in almost every ocean. With such a pretty name and shape it is no surprise that their main food source is sea butterflies, an equally interesting-looking sea creature. To eat, sea angels shoot tentacles out of their mouth to grab onto their prey and quickly retract them to gobble the food whole!

The Aegires villosus is a dorid nudibranch that lives in the Indo-West Pacific and grows to be 1.5 cm long. It feeds on calcareous sponges, which all have spicules (features in sponges that deter predators and provide structural support) made of calcium carbonate.

The Hypselodoris bullocki is a well-known dorid nudibranch that comes in many varying colours, from light peach to dark purple. It eats almost exclusively sponges, and sometimes is sold as a pet, although because of its narrow diet it is not recommended to get one. It lives in the Indo-Pacific and grows to be about 4cm long.

The Halgerda toliara is found near Madagascar and South Africa, and is a dorid nudibranch. It is known for its geometric ridges and yellow median line on its back, although it is often confused for the Halgerda formosa! It grows to be about 4cm long.

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The Fried-Egg Nudibranch (Chromodoris annulata) has interesting colouration and an equally interesting (yet fitting) name. Growing to be 10cm long, this slug naturally lives in the Red Sea and Indian Ocean, as well as the East Coast of South Africa to Thailand. However, because of the Suez Canal the nudibranch is an invasive species in the Mediterranean Sea.

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The Spanish Dancer Nudibranch (Hexabranchus sanguineus), is famous for being one of the largest nudibranchs out there- while typically reaching 20 - 30cm, it has been seen growing to be 60cm long! But although this nudibranch is relatively heavy compared to its smaller cousins, it doesn’t let that way it down, as when alerted this nudibranch can swim by contracting and waving its mantle. In fact, this movement it where it gets its name, as the undulations are reminiscent of a spanish dancer moving her dress. Its rhinophores are retractable, and only turns its signature bright red colour as it matures. It feeds on sponges on coral reefs 1 - 50m deep, from the Eastern coast of Africa to Hawaii and Japan!

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