quinacridone

Lovely story from The Guardian

It was September 2014. I’d just started working front of house in a fancy hotel in Edinburgh. I spent most of my shifts with a paper napkin pressed to my nostril, as I had been getting lots of nosebleeds. I would soon find out why.

A few weeks earlier, I’d been travelling in Vietnam. I had rented a moped and had the time of my life driving around. I soon crashed but luckily was wearing a helmet, so only got a small bump on my head.

A few days afterwards, I started to intermittently spot blood from my right nostril. I assumed it was from the crash and didn’t think too much of it. I was 24 and too busy partying to take anything like that seriously. I danced the nights away while ignoring the persistent blockage in my nose.

Reality came flooding back after returning to cold Glasgow. Nothing had changed with my nose, so I went to the GP. The doctor told me that it didn’t sound like anything to worry about. I was advised to use Vaseline on the area to keep the nostril lubricated and was sent on my way.

A week later, I moved to Edinburgh for my job. That’s when I started to feel frustrated with my constantly stuffy nose. I wasn’t in pain, but sleeping was difficult. I would blow my nose to try to clear the blockage, but it would only lead to nosebleeds. Things started to get particularly weird when I was having showers. Through all the humidity, I could feel a thick, slimy thing moving down my nose.

I had a day off work; it had been a month since I returned from abroad. My friend Jenny was coming from Glasgow to meet me for dinner. I was in the shower when I felt the all-too-familiar feeling, but this time I glimpsed something hanging out of my nostril. I jumped out and raced to the mirror, frantically wiping off the steam. I saw a clot hanging out – then recoiled in horror when I saw ridges running along a thick black body.

I rushed out of the house to see my friend, screaming, “It’s a full-on worm!” Jenny knew about the problems I’d been having with my nose, but she didn’t believe me at first. I stuck my nose in the air so that she could see for herself. Her mouth hung wide as she gaped and said: “Yep, there really is a worm in there.”

At first, it was the most hysterical thing that had ever happened to us. We couldn’t stop laughing. Because it had been in there for so long, I felt very blase about the whole thing. We rang the NHS helpline. The call adviser was crying tears of laughter over the phone, as it was the most bizarre thing she’d heard.

We went to A&E. Doctors were bewildered and didn’t take me too seriously at first. But once the nurse looked up my nose, she gasped. I was placed on a gurney as they stretched my nostril open with forceps. The doctors spent 30 minutes using different tools to try to prise the leech away. Leeches release an anaesthetic when they bite so they can stay on a body for longer, which is why I couldn’t feel the pain before – but it was agony when the doctors tried to pull it out. When they finally succeeded, I felt a wave of cold air shooting through the blocked nostril. It was like being in a nightmare, seeing the leech held up high, squirming. It was longer than my finger.

I’d swum a lot on holiday, so we guessed that it most likely came from there rather than having anything to do with the motorcycle accident. The leech was put in a jar and sent to a specialist hospital in London for further testing – they were worried that it may have passed on further diseases to me. Suddenly, something that was so funny seemed much more serious.

Luckily, all of my tests came back clear, and I had no side-effects. I was given the leech back in a pot and told to dispose of it. The leech was rock hard because it had so much of my blood inside. It made me squirm just looking at it.

Now, a decade later, the story of the leech and me has become a go-to anecdote whenever I meet someone new. I even had someone message me on LinkedIn recently asking about it. So while the leech was attached to me in a very physical sense, I guess we’re still attached metaphorically. But I’m very glad it’s out.

Main image, Glossodoris Sedna by Cajo Producciones

Above Glossodoris stellatus by digidiverdeb

Above Glossodoris angasi by Brian Mayes

Above Glossodoris acosti by Rafi Amar

Above Glossodoris hikuerensis by @halimeda

Above Glossodoris atromarginata by Wisnu Purwanto

Above Glossodoris sedna by Guillem Mas

Above Colemans Glossodoris by Steve Gillespie

Above Glossodoris cincta by Luc L. Legrand (thanks for 7 M views)

Above Glossodoris rufomarginata by divemecressi

Above Gossodoris cincta by jack pokoj

Above Glossodoris atromarginata by divemecressi

Above Glossodoris rufomarginata mating by Ludovic

Above Glossodoris cruenta by Tavistock

Above Averns Glossodoris with a Colemans Glossodoris by Steve Gillespie

Above Glossodoris sp. 16

Above Glossodoris sibogae by Thomas Vignaud

Above Glossodoris sp. 10

Above Glossodoris electra

Above Glossodoris rubroannulata

Above Glossodoris buko by Bernard Picton

Main photo by ilan Lubitz

Elysia marginata are Sacoglassons (a type of sea slug) and are found in the Indo-Pacific ocean at depths of 0-10 metres

Above photo by budak

They eat algae and store the chloroplasts in its body. The chloroplasts continue to photosynthesize and provide its host with a source of food!

Above 'Pair of leaf slugs on algae. They feed on green algae and can grow from 3 to 8cm long. Photo by Wesley Oosthuizen.' source

They have the ability to regenerate a completely new body (including a new heart) from their head, after it detaches itself from its old body! (A process called autotomy- self amputation)

Above photo by Sonja Ooms

Their ability was discovered by Sayaka Mitoh, a doctoral student at Nara Women's University in Japan, who spotted the decapitated head of E. marginata circling its separated body in one of the tanks in the lab

Above 'This image shows the head and the body of Elysia cf. marginata, a day after autotomy.' (Image credit: Sayaka Mitoh) source

Quite naturally she thought the slug would soon die, however..

"After a few days, the head started regenerating the body and I could see [the] beating of the heart. It was unbelievable," Mitoh told Live Science. "I was really happy and relieved when I found it could regenerate the body." source

• A, Head and body of Elysia cf. marginata, just after autotomy (day 0), with the pericardium (heart) remaining in body section (arrow)
• B, day 7
• C, day 14
• D, day 22, showing whole-body regeneration.
• E, Head and body of Elysia atroviridis (individual no. 1) just after autotomy (day 0).

Above text and photo source

The head continued to grow its new body over the next 3 weeks, including all vital organs, reaching about 80% of its original size!

Above gif source

"The [original] body continues to move and live for days to months," Mitoh said. "You can see the heart beating" inside them, she added. However, the decapitated bodies did not appear to be capable of growing new heads themselves. source

The old bodies remained active for several days to months, until they started to shrink, turn pale due to the chloroplast loss, and eventually died. The beating heart remained visible until the body had fully decomposed!

So, why such an extreme behaviour?

In other animals self amputation usually occurs when escaping a predator, however this may not be the case here....

Above photo by budak

The head can take several hours to detach from the body, so not exactly a quick get away from a predator

Instead it is suspected that it is a means of ridding itself of parasites. There is a slight groove towards the end of the head which acts as a breakage plane, and the similar head severing species Elysia atroviridis all had internal parasites when they detached from their bodies....

However, no parasites were detected in Elysia marginata that did the same.....

Above photo by Javier Diaz Frogmen

The ingested chloroplasts are thought to help in the regeneration of the new body and keep the head alive in the absence of the digestive system organs (which remain with the body).

One individual that was studied underwent autonomy and regeneration twice, which researches think is the limit...(which probably means it didn't survive the third time scientists went to work with a scalpel)

Interestingly this behaviour was only exhibited by young Elysia marginata. When older animals were decapitated their heads survived up to 10 days, and didn't regenerate before dying

Above photo by Antonio Venturelli

All information from wikipedia, here, here, here, here, here and here

As always I'm not an expert, any errors let me know in the comments and I'll edit

And I shall leave you all with a reprise of my current favourite gif....

Main photo by Ocean Networks Canada

Above photo via MBARI

Sea Pigs (Scotoplanes) are a type of Sea Cucumber

They live in the deep sea, specifically on the abyssal plain up to depths of 5000m

They can grow up to 4-6 inches

They have 6 pairs of enlarged tubal 'feet', and use water cavities in their bodies to inflate and deflate them in order to move around, as well as ten buccal tentacles lining their oral cavity

Above photo via Ocean Networks Canada

They live on the sea floor feeding on delicious foods such as decaying animals, poo and mucus!

If they are disturbed they can swim! In fact some Sea Pigs spend most of their lives swimming around in the water column using their frontal and anal lobes to propel themselves around!

They will gather in large numbers around whale corpses to feed and perhaps find a mate

Above, a congregation of Sea Pigs feeding on a whale carcass via MBARI

Their reproductive system is unique, the males only have one testis, and the females one ovary!

Also their skin contains a toxin called holothurin which is poisonous to predators...

They have a poorly defined respiratory system, and have to breathe through their anus!

Above photo by Oceans Network Canada via Treehugger

As they have evolved at deep sea depths they would swell and burst if brought to the surface

They are hosts to several parasitic invertebrates, including snails and small crustaceans

But wait! What's this...?

Above Above photo via MBARI

What's that red thing hiding under the Sea Pig?

Above photo via wikipedia

It's a King Crab!

Above photo via MBARI

Peek-a-boo!

Above photo by Josi Taylor via MBARI

Why do King Crabs ride on Sea Pigs?

Usually King Crabs like to hide in rocks and seaweed from predators, but it is thought that these King Crabs were carried by the ocean current while they were small larvae and ended up in the deep sea....an area devoid of such hiding places!

“It’s like looking for a port in the storm,” said James Barry, ecologist and lead author of the study at the Monterey Bay Aquarium Research Institute (MBARI) in Moss landing. Sea cucumbers are the ports or the biggest buildings to hide next to in an otherwise empty area.” Scientific American

Above, ' This photograph of the muddy seafloor offshore of Monterey Bay shows three Scotoplanes sea cucumbers, at least two of which are host to juvenile king crabs.' MBARI

Barry and his team found a total of 600 juvenile crabs, 96 percent of which were either clinging onto sea cucumbers or hanging around right next to them. Sometimes the crabs were upside down holding onto the belly of the sea pig and other times they were crawling on its side. In some cases, the researchers found more than one crab on a sea cucumber. Of the nearly 2,600 sea cucumbers videotaped, 22 percent had at least one juvenile crab clinging to them

Goodbye Sea Pig, and your King Crab jockey!

Above photo via MBARI

edit- I completely forgot to add my sources.....wikipedia and MBARI, unless specified

Remnants of prehistoric worm Radnorscolex latus, unearthed in Herefordshire. Photograph: Richie Howard/Luke Parry/National History Museum/PA

An ancient worm unearthed in Herefordshire was a carnivorous predator that shoved its throat out to catch and eat prey, according to scientists.

The creature, named Radnorscolex latus, was found at a disused Victorian quarry site in the village of Leintwardine, near the Welsh border.

This marine worm is believed to have lived on the ocean floor about 425m years ago, when the region was under water. Analysis suggests it had a retractable throat that could extend out on to the seabed to capture prey hidden within the sediment.

According to Dr Richie Howard, curator of fossil arthropods at the Natural History Museum, Radnorscolex is reminiscent of giant worms in the Hollywood blockbuster Dune.

Howard said: “We think they weren’t too picky when it came to feeding and likely just shoved their throat out into the mud and grabbed anything they could find.

“They certainly make you think of the sandworms in Dune in that respect.”

Although fossil remains of Radnorscolex were first discovered a century ago, the technology was not advanced enough to allow palaeontologists to examine these in great detail.

Experts from the Natural History Museum in London used state-of-the-art imaging techniques to analyse the remnants.

Findings showed Radnorscolex had rows of sharp teeth and hooks on its head, which it would have used to anchor itself to the ground and drag its body forward to move.

Despite being a predator, analysis suggests the creature only grew to be about 8cm long.

The researchers said Radnorscolex belongs to a group of extinct worm-like animals known as Palaeoscolecids, which were wiped out completely about 400m years ago due to rapid climate and sea level change.

The findings are published in the journal Papers in Palaeontology.

Image and text from the original article in The Guardian

Main photo, Halgerda batangas by Gerhard Batz

Firstly, the vast majority of photos are taken at depth so it's probably a good idea to be able to scuba dive.....and also most nudibranchs tend to look like this without the use of special lighting set ups

Above, by McChuckerson

Above by Go Zilla

(Please note, I'm not criticizing or taking the piss out of these photos or the photographers, I just want to show how nudis look under normal lighting)

A lot of nudi photos have black backgrounds which are created by using a strobe lighting set up configured like this...

Above, 'This is how... (Bryan Chus) setup looks to get a successful test shot on land, using my 60mm macro lens (120 mm full frame equivalent).'

Above, 'Non-lit test subject using black background settings (1/320 sec, f/14, ISO 100).'

Above, 'Properly lit test subject with inward facing strobes.'

The photos give results like these...

Above, Janolus nudibranch

Above, 'Oxynoe jordani feeds on Caulerpa taxilfolia Canon 5DSr 100mm Lens ISO100 1/250 f/25' by Jenna Szerlag

Above by Andrey torchuck

Of course there's slightly more to getting an amazing photograph than just having the right set up....

Composition, highlighting natural features, symmetry, depth of field, background contrast, animal behaviour all play their role

Above, 'Showing nudibranch symmetry works well, like with this shot of a Nebrotha kuberyani. [Mike Bartick] particularly like[s] to shoot these guys because of their interesting facial features, texture and vibrant colors.'

Above, 'Chromodoris leopardis. Laying eggs is always a very interesting behavior to capture. The eggs are often brightly colored and textured. If eggs are found alone, inspect them, as other nudibranchs often feed on them.'

Above, 'Nembrotha chamberlaini. If there is an anomaly of some sorts that sets your subject apart for the norm be sure that this anomaly is the center of the viewers’ attention.'

Above, 'Extreme depth of field isn’t always necessary, but on a larger subject its hard to resist, especially when one is as colorful as this Hypseledoris. Backing away from your subject is an easy way to slightly increase your DOF when working with nudibranchs.'

Above, 'Using a quality diopter of +10 or greater will dramatically increase the size of very small subjects and allow you to fill the frame with very little cropping. These Castosiella kuroshimae are miniscule and nearly impossible to detect. Look on small algae on sandy dive sites.'

Above, 'Nembrotha lineota. Get low, get close and shoot up. Use negative space and be sure your subject's Rhinophores are sharp.'

Above, 'Miamira tenue aka Ceratasoma tenue can grow to impressive sizes. Some are large enough to sport accessories like this emperor shrimp that lives a symbiotic lifestyle with its host. Keeping its hosts gills cleaned and rummaging for food as the nudi moves along the substrate is priority number 1 for the shrimp, and getting photos of them on the nudi are great behavioral images.'

Above, 'Mimicry is another behavior that an entire article could be written about, especially with these amazing Lobiger sp. Sap suckers live on algae that resembles green grapes. This image was shot in very shallow water in broad daylight. Using a high shutter speed will enable you to control the incoming light, even on the sunniest days. When a subject is tall, try turning your camera to the portrait position.'

Above, 'Glossodoris cincta. These larger nudis will fill your frame easily with or without a diopter. Paying close attention to the camber of your subject's Rhinophores will help with head-on composition. The gills of the cincta actually vibrate as they move and are fun to watch.'

Not all photographers use black backgrounds for their photos and the results are just as beautiful....

Above photo Thorunna australis, by elebe.foto

Above photo Hypselodoris bullockii laying eggs by Sonja Ooms

Above photo of Oxynoe olivacea by Jose Salmerón

Beautiful photo that pops with contasting colours of Elysia marginata by elebe.foto

And also lets not forget the role of the computer in adding the final touches to a well composed and well lit photograph

Some photos may need a bit of work to either remove debris in the foreground or background that distract from the main focus point...

Others need work in making them pop more. Of course images can suffer through too much retouching, and also no amount of photoshop can save a poorly composed image....both sides of the debate are discussed here

Above, 'Here's how to make Texture, Clarity and Dehaze work for you.' photo by Erin Quigley

And finally a Super Pro photo by David Hall, below

"Imagine a bull kelp forest in which the plants are completely covered with ghostlike animals expanding and contracting rhythmically,” photographer David Hall writes of shooting the hooded nudibranch, Melibe leonine, for his award-winning book Beneath Cold Seas: The Underwater Wilderness of the Pacific Northwest.

HOW HE GOT THE SHOT Hall used a Nikonos RS camera with a 50mm lens, two Ikelite SS-50 strobes and Fujichrome Velvia 50 film. Hooded nudibranchs are transparent, like jellyfish, and correct exposure can be difficult to estimate, so Hall bracketed the exposure generously. here

All information from here and here, unless otherwise stated

As always I'm not an expert, and certainly not one in underwater photography (I'm still trying to get to grips with terrestrial photography)

Main photo 'A giant dendronotid nudibranch swimming in mid-water'

Above, 'The opalescent nudibranch is a predatory mollusk with no shell'

Above, 'Hooded Nudibranchs on Kelp'

Above, 'Hooded Nudibranchs'

Above, 'Hooded Nudibranch, Melibe leonina - British Columbia, Canada'

Above, 'Opalescent nudibranchs and ascidians'

Above, 'Sea Lemon Nudibranch, Anisodoris nobilis - British Columbia, Canada'

Above, 'Nudibranchs (Nembrotha kubaryana) feeding on stalked ascidians. All nudibranchs are carnivorous, mostly preying upon sessile invertebrates such as ascidians, sponges, bryozoans and cnidarians (hydroids, corals, anemones). (Komodo, Indonesia) (photo: Gayle Jamison)'

Above, 'Nudibranch, Miamira magnifica - Izu, Japan'

Above, 'Hypselodoris infucata; Lembeh Strait, Indonesia'

Selected underwater photography here, more nudibranchs, and his books

Title photo by Doug Anderson

More photos of Emperor shrimp (Periclimenes imperator) riding on various nudibranch hosts...

Solo riding....

Above photo of Ceratosoma trilobatum, by Jack

.....or with a pal....

Above photo of Ceratosoma trilobatum, by Jack

...Tandem....

Above photo by Stefano Scortegagna

Above photo of Ceratosoma gracillimum with eggs by Pauline Walsh Jacobson

Above photo of Ceratosoma tenue by Eric Cheng

Above photo of Nembrotha lineolata, by Colin Salmon

Above photo by Doug Anderson

Above photo by Michel Duchayne

Above photo of Dendrodoris tuberculosa, by Brian Mayes

Above photo of ceratosoma nudibranch, by KIYOSHI OKADA

Above photo of Ceratosoma tenue, by Gomen S

Above photo by Colin Robson

.... Hail The Emperor!

Above photo of Hypselodoris infucata, by Anilao~Critters

Title photo by Todd Aki

• Nudibranchs are hermaphrodites (having both male and female sex organs), but they still require a mate in order to reproduce as they cannot self fertilize

Above nudibranch reproductive system by Carissa Shipman, found here

• The reproductive organs are usually next to each other inside the nudibranchs body, and the exterior reproductive opening being on its right lateral side

Above, 'External anatomy of a Tambja verconis nudibranch (by wadeangeliart) found here

• Being simultaneous hermaphrodites increases their opportunities to find a mate, as both partners will transfer sperm, and lay eggs, via reciprocal reproduction.....although there are some exceptions as we will discover!

Above photo Bennett's nudibranchs Mating' by John Turnbull

• Nudibranchs will follow the scent trail left by potential partner. When they catch up with them they start courtship which involves the gentle touching of each other

Above photo by ilan Lubitz

• Depending on the species, the nudibranchs will then orientate their bodies so that their reproductive openings are facing, allowing their swollen gonopores to connect

Above photo of Nembrotha chamberlaini mating, by Jim Greenfield

Above photo of Nembrotha purpureolineata, by Brian Mayes

• Nudibranchs will take every opportunity they can to mate when finding a partner. One quirk of their anatomical development whilst maturing into adults is that the male reproductive organs will grow, and be functional before their female organs. This is called protandry....

Above photo of Hypselodoris bullocki mating, by Coppertane....a possible protandry mating, due to size difference

• They can still take the opportunity to mate though as a 'male'..... It has been suggested that any sperm passed to the 'male' partner, can be stored within their bodies until their female organs have matured. It will then use the stored sperm to fertilize its eggs!

Above photo of pelagic nudibranchs mating by Rajiv Bhambri

• Mating duration depends on species, and can vary from brief encounters to several hours!

Above photo by Tony Wu

• There are 3 basic mating positions depending on species- right side to right side..... (see photo below)

Above, Nembrotha chamberlaini, by Andrew Wu

• .....Head to head.....(see photo below)......

Above, Lobiger viridis, from here

• ......And head to tail, which is either a reciprocal, or a unilateral process depending upon flexibility of the species, or even partner aggression......(see photo below)...

Above, Mariaglaja inornata, from here. The genitals are separate in this species- the penis is in the head, and the vagina in the tail

[Above] The gastropterid sea slug Sagaminopteron ornatum will sometimes form a circle of two to achieve reciprocal mating, or at other times as illustrated here, act unilaterally as a male by approaching from behind to copulate with another acting as a female. source

• Hypodermic Insemination is the preferred method used by some species. The penis has a sharp point which is used to stab the partner in order to deliver a packet of sperm. This can be done either as a mutual act, or happening unilaterally with one nudibranch taking advantage to inseminate another....This can occur amongst some of the sacoglassans

Above photo of Costasiella usagi, by eunice khoo....not as cute as I originally thought....

• Goniobranchus reticulatus is an unusual nudibranch as after it has mated the external part of its penis detaches! And within 24 hours it grows back.....!

Scientists think this mating strategy has evolved so the sperm of rival nudibranchs stored in the vagina of their mate will not accidentally get passed on to future mates source

Above photo of Goniobranchus reticulatus by Bernard Picton...with or without penis...(Schrodinger's penis?)

...And finally a shrimp jockey on a pair of mating nudis....

Above photo by Ludovic

Information from-

here

here

and the fantastic Nudibranch Domain

As always, I'm not an expert...any errors let me know in the comments, and I'll edit my post!

Main photo by Dusan Beno

Above, 'Chrysis semicincta' by Jessica JOACHIM

Above, 'Cotinis Mutabilis, also known as the Figeater Beetle' by Cotinis Mutabilis

Above photo by philux66

Above, 'Green Tortoise Beetle, Cassida viridis' by Duncan Cooke

Length; 7 - 10mm.

Distribution; Widespread in England and Wales, although sparse in the north and rarer in Scotland.

Habitat; Grassland, Heathland & Moorland, Farmland, Wetlands, Woodland & Gardens.

Found; April to October.

The Green Tortoise Beetle is one of a group of several closely related beetles. Host plants include White Dead-nettle, Hemp Nettles, Hedge Woundwort, Gypsywort and Water Mint and is often found in gardens. When disturbed, the adults behave just like tortoises, retracting their antennae and feet, and pulling their 'shell' tight down around them as they grip tightly on to the leaf they are.

The Green tortoise beetle is round, flattened and lime green. Tortoise beetles are easy to identify as a group, but there are several closely related species that are very difficult to tell apart. the Green Tortoise Beetle is entirely green and generally lacks the markings of other species. Cassida viridis is similar to Cassida rubiginosa but can be distinguished by the rounded rear corners of the pronotum which are sharp in C. rubiginosa. It is also usually more apple green in colour.

Adults spend a few weeks feeding on host foliage and possibly also pollen before mating in April and May and ovipositing from May to July. Between 1 and 10 eggs laid in firm-walled and distinctive egg cases which are stuck to stems or under lower leaves and covered with frass and leaf fragments. They hatch within 6 to 10 days and the larvae initially feed below the leaves, moving to the upper surface as they grow, they pass through 5 instars and develop rapidly. They are fully grown within 4 to 6 weeks.

Pupation occurs from June to September. The fully grown larvae move to stems and petioles and become attached by a secretion before they pupate. This stage is also brief, generally lasting about a week, and new generation adults emerge from July to October.

Above 'Green vegetable or Shield bug' by Bernard Spragg. NZ

Nezara viridula, commonly known as the southern green stink bug, southern green shield bug or green vegetable bug, is a plant-feeding stink bug. Believed to have originated in Ethiopia, it can now be found around the world.

Above, 'Golden Beetle' by Ivan Anisimov

Main photo 'Wasp' by Joshua Coogler

Above, 'Pachyrrhynchus ocelatus' by Raúl García Navarro

Above, 'Mite SP' by Harry Sterken

Above, 'Golofa claviger - Giant rhinoceros beetle' by André De Kesel

Above, 'Jumping spider SP (male)' by Harry Sterken

Above, 'Alcidodes Ocellatus' by Raúl García Navarro

Main photo..........Spanish Dancer Nudibranch. Photograph by David Doubilet

There are more than 3,000 known nudibranch species, and scientists estimate there are another 3,000 yet to be discovered. So-called Spanish dancers, like this one off the coast of New South Wales, Australia, boast some distinctions over other nudibranchs: First, they can be enormous, reaching a foot and a half (46 centimeters) long. Most nudibranchs are finger-size. Second, it can swim, a skill most of its cousins lack.

Above, Tritonia Nudibranch. Photograph by Jeffrey de Guzman

Members of the mollusk family, nudibranchs abandoned their shells millions of years ago. Their scientific name, Nudibranchia, means "naked gills," and describes the feathery gills and horns that most, like this Tritonia species, wear on their backs.

Above, Nudibranch, Philippines. Photograph by Libor Spacek

Nudibranchs, nicknamed "nudis," are best known for the impossible array of colors and designs they sport. They derive coloring, as well as toxicity, from the food they eat. Their wild hues tell potential predators, "You'd best look elsewhere for a meal."

Above, Nudibranch, Palau. Photograph by Ernie Collier

Though partial to tropical climes, nudibranchs thrive throughout the oceans, in warm water and cold, from sandy shallows and reefs to the murky seabed a mile down. Chromodoris nudibranchs, like this one photographed near Palau, are generally a warm-water species.

Above, Egg-Laying Nudibranch. Photograph by Jeffrey de Guzman

Nudibranchs are hermaphroditic, carrying both male and female reproductive organs. Mating pairs fertilize one another and lay up to two million eggs in coils, ribbons, or tangled clumps, as this purple-painted Hypselodoris is doing.

Above, Green-and-Orange Nudibranch. Photograph by Jeffrey de Guzman

Nudibranchs are blind to their own beauty, their tiny eyes discerning little more than light and dark. Instead the animals smell, taste, and feel their world using head-mounted sensory appendages called rhinophores and oral tentacles.

All text and photos from National Geographic