#headshield slugs

[taxonomytournament]

Taxonomy Tournament: Gastropods

Cephalaspidea. This order is made up of headshield slugs, so-called because they have a broadening of the head used to plow beneath sand

Nudipleura. This superorder is made up of sea slugs, which are typically colourful. Members include the sea bunny, variable neon slug, and blue dragon

[sitting-on-me-bum]

Headshield slug (Chelidonura amoena) portrait, Triton Bay, West Papua, Indonesia, Pacific Ocean.

Photographer: David Hall

[scienceisdope]

A bubble snail is a type of marine gastropod that is between a sea slug (nudibranch) and a snail. They have fragile, small shells that often do not cover the snail’s entire body. These marine snails use their large heads, called headshields, to burrow through the sand.

This elusive sea snail is found throughout the Indo-West Pacific and Atlantic Oceans, including off the coast of the US, South Africa, Japan, Thailand, and in very rare cases, Australia.

Video credit (and permission by): @uw.animals

[slugrard]

This Gee as the Blue Velvet Headshield Slug

[wallofbubbles]

Another very graceful headshield slug, Chelidonura amoena.

Luma' Selakan, Sabah (Malaysia), 2022

[calamondinblooms]

i saw your reply to the triboniophorus photo, what's your favourite snail/slug? my top 3 are probably Echinix (in general), Pupinella rufa, and Chiliborus rosaceus.

Thank you for the ask! Those are some great favorites. I love the shape of Echinix especially. I have got so many favorites! I absolutely love gastropods. I really love colorful species, so a lot of my favorites are very colorful. I couldn’t narrow it down to a top 3, so here are my top 10 in no particular order.

I really love Jenner’s cowry, Jenneria pustulata, I think it’s got such interesting texture, and I really love cowries in general.

© Salvador Jauregui

I think Sea Swallows, genus Glaucus, are really neat. Their shape is something really unique, and I love that they incorporate stinging cells from the man o wars they eat. I’m also a big fan of blue critters.

© Patrys

Flamingo Tongue Snails, Cyphoma gibbosum have absolutely gorgeous patterns on their mantles, and I’ve been lucky enough to find their shells washed up on the beach before. I would love to see a live one some day.

© Frank Krasovec

Julia exquisita is really fascinating to me because it is bivalved, which is something you don’t typically see in gastropods. It’s also carries out kleptoplasty, meaning that it steals the chloroplasts from the cells of the algae it eats, and incorporates them into its own cells, where they can continue to function and provide the snail with ATP for months. I hope to find one of them this spring.

© uwkwaj

I really like the Colorful Moon Snail, Naticarius canrena because it has such gorgeous patterns on its shell, and its body is a very pretty color. I have found their shells before but I have yet to find a live one.

© Mike Krampf

I think the Swallowtail Headshield Slug, Chelidonura hirundinina is super cool looking. I love its body shape and the way its colors contrast. It reminds me of neon paint splattered on a black canvas in the best way possible.

© emgee4

I really like Colpodaspis thompsoni, it’s so goofy. It reminds me of little sunny side up eggs if they were fried on a hammerhead shark.

© uwkwaj

Lamprohaminoea cymbalum is so cool with its little orange spots, and I love that you can see the eyes clearly.

© kaeliswift

I really like Long-tailed Semi-Slugs, their texture reminds me of little snakes. Their tiny shells are so cute. And I can’t get over their color.

© Arnold Wijker

I also really like Athoracophorus, I think they look so interesting, just like new leaves. I think if I saw one in person I would have a difficult time realizing it was a slug!

© Shaun Lee

I also just remembered how much I love leatherleaf slugs, but I said I would keep it to 10, so that will have to be a post for another time.

Thank you Anon, I had a lot of fun putting this together, and I really liked seeing your favorites too!

[aquariuminfobureau]

Although some of the larger marine flatworms are photogenic enough, to appear regularly in reef life guides and aquarium books, the mention of flatworms in reef aquariums usually relates to a small number of species, that are often labelled 'redbugs', or that actively eat coral tissues. These species are smaller, not so visually striking, and widely regarded as pests and not pets. This leads often to senseless panic, when quite harmless species of flatworms are encountered, such as Amphiscolops - not all of such 'hitch hiking' flatworms are bad.

However, conflicts do arise from the presence of corallivorous flatworms, such as those plaguing the acroporid corals, and the red or rust 'planarian' genus, or Convolutriloba, which accommodate photosynthetic symbionts. Convulotriloba sp. are not, as is often misreported, actual coral eaters themselves. Rather they compete with photosynthetic corals for access to light, and their populations can increase so fast, through fission, that they can simply swamp out the growing corals beneath them.

These flatworms are toxic, involving tetrodotoxin, and this defence seems to deter most foragers from guzzling them. Toxicity problematizes the potential of chemical treatments, because when the Convolutriloba flourish in quantities, their mass death causes the stressed and dying animals, to secrete toxins into the aquarium water. So although a chemical treatment might not itself harm corals etc, it can still be disastrous. As an aside, this genus dislikes settling where it is subject to strong current, and is therefore less likely to be troublesome in high flow systems or locations.

A number of fish and crustaceans will eat Convulotriloba sp. and other 'pest flatworms', but not eagerly enough for them to control their numbers properly, and this is likely because they bear toxins. So that a number of carnivorous foragers may nibble at Convulotriloba numbers, but are not willing to wulf them down, as aquarists would like them to. This fits what I and others have seen of foraging dragonets, wrasse, butterflyfishes, arrow crabs, and boxing shrimp. A closer examination may show that the worms are more often rejected after sampling as potential food.

The falsely named 'blue velvet nudibranch' - which is really a headshield slug, Chelidonura varians - reportedly dies after consuming only Convulotriloba. In nature Chelidonura sp. have a broad diet, including molluscs moreso than flatworms. Like the other foragers that consume red flatworms, their nature is surely to sample vagile animals, and then move on. In truth, chemically well defended organisms such as Convulotriloba sp. might not be immune to sporadic predation, but their arsenals would not have come to exist through natural selection, were they ineffective against bulk consumption.

More than one species of Convulotriloba is encountered in aquariums, but there is probably little need to fret about their identification. Another less notorious genus named Waminoa, has a similar carpeting habit, resting upon coral tissues, but is seemingly not so toxic to other animals, or their toxicity is not so well studied. Less is reported about Waminoa in relation to corals or other sessile organisms, or to their potential predators. It seems the usual flatworm consumers will eat them.

The other dreaded flatworms actually are obligate coral feeders, the Acropora and Montipora eating polyclads. Fortunately a number of regularly encountered reef fish and shrimp, will eat these flatworms at different stages of there life cycles. Pseudocheilinus wrasse are certainly proven to consume them under observation, although they appear to spit out Convulotriloba. The peppermint shrimps, a species complex of broad spectrum foragers, consume both the adult worms and their eggs. These are the same shrimp admired for their consumption of Aiptasia anemones, but for that reason they could also consume corals themselves.

Specialized coral feeding polyclads also bother other corals such as euphyllids, particularly Euphyllia senso stricto and the related Fimbriaphyllia, and may cause more damage than is often recognised. This is because the feeding of certain (but not all) polyclad flatworms on coral tissues, clearly damages and behaviorally stresses these corals. But the corallivorous flatworms may be difficult to spot, and to recognize for what they are, and problems with euphyllid polyp expansion are likely to often remain undiagnosed. A mixture of temporary dips and natural biological control is advised, but the strong stings of euphyllids may ironically deter flatworm eaters.

[uncharismatic-fauna]

Fun fact: The relationship between nudibranchs and sea slugs is like that of squares and rectangles: all nudibranchs are sea slugs, but not all sea slugs are nudibranchs. Nudibranchs are a specific group of sea slug that have exposed gills on their back that are shaped into colorful plumes. They are also bilaterally asymmetrical, meaning that they have sexual openings on the right side of their body but not the left side.

The Chelidonura hirundinina is not a nudibranch - still, this colourful headshield slug can grow up to 4 cm long, and lives in the western Indo-Pacific. See the little hairs around the edge of its head (closest to the camera)? Those are cilia, and are used as sensors to detect their prey: flatworms. This species is also known as the Swallowtail Headshield slug, because of its split back end.

Photo source

[cephalogodess]

Have you ever seen such a beautiful slug??? They are called swallowtail sea slugs for obvious reasons :) I saw hundreds in Kauai last summer, lots of which were mating and laying eggs. Yay! There will be many more generations of these beauties! 

Chelidonura hirundinina

Anini Beach

Kauai, Summer 2018

[thefreakylobster]

Chelidonura varians sketches!!!

Drew my 2nd favourite sea slug:)

[montereybayaquarium]

It's Sea Slug Day!

Send nudibranchs! Or sea hares or headshields or sap-suckers or side-gills or sea butterflies—whatever the slug, it’s time to share the love!

[c0smicw4rp]

Technically sea slugs is the informal name, cause not all of them are slug-like, and they're actually called Nudibranchs (pronounced like bronk not branch). This comes from latin meaning Naked Gills, as their gills are outside their body

See the spikes? Those are gills!

While the "Antennae" are actually noses!

Not all sea slugs are nudibranchs though, some are in other groups like this fine Headshield Slug in the Aglajidae family!

Cool! i thought gills were just where they exhale. There's more to it than that?

[worldofgoo]

well the main gist of it was that most sea slugs are nudibranches but there’s a couple other shell-less sea snails that also get referred to as sea slugs, which are (in order of pictures) 1. sacoglossans (which can photosynthesize using the chloroplasts of algae they eat), 2. Aglajidae, a shell-less group of bubble snails (also known as headshield snails), 3. sea hares (Anaspidea), 4. sea butterflies (Thecosomata) and 5. sea angels (Gymnosomata)

Nudibranches themselves undergo a process called detorsion, which is poorly explained, but apparently regular gastropods have their anatomy fucked up during development and they just live like that. Apparently because of it nudribranches are uniquely bilaterally symmetrical on the outside while most gastropods arent (? but its also not well explained)

Also, I found this video, and while I’m not sure of whether the identification is accurate, looks pretty cool :-)

[centuriesofooze]

spare nudibranch? 🦇

Chelidonura varians (Ive seen this one be called a “blue velvet nudibranch” but Its a headshield slug)

[wallofbubbles]

Headshield slug (fairly confident this is Chelidonura varians) , with metallic blue accents.

Luma' Selakan, Sabah (Malaysia), 2022

[aquariuminfobureau]

One of the problems facing marine aquarium owners, is the growth of turning green algae. In reality such algae are useful for their role in the ammonium cycle, and in oxygenation. However they can be unsightly, and they compete with our ornamental species for space. When faced with algal turfs, aquarists often turn to livestock in an effort to control it. Not infrequently they purchase a sea hare. Sea hares or aplysids are snails that have their charming vernacular name, because their bodies have a rounded shape like that of a rabbit, and their sensory structures called rhinophores, outwardly resembles tbe ears of a rabbit or hare. Although the rhinophores of sea hates have a sensory function, they are not ears. Most often the sea hare purchased for the aquarium, is the well studied species, Dolabella auricularia, also known as the wedge, blunt end, or Japanese sea hare. But it is rarely labeled as anything other than just the generic label of sea hare, and other kinds of sea hare also enter the aquarium trade

D. auricularia are of variable coloration but they are always mottled in shades of green and brown. Sometimes this species is labeled as the green sea hare, but this name is shared by more than one Dolabella species. Although D. auricularia is sometimes called the Japanese sea hare, it actually has a far broader distribution in the Indo-West Pacific region. Usually this species is purchased when much smaller than it's potential size, with records existing of 40 centimeters or 16 inches long individuals.

Although sea hares appear to lack a shell, their shell is in fact present in sea hares, but it has become internalized. Rather than retreating into a shell like most snails when disturbed, sea hares are protected by toxins that make them distasteful to predators. They are even able to expel an ink from their bodies, which includes a chemical called aplysioviolin. This distasteful biochemical is derived from the metabolites of red algae, which are ironically a chemical defence of the algae itself, that are sequestered by the sea hare. Marine snails with hidden or absent shells are often referred to as sea slugs. In fact snails are an enormous clade, that have shown repeated tendencies across their evolutionary lineages, towards independently reducing, internalizing, and eventually losing their shells.

Sea slugs are not a natural grouping by descent, and are scattered amid those gastropods retaining large shells. In fact the sea hares or aplysids are more closely related to most land snails (which happen to include the land slugs) than to the colorful nudibranchs But they are still more closely related, to the faunivorous headshield slugs and pterobranchs. Amid this branch of the tree of gastropod life, the sra hare subclade is remarkable for their atypically herbivorous diet

D. aurantiaca are most normally found in sheltered bays and lagoons, away from rough currents, amid seagrasses and in association with soft substrates. This species can also be encountered in large, intertidal rockpools. It is well understood that D. auricularia is a herbivore, feeding on a broad variety of red and green macroalgal species. Dolabella are relatively unaffected by the chemical defenses of macroalgae, but they are reluctant to feed on calcified or tough species. Because Dolabella can find a use for algal secondary metabolities, it does not avoid ingesting certain algal species incorporating noxious chemical defences.

D. aurantiaca are not offensive to other animals sharing their aquarium. However if they feel threatened, there is a possibility they might secrete their noxious ink into the water, even though this behavior is infrequent Reportedly the discharged ink irritates corals in the aquarium, but although it contains a toxic deterrent, the ink is not severe enough to kill fish It also has effects on crabs, echinoderms, annelids, and other gastropods. There is always the problem that sea hares will run out of suitable foods in their aquarium, when they have eaten all of the algae to their taste, which are usually green turf algae. At this point the aquarist will need to feed the sea hare by providing foods of suitably algal origin, perhaps by actually culturing suitable algae, to put it into the tank.

Sea hares can also eat nori, and even vegetables such as lettuce, if it is first blanched to reduce its toughness, though they deserve hair algae. If it is available, sea lettuce or aonori, a macroalgae consumed by humans, in countries like France and Japan, is known to be consumed by D. aurantiaca in the wild. The best substitute food for sea hares, is sea vegetables sold for consumption by people or tangs. Unfortunately, this species will consume some desirable aquarium macroalgae, such as Dictyota, Padina, and Sargassum.