#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

[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

[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

[tiger-bisczit271]

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)

[eurodiverslanzarote]

The "aglaja tricolorata" is not a nudibranch they are headshield slugs.

We find them often at the night dive. 🐌

[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.

[anudibranchaday]

Chelidonura varians is a species of headshield slug (not nudibranch) that grows a maximum of 7 cm long. They are found throughout the Indo-West Pacific. Interestingly, the two 'tails' at the rear of the slug (the left side of the picture) are common to all species in the Chelidonura genus, and the left tail is always the longer of the two.

Photo source

[inaturalist]

Sea Slugs on the Elkhorn Slough - Observation of the Week, 7/7/19

Our Observation of the Week is this Navanax inermis sea slug, seen in the United States by lmkitayama! 

“At work they call me the Slug Queen,” says Lauren Kitayama, an Assistant Manager at Kayak Connection in California. “Daylight permitting, I paddle once a week before work on the Elkhorn Slough. A couple of years ago, if you'd asked any of the local guides they might have said there were 5 species of sea slug on the slough. Last year I documented 27!”

The slug seen above was one of twenty Navanax inermis she spotted that morning, and said they were mating on the sea lettuce near the dock at work. “They are one of my favorite slugs,” she says,

They are large enough for people to appreciate, and so absolutely beautiful! I love using them to get people excited about the unloved slimy things that live in the ocean. One of my goals is always to show people something they never even imagined existed on the planet, and Navanax are a great opportunity to do that. As a kayak guide I work with a lot of school children, and love having the chance to inspire them to protect and appreciate the natural world around them.

While nudibranchs are the most commonly known order of sea slug, the Navanax inermis belongs to an entirely different order: Cephalaspidea, or the headshield slugs. Most members of this order, including the California Aglaja, do have a shell, but it is usually either tiny or internal. Navanax inermis are large slugs, growing anywhere from 2.5 to 10 inches (6.35 - 25.4 cm) in length, and they prey upon other gastropods and even small fish!

Lauren (above) earned a Masters in Marine Conservation from the University of Miami (FL), where she focused on the impacts of marine debris. “I am zealous about protecting the oceans from plastic...[and] someday I hope to work for the UN attacking the plastic pollution problem in Southeast Asia.” For now, however, she says she loves her current job, and tells me 

My favorite thing is to see something I've never seen before. "I don't know" is my favorite answer to the question, "what is it?" I think that's how this whole slug thing started. They are beautiful, and most people would never look for them/see them without a guide. For whatever reason my slug observation skills are great. Can't find my keys half the time (or the sunglasses that are on my head), but a 9 mm sea slug hiding in a patch of kelp... no problem.

With my ecologist brain, I am excited to continue documenting slugs on the slough to see if a temporal pattern emerges (when are particular species showing up? Are they predictably in the same locations year after year?) I try very hard to get a photo of every species I see every week so that I can continue to document their presence/absence on the slough.

- by Tony Iwane.

>

- Check out Lauren’s Litter Mermaid projects and blog!

- And her sea slug observations.

- Watch a Navanax inermis eating a California Seahare.

- And watch a pair mating!

[lumbalumbadivingmanado]

This is a blue velvet headshield slug (Chelidonura varians). To be precise, it is 2 of them, entangled in probably a mating session. Sea slugs belong in the order of Mollusca, which basically means an animal that has no real skeleton. Nudibranches are, for example, part of the same order but also sepia's and octopus. Many Mollusca have specialized diets. Our blue velvet slug, only feeds on flat wurms. Like a vacuum cleaner, they literary hoovers them up. For that reason they are also popular in aquariums. We see them regular at our reefs and they are excellent models for underwater photographers. #lumbalumbadivingmanado #bunaken #wonderfulindonesia #northsulawesi #seaslug #housereef #uwphotography #snorkeling #snorkelingholiday #diving #divingholiday #diveholiday #diveindonesia #duiken #duikvakantie #tauchurlaub #tauchen #plongee #dyk #holiday #aftercorona #oceanlover #coralreef (at Lumbalumba Diving - Manado) https://www.instagram.com/p/CQcfo28ByVw/?utm_medium=tumblr

[samoceanwarrior]

Chelidonura punctata #nudibranch These are headshield slugs or cephalaspideans. Taken by #Underwaterphotographer #DanielSasse #poseidondivecenter #natgeoyourshot #Scubadiving #Aonang #Krabi #instadive #Marinelifeprotection #Ouroceans #Underwaterphotography #natgeo #nature #uwpic #Savetheoceans #Marineconservation #Oceandefender #Saveourseas #underwaterlife #fish #ecowarrior #natgeowild #blueplanet #scubashooter (at Poseidon Dive Center) https://www.instagram.com/p/CERHA4chWGp/?igshid=1xv0h5vvquocc