#Isistius

[todropscience]

MOONLESS NIGHT INCREASE COOKIECUTTER SHARK BITES

Cookiecutter sharks are well known for feeding on large animals, and leaving a cookie-cutter-shaped wound, hence that comically name. These are small and dark sharks, typically found in deep tropical and subtropical waters. Despite their small size, these sharks can pose a significant threat, although rarely. Of the seven reported cookiecutter shark attacks on humans worldwide, six occurred in Hawaiʻi. A new research connect the interactions between cookiecutter sharks (Isistius brasiliensis) and humans, particularly among channel swimmers in Hawaiʻi. The study showed how environmental conditions such are moonless night can increase the likelihood of these attacks.

- swimmer bitten twice by cookiecutter sharks.

The nocturnal feeding behavior and zoogeographical habitat of cookiecutter sharks greatly reduces interaction of this species with live humans. However, the growing popularity of channel swimming in Hawaiʻi and swim start times have contributed to an increasing likelihood of live human and cookiecutter shark, according to the researchers, moonless night sky is a significant risk factor for night swimmers.

Photo by Will Stahnke

Reference (Open Access): Minaglia & Liegl 2024. Moonless night sky increases Isistius species (cookiecutter shark) and live human contact. PLoS ONE

[fishenjoyer1]

Fish of the Day

today's fish of the day is the cookiecutter shark!

The cookiecutter shark, also known as the cigar shark, scientific name  Isistius brasiliensis, is well known for their distinctive bite marks. Often referred to as "the leach of the shark world" the cookiecutter shark has an extensive diet. Any animal that is large enough to support a bite from a cookiecutter shark, can and will be bit. prey includes, but is not limited to: whales, dolphins, seals, dugongs, almost every shark that shares a range with cookie cutter sharks (great white, blue, megamouth, tigar, etc), bony fishes, squids and other soft bodied animals. That includes humans, and biting of humans by cookiecutter sharks rises every year.

The cookiecutter shark is parasitic, leaving carter wounds that measure about 2 inches across and about 7cm deep into its prey. The shark can make these marks through several adaptations of the mouth. The spiracles, behind the eyes, close, and the tongue is retracted, to create a suction to their prey, sealing them together. Then, the shark will twist around, rotating the body in a circle, aided by a saw-like movement of the jaw, which moves the teeth back and forth. This is how they feed. This diet supports them getting as large as 17-22 inches in length.

The range for these fish stretches from the latitude of 20 degrees North to 20 degrees South all across the world, although in the warmer seasons for each hemisphere they can migrate as far as 30 degrees North and South respectively. The cookiecutter shark prefers living near the equator, in tropical or warmer temperate areas. This shark takes place in diel vertical migration, a kind of daily migration that occurs at night where animals that tend to live in deeper waters come to the surface. The cookiecutter shark can travel up to 2 miles up and down in the migration each day!

A smaller known fact other than this shark's feeding habits, is based on its bioluminescence! The cookiecutter shark has the strongest bioluminescence of any shark species known. A darker collar on the underside of the shark is thought to act as a lure for attracting prey. Their life is similar to that of other dogfish sharks, despite their many adaptations. A litter of pups bore at a time is between 6-12 and are gestated in the female by sustaining off of the yolk until birth. When born the bioluminescent collar is yet to form, and they are only 6-6 inches in length. Sexual maturity is achieved once they reach 14-15 inches in length, and it is unknown how long their lifespans are.

Have a wonderful Monday, everyone!

[i-give-you-a-fish]

can i have a small bioluminescent fish please? :]

You get a Cookiecutter Shark

Isistius brasiliensis

[bethanythebogwitch]

Wet Beast Wednesday: cookie cutter shark

There are some words that just shouldn't go together, like "edible radium", "reasonable conspiracy theorist", and "sandpaper underwear". Well here's a new one for you: "parasitic shark". The only problem is, that one is real. Yeah, this is one of those animals that's so bizarre it would be mocked as too silly if a fiction writer came up with it. Welcome back to Wet Beast Wednesday, where we discuss the cookie cutter shark.

(Image: a cookie cutter shark said on a patch of fabric. It is a small, brown shark with a darker collar region. Its fins are small and the head is blunt. It is widest around the middle. A pencil has been placed next to it for scale. End ID)

There are two known species of cookie cuter shark: Isistius brasiliensis and Isistius plutodus. The latter, common name: largetooth cookie cutter shark, is much rarer and less well known than the former, which will be the main topic of this post. The cookie cutter shark is a very small shark, measuring between 42 and 56 cm (16-22 in) in length as adults. They have multiple adaptations that set them apart from other sharks, even other members of the dogfish order. Their bodies are described as cigar-shaped, which is why another common name is cigar shark. The head is short and rounded and the mouth is large, with prominent teeth and large lips. The upper teeth are small and narrow while the lower teeth are larger and form a saw-like edge. Unlike other sharks, they do not replace one tooth at a time, but instead lose and replace the entire front lower row at once.

(Image: a closeup of the head of a preserved shark. The lips have been pulled back to expose the mouth showing the large, saw-like lower teeth and much smaller upper teeth. End ID).

Cookie cutters are among the few sharks that are strongly bioluminescent. Their underbellies and a collar around the neck area have luminescent cells called photophores. The cells on the belly mimic light from above, making it difficult for predators below to distinguish the shark from the surface of the ocean. The cells on the neck are believed to be used for attracting prey by mimicking a small fish. Cookie cutter sharks have large livers with a high oil content that helps them maintain buoyancy. While most fins are small (or in the case of the anal fin, missing), the tail fin is large and suited for sudden bursts of speed. Longtooth cookie cuter sharks are larger, with longer bottom teeth and smaller fins.

(Image: photos of the underside of a cookie cutter shark showing the bioluminescent photophores, which make the belly look blue. End ID)

The common name of the cookie cutter shark comes from its unique feeding mechanism. The sharks are deep-sea ambush predators that use their natural buoyancy to remain motionless in the water column while using their bioluminescence to attract prey. When prey approaches, the shark will dart forward and attach to the larger animal. Using its lips to form a seal, the shark can generate suction to make it very hard to remove. It then uses the upper teeth as an anchor to help the larger bottom teeth pierce the skin. Then , the shark spins around (the thrashing of its prey may help) to cut out a roughly circular plug of skin and muscle. The circular holes left behind are reminiscent of bits of cookie dough cut out by a cookie cutter, hence the name. The sharks will also eat small fish and squid whole and are known to scavenge carrion. They will sometimes school, possibly to help attract prey while discouraging predators. Just about any medium to large animal in the shark's territory is a possible target. Scars from cookie cutter shark feeding have been found on cetaceans (whales and dolphins), pinnipeds (seals and sea lions), other sharks, rays, and bony fish. Because the sharks feed off of other animals without killing them, they are considered parasites. Specifically, they are facultative ectoparasites, meaning they attach to the outside of their hosts and are not fully dependent on parasitism to survive.

(Image: a swordfish with multiple fresh bites from cookie cutter sharks. The bites look like pink pits dug into the swordfish's side. End ID)

Cookie cutter sharks are found worldwide in the mesopelagic zone (roughly 200 - 3000 ft deep), though they have been known to move to shallower water. They are found worldwide and seem to prefer the open ocean. Most sightings are around islands, but its not clear if they do congregate around islands or this is a case of sampling bias. Because of their remote habitats, little is known about their behavior in the wild. Likewise, we don't know much about their reproductive behavior, though like other dogfish, they are viviparous. The embryos are raised in two uteruses and there can be up to 12 of them. They likely have a very long gestation period.

(Image: a slender cookie cutter shark seen from the side)

Cookie cutter sharks are classified as least concern by the IUCN. There is no fishery for them and they are only caught as bycatch. People have been able to see the scars left by the sharks on their prey for a very long time and there were several hypotheses for what was leaving the scars, including lampreys and bacteria. In 1971, scientist Everett Jones was the one who discovered that the cigar sharks (as they were then known) were responsible. The name cookie cutter shark became popular after that. Human interaction with the sharks are rare, but multiple attacks have been recorded, most of them on swimmers trying to cross the channels in Hawai'i. There have also been reports of shipwrecked sailors being attacked and bodies have been recovered with signs of cookie cutter shark scavenging. Generally though, the sharks are not considered dangerous to humans due to their remote, deep-sea habitat. Back in the 1970s, US Navy submarines kept finding circular holes in the neoprene coating of their sonar domes, which let components leak out and impaired the subs' navigation abilities. Putting fiberglass over the domes solved the problem, but it wasn't realized until much later that the damage was caused by cookie cutter sharks mistaking the subs for prey and not an unknown weapon. This wasn't even the only time this happened. In the 1980s, it happened again with the robber coating for some electric equipment. If only we could all setback militaries as easily as this little shark.

(Image: a circular scar left on someone's calf by a cookie cutter shark bite. End ID)

[shark-of-tha-day]

shark of the day: cookiecutter shark, isistius brasiliensis

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cookiecutter sharks, also called cigar sharks, are small deepwater sharks named for the particularly circular bites they leave on their prey. they only grow to be around 55 cm(~22 in) long. cookiecutter sharks are found in deep tropical waters around the world. they feed on a variety of larger animals, including large fish, sharks, and marine mammals. cookiecutter sharks latch onto their prey with suction and use their uniquely fused-together teeth to bite off near perfectly circular chunks of flesh. they are also bioluminescent, emitting an greenish light on their undersides excluding the dark band around their gills.

requested by @underwaterstrawberries :)

[dailymarinefish]

day 174, 19/07/24 - fish of the day is the cookie cutter shark (Isistius brasiliensis)

[sharkshowdown]

Time to meet our contestants:

On one side, this bitch looks like a ray, on the other this other bitch is known for chomping on submarines and - well - anything.

Some facts:

Angel shark (genus: Squatina): these sharks spend their days under the sand with only its eyes out, waiting to surprise their prey. They grow up only to around 2,1 meters (7 feet). They're known for getting back problems such as scoliosis due to stress (same dude). Most of them are innofensive to humans but can leave a bite if annoyed.

Cookie Cutter Shark (Isistius brasiliensis): these Sharks are named due to their bite, round and cookie sized, they're parasitic animals that attach themselves to chomp. The underside of their body have bioluminescence, so they glow. Despite the fact that attacks on humans have been knowns, they still aren't a threat to us.

[sharkest-sharks]

Cookie cutter shark (Isistius brasiliensis) | Greenland shark (Somniosus microcephalus)

Sharkest shark polls

[just-a-girl-who-likes-sharks]

This is a cookie cutter shark appreciation post ❤️

Isistius brasiliensis

(Picture credit in the image)

[brooklynislandgirl]

Stuttering lights and crowded bodies, whining metal and electricity, the subway hummed with life shuttled through the liminal. The dangling sharks' sway caught his eye, novel, rhythmic (almost circling) where they guarded her ears. Before he could catch himself, the confession slipped out, 'Sharks are amazing.' An almost imperceptible swallow, something apologetic, 'Cookie-cutters. Nightmare fuel. Amazing, though.'

Jurassic Asks || The Lost Meme

For far too long Beth is entirely oblivious to her fellow travellers on their own way to work, or like her, finally heading home after a gruelling over-nighter. The city, regardless of one's shift, tends to suck a little soul from the body's marrow. The lights here was her out, make her far paler than she cares to admit. Almost sickly. Or maybe it's the black coat and blacker scarf, the first thing she grabbed on her way out the previous night. Cup of coffee in one hand, and entirely lost to the flow of internal thought; mostly going over the stops she needs to make when she gets back to Bay Ridge, she doesn't immediately recognise the close press between her and the other passengers. Here she's used to the crowds, she's used to the crushing press in the hospital, on the subway, in the clubs. She also doesn't realise what she's heard other than catching the word "Shark" which will always draw her attention. Then she realises it's all about the earrings she's wearing and a hint of colour brightens her pallor. She reaches her empty hand up to touch the dangly bronze Isistius brasiliensis. She smiles. Shows her own teeth; small, sharp, a little crooked. Raises her voice just loud enough to be heard over the interminable clacking-rumble of the tracks. "Mahalo! An' really, a survival trait. Wen dat small...gotta get ya own any way you can."

[sabbathercio]

Na Guerra Fria, 30 submarinos com mísseis nucleares dos EUA foram danificados e ficaram inoperantes. O governo achou que era uma nova arma soviética criada para destruir submarinos. O que estava destruindo os submarinos eram tubarões-charuto de 40 cm de comprimento. Resumindo, o tubarão-charuto (Isistius brasiliensis) é um tubarãozinho que brilha no escuro, vive em profundidades de 3 km e, diariamente, nada até a superfície para parasitar grandes animais, arrancando pedaços circulares de carne de seus corpos. Na década de 70 os EUA lotaram o Pacífico de submarinos nucleares. Basicamente, os revestimentos dos sonares eram feitos de Neopreno e começaram a ser destruídos (e o submarino tinha que voltar) Basicamente os tubarões confundiam o neopreno com pele e tentavam roubar um pedaço🥺 https://www.instagram.com/p/CnCTsVJu7Qy/?igshid=NGJjMDIxMWI=

[i-give-you-a-fish]

can u do the cookie cutter shark?! (Pls!🙏)

Sure thing!

You get a Cookiecutter Shark

Isistius brasiliensis

[evilkitten3]

For that animal ask: 16, 21 and 26?

16. Do you know any animals you would affectionately describe as ‘freaks of nature’?

the cookiecutter shark. like i love it to death but it looks like a cartoon drawing of an offensive caricature of itself 21. If parasitic aliens invaded Earth and could be hiding anywhere and you’d been given the power to morph into animals in order to fight back, which animals would you pick for 1) stealth, 2) flight, and 3) battle?

for stealth, i’d pick an insect of some kind, probably a cockroach or a stick bug, maybe a leaf katydid. for flight, i think i’d go with a saker falcon. they’re not quite as fast as peregrines while diving, but they can go faster horizontally, which is somewhat more important for getting places. not that their dive is anything to scoff at, mind you, but it’s not what i’d be prioritizing. for battle... well, not to sound like a meme, but the honey badger ain’t nothing to fuck with.

26. If you could have any animal as your pet/companion, and money, housing, proper care, and other logistics wasn’t an issue, which animal would you pick?

DRAGON. I WANT A DRAGON.

[sharkshowdown]

Through popular request, the shark of the day is the Cookie Cutter Shark.

Two people already have been sad he was not included and to be honest the reason is that it was hard to find images of it in nature, since not many people would like to see drawings or the animal after being fished.

But here it is, and a few fun facts.

The cookie cutter shark's scientific name is Isistius brasiliensis (we share a country).

The shark appears in warm waters worldwide (the name brasiliensis coming because the type specimen, the one in which they get described by science, was caught in Brazil), mainly close to islands.

Its very tiny, reaching 42-56cm (16.5 to 22 inches)

The name comes from leaving a round bite mark on it's preys, around cookie-sized, it has even been found biting submarines.

They have a parasitic lifestyle.

They are bioluminescent around the under side of it's body.

They stay deep in the sea during the day, but getting slightly closer to the surface during the night.

Their mouth to be kinda creepy tho.

[sharkest-sharks]

Silvertip shark (Carcharhinus albimarginatus) | Cookiecutter shark (Isistius brasiliensis)

[numbnutsarts]

Shark Week 2020: Day 06 - Cookiecutter Shark