Information

What are the predators of Glaucus atlanticus?


I'm researching the Glaucus atlanticus, also known as the blue glaucus, among various other names, but after reading quite a few articles and searching on the Internet as many different ways as I can think of, I can't find any of its predators, or any indication it has no natural predators. Everything I've read is just silent on the issue. Does anyone know what, if any, predators this has? Thanks!


Try out using Google Scholar to take a more scientific literature-based approach to your search.

Frick et al. (2009)1 found that about 42% of logerhead sea turtle (Caretta caretta) stomachs contained remnants of G. atlanticus.

We were able to identify G. atlanticus in the diet of loggerheads because whole or nearly intact specimens were present.

Loggerhead turtle mouth and throat with sharp papillae. Source NCSU CMAST (Photo by Craig Harms)

Bieri (1966)2 observed G. atlanticus frequently attacking one another and biting off pieces of each other. In one case, one individual ate all but the head and trunk of a smaller specimen.


Citations:

1, Frick, M.G., Williams, K.L., Bolten, A.B., Bjorndal, K.A. and Martins, H.R., 2009. Foraging ecology of oceanic-stage loggerhead turtles Caretta caretta. Endangered Species Research, 9(2), pp.91-97.

2. Bieri, R., 1966. Feeding preferences and rates of the snail, Ianthina prolongata, the barnacle, Lepas anserifera, the nudibranchs, Glaucus atlanticus and Fiona pinnata, and the food web in the marine neuston.


Poisonous Prey Turned Into Hunter’s Defense

Delicate beauty can often belie dangerous weapons. Take the cnidarians (pronounced ni-DAR-ee-uns), a group of animals that includes jellyfish, corals, hydroids, and other predators both small and large. Many are colorful and beautiful, and all of them are loaded with stinging capsules that each contain a neurotoxin-filled harpoon.

Cnidarians deploy these harpoons by the thousands to catch food and discourage (and even kill) predators. When stimulated, the harpoons shoot out of the capsules, pierce the target and inject poison. Depending on the species of cnidarian and the type of stinging capsule, this attack can be barely perceptible or intensely painful. Cnidarians are naturally abundant in the oceans and, especially when coastal populations of stinging jellyfish sometimes bloom, these stinging animals can be a nuisance to swimmers.

Despite this potent deterrent, some animals specialize in eating even the most toxic cnidarians. Among these predators is a remarkable group of nudibranchs. These sea slugs have several lines of defense that allow them to eat cnidarians, stinging capsules and all. They use mucus to stop many of the stinging capsules from firing. They have a hard lining in their mouth and esophagus to protect them from the harpoons that do discharge. And their stomachs and skin are lined with cells that contain small chitin disks that act like sandbags, absorbing the force of the poisonous projectiles.

In this episode of CreatureCast we meet Glaucus atlanticus. It is a nudibranch that takes this tolerance one step further. Not only can it eat cnidarians, it collects their stinging capsules and uses them as weapons against its own predators. Glaucus feeds on the Portuguese man-of-war, a siphonophore that floats at the surface of the ocean and has one of the most painful stings of all cnidarians.

This video was made as a final project by Lauren Cheung, a student in my Invertebrate Zoology Course at Brown University. Her Glaucus illustration is based on the beautiful photo by Taro Taylor. The music is by Gillicuddy.


Indo-Pacific tarpons

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Saturday, August 15, 2020

Our new members to the family

Yesterday my Mum went out to Totra North and got 4 little baby chicks. They are only 6 weeks old and are brown they are super fluffy and soft. This morning my Mum and I took them outside and put them in the chicken cage. We already had 2 hens and one rooster but they would atack the babys, so we took them out of the cage and put the little babys in. The big chickens are just roming around in our garden.

Here are some pictures of them.


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Indian Gharial

The Indian gharial is a unique crocodile that looks a lot more like a duck than an alligator. It reaches up to 20 feet in length and is mostly recognized by its unique snout.

You can find these carnivores mostly around the northern Indian subcontinent. Humans are rushing to fix this before it goes fully extinct.


What are the predators of Glaucus atlanticus? - Biology

This is the only species in the genus Glaucus, but is closely related to Glaucilla marginata, another member of the family Glaucidae. The normal size of this species is up to 3 cm. It has dark blue stripes along the edge of its foot. It is silvery grey on its dorsal side and dark and pale blue ventrally. It has a tapering body which is flattened and has six appendages which branch out into rayed cerata. Its radular teeth bear serrated teeth on their blades. This nudibranch is pelagic, and is distributed throughout the world's oceans, in temperate and tropical waters.

Regions where this slug is found include the East and South Coast of South Africa, European waters, the east coast of Australia and Mozambique. This species floats upside down on the surface tension of the ocean.

G. atlanticus eats other, larger pelagic organisms: the dangerously venomous Portuguese Man o' War Physalia physalis the by-the-wind-sailor Velella velella the blue button Porpita porpita and the violet snail, Janthina janthina. Occasionally, individual Glaucus become cannibals given the opportunity.

Because Glaucus stores the venom, it can produce a more powerful and deadly sting than the Man o' War upon which it feeds.

With the aid of a gas-filled sac in its stomach, Glaucus atlanticus floats at the surface. Due to the location of the gas sac the sea swallow floats upside down. The dorsal surface, actually the foot and underside, has either a blue or blue-white coloration. The true dorsal surface is completely silver-grey. This coloration is an example of counter shading, which helps protect it from predators from below, sides and above.

Like most sea slugs, Glaucus is a hermaphrodite, containing both male and female reproductive organs. Unlike most nudibranchs, which mate with their right sides facing, sea swallows mate with ventral sides facing. After mating, both animals produce egg strings.

Scientists have often argued over whether Glaucus atlanticus moves on its own or depends on wind for locomotion.


This species looks similar to, and is closely related to, Glaucus marginatus, which is now understood to be not one species, but a cryptic species complex of four separate species that live in the Indian Ocean and Pacific Ocean.

At maturity Glaucus atlanticus can be up to 3 centimetres (1.2 in) in length. It is silvery grey on its dorsal side and dark and pale blue ventrally. It has dark blue stripes on its head. It has a flat, tapering body and six appendages that branch out into rayed, finger-like cerata.

The radula of this species bears serrated teeth.


Animal Facts

GLAUCUS ATLANTICUS is a specialist predator of siphonophores, jellyfish-like creatures such as the Portuguese Man o&rsquo War which float near the surface of the ocean and are often herded into large groups by the currents. G. Atlantici spend their lives floating amongst these aggregations, periodically gulping bubbles of gas into their stomachs to maintain buoyancy, and clinging to the surface tension with their muscular feet.

Siphonophores, like jellyfish, use venomous stinging cells (called nematocysts VIDEO) to capture prey and defend themselves against predators. G. Atlanticus, however, is immune to nematocysts and consumes them without harm. The inside of their mouths and esophagi are lined with a hard cuticle (made of chitin) which acts to absorb the impact of discharging nematocysts and keep the underlying muscle tissue safe. Additional protection comes from specialized mucus that inhibits nematocyst discharge by interfering with the trigger mechanism.

G. Atlanticus&rsquos domination of nematocysts does not stop at neutralization. Unfired nematocysts pass through the digestive system undamaged and eventually become incorporated into the body as fully functioning defensive weapons. Intestinal protuberances guide nematocysts to G. Atlanticus&rsquos rayed appendages where they are absorbed into muscularized chambers at the tips. Here they are nourished and stored, ready to be squeezed out if their new body comes under attack. A lifetime of meals concentrates powerful nematocysts from dozens of individual siphonophores, making the sting of G. Atlanticus a very potent cocktail.

Glaucus Atlanticus is a nudibranch (or sea slug), a gastropod mollusk closely related to marine snails. They drift with the currents in tropical and temperate oceans throughout the world. Their bodies measure between 3-5cm in length and possess 3 pairs of appendages that fan out into rayed cerata. Small chemosensory tentacles (called rhinophores) located on either side of the mouth help them find food, and they feed by using a toothed tongue (called a radula) to scrap and tear flesh from prey. They are short lived, typically spending their entire lives within a particular cluster of siphonophores. Like other nudibranchs, G. Atlanticus is hemaphroditic, possessing both male and female reproductive organs. After mating, which is reciprocal, both slugs lay egg strings, often on the bodies of their victims to endow their offspring with nourishment.

Video Credits. 1. Killer Jellyfish. Australian Natural History Unit.


Glaucus Atlanticus –AMAZING Blue Dragon

What is Glaucus Atlanticus? If you see it, you will inevitably remember dragons. However, in fact Glaucus Atlaticus is a marine gastropod mollusk, member of Glaucidae family, that has 2 genus: Glaucus Atlanticus and Glaucilla marginata. Blue dragon is found in temperate and tropical waters of South Africa, Europe and east coast of Australia and Mozambique.

Name belongs to the group of mollusks but it cannot produce shell. It is also known as blue sea slug or blue dragon. Name Glaucus takes us to the ancient Greece. According to Greek mythology, Glaucus was sea god, who was forced to live in the sea for his entire life. As for Glaucus Atlaticus it was first studied in 17th century by Foster and until 19th century was considered as insect that lives in the sea.

This slender animal is up to 3 cm long, it has air bubble inside its belly and this why GlaucusAtlaticus floats on the surface of ocean. They habitant is pelagic- wind or current can take it. Blue dragons are good at orientation too, if something turns them over, Glaucus return to their old condition, because they know on which side should be facing.
Some people may reckon that this is tiny creature, that has most carefree life in the world, is the cutest and the safest animal in the world but in fact, it can be very dangerous.
Small invertebrate eats hydrozoans – most poisonous Portuguese Man-o-war. (This by the way is fatal for human) Glaucus Atlaticus can easily swallow it. It has protective barriers (hard disks) inside body that secretes special mucus.
After eating, Glaucus Atlaticus stores poison inside body for future to defend itself. It sucks poison by special structure – cerata and keeps it in canidosacs, 84 small sacs on the upper surface of the body. Some scientists say that, if this creature collects much poison inside body, can become far more dangerous than Man-o-War.

Another instrument against predators is – camouflage called countershading. Blue dragon has silver grey color from its dorsal side and dark pale blue ventrally. It helps Glaucus Atlaticus to stay invisible for air predators, as well as sea enemies and continue safe floating on the ocean surface.
One more fact that is interesting is cannibalism among members of this species. Blue dragons eat each other if they cannot find enough food.

As all heterobranches, Glaucus Atlaticus is also hermaphrodite. It has both reproductive organs. After mating, both slugs produce eggs. They lay eggs on driftwood some of them use skeletons of enemies. As skeletons also float, young blue dragons live there until airbags are developed.
If one takes out Glaucus Atlaticus from water it rolls itself and becomes a ball, as soon as you put it back in the water it opens.

Considering all these fact, we must be careful if we suddenly meet these tiny creatures while surfing or swimming.


Watch the video: The Real Life Sea Dragon (January 2022).