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Nudibranch The World’s Prettiest Slugs

Nudibranch The World's Prettiest Slugs

Nudibranch The World’s Prettiest Slugs

Description
Nudibranchs are mollusks in the class Gastropoda, which includes snails, slugs, limpets, and sea hairs. Many gastropods have a shell. Nudibranchs have a shell in their larval stage, but it disappears in the adult form. Gastropods also have a foot and all young gastropods undergo a process called ​​torsion in their larval stage. In this process, the entire top of their body twists 180 degrees on their foot. This results in the placement of the gills and anus above the head, and adults that are asymmetrical in form.
The word nudibranch comes from the Latin word nudus (naked) and Greek brankhia (gills), in reference to the gills or gill-like appendages which protrude from the backs of many nudibranchs. They also may have tentacles on their heads that help them smell, taste, and get around. A pair of tentacles called rhinophores on the nudibranch’s head have scent receptors that allow the nudibranch to smell its food or other nudibranchs. Because the rhinophores stick out and can be a target for hungry fish, most nudibranchs have the ability to withdraw the rhinophores and hide them in a pocket in their skin if the nudibranch senses danger.

Species
There are over 3,000 species of nudibranchs, and new species are still being discovered. They range in size from microscopic to over a foot and a half long and can weigh up to just over 3 pounds. If you’ve seen one nudibranch, you haven’t seen them all. They come in an astonishingly wide variety of colors and shapes—many have brightly colored stripes or spots and flamboyant appendages on their head and back. Some species are transparent and/or bio-luminescent, like the Phylliroe.
Nudibranchs thrive in an enormous variety of underwater environments, from shallow, temperate, and tropic reefs to Antarctica and even hydrothermal vents.

Suborders
Two main suborders of nudibranchs are dorid nudibranchs (Doridacea) and aeolid nudibranchs (Aeolidida). Dorid nudibranchs, like the Limacia cockerelli, breathe through gills that are on their posterior (back) end. Aeolid nudibranchs have cerata or finger-like appendages that cover their back. The cerata can be a variety of shapes—thread-like, club-shaped, clustered, or branched. They have multiple functions, including breathing, digestion, and defense.

Habitat and Distribution
Nudibranchs are found in all the world’s oceans, from cold water to warm water. You might find nudibranchs in your local tide pool, while snorkeling or diving on a tropical coral reef, or even in some of the coldest parts of the ocean or in thermal vents.
They live on or near the sea floor and have been identified at depths between 30 and 6,500 feet below the ocean surface.

Diet
Most Nudibranchs eat using a radula, a toothed structure that they use to scrape off prey from the rocks they cling to; some suck out the prey after predigesting its tissue with selected enzymes, rather like a wasp. They are carnivorous, so that prey includes sponges, coral, anemones, hydroids, barnacles, fish eggs, sea slugs, and other nudibranchs. Nudibranchs are picky eaters—individual species or families of nudibranchs may eat only one kind of prey. Nudibranchs get their bright colors from the food they eat. These colors may be used for camouflage or to warn predators of the poison that lies within.
The Spanish shawl nudibranch (Flabellina iodinea) feeds on a species of hydroid called Eudendrium ramosum, which possesses a pigment called astaxanthin that gives the nudibranch its brilliant purple, orange, and red coloration.
Some nudibranchs, like the Blue Dragon, create their own food by eating coral with algae. The nudibranch absorbs the algae’s chloroplasts (zooxanthellae) into the cerata, which acquire nutrients by photosynthesis using the sun to sustain the nudibranch for months. Others have evolved other ways of farming zooxanthellae, housing them in their digestive gland.

Behavior
The sea slugs can see light and dark, but not their own brilliant coloration, so the colors are not intended to attract mates. With their limited vision, their sense of the world is obtained through their rhinophores (on top of the head) and oral tentacles (near the mouth). Not all nudibranchs are colorful; some use defensive camouflage to match the vegetation and hide, some can change their colors to fit, some hide their bright colors only to bring them out to warn off predators.
Nudibranchs move on a flat, broad muscle called a foot, which leaves a slimy trail. While most are found on the ocean floor, some can swim short distances in the water column by flexing their muscles. Some even swim upside down.
Aeolid nudibranchs can use their cerata for defense. Some of their prey such as Portuguese man-of-wars have a specialized cell in their tentacles called nematocysts that contain a barbed or venomous coiled thread. Nudibranchs eat the nematocysts and store them in the nudibranch’s cerata where they can be used late to sting predators. Dorid nudibranchs make their own toxins or absorb toxins them from their food and release those into the water when needed.
Despite the unsavory or toxic taste they can present to their non-human predators, most nudibranchs are harmless to humans, except those like Glaucus atlanticus which consumes nematocytes and so may consider you a predator and sting.

Reproduction and Offspring
Nudibranchs are hermaphrodites, meaning that they have reproductive organs of both sexes. Because they can’t move too far, too fast and are solitary in nature, it’s important for them to be able to reproduce if the situation presents itself. Having both sexes means that they can mate with any adult that happens to pass by.
Nudibranchs lay masses of spiral-shaped or coiled eggs, which are for the most part left on their own. The eggs hatch into free-swimming larvae which eventually settle onto the ocean bottom as adults. Only one species of nudibranch, the Pteraeolidia ianthina, exhibits parental care by guarding the newly-laid egg masses.

Nudibranchs and Humans
Scientists study nudibranchs because of their complex chemical makeup and adaptations. They have rare or novel chemical compounds which possess anti-microbial and anti-parasitic traits which may aid in the fight against cancer.
Studies of nudibranch DNA also offer assistance in tracking ocean conditions relative to climate change.

Threats
These beautiful animals don’t live very long; some live up to a year, but some only for a few weeks. The global population of nudibranchs is currently unassessed—researchers are still discovering new ones each year—but field observations such as that conducted by Endangered Species International suggest that many species are becoming rare, due to water pollution, degradation, habitat loss, and biodiversity decline associated with global warming.

Source : https://www.thoughtco.com/facts-about-nudibranchs-2291859 

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Komodo The Last Dragon on Earth

Komodo

Komodo

Physical Description
Komodo dragons are large lizards with long tails, strong and agile necks, and sturdy limbs. Their tongues are yellow and forked. Adults are an almost-uniform stone color with distinct, large scales, while juveniles may display a more vibrant color and pattern.

The muscles of the Komodo’s jaws and throat allow it to swallow huge chunks of meat with astonishing rapidity. Several movable joints, such as the intramandibular hinge opens the lower jaw unusually wide. The stomach expands easily, enabling an adult to consume up to 80 percent of its own body weight in a single meal, which most likely explains some exaggerated claims for immense weights in captured individuals. When threatened, Komodos can throw up the contents of their stomachs to lessen their weight in order to flee.

Although males tend to grow larger and bulkier than females, no obvious morphological differences mark the sexes. One subtle clue does exist: a slight difference in the arrangement of scales just in front of the cloaca. Sexing Komodos remains a challenge for human researchers; the dragons themselves appear to have little trouble figuring out who is who.

Size
The Komodo dragon is the largest living lizard in the world. These wild dragons typically weigh about 154 pounds (70 kilograms), but the largest verified specimen reached a length of 10.3 feet (3.13 meters) and weighed 366 pounds (166 kilograms). Males tend to grow larger and bulkier than females.

Native Habitat
Komodo dragons are limited to a few Indonesian islands of the Lesser Sunda group, including Rintja, Padar and Flores, and of course the island of Komodo, the largest at 22 miles (35 kilometers) long. They have not been seen on the island of Padar since the 1970s.

They live in tropical savanna forests but range widely over the islands, from beach to ridge top.

Food/Eating Habits
Komodo dragons eat almost any kind of meat, scavenging for carcasses or stalking animals that range in size from small rodents to large water buffalo. Young feed primarily on small lizards and insects, as well as snakes and birds. If they live to be 5 years old, they move onto larger prey, such as rodents, monkeys, goats, wild boars and deer (the most popular meal). These reptiles are tertiary predators at the top of their food chain and are also cannibalistic.

Although the Komodo dragon can briefly reach speeds of 10 to 13 mph (16 to 20 kph), its hunting strategy is based on stealth and power. It can spend hours in one spot along a game trail — waiting for a deer or other sizable and nutritious prey to cross its path — before launching an attack.

Most of the monitor’s attempts at bringing down prey are unsuccessful. However, if it is able to bite its prey, bacteria and venom in its saliva will kill the prey within a few days. After the animal dies, which can take up to four days, the Komodo uses its powerful sense of smell to locate the body. A kill is often shared between many Komodo dragons.

Monitors can see objects as far away as 985 feet (300 meters), so vision does play a role in hunting, especially as their eyes are better at picking up movement than at discerning stationary objects. Their retinas possess only cones, so they may be able to distinguish color but have poor vision in dim light. They have a much smaller hearing range than humans and, as a result, cannot hear sounds like low-pitched voices or high-pitched screams.

The Komodo dragon’s sense of smell is its primary food detector. It uses its long, yellow, forked tongue to sample the air. It then moves the forked tip of its tongue to the roof of its mouth, where it makes contact with the Jacobson’s organs. These chemical analyzers “smell” prey, such as a deer, by recognizing airborne molecules. If the concentration of molecules present on the left tip of the tongue is greater than that sample from the right, the Komodo dragon knows that the deer is approaching from the left.

This system, along with an undulatory walk, in which the head swings from side to side, helps the dragon sense the existence and direction of food. At times, these reptiles can smell carrion, or rotting flesh, up to 2.5 miles (4 kilometers) away.

This lizard’s large, curved and serrated teeth are its deadliest weapon, tearing flesh with efficiency. The tooth serrations hold bits of meat from its most recent meal, and this protein-rich residue supports large numbers of bacteria. Some 50 different bacterial strains, at least seven of which are highly septic, have been found in the saliva. Researchers have also documented a venom gland in the dragon’s lower jaw. In addition to the harmful bacteria, the venom prevents the blood from clotting, which causes massive blood loss and induces shock.

The Komodo’s bite may be deadly, but not to another Komodo dragon. Those wounded while sparring with each other appear to be unaffected by the bacteria and venom. Scientists are searching for antibodies in Komodo dragon blood that may be responsible.

The lizard’s throat and neck muscles allow it to rapidly swallow huge chunks of meat. Several movable joints, such as the intramandibular hinge, open its lower jaw unusually wide. The dragon’s stomach also easily expands, enabling an adult to consume up to 80 percent of its own body weight in a single meal. When threatened, Komodo dragons can throw up the contents of their stomachs to lessen their weight in order to flee.

Komodo dragons are efficient eaters, leaving behind only about 12 percent of their prey. They eat bones, hooves and sections of hide, as well as intestines (after swinging them to dislodge their contents).

At the Smithsonian’s National Zoo, the Komodo dragon eats rodents, chicks and rabbits. Occasionally, he consumes fish and carcass meals of beef.

Social Structure
Because large Komodos cannibalize young ones, the young often roll in fecal material, thereby assuming a scent that the large dragons are programmed to avoid. Young dragons also undergo rituals of appeasement, with the smaller lizards pacing around a feeding circle in a stately ritualized walk. Their tail is stuck straight out and they throw their body from side to side with exaggerated convulsions.

Reproduction and Development
Determining the sex of a Komodo dragon is challenging for researchers, as no obvious morphological differences distinguish males from females. One subtle clue is a slight difference in the arrangement of scales just in front of the cloaca. Courtship opportunities arise when groups assemble around carrion to feed, and mating occurs between May and August.

Dominant males compete for females in ritual combat. Using their tails for support, they wrestle in upright postures, grabbing each other with their forelegs as they attempt to throw the opponent to the ground. Blood is often drawn, and the loser either runs away or remains prone and motionless.

Females lay about 30 eggs in depressions dug on hill slopes or within the pilfered nests of megapodes — large, chicken-like birds that make nests of heaped earth mixed with twigs that may be as long as 3 feet (1 meter) in height and 10 feet (3 meters) across.

Delays in egg laying may occur, which could help the clutch avoid the brutally hot months of the dry season. Additionally, unfertilized eggs may have a second chance with subsequent mating. While the eggs incubate in the nest for about nine months, the female may lay on the nest to protect the eggs. No evidence of parental care for newly hatched Komodos exists.

The hatchlings weigh less than 3.5 ounces (100 grams) and average 16 inches (40 centimeters) in length. Their early years are precarious, and they often fall victim to predators, including other Komodo dragons. At 5 years old, they weigh about 55 pounds (25 kilograms) and average 6.5 feet (2 meters) long. At this time, they begin to hunt larger prey. They continue to grow slowly throughout their lives.

Sleep Habits
They escape the heat of the day and seek refuge at night in burrows that are just barely large enough for them.

Lifespan
Komodo dragons live about 30 years in the wild, but scientists are still studying this

Article by https://nationalzoo.si.edu/animals/komodo-dragon 

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