70 years of helping people to care for our ocean

Teaching Tuesdays - Fun Facts

Mariana Trench
The Mariana Trench is the deepest part of the ocean, and more people have visited the moon than have been down to the Mariana trench. The pressure down there is so great, it would be like you were holding up 50 jumbo jets. Scientists have sent down Remotely Operated Vehicles that are under the control of a human operator at the surface in order to gather data from this ecosystem.
We know that the world's oceans cover 70% of the earth's surface, and yet less than 5% of our ocean has been explored. This is because we are unable to dive to the depths of the ocean (4km deep) and reply on submersibles. We can only imagine what might be down there.
Light only penetrates to 200m in the water column. This means that anything living below this depth lives in darkness all the time. Animals that live at these depths need to adapt to be able to feed. Some of them generate a light to attract prey, like the angler fish which has a modified luminescent fin that acts as a lure for other fish.
Turtles, jellyfish and plastic.
Did you know that around 8 million tons of plastic ends up in the ocean every year, and that at this rate, by 2050 the ocean may contain more plastic than it will fish. We have less than 30 years to become more sustainable.
The Earth's magnetic field is generated by the convection of molten iron in the planet's core, around 2 900 km beneath our feet. Scientists believe that this field acts like a GPS for various marine species, for example turtles and sharks who will use it to navigate and migrate. Sharks have Ampullae of Lorenzini, a special sensing organ of electroreceptors that can detect magnetic fields. Currently scientists believe our poles are reversing. This reversal is when the Earth’s magnetic north and south poles swap locations. While that may sound like a big deal, pole reversals are common in Earth’s geological history with the last one taking place about 780,000 years ago. But what effect this will have on marine species, we don't know.
Did you know that the world's longest mountain range actually occurs under water? This mountain range is formed at the mid atlantic ridge in the Atlantic ocean where two continental plates meet and converge upwards. This mid-ocean ridge stretches for 65 000km, is 2.5km high and 20-40 km wide.
I am sure if you think about all the animals you can identify on land you would think that it is a lot. Marine species outnumber those on land by 94%. What is even more alarming is that two thirds of marine species remain unidentified.
Jellyfish are members of the phylum Cnidaria which includes corals, anemones and bluebottles. Jellyfish are typically bell-shaped and fringed with stinging tentacles. Jellyfish swim by contracting and relaxing muscles at the margin of their bells. By contracting these muscles, they tighten the bottom of the bell which forces water out and propels them forward. Some feed on the organic particles that float around them as they drift through the sea whilst others capture small fish. Jellyfish are an important food source for leatherback turtles, sunfish and beach dwelling scavengers such as plough snails and ghost crabs. The adult stage is called a medusa after the unfortunate woman of Greek mythology who was loved by the god of the sea and as a result had her hair changed into snakes by a jealous goddess.
We all know the dangers of too much sun exposure and the need for sunscreen, but did you know that corals face a similar problem? As most corals are found in shallow water, they are exposed to UV radiation. Too much light can damage the zooxanthelle, a symbiotic algae that lives inside the coral. Some corals cope with this through fluorescence. As they fluoresce, they produce a protein, and this protein pigment forms a shield around the zooxanthelle, protecting them from harmful UV rays.
Did you know that pyjama cat sharks are endemic to South Africa? These sharks are called pyjama catsharks because of the stripes on their skin resembling that of pyjamas. They are bottom dwellers and can be found on coastal shallow rockery areas. The pyjama shark is predominantly nocturnal, spending most of the day hiding in a cave, crevice, or among plants. Cephalopods, crustaceans, bony fish, hagfish, bivalves, and bristle worms are among the creatures they prey upon. Female pyjama cat sharks produce eggs which are usually attached to kelp. Gestation is between 6 to 12 months and as is the case with all sharks, there is no parental care.
Sea anemones are well known for their link with clownfish, but these fascinating creatures are more than simply a home for fish. They come in many different forms and sizes, each with their own set of characteristics. Anemones lack a hard skeleton and instead are supported by water pressure. They have a cylindrical body with a collection of tentacles surrounding their mouths which are situated in the middle of their bodies. Sea anemone's stinging tentacles are used to sting prey as well as a defence mechanism. Their tentacles resemble those of their close relative the jellyfish.
Sea stars are marine creatures in the shape of a star and are commonly known as star fish. They are not fish because they do not have either gills, fins or scales. Although they lack a brain, they do have a complex nervous system and belong to the phylum echinoderm., While they lack advanced structures like other high order animals, their tube feet serve as sensors while moving in any direction and a light sensing organ at the end of each arm which helps keeps an eye on their surroundings.
A Hermit crab is an animal that does not move around without their home. There are over 800 species of hermit crab. They have two sets of antennae, as well as jointed limbs, claws, a strong exoskeleton, and eyes on stalks as do most crabs. The hermit crab is unique among crabs because its abdomen is not protected by a hard exoskeleton therefore this crab lives in an empty snail shell to protect his abdomen. Another interesting fact about the Hermit crab is that they need their gills to stay moist in order to breathe, so they have the ability to store water inside their shell in order to breathe when out of the water.
The tiger cowrie is one of the largest species of cowrie. These sea snails can grow up to 15cm in length. Did you know that tiger cowries are nocturnal? Tiger cowries have a mantle which they stretch over their shell as they move about. The mantle serves to repair and protect the cowries shell, often helping to camouflage it amongst its surroundings. However, this doesn’t stop octopus and some fish species feast on them by biting through their shells.
Is it a stone or a fish? Stonefish are the most venomous fish and are masters of camouflage. They are found on coral and rocky reefs, mud flats and in estuaries. Their powerful large mouths enable them to swallow their prey whole and at great speed. The neurotoxin of these fishes is the deadliest of all fish venoms. When stepped on, they can inject venom through grooves in the spines on their dorsal fins. Their venom is extremely painful and can be fatal to humans if not treated.
Some bony fish have more than one set of nostrils. These are not for breathing, but rather for smell. These nostrils are connected to their olfactory organ and are very sensitive. This enables predator fish to find food over long distances or in murky water.
Sea urchins have globular bodies encased in a calcium carbonate shell, which is also known as test, covered with spines. They have five radiating rows of tiny holes through which tube feet project. Did you know that sea urchins have teeth? Yes teeth. Their mouth is located in the centre on the underside and has five massive teeth. Most sea urchins are herbivores and feed on seaweed or microscopic algae. Their teeth are extremely sharp enabling them to scrape of the algae of the rocks. When reproducing, the males and females will release sperm and eggs into the water where fertilization will take place, and the larvae will form part of the plankton cycle until they settle out.
Bioluminescence. Pineapple or pinecone fish have sharp pointy scales and yellow colouration. But this is not the only interesting thing about this fish. They have organs on either side of their lower jaw which light up as their mouths open and close. These organs are filled with light producing bioluminescent bacteria which attract plankton, thus enabling the pineapple fish to feed at night.
Four Eyes? Are you seeing right? Does this fish have two eyes on the same side of its head or does it have four eyes? Sole are born as tiny round fish with one eye on each side of their body much like all other fish. They are however different from most fish in that during their first two weeks, they begin to change shape and flatten out. For most sole, the left eye moves to the right side of their head and their entire skull is shifted in the process. How does this benefit the fish? Having both eyes located on the same side of their body enables these skilled predators to see and catch their prey whilst remaining camouflaged in the sand
Have you ever wondered how a sea star feeds? Well it pushes its stomach out of its body and into its prey. It then secrets enzymes that digest the prey's soft body tissues which can then be absorbed into the sea stars stomach. After devouring the liquified victim., the stomach is then pulled back into the sea stars body. Many sea stars are carnivorous and prey on molluscs including clams, mussels and oysters.
Do dolphins sleep? Yes, but not like we do. While sleeping, a dolphin shuts down only half of its brain, along with the opposite eye. The other half of the brain stays awake at a low level of alertness. This allows the dolphin to control their breathing as they are conscious breathers. Dolphins are often found resting or sleeping in pairs or groups.
Did you know that shark teeth regrow? Sharks lose thousands of teeth over their lifetime, but they can also regenerate their teeth. This happens over a period of months, and the shark is capable of replacing lost teeth as many as 50 times over during the course of their life.
The body of a moray eel resembles that of a snake. Its enormous mouth is lined with rows of sharp, lethal teeth. They have two sets of jaws with teeth that point backwards to prevent prey from escaping. The honeycomb moray eel is the second largest of the moray eel species with a maximum length of 300cm and a weight of 29kg. These animals secrete transparent mucus that forms a protective layer over their skin enabling them to glide through the water. They are nocturnal and generally only hunt at night. Moray eels are carnivorous and prey on shellfish, crayfish, squid, octopus, shrimp, krill, as well as other sea creatures.
Can you curl your tongue into a tube? Well dolphins can! Along the edges they have tiny frills that connect like a zipper and when curled they form a watertight straw. Baby dolphins insert this tongue straw into the mother’s mammary slit to enable them to nurse while swimming.
Do penguins have teeth? No. Well not normal teeth. Penguins have papillae, structures on the tongue and palate comprised of soft keratin spikes. They curve backwards toward the back of the mouth and work a bit like a fish hook by grabbing onto a slippery fish and moving the fish down the penguin’s throat!
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