What are sand dollars?

When alive, they look like huge coins with their flat, disk-shaped body. But mostly you would come across them when they have deceased. You might notice these patterned white shells in the sand. These star-stamped skeletons (tests) are much sought-after by beachcombers. (But let us warn you, it is never advised to pick up these creatures, dead or alive). Meet sand dollars, the bottom-dwelling creatures in the ocean.

Also called sea biscuits or sand cakes, the sand dollars belong to the order Clypeastroida. They are close relatives of sea urchins and heart urchins and are adapted to burrow themselves in sandy substrates. They dwell in the tropical and temperate waters throughout the Northern Hemisphere. Measuring from 5 to 10 cm in diameter, the sand dollars are invertebrates belonging to the class of marine animals known as echinoids. They have a radiating arrangement of parts.

The holes in their skeleton are what you notice first. But these aren't there just for design sake. Arranged in a unique petal fashion these sets of gas-and water-processing pores are called lunules and act as pressure drainage channels.

The upper surface of their body showcases what is called pentaradiate (five-fold) symmetry From its centre, a pattern of five "petals" spread out. The mouth of this unique creature is located at the centre of its body's underside.

While alive, the sand dollars have bristles known as spines which even cover their star design and they appear in hues ranging from reddish-brown to purple. When they die, these skeletons turn white, bleached by the sun, which is how you may often find them on the beach.

They breathe through the "petaloids", a set of tiny holes in the skeleton. They live in the sand, using their spines to burrow into the sand. If the water is still, they can be seen standing upright, with one of their ends buried in the sand and they lie down or burrow themselves under the sand if the waters get rough.

Adult sand dollars live on the sea floor while the larva (also called pluteus) floats among the ocean's planktons. The juveniles are seen in the subtidal zones while the adult sand dollars live in the intertidal zone.

Some of the threats these creatures face include bottom trawling, ocean acidification, climate change and so on. It is illegal to remove the sand dollars in most regions. Why we suggest that you should never pick them up is that you may not know if they are dead or alive. They can survive out of water for only a few minutes.

TRIVIA

Sand dollars use their spines to eat. They feed on small food particles in the sand and are said to take two whole days to digest food.

The creature gets its name from the resemblance it has to dollar coins. Other names include "sand cake," "sea biscuit," "cake urchin," "pansy shell", "sea cookie" and so on.

A sand dollars age can be ascertained by the number of rings it sports on the plates of the creature's test. As they grow, the number of rings increases.

The larva of the sand dollar splits itself into two identical clones to hide from predators.

* The mouth of a sand dollar is called Aristotle's lantern.

Picture Credit : Google

WHAT IS A BAYMOUTH BAR?

When the movement of waves deposits gravel and sand in a manner that prevents access to a bay, it builds up a baymouth bar. The existence of the bar creates a shallow lake known as a lagoon that is separated from the sea by a beach.

A baymouth bar is a depositional feature as a result of longshore drift. It is a spit that completely closes access to a bay, thus sealing it off from the main body of water. These bars usually consist of accumulated gravel and sand carried by the current of longshore drift and deposited at a less turbulent part of the current. Thus, they most commonly occur across artificial bay and river entrances due to the loss of kinetic energy in the current after wave refraction.

In most cases, a Sand Bypass System is built to prevent these bars forming across the entrance of man-made seaway's, eliminating the danger posed to commercial and recreational boat owners passing through.

credit: en-academic.com

Picture Credit : Google 

Which is the world’s first omnivorous shark?

Bonnethead sharks were thought to be solely carnivorous, but according to University of California researchers, they're omnivorous they can eat both animals and plants.

Bonnetheads, one of the smallest members of the hammerhead family, are abundant in the waters of the Americas, where they usually feed on crab, shrimp, snails and bony fish. Its plant of choice is seagrass. Researchers fed five bonnetheads on a three-week diet of seagrass and squid. All the sharks put on weight over the course of the study. Tests on the sharks showed that they successfully digested the seagrass with enzymes that broke down components of the plants. A possible reason for the sharks' omnivorous lifestyle is potentially avoiding conflict with other species such as bull sharks or nurse sharks for food.

It is one of the most radical rebrandings in history: contrary to their bloodthirsty image, some sharks are not irrepressible meat eaters, but are happy to munch on vegetation too. According to US researchers, one of the most common sharks in the world, a relative of the hammerhead which patrols the shores of the Americas, is the first variety of shark to be outed as a bona fide omnivore. The bonnethead shark is abundant in the shallow waters of the eastern Pacific, the Western Atlantic, and the Gulf of Mexico, where they feed on crab, shrimp, snails and bony fish. Though small by shark standards, adult females – the larger of the sexes – can still reach an impressive five feet long. Scientists at the University of California in Irvine, and Florida International University in Miami, decided to investigate the sharks’ dietary habits after reading reports of the fish chomping on seagrass, the flowering marine plant that forms subsea meadows in some coastal waters.

To see whether the sharks are truly flexitarian, the scientists retrieved sea grass from Florida Bay and hauled it back to the lab where they re-planted it. As the seagrass took root, the researchers added sodium bicarbonate powder made with a specific carbon isotope to the water. This was taken up by the seagrass, giving it a distinctive chemical signature. The researchers next caught five bonnethead sharks and brought them back to the lab. Once the fish had settled in, they were fed on a three week diet of the seagrass and squid. All of the fish put on weight over the course of the study. The scientists then ran a series of tests on the sharks. These showed that the fish successfully digested the seagrass with enzymes that broke down components of the plants, such as starch and cellulose. Lacking the kind of teeth best suited for mastication, the fish may rely on strong stomach acids to weaken the plants’ cells so the enzymes can have their digestive effects. In all, more than half of the organic material locked up in the seagrass was digested by the sharks, putting them on a par with young green sea turtles.

Credit : The Guardian

Picture Credit : Google 

What jellyfish looks like a plastic bag?

First discovered in the 1960s, Deepstaria enigmatica — named for underwater explorer Jacques Cousteau's submersible Deepstar 4000, and the jellyfish's mysteriousness - has only made rare appearances since.  It is looking like a plastic bag. In November 2017, Deepstaria was spotted off the coast of San Benedicto Island, around 3,195 feet deep down in the Pacific Ocean.

Resembling a plastic bag, it has a large, thin bell and no tentacles. Since most jellyfish use tentacles to catch their prey, Deepstaria has to rely on another method. Since its bell can open up to a metre across, Deepstaria uses it to catch upward-moving prey. closing around the prey like a bag.

Deepstaria enigmatica have been observed during jelly-falls. This happens when a jellyfish carcass falls through the water column to the ocean floor. A Deepstaria enigmatica jelly fall was first observed in the lower portion of the oxygen minimum zone of the ocean. It was observed as shrimp and crabs were scavenging its carcass.

These jelly falls are advantageous to the ocean floor, causing a source of organic enrichment, similar to a whale fall; as carcasses decay away from light and the more oxygen-rich environments of the upper ocean, the animal decays far slower, providing a longer-lasting source of nutrients. The carcasses lead to a restoration of degraded mineral content in the water column. The contribution of these jelly falls is underestimated. The Deepstaria enigmatica fall shows an increase in oxygen availability and organic matter, benefitting the ecosystems found at the bottom of the ocean.

The Deepstaria jellyfish, unlike many jellyfish, lacks tentacles of any kind, which other species of jellyfish commonly use to entrap and consume prey. Instead, Deepstaria trap prey inside their bell, where they are consumed. This method also provides for isopods, who may live inside the jellyfish's bell in a symbiotic relationship

In the 1960s Jacques Cousteau, a French explorer, unexpectedly found the Deepstaria jellyfish in a deep-sea exploration mission. He was exploring the deep sea near Southwest Baker Island in a submarine called the Deepstar 4000, which became the inspiration for the name of this jellyfish. The Deepstaria jellyfish has been found in the Gulf of Mexico, Antarctic, and the Pacific Ocean. In all of these locations, the jellyfish was found 3,000 ft (910 m) below sea level.

Credit : Wikipedia 

Picture Credit : Google 

Do Seahorse males give birth?

When it comes to seahorses, it is the male that gets pregnant and gives birth to baby seahorses. The female swims to the surface of the water with the interested male in tow. It transfers its orange eggs into the pouch of the male which then adds its sperm and seals the opening. The growing babies will remain in their dad's pouch till they develop. Once they are born the babies are on their own.

After completing an elaborate courtship dance that may go on for hours or days, the female seahorse transfers her mature eggs into the male’s brood pouch, where they are fertilized. At the end of a gestation period usually lasting from two to four weeks, the pregnant male’s abdominal area begins to undulate rhythmically, and strong muscular contractions eject from a few dozen to as many as 1,000 fully formed baby seahorses into the surrounding water. After that, the offspring must fend for themselves. Large litters are necessary because only about 0.5 percent will survive to adulthood.

Many, if not all, of the 47 known seahorse species—14 of which were identified only in the 21st century—are in decline worldwide.

Because seahorses generally live in shallow, near-coastal waters, human activities including development, pollution, fisheries, and traditional medicine have reduced their numbers. At the same time, their universal appeal has worked against them; until recently, wild seahorses were often captured for the aquarium trade. The delicate creatures tend to fare poorly in aquaria, however. In recent years, captive-bred seahorses have shown promise as hardier tank-dwellers than their wild relatives.

Credit : National Ocean Service

Picture Credit : Google

What is seashore?



 



 



 



The seashore is where the land meets the sea. Sometimes seashores are rocky and have high cliffs. Other seashores are gently sloping, sandy beaches. In some places seashores are made from lots of smooth stones.



 



 



 





 



 



These waves are crashing against cliffs.



This seashore is made from hard rock and has steep cliffs. When waves smash against the cliffs, they slowly wear them away or crack the rock. Sometimes the cliff breaks apart and large pieces of rock fall down into the sea. Under the water, the fallen rocks are tumbled together by the waves and break up into tiny pieces.



 



 





 



 



A sandy beach slopes down into the sea.



When land made from soft rocks meets the sea, the seashore is flat and sandy. Sand is made up of billions of tiny pieces of rock and broken shells.



 



 





 



 



Shingle beaches are covered with stones.



Shingle beaches are made up of small pebbles that have been smoothed by the waves. Shingle seashores are hard places for animals and plants to live because the sea moves the stones around. Most wildlife lives high up on the shore out of reach of the waves.


Different seashores



 



 



 



There are different seashores all over the world. Some seashores are hot and some are icy cold. The animals found on icy seashore can live where it is very cold. They keep warm by having thick fur or oily feathers and a layer of fat under their skin.



 



 



 





 



These birds are looking for food in the mud.



When rivers reach the sea they spread out into wide, muddy seashore called an estuary. Huge flocks of birds feed on muddy estuaries. They hunt for worms, shellfish or crabs in the mud. When the sea flows into the estuary and covers the mud, the birds fly ashore and wait until it goes out again.



 



 





 



 



These penguins live on cold, icy seashore.



In very cold parts of the world, the seashore is icy. Penguins nest on the icy seashores of the Antarctic. It is so cold that they huddle together to keep warm. They keep their egg on top of their feet to stop it from freezing on the ice.



 



 



 





 



 



This seashore is in a hot part of the world.



Coral reefs grow in warm, shallow seas. Coral reefs are made by small animals that live close together. They protect themselves by building hard cases. It is the hard cases that form the coral reef. Coral reefs are important because they are home to many animals.


Changing tides



 



 



Twice a day, the sea moves up and down the seashore. It is high tide when the beach is covered with sea. After high tide, the sea turns and goes back out again. When the sea is far out and the beach is uncovered, it is low tide.



 



 





 



At high tide the seashore is covered.



At high tide, the seashore is covered with water. The high tide line is the highest place the water reaches up the seashore. The tides are caused by the gravity of the Moon and Sun pulling the seawater towards them.



 



 





 



The seashore is uncovered at low tide.



At low tide, the seashore is uncovered and the sea is far out. On some seashore the difference between high and low tides is big. On others it is small. Low tide happens twice in about 25 hours.



 



 



 





 



Waves are made by the wind.



The waves that move across the sea and break on seashore are made by the wind. When the wind blows over the sea, it pushes and drags against the surface and forms waves. Strong storm winds make huge waves. On days when there is no wind blowing, the sea is calm and the waves are very small.


Seashore plants and animals hold on tight

The waves that crash on to a seashore are very strong. Seashore plants and animals must hold on tight to keep themselves safe. If they let go, they could be washed away or smashed on the rocks.





 



 



These limpets are holding on to a rock.



Seashore animals have different ways of holding on. Limpets use their strong foot to grip tightly on to rocks and stop them from being washed away. Some animals, like sea urchins, cling on to rocks with lots of tiny feet that look like tubes. Mussel shellfish anchor themselves down to rocks with tough threads.



 



 





 



 



This seaweed grips on tightly to the rocks.



Seaweeds anchor themselves on to rocks to stop them from being washed away by strong waves. Large seaweeds grip on to rocks with strong, finger-like rootlets called holdfasts. During storms, seaweed is ripped off rocks.



 





 



 



 



 



Sea otters wrap themselves in seaweed.



When sea otters sleep, they wrap themselves in giant kelp seaweed. They grab a floating end of kelp and spin around in the water. The kelp wraps around the otter and anchors it down. It stops the sea from carrying the sea otter away in its sleep.



 


Seashore Shells



 



 



 



Shellfish are small animals that live inside shells. Their hard shells help to keep them safe from being eaten by other animals or smashed by waves. When shellfish are out of water, their shells stop them from drying out.



 



 



 





 



 



      These shellfish live in one shell.



Some shellfish live in one shell. The animal that lives inside has a very strong, muscular foot which it uses to move itself and to cling to rocks with. If the animal is in danger, it withdraws and hides inside its shell. These shellfish feed on seaweed or on other animals.



 



 





 



 



This shellfish has two shells joined together.



Some shellfish have two shells that are hinged together. Scallop shellfish swim by flapping their shells open and shut. Shellfish with two shells feed by sucking in water, and straining out small bits of food.



 



 



 



 





 



This hermit crab lives in an old shell.



Hermit crabs have a long soft body which they protect by living in an empty shell. They have a pair of strong hooks on their rear end to hold them safely in their shell. When a hermit crab grows too big for its shell, it will find a bigger shell to live in.


Life in a rock pool



 



 



When the tide goes out, some water is left behind in hollows in the rocks. Many different seaweeds and animals live in these rock pools. They can stay safely underwater in the rock pool until the sea comes in again.



 



 



 





 



 



Starfish live in rock pools.



 



The underside of a starfish is covered with lots of tiny tube feet. It uses the feet to move and to grip on to rocks. Starfish feed on shellfish and use their arms to force open the shells to reach the soft animal inside. If a starfish loses any of its arms, it can grow new ones.



 



 





 



 



 



Sea anemones are animals.



Sea anemones look like flowers, but they are animals. They catch food with their tentacles. When a sea anemone is out of the water, it pulls in its tentacles to stop itself from drying out. It looks like a blob of jelly!



 



 





 



 



 



This is a rock pool food chain.



A food chain shows the link between plants and animals in a habitat. All food chains start with plants, which are eaten by plant-eating animals. Plant-eaters are eaten by flesh-eating animals. In a rock pool, seaweeds are food for animals like limpets. Limpets are eaten by whelks.


Seashores animals - Digging in



 



 



 



Many seashore animals bury themselves in the sand, mud or rock. They dig themselves in to try to keep themselves safe from being eaten. Some animals hide in the sand when the tide is out. This stops the animal from drying out in the wind or Sun.



 



 



 





 



 



These are lugworm casts on a sandy beach.



Lugworms live in U-shaped burrows on sandy or muddy seashores. They swallow mud and eat any pieces of food they find in it. The sand comes out of the worms’ bottom at the other end of the burrow, and makes a squiggly worm cast on the surface of the mud.



 



 





 



This dog whelk hides in cracks in rocks.



Some shellfish protect themselves by digging into rock or squeezing into gaps between rocks. Dog whelks hide under rocks, crawl into cracks and wedge themselves into crevices on rocky seashores when the tide goes out. When the tide comes back in the dog whelks come out to feed.



 



 





 



 



Cockles bury themselves in the sand.



Cockles use their muscular foot to bury themselves in the sand. This helps to protect them from being eaten by birds and animals. Cockles and razorshells feed using long siphons that suck water and strain food from it.


Seashore plants



 



 



Many plants live on the seashore. Seaweeds are seashore plants that can live in salty seawater. Some seashore plants can only live on the land. They grow high up the shore, out of the reach of the waves.



 



 



 



 





 



This seaweed floats in the water.



Bladder wrack seaweed has pockets of air and jelly to help it float in the water. Its tough leathery leaves are covered in a slippery, gummy substance to protect it from drying out at low tide. Bladder wrack can survive out of water while the tide is out.



 


 


 


 


 




 


 


 



 



Kelp seaweed grows very fast.



Californian kelp seaweed is the fastest growing plant in the world. It can grow up to one metre in a day and can reach lengths of 100 metres. Kelp grows in huge underwater forests, which are home to many fish and other animals.



 



 



 





 



 



 



These tough grasses grow on sand dunes.



Marram grass is a tough plant that grows on sand dunes at the seashore. It has thin, curled leaves to protect it from drying out in the wind and the Sun. Marram grass has long roots to reach down to water. The roots stop the plant blowing away.




 

Seashore birds



 



 



Seashore birds feed on different foods. They hunt for food on the land and in the sea. Some birds dig in the sand to find worms and shellfish. Fish-eating birds dive into the sea to catch their food.



 



 



 



 



 



 





 



 



Seashore birds build their nests on steep cliffs.



Seashore birds often nest together in huge, noisy colonies. They make their nests on high, rocky cliffs because it is very difficult for predators to reach them there. Some seabirds make nests, but others just lay their eggs on a rocky ledge.



 



 


Continue reading "Seashore birds"

Seashore Fishes



 



 



 



At low tide, seashore fish hide. They squeeze into cracks in rock pools or hide under the sand. When the tide comes in, they come out to feed. Seashore fish have eyes near the top of their head. They look out for seabirds that try to catch them from above.



 



 



 





 



 



This fish lives in rock pools.



Goby fish live in rock pools. Their skin is patterned to help them hide against the rocks and seaweed. Some goby fish have their lower fins joined together to make a sucker. They use the sucker to cling on to rocks and stop them from being swept away by waves.



 



 





 



 



These pipefish are hard to see.



Pipefish can hide themselves so well that they are very hard to see. They have a long, thin body that helps to disguise them when they hide in seaweed. They live in rock pools and feed on other small fish and shellfish.



 



 





 



 



This fish can breathe air.



Mudskipper fish live on warm, muddy seashores. Most fish can only breathe in water. Mudskipper fish can breathe in air and water. They use their front fins as legs and crawl about on mud to look for food.