One of the main reasons sharks are such effective predators is their keenly attuned senses.  However, when you take one of these super-senses away, it significantly hinders the shark's hunting ability. By themselves, none of a shark's sense organs would be adequate for effective hunting. But by combining all of these senses, the shark becomes an incomparable predator.

A unique sense organ of the shark is its lateral line. The lateral line is basically a set of tubes just under the shark's skin. The two main tubes run on both sides of the body, from the shark's head all the way to its tail. Water flows into these main tubes through pores on the skin's surface. The insides of the main tubes are lined with hair-like protrusions, which are connected to sensory cells. In some species, the receptive organs of the lateral line have been modified to function as electroreceptors, which are organs used to detect electrical impulses, and as such these systems remain closely linked. When something comes near the shark, the water running through the lateral line moves back and forth. This stimulates the sensory cells, alerting the shark to any potential prey or predators in the area. The lateral line plays an essential role in orientation, predatory behaviour, and social schooling.

Initially, scientists thought of sharks as giant swimming noses. When researchers plugged the nasal openings in captive sharks, the sharks had trouble locating their prey. Showcasing the theory that a shark needs all of its senses working together as a team. The shark's nose is definitely one of its most impressive (and prominent) features. As the shark moves, water flows through two forward facing nostrils, positioned along the sides of the snout. The water enters the nasal passage and moves past folds of skin covered with sensory cells. In some sharks, these sensitive cells can detect even the slightest traces of blood in the water. A great white shark, for example, would be able to detect a single drop of blood in an Olympic-size pool. Most sharks can detect blood and animal odours from many miles away. Another amazing thing about a shark's sense of smell is that it's directional. The twin nasal cavities act something like your two ears: Smell coming from the left of the shark will arrive at the left cavity just before it arrives at the right cavity. In this way, a shark can figure out where a smell is coming from and head in that direction.

Did you know that sharks also have a very acute sense of hearing? Never seen a shark with ears? Well, sharks only have an inner ear. Two holes on either side of a shark's head might be the only clue you'd have to the presence of shark ears. Yet sound is often the shark's first tip-off that prey is nearby. Research suggests they can hear low pitch sounds well below the range of human hearing. Sharks may track sounds over many miles, listening specifically for distress sounds from wounded prey. Because sound travels farther and faster underwater, sharks are easily able to detect their prey from distances of more than 800 feet (243 meters). The shark's ear is made up of three semicircular canals, which primarily provide the shark with balance. However, inside each canal are four sensory maculae, some of which are tasked with auditory function.

In sharks, eyesight varies from species to species. Some less active sharks that stay near the water's surface don't have particularly acute eyesight, while sharks that stay at the bottom of the ocean have very large eyes that let them see in near darkness.

Many shark species also rely heavily on their sense of taste. Before these sharks eat something, they will give it a "test bite" first. The sensitive taste buds clustered in the mouth analyze the potential meal to see if it's palatable. Sharks will often reject prey that is outside their ordinary diet (such as human beings), after this first bite.

These physiological advances have helped sharks evolve into successful apex predators, surviving and thriving for millennia . . .

Sharks and rays share our senses – those of smell, taste, hearing, touch, and sight – but they inhabit a world very different from ours: in the ocean, light and sound move at very different angles and speeds than in air. To travel the globe, locate other fish and hunt prey in an aquatic medium, both sharks and rays have evolved two additional ways of perceiving their environment: they can sense electrical pulses and perceive both vibrations and pressure changes. Thanks to their super-power-like Ampullae of Lorenzini.

The ampullae of Lorenzini are special sensing organs called electroreceptors and they were first described by Stefano Lorenzini in 1678.  It was not until 1960 however that the ampullae were clearly identified as specialized receptor organs for sensing electric fields.

Each ampulla is visible on the surface of the skin as a small pore, with each pore connecting to a long, jelly-filled canal in which a bundle of sensory cells innervated by nerve fibres is located.  The ampullae of Lorenzini allow sharks, skates, and rays to detect weak electric fields emitted by fish in distress, and it may also respond to mechanical stimuli. The ampullae may also allow the shark to detect changes in water temperature.

Sharks may be more sensitive to electric fields than any other animal, with a threshold of sensitivity as low as 5 nV/cm. Since all living creatures produce an electrical field due to muscle contractions, it is easy to imagine that a shark or ray can locate prey buried in the sand thanks to the electrical stimuli.

The electric fields produced by oceanic currents moved by the Earth's magnetic field are of the same order of magnitude as the electric fields that sharks and rays are capable of sensing. This could mean that sharks and rays can orient to the electric fields of oceanic currents, and use other sources of electric fields in the ocean for local orientation. Additionally, the electric field they induce in their bodies when swimming in the magnetic field of the Earth may enable them to sense their magnetic heading.

Sharks typically have several thousand ampullar pores; the scalloped hammerhead shark, for example, has over 3,000, and the number remains the same during the shark’s life. In many elasmobranch species, the pores are most dense near the mouth, where prey movements are last sensed before being captured.

Hammerhead sharks are particularly skilled in this behaviour: their broad head is thought to be an evolutionary result of placing importance, or more dependence, on this sixth sense while hunting and migrating. Having a head with a large surface area allows hammerhead sharks to host a greater number of ampullae and higher pore density on the ventral surface of the head compared to other shark species. How cool to have you very own built-in GPS!?

 

Scientists fear that ocean acidification could pose further problems for sharks, whose numbers are shrinking worldwide due to human activity.

No one knew how juvenile sharks might respond to climate change until now. Scientists found that the condition and survival of young tropical bamboo sharks (Chiloscyllium punctatum) fell sharply if they developed and hatched in warmer, more acidic water. 

Acidic water affects how some ocean animals take up calcium to build their bones and shells. But without bones, sharks should have no such problems, since sharks’ muscles attach to a lightweight framework of cartilage unlike the boney skeletons of other fish.

In a laboratory, researchers observed the embryos’ survival at their native temperature and pH, and with combinations of a 4° C increase in temperature and/or a 0.5 lowering of pH. Initially, most of the shark embryos survived. But after they hatched, the young sharks’ condition deteriorated. In the group exposed to both warming and lowered pH, more than half the young sharks died within 30 days after hatching. 


The sharks may adapt over several generations. However, the long lifespans of many species and their relatively low rates of reproduction might limit how quickly they can change.

In another experiment to investigate the impact of ocean acidification on sharks, researchers experimented by exposing sharks to atmospheric carbon dioxide levels that averaged either 401 or 993 parts per million for one month. The sharks exposed to the high carbon dioxide levels showed altered blood chemistry. They accumulated bicarbonate to keep their blood acid levels normal, much like how people with indigestion might take antacids to quell stomach acidity.

Elevated carbon dioxide levels impaired the odour-tracking behaviour of the smooth dogfish, a shark whose range includes the

Atlantic Ocean off the eastern United States. Adult sharks significantly avoided squid odour after swimming in a pool of water treated with carbon dioxide. The carbon dioxide concentrations tested are consistent with climate forecasts for midcentury and 2100. The study suggests that predator-prey interactions in nature could be influenced by elevated carbon dioxide concentrations of ocean waters. Sharks are like swimming noses, so chemical cues are really important for them in terms of finding food.

This research shows that ocean acidification impairs sensory functions and alters the behaviour of aquatic organisms.

Carbon dioxide released into the atmosphere is absorbed into ocean waters, where it dissolves and lowers the pH of the water. Acidic waters affect fish behaviour by disrupting a specific receptor in the nervous system, called GABA, which is present in most marine organisms with a nervous system. When GABA stops working, neurons stop firing properly.

Live food was not used as the odor cue because sharks can detect prey with their other senses, such as hearing and their ability to detect electrical impulses. By using an odor cue, the researchers were focusing on only the chemical sensing of sharks. Future work will explore how sharks’ other senses might be affected by ocean acidification.

Sharks are an ancient species, and in the past have adapted to ocean acidification conditions projected for the future. But they’ve never had to adapt to changes happening as quickly as they are today.

 

The remoras, sometimes called suckerfish, are a family (Echeneidae) of ray-finned fish in the order Perciformes.They grow to 30–90 cm (0.98–2.95 ft) long, and their distinctive first dorsal fins take the form of a modified oval, sucker-like organ with slat-like structures that open and close to create suction and take a firm hold against the skin of larger marine animals.By sliding backward, the remora can increase the suction, or it can release itself by swimming forward. Remoras sometimes attach to small boats. They swim well on their own, with a sinuous, or curved, motion. Remoras are not to be confused with pilot fish, another fish that travels with sharks in a similar symbiotic relationship. Pilot fish swim alongside sharks but do not attach themselves.

Remoras are primarily tropical open-ocean dwellers, occasionally found in temperate or coastal waters if they have attached to large fish that have wandered into these areas The sucking disc begins to show when the young fish are about 1 cm (0.4 in) long. When the remora reaches about 3 cm (1.2 in), the disc is fully formed and the remora can then attach to other animals. The remora's lower jaw projects beyond the upper, and the animal lacks a swim bladder.

Some remoras associate primarily with specific host species. They are commonly found attached to sharks, manta rays, whales, turtles, and dugongs (hence the common names "shark-sucker" and "whale-sucker"). Smaller remoras also fasten onto fish such as tuna and swordfish, and some small remoras travel in the mouths or gills of large manta rays, ocean sunfish, swordfish, and sailfish.

The relationship between a remora and its perfect host is most often taken to be one of commensalism. Though it was originally thought that the host to which it attaches for transport gains nothing from the relationship, researchindicates that hosts also benefit, given that remoras feed on parasites (such as copepods) and clean sloughing epidermal tissue as well as ingesting scraps of food, faeces. By keeping the waters clear of scraps around the shark, the remoras prevent the development of unhealthy organisms near the shark.  The remora benefits by using the host as transport and protection, and also feeds on materials dropped by the host. Controversy surrounds whether a remora's diet is primarily leftover fragments, or the faeces of the host. In some species consumption of host faeces is strongly indicated in gut dissections. For other species, such as those found in a host's mouth, scavenging of leftovers is more likely. Studies have shown that many species of shark seem to be aware of the benefits a remora has on its life and well-being. Experiments in captivity have demonstrated a change in a shark’s behaviour in the presence of remoras. Sharks have been observed slowing down in the water, even risking their own survival, in order to allow remoras to attach themselves. However, this is not true of all shark species. On rare and even more rarely filmed occasions, such as the 2010 episode of Shark Week known as "Shark City", remoras that associate with sharks may end up as their prey as was the case of a lemon shark devouring a remora. Despite these rare instances where the behaviour deviates from the general course, the shark and remora relationship is one of the ocean’s most steadfast, and will likely continue for millennia.

 

Personality, by its very name, seems to apply only to a person, e.g., a human. But can a shark actually be shy? Social? A risk-taker? Fierce or mellow?

Imagining primates and even pets with their own personalities isn’t so hard. But some of the most fascinating work has been done on less predictable animals – birds, fish, hermit crabs and spiders, but strangely, sharks have never really been tested for their social skills. However, it appears that sharks are indeed no exception and research has now shown for the first time, that individual sharks actually possess social personalities that determine how they interact with group mates in the wild.

Jean Sebastien Finger, a biologist at the Bimini Biological Field Station in the Bahamas has been trying to find out whether sharks really do have personalities. Finger’s species of choice is the lemon shark, and with good reason. These sharks are the lab mice of the sea. Scientists know a ton about the biology of lemon sharks – they are easy to capture and handle, and they are amenable to captivity.
His work fits in with a growing field of research investigating what scientists call “behavioural syndromes,” or ways of acting that differ from one individual to another but are consistent across time and situation.

After catching and tagging these juvenile Lemon sharks in the shallow waters of Bimini,  Finger and his colleagues run a battery of tests in experimental pools. In a test looking for sociability, they allow the sharks to swim around together for about 20 minutes, documenting every 30 seconds whether a shark is interacting with its mates. “If you see two sharks following each other, that is typical social behaviour,” says Finger. “It’s very similar to humans in the sense that some people will be in groups more often than other people.” In another test looking for an interest in novelty, Finger and his team put sharks, one at a time, in a 40-by-20 foot pen that the sharks have never experienced. The team documented how much each shark explored the pen. Preliminary results show that individual lemon sharks do have different degrees of sociability and novelty-seeking.

What’s more, initial data hint at a trade-off: Sharks who are more interested in novelty tend to be less social, and vice versa. Finger suspects that animals that have the safety of a group take fewer risks. Novelty-seekers venture off on their own and, though they are more prone to danger, they don’t have to share the food they find with others. It’s sort of how the risk-takers and game-changers in human societies aren’t always so good at playing well with others.

In another trial to test for social personality, researchers recorded the social interactions of groups of juvenile small spotted catsharks (Scyliorhinus canicula) in captivity under three different habitat types. These sharks are found throughout the northeast Atlantic and Mediterranean and they like to group together by resting around and on top of one another near the bottom of the seafloor.

For the study, 10 groups of sharks were tracked in large tanks containing three habitats which differed in their level of structural complexity. Some sharks were found to be gregarious and with better social skills, while others were loners, preferring to remain hidden in the background. More sociable sharks stayed safe from threats by remaining within a large group, while less sociable individuals were compelled to use camouflage to blend into their surroundings.

Finger’s big message is that “you can’t generalize behaviour of one individual to a species.” Even if a species as a whole tends to be more aggressive than another, some individuals within that species could still be pretty mellow.

 

Is this spotted catshark a loner or a social butterfly? Credit: Susana_Martins/Shutterstock.

 

Think Twice!

Thousands of balloons or lit lanterns released into the sky: we have all seen it at least one, and it’s a very mesmerizing sight. People release balloons for various occasions: weddings, birthdays, memorials, graduations, charity events…Unfortunately, what goes up, must come down; these balloons and lanterns have to come back down to Earth at some point, and end up creating an environmental disaster.

 Balloons usually slowly deflate overtime, and end up getting stuck on trees, bushes, or floating in the middle of the oceans. They also take years to break down, as it is with many other forms of plastic. Latex balloons are falsely-marketed as biodegradable, and can take years to break down. Once in the air, free-flying balloons and lanterns can travel as far hundreds of kilometres away from its release site. 

Many terrestrial and marine species, such as turtles, dolphins, or birds have been hurt or killed by balloons. If ingested, a balloon will block the digestive tract of the animal, thus letting them starve to death. Other animals may become entangled in the ribbon or the balloon, impeding their movements or causing them to choke. Sea turtles are some of the most at-risk animals, as deflated balloons floating in the sea looks dangerously similar to their favourite food: jellyfishes.

A few US states and cities have anti-balloon laws:  Ocean City and Baltimore in Maryland, Louisville in Kentucky, Huntsville in Alabama, and the entire states of California, Connecticut, Florida, New York, Tennessee and Virginia. Plymouth in the UK, and New South Wales and Sunshine Coast-Queensland in Australia also have laws in place. Check if your city has this law in place and if it does not, see what you can do to bring it to the attention of your local government.

The thing is, balloon pollution is completely avoidable. Just don’t do it! Is your joy and wonder of letting a balloon go really worth the death and pain of other living organisms? There are plenty of alternatives to releasing plastic into the sky. And if you were to stumble upon a balloon on the beach or while out on a boat, please make sure you pick it up. 

(Rusty Blackbird found dead due to entanglement in balloon

ribbon. Photo: David E. Gurniewicz)

(A sea turtle entangled in ribbons. Photo by FWC)  (A sea turtle that appears to have ingested a balloon. Photo by L. Byrd – Sea Turtle Hospital, Mote Marine Laboratory)

The KwaZulu Natal Sharks Board in South Africa is testing an electronic cable as a shark repellent. KZN Sharks Board is committed to investigating alternative bather-protection systems that will reduce the death and injury rates of sharks, dolphins, turtles and other marine species.

The 100m long cable was installed in Cape Town’s Glencairn beach, in early October 2014. It will be activated on certain days during daylight hours from the beginning of November until the end of March 2015.

 The testing period was selected to coincide with the end of the whale season, (to minimise the risk of whale encounters), and the peak white shark season, (to maximise the number of white shark encounters). The system has been specially adapted to prevent whale entanglements by employing semi-rigid risers, not rope or wires. In addition, a specialised team will be on standby in case a whale does approach the area. No other marine animals displayed any effects whilst being exposed to the signal.

In 2012, the Institute for Maritime Technology (IMT), was contracted to design and build the cable. The system consists of a main cable fixed to the sea floor, with vertical ‘risers’ supporting the electrodes that are fitted on either side of the cable. The risers are semi–rigid and are kept upright by small sub-surface buoys.

The purpose of the testing is to find out how the pulse emitted from the cable, acts as a barrier to white sharks.  The cable emits a low frequency, low power, pulsed electronic signal, which has been shown to repel white sharks. These sharks are highly sensitive to electromagnetic fields, thanks to their electrical receptors, Ampullae of Lorenzini.  If a shark experiences any discomfort it is able to move away from the cable. If this hi-tech experiment is successful, it will provide the basis to develop a barrier system that can protect humans without killing or harming sharks or any other marine animals.

The electronic shark repellent cable has been subjected to extensive safety evaluation by a medical and scientific team. The same form of pulsed electronic signal has been used within personal shark diver protection devices for many years.  The cable system is calculated to deliver less than 200 micro Coulombs even with direct contact. It would be expected that 100 times the charge produced by the cable, would be needed to cause a life-threatening shock.

Throughout the testing period there will be continuous monitoring of the cable and the area where it is deployed. This will be done by means of a video camera high above the beach and by Shark Spotters who will track the movements of any sharks sighted near the cable. The data will be analysed by KZNSB scientists to see how the signal emitted by the cable affects white sharks. 

Since shark nets were first deployed on the Durban beachfront in 1952, there had not been a single shark attack off the city’s beaches. Along the rest of the KZN coast, where there are 36 other protected beaches, there had been only two (non-lethal) attacks over the past three decades. But at what price? An average of 1 400 sharks were caught in the nets every year during the 1980s, compared with current levels of about 570 a year (of which more than 10 percent were released alive). Thankfully there has been a 64 percent drop in sharks killed in the KZN shark nets over the past 30 years.

But could this electronic cable finally mean the end of shark nets and baited drum lines? Well I certainly hope so and I am crossing my fingers and toes too!

And in other shark related news;

Donald Gibson found the first vertebra just as he had begun to dig out the space for the sunroom he had promised to build in the back yard of his parents' home in Calvert County, Maryland, USA.Over the following week more and more vertebrae were found — each one about 18 inches deep into the groundBut then they found a straight column of vertebrae, two feet long as well as a tooth.

The digging stopped.

What the Gibsons unearthed were the remains of a 15-million-year-old Snaggletooth shark found, which palaeontologists say is more complete than any other fossil of its kind in the world.

The Gibsons' discovery is so unusual because of the number of bones they found — more than 80 vertebrae and hundreds of teeth, all from the same shark — as well as the position they were in and their unusually good preservation.

Palaeontologists Godfrey and Nance were called to the scene and they were amazed at the find. They immediately wrapped the entire skull cavity in a stiff plaster cast, like one used to set a broken bone.

Sharks' skulls are made mostly of cartilage, not bone, so they almost never withstand the ravages of time. Yet somehow, the shark that came to rest in the Gibsons' backyard sank belly-up when it died during the Miocene Epoch. It became buried in sand, then by sediment eroding from the Appalachian Mountains. And its skull cavity — containing hundreds of the distinctively shaped teeth, up to an inch-and-a-half long, that give the snaggletooth its name — kept its shape.

Using a microscope, the scientists digging in the Gibsons' yard were able to see the distinctive hexagonal shape of shark cartilage, fossilized and preserved.

Godfrey said that this shark was 8 to 10 feet long during its life.

Having preserved the teeth and surrounding remnants of cartilage in exactly the positions they were found in, the palaeontologists will be able to take CT scans of the cast and analyze the specific three-dimensional layout of the prehistoric shark's mouth, something scientists have never done.

"For the first time, we're going to be able to know what the dentition — what the teeth — looked like in this kind of shark," Godfrey said.Then they will remove the cast, gently clean each piece and put the discovery on exhibit.

Godfrey said he is receiving emails from palaeontologists up and down the East Coast who are excited about the discovery.The skeleton will allow scientists to compare the prehistoric snaggletooth, an extinct species, and modern snaggletooths, a descendant species that lives in the Pacific.

Comparing the teeth of snaggletooths then and now will help scientists understand the workings of shark evolution, the likely diet of prehistoric species and the climate during the Miocene Epoch.

And the fact that the spine and the skull cavity of the shark found by the Gibsons are definitively associated with each other, the most complete snaggletooth skeleton ever found will allow scientists to identify whether smaller pieces of future fossils come from snaggletooths or other species.

"When in the future we find just a single vertebra, we'll be able to say, 'This comes from that kind of shark.' And only because we have this association being made," Godfrey said. "It's just incredibly unlikely that we would make this kind of discovery."

Love, that curious, chemically charged emotion which we feel towards our favourites, will be celebrated again on Valentine’s Day, this coming Saturday. (And yes, it is my pleasure to have reminded you . . .) If you are reading this, then there is no doubt in my mind that you are a shark lover! And so why not combine the two? Valentine’s Day with Sharks as the emphasis? How preposterous, right?! Shark lovers will probably find this idea adorable but really, what’s the relationship between sharks and couples? 

Well, we all know that shark fin soup is usually a must-have core dish served at Chinese weddings. The team from wedding.com.my aims to raise awareness under their platform to encourage their fans to not feature shark fin soup at wedding banquets. Co-founder of Wedding.com.my, Petrina Goh, told Vulcan Post said that “The whole idea came about when we were thinking… What will be a better way for couples to celebrate their love while doing a good cause at the same time?”

In March 2014, Shark Savers Malaysia (SSMY) was launched and powered by Malaysian volunteers with the support of corporate pro bono resources and local NGO partners. The Malaysian government instituted a ban on shark fin soup at all official state level dining and entertainment in October 2014. 

The wedding.com.my team planned a 3-part event for Valentine’s Day – the main event being the Shark Savers Couple Challenge where they aim to raise public awareness and hand out pledges which says “I’m FINished with FINS”. As an online wedding marketplace, they feel that they have a strong social responsibility to bring awareness to their 200,000 bridal community, since shark fin soup is mostly consumed at wedding banquets.

According to the latest reports, Malaysia is globally ranked 8th for shark catchment and 4th for shark fin imports. Hopefully the efforts of wedding.com.my and Shark Savers will filter through the Malaysian population and help to reduce the above mentioned statistics. 

Conversely, what will you and I be doing to show our love for sharks this Valentine’s Day?

Well, let’s look at what we can do:

  • Take your loved one for a walk on the beach, clean up some debris and then enjoy a lovely romantic picnic on the beach at sunset.
  • Buy your lover a t-shirt or jewellery from a shark conservation organisation.
  • Adopt a shark as a gift for your Valentine!
  • Donate funds to a shark NGO on behalf of your Sweetheart.
  • Spend a day volunteering together at a shark organisation.
  • And on Valentine’s Day, as with every other day of the year, be the best Shark Ambassador you can be! Say no to shark products!

 Wishing you all a very Happy Valentine’s Day!

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