Tag Archives: Senses

Navigation: It’s Possible in a Featureless Ocean

Navigation is the ability for an organism to travel to a relatively precise target, generally at a considerable distance, without the need for familiar landmarks. It is an extraordinary feat requiring a variety of senses, techniques, and adaptions to allow for successful navigation. 

Humans and Sight

For humans, sight is the most commonly used sense to navigate. Tracing back a thousand years ago to traditional Polynesian cultures, people have been using the stars, specifically fixed stars, for tracking and to stay en route towards their destination. Nowadays, we have technological advances that aid us in navigation, like Google Maps, satellites, and compasses, but celestial bodies remain a constant and dependable asset. In addition to sight, different animal species have evolved specific senses to assist them in the open ocean.

Human Navigation 

Photo: http://www.hokulea.com/education-at-sea/polynesian-navigation/the-star-compass/ 

wayfinding

Photo: https://theconversation.com/how-far-theyll-go-moana-shows-the-power-of-polynesian-celestial-navigation-72375

Dolphins and Hearing

Some animals, such as dolphins, utilize their sense of hearing through a process called echolocation to navigate through the open ocean during times of low visibility. These animals produce high-frequency sound waves that echo back with information such as the direction they are traveling and the location of objects around them.

Echolocation

Photo: http://www.dolphinspotter.karoo.net/factecho.htm

dolphin pic

Photo: https://aqua.org/Experience/Animal-Index/atlantic-bottlenose-dolphin

Crabs and Taste

Crabs, who often live in dark and murky areas, need to be able to navigate to food sources. Crabs use chemoreceptors found on thin, short hairs of their inner antenna, call aesthetascs, which allow them to smell chemicals in the water released by their prey. They not only have a well-developed sense of smell, but have the ability to taste biomolecules in the water using specialized hairs on their mouthparts, pincers, and feet to detect prey. Their acute senses are so crucial to survival, that the majority of their brains are detected to processing scents and tastes!

green crab

Small hair-like appendages of the Green Crab that aid in prey detection by taste. 

Photo: https://wsg.washington.edu/crabteam/about/newsletter/2018-1/

Seabirds and Scent

For some seabirds like the Arctic Tern, the Wandering Albatross, or the Sooty Shearwater, navigation is no joke! Traveling thousands of miles for up to seven years at a time over a featureless blue ocean is quite a feat, requiring some fine-tuned navigational techniques. Studies have shown that many migratory birds use celestial navigation to determine North and Southward orientation, just like humans! But certain hypothesizes suggest that seabirds also use their sense of smell to create scent maps.  In a study where birds had their sense of smell blocked, the test group was less likely to find food sources and their nesting grounds, suggesting that olfactory navigation is a technique adopted by many seabirds!

wandering albatross

The Wandering Albatross has been observed to spend anywhere between 5-7 years at a given time at sea, making them expert navigators. 

Photo:  https://www.hbw.com/ibc/photo/wandering-albatross-diomedea-exulans/old-adult-male-flight-dorsal-view

arctic tern

The Arctic Tern has the longest migration of any animal, traveling from Greenland go Antarctic in a zig-zag route, resulting in over 40,000 miles traveled every year! 

Photo:https://www.npolar.no/en/species/arctic-tern/

Fish and Touch

The lateral line system is an extensive network of canals and sensory receptors that can detect disturbances in the water. The majority of fish species have this lateral line that assists in navigation by sensing pressure changes and providing spatial awareness to avoid underwater obstacles.  Some fish are able to use the lateral line as a type of sonar to feel the movement of water reflect off objects around it, which is especially useful in low visibility areas, such as the deep sea. 

Lateral lines

The lateral line consists of hundreds of superficial neuromasts, or sensory structures of cilia. Many of these neuromasts are embedded in lateral line canals open to their environment through pores that allows them to detect water movements.

Photo: https://www.trails.com/facts_8518_functions-lateral-line-fish.html

Sea Turtles and Magnetoreception

Magnetoreception, the sixth navigational tool illustrated in the video, is an animal’s ability to detect the Earth’s magnetic field in order to determine North and Southward orientation. Many invertebrates like mollusks and insects, as well as vertebrates like birds and sharks,  use this as a natural global positioning system when navigating long migration routes. One example, sea turtles, use magnetoreception as hatchlings when swimming out to the open ocean, and as adults when traveling towards specific feeding, mating, and nesting locations.

Magnetite is found in sea turtles as well as some bird and fish species. This iron mineral can tell animals their position on the globe as well as the direction they are heading. This explains why sea turtles can migrate all around the ocean and find themselves nesting on the same beach as their female ancestors.

compass turtle

Photo:https://www.sciencemag.org/news/2016/06/body-s-hidden-compass-what-it-and-how-does-it-work

Navigation Poles

Photo: https://webstockreview.net/image/field-clipart-campo/1087594.html

The open ocean can be a challenging place to navigate, but the animals that live there utilize their senses to the max in order to find food, avoid underwater obstacles, and be completely aware of their direction of travel.

Sources:

https://www.thoughtco.com/how-do-crabs-find-food-2291888

https://blogs.scientificamerican.com/thoughtomics/terrestrial-hermit-crabs-only-smell-their-favourite-snacks-when-water-is-around/

http://lohmannlab.web.unc.edu/magnetoreception/

https://www.cell.com/current-biology/pdf/S0960-9822(07)00819-6.pdf

https://www.wonderopolis.org/wonder/how-do-dolphins-use-echolocation

https://www.smithsonianmag.com/smart-news/seabirds-use-their-sense-smell-navigate-open-water-180964674/

https://www.ncbi.nlm.nih.gov/pubmed/21392273

Written By: Alyssa Backman, Kyler Mose, and Leanne Murray

Sensitive Sharks! Everything You Want to Know!

According some experts estimations, sharks have been around planet Earth for somewhere between 425 and 450 million years making them just as old or even older than trees themselves! As such, sharks have had time to evolve numerous methods of sensing their environment, making them expert hunters. In order to understand shark senses, one must first understand where the perception of these different sensations occur in the shark brain.

The shark brain is a Y shaped organ located in the chondrocranium of the shark. The shark brain can be split up between the forebrain, midbrain and hindbrain, each of which will specialize in a different sense. The forebrains specializes in olfactory, midbrain in visual, and the hindbrain specializes in hearing, touch, and electroreception.

sharks

Depending on the species sharks can smell up to 1km or more away, hear about 100m away, see about 10m away depending on water clarity. Depending on the sharks environment/habitat there will be corresponding enlargements in the brain. If the shark lives in deeper water where not much light exist or live mostly in the open ocean where food availability tends to be low, they might have enlargements in their forebrains because they have to rely on olfaction to find their food. With over 400 different species of sharks, not all sharks are necessarily the “swimming noses” that we think they are. With such diversity, sharks will specialize in different senses based on the environment of which they live. Even with one sensory specialization, it is the combination of all the shark’s senses that make them such great predator.

sharks 1

As sharks draw in closer to their prey they use electroreception. Imagine the brain as a biological computer, sending electrical impulses down a highway of motor neurons in order to move the muscles of the body. Sharks are able to detect those electrical impulses from up to 1 meter away. Some sharks, such as the scalloped hammerhead, can sense as low as half a billionth of a volt of electricity. They use special gel filled pores called the Ampullae of Lorenzini in order to sense these weak electrical impulses.

sharks 3

Sharks will continue to dazzle and amaze us with their sensory capabilities. New research indicates that sharks can even use electroreception to navigate the earth by sensing the magnetic poles. Such extraordinary evolutionary advantages are what will continue to make sharks a dominant predator for a very long time.

COVER PHOTO CREDIT:

Brian Skerry, www.brianskerry.com from https://ocean.si.edu/ocean-life/sharks-rays/hammerhead-shark-sunset

References

Fig5

https://www.sharkbanz.com/pages/how-it-works

Fig4

http://blogs.uwa.edu.au/3dbrainprinting/files/2016/03/March_OB-x9twud.jpg

Fig.3

https://sharkopedia.discovery.com/wp-content/uploads/2015/07/sharkopedia-hierarchy-of-senses-550×350.jpg

Fig2

William E. Bemis 2016

Fig1

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcScxaP3GxhkC1Xcxwn_Gyx1RT6CR5ujdp44RF9wYeC_dRcPshLV

Hammerhead video

https://www.smithsonianmag.com/videos/category/science/hammerhead-vs-stingray/

The Sixth Sense of Sharks

Sharks have been on this planet for a pretty long time, around 400 million years, and during that time have cemented themselves as some of the oceans top predators. One reason why these animals have been so successful is due to their incredible senses that allow them to smell, hear, and track down prey with incredible accuracy. Sharks however have a very distinct advantage over most of their fishy friends in the ocean, they can actually detect electrical pulses in the ocean to help them locate prey and navigate the oceans using an organ called the Ampullae of Lorenzini. This is called electroreception. Today, we are going to dive into shark infested waters and learn more about how this amazing sense works!

The Ampullae of Lorenzini are small clusters of jelly filled pockets that lead to jelly lined canals ending in small open pores located all over the heads of sharks. These pores can be easily seen on the heads of sharks as dark spots and run just underneath the skin centered around the nose and behind the eye (Fig 1). Interestingly, the ampullae of lorenzini is an extension of the lateral line that most fish have in the ocean to detect vibrations in the ocean. The jelly that is inside of these pores is called Keratan Sulfate and is the most conductible of all biological compounds! Shocking, I know. These canals are filled with multiple nerve fibers that run through the jelly lined canal connecting to the pore on the outside. Seawater is a great conductor of electricity which allows the ampullae to do its job. These organs are so sensitive that their threshold of sensitivity can be as low as 5 nV/cm, which means they can detect electrical currents as little as 5 billionths of a volt per square centimeter. Scientists believe that sharks, on average, have 1,500 ampullae on their heads and some can detect the difference of electricity when two AA batteries were connected 10,000 miles away.

sharks

Sharks are believed to have the strongest electroreception of any animal on the planet earth. Primarily, the ampullae of lorenzini is meant to pick up the weak electrical stimuli from their prey’s muscular contractions. It can even detect electrochemical fields emitted from paralyzed animals! Many bottom dwelling sharks use their ampullae to draw a picture of potential prey that rests under the sand without them even knowing the shark is intending to feast on them. Great Hammerheads use their large heads as metal detectors and wave them over the sand to located sting rays (Fig 2). This sense is especially useful when the shark is hunting in murky waters or at night. Sharks also use this ability to navigate through the earth’s oceans. The earth’s magnetic field surges through the oceans currents and is on the same magnitude as sharks are able to sense. So, sharks and rays are able to use the earth’s magnetic field for local orientation. This is paramount for Great White Shark migration as they swim 2,500 annually to get from reproducing waters to foraging waters. Another debatable use of the ampullae is that it can detect changes in temperature of the water as well.

There are many animals on this planet earth that have electro-receptive capabilities such as bees, platypus, and echidnas but none are on the same level as sharks and rays. It may seem scary that a shark can sense that you are swimming around them without them even seeing you, but remember that sharks are more threatened by us then we are from them.

Sources:

http://www.elasmo-research.org

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