Friday, 01 March 2019 08:28

Dolphins call each other by name

Researchers in Florida say bottlenose dolphins come up with their own names when they are very young and use these names to communicate with one another. Bottlenose dolphins call out the specific names of loved ones when they become separated, a study finds. Bottlenose dolphins surfs the waves Bottlenose dolphins surfs the waves Other than humans, the dolphins are the only animals known to do this, according to the study, published in the latest Proceedings of the Royal Society B. The big difference with bottlenose dolphins is that these communications consist of whistles, not words. Earlier research found that bottlenose dolphins name themselves, with dolphins having a “signature whistle” that encodes other information. It would be somewhat like a human shouting, “Hey everybody! I’m an adult healthy male named George, and I mean you no harm!” The new finding is that bottlenose dolphins also say the names of certain other dolphins.z“Animals produced copies when they were separated from a close associate and this supports our belief that dolphins copy another animal’s signature whistle when they want to reunite with that specific individual,” lead author Stephanie King of the University of St. Andrews Sea Mammal Research Unit told Discovery News. King and her colleagues collected acoustic data from wild bottlenose dolphins around Sarasota Bay, Fla., from 1984 to 2009. The researchers also intensely studied four captive adult male dolphins housed at The Seas Aquarium, also in Florida. The captive males are adults that keepers named Calvin, Khyber, Malabar and Ranier. Bottlenose dolphins communicate through a series of whistles. Bottlenose dolphins communicate through a series of whistles. These bottlenose dolphins, however, as well as all of the wild ones, developed their own signature whistles that serve as names in interactions with other dolphins. “A dolphin emits its signature whistle to broadcast its identity and announce its presence, allowing animals to identify one another over large distances and for animals to recognize one another and to join up with each other,” King explained. “Dolphin whistles can be detected up to 20 km away (12.4 miles) depending on water depth and whistle frequency.” The researchers said dolphins copy the signature whistles of loved ones, such as a mother or close male buddy, when the two are apart. These “names” were never emitted in aggressive or antagonistic situations and were only directed toward loved ones. The whistle copies also always had a unique variation to them, so the dolphins weren’t merely mimicking each other. The dolphins instead were adding their own “tone of voice” via unique whistling. While researchers often hesitate to apply the “l word” -- language -- to non-human communications, bottlenose dolphins and possibly other dolphin species clearly have a very complex and sophisticated communication system. he bottlenose dolphin is probably the most widely recognized marine mammal. he bottlenose dolphin is probably the most widely recognized marine mammal. “Interestingly, captive dolphins can learn new signals and refer to objects and it may be that dolphins can use signature whistle copies to label or refer to an individual, which is a skill inherent in human language,” King said. Heidi Harley, a professor of psychology at New College of Florida, is a leading expert on cognitive processes in dolphins. She agrees with the new paper’s conclusions. Harley told Discovery News that it can be challenging to study dolphin signature whistles, since it’s difficult to identify which particular dolphin is emitting the sounds, and whether or not the sounds are just mimicked copies. Dolphin-speaker-1-640x477 “Interestingly, captive dolphins can learn new signals and refer to objects and it may be that dolphins can use signature whistle copies to label or refer to an individual, which is a skill inherent in human language,” King said. Heidi Harley, a professor of psychology at New College of Florida, is a leading expert on cognitive processes in dolphins. She agrees with the new paper’s conclusions. Harley told Discovery News that it can be challenging to study dolphin signature whistles, since it’s difficult to identify which particular dolphin is emitting the sounds, and whether or not the sounds are just mimicked copies. “This study provides evidence that copies of signature whistles include elements that differ from the whistles of the original whistler, while still maintaining the changes in frequency over time that allow a listener to identify the original whistler,” Harley said. “In addition, that signature whistle copying occurs between close associates, suggesting it is used affiliatively.” King and her team are now using sound playback experiments to see how wild, free-ranging dolphins respond to hearing a copy of their own signature whistle.

Published in Dolphins

 

Toxic algal bloom off Washington, US. Left is the natural colour, right has been enhanced to reveal chlorophyll concentrations (Image: SeaWiFS Project, NASA/Goddard Space Flight Center/ORBIMAGE) Toxic algal bloom off Washington, US. Left is the natural colour, right has been enhanced to reveal chlorophyll concentrations (Image: SeaWiFS Project, NASA/Goddard Space Flight Center/ORBIMAGE)

Toxic algal blooms are bad enough on the ocean surface, but now it turns out that the toxin in them sinks to the ocean floor – where it persists for weeks.

Far from degrading soon after the bloom, as previously assumed, new research suggests that the neurotoxin that causes shellfish poisoning, domoic acid, sinks to the ocean floor and could poison marine mammals, birds and humans.

"The first signs of an algal bloom are often birds washing up on the shore or seals acting funny, aggressive and twitching, looking as if they were drunk," says Claudia Benitez-Nelson of the University of South Carolina.

"We used to think that once the bloom died, the danger was over, but now it turns out that domoic acid is a 'gift' that just keeps on giving."

Benitez-Nelson's team are the first to look for the chemical in algae particles sinking through the ocean, as well as in sediment samples on the ocean floor, up to 800 metres down. They found copious amounts of the neurotoxin, reaching concentrations eight times the US federal limit for the substance in shellfish.

Toxic shock

The team also compared the peak of domoic acid levels from the sediment with those of algae blooms at the surfaces. Their findings indicate that the toxin reaches the bottom of the ocean in only three days but stays there for much longer – at least several weeks.

The speedy trip to the bottom is probably driven by dead algae clumping together at the surface to form heavier aggregates, says the team, a process that also protects the toxin from degradation.

Domoic acid gets broken down easily in water and by sunlight, but once the clumped algae are buried in the sediment, the toxin may stay protected until a bottom-dwelling organism eats it.

"Domoic acid is a rich amino acid that will be tasty to worms and other critters, who may suffer no ill effects from it," says Benitez-Nelson.

Raphael Kudela at the University of Santa Cruz in California says that the new work is "the missing link to explain why domoic acid also shows up in bottom-dwelling organisms like crabs and flatfish. These contain lots of commercially important species, but they are not yet monitored for domoic acid."

The new data warrants studies to test if these species should be included in future monitoring efforts, according to Kudela. So far, only shellfish that live close to the water surface are monitored.

To Benitez-Nelson, the most important next step now is to work out in more detail how much longer the domoic acid sticks around and into how many more organisms it gets.

"It is clearly a lot more prevalent and spread out than we thought before and this problem affects many areas, not just California. On top of this, all signs seem to point to further increases in the future as people dump more and more algae feeding nutrients into the ocean."

Published in Marine Wildlife

Sperm whale mass strandings are mysterious events, which raise the concern and curiosity of the public opinion. The causes remain largely unknown, although many hypotheses have been considered and analyzed, including natural factors, such as biologic disease agents ; impairment of the navigation and echo-location systems due to bathymetric features, acoustic dead zones or anomalies of the Earth's geomagnetic field due to solar activity , the effects of lunar cycles meteorological and oceanographic factors like local disturbances or basin-related temperature variations influencing prey distribution and large-scale climatic events. Furthermore, anthropogenic factors like noise pollution or environmental contaminants have been also proposed as possible causes of strandings.

Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea.

A strong social component, which may prompt healthy animals to follow sick or disordered members of a pod, has been also considered as an additional relevant feature to be pondered in investigating the causes of mass strandings Mass mortalities involving sperm whales are usually clustered in determined geographical areas, such as the North Sea and in the Southern Australian and New Zealand

The seven sperm whales took the same “wrong way” into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales.

The seven sperm whales took the same “wrong way” into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. The seven sperm whales took the same “wrong way” into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales.

Although in the Mediterranean Sea the sperm whale is one of eight cetacean species considered to be regular inhabitants, mass strandings are rarely reported. In December 2009, a pod of seven sperm whales stranded along the coastline of the Gargano Promontory (Italy), in the Southern Adriatic Sea. Three animals were still alive and died within 48 hours after stranding.

Sperm whales are considered to be vagrant or absent in the waters surrounding the stranding place, and particularly in the Central and Northern areas of the Adriatic Sea, where the habitat is not proper to this deep-diving species. Sperm whales in the Mediterranean Sea occur preferentially in deep continental slope waters where mesopelagic cephalopods are most abundant .In the Adriatic Sea, sperm whale mass strandings have occurred five times since historical times, with the oldest known instance dating back to 1584. sperm whale standing ancient

In addition, some reports of single individuals stranded dead or alive included mention to one or more other sperm whales sighted at sea in the close proximity to the stranding location, sometimes for several days . Groups stranded on the Adriatic Sea coasts (range 3–8 individuals) are smaller compared to the mean size of groups stranded outside of the Mediterranean Sea .

sperm whale starndings 31 Nocturnal necropsy and gas bubbles.
Fig. A shows a scene of the nocturnal necropsy on animal no. 7. In Fig. B and C gas bubbles in the heart veins (black arrows) and in an intra cardiac clot of animal no. 5 are shown.

Despite all these observations, we were not able to confirm that these stranded sperm whales formed a single stable group with asocial hierarchy, although we would rather suggest that more than one loose male aggregation and/or several solitary individuals could have coalesced in a limited sea area, most likely in the Ionian Sea, between summer and fall. From there they subsequently entered the Adriatic Sea for unknown reasons.

To the best of our knowledge, no relevant unusual natural events (i.e. seaquake or weather storms) or noxious anthropogenic activities (military drills using sonar) that could have caused an avoidance behaviour occurred temporally and spatially associated with the event.

The only relevant anomaly reported by the marine data archives was the increased sea superficial temperature in November and December along the Hellenic Trench and Eastern part of the Adriatic Sea, possibly constituting a thermal front in which upwelling and/or down welling could have been favourable to the development of cephalopod populations.

 

Published in Marine Wildlife

Tiny cameras attached to back of gannets Tiny cameras attached to back of gannets

Researchers attached the tiny cameras to the gannets, to learn more about their habits and how they survive flying up to 300 miles out at sea. They found that the seabirds circle at 30 meters high before diving into the water at speeds of up 60mph.

Gannets are seabirds comprising the genus Morus, in the family Sulidae, closely related to boobies. The gannets are large black and white birds with yellow heads; long, pointed wings; and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up to 2 metres. The other two species occur in the temperate seas around southern Africa, southern Australia and New Zealand.

Gannets are large black and white birds with yellow heads and pointed beaks. Gannets are large black and white birds with yellow heads and pointed beaks.

Gannets hunt fish by diving from a height into the sea and pursuing their prey underwater. Gannets have a number of adaptations which enable them to do this:

  • they have no external nostrils, they are located inside the mouth instead;
  • they have air sacs in their face and chest under their skin which act like bubble wrapping, cushioning the impact with the water;
  • their eyes are positioned far enough forward on their face to give them binocular vision, allowing them to judge distances accurately.

 

Published in Marine Wildlife
Thursday, 28 February 2019 13:36

White Shark Facts

Did you know that....

  • White Sharks are also known as Great White Sharks, Carcharodon carcharias(Latin) and White Pointer Sharks.
  • 070507ali1 080812IMG_9024
  • Their bodies are counter-shaded with a charcoal to black, grey or even dark brown top (dorsal surface) and completely white underneath (ventral surface)
  • Counter-shading makes it difficult for their prey to see them
  • One of the most successful predators in the world
  • Live on a diverse diet of fish, other sharks, seals, dolphins and even scavenge on dead whales
  • They have many different ways to catch their food from chasing fish, to sneaking up on stingrays to attacking from below when trying to eat seal
  • Have taste buds inside their mouth and throat and are more fussy than other sharks like tiger sharks
  • Have a lateral line made of special hair-like cells which runs from their tail to their head and can detect small water vibrations and currents 090711DSC_0286
  • Use their electrosense to detect the electric field given off by all living animals and can even find prey hidden under the sand
  • They are sensitive to low frequency sounds as produced by struggling prey
  • They use body language and smell to communicate with one another

  • Deepest recorded dive was over 1200
  • Can breach out of the water over 2m into the air
  • One of the most widely distributed sharks found in all oceans, except the polar seas
  • Areas with the highest concentrations are Western Cape, South Africa, South Australia, West coast USA, Guadalupe Island Mexico and New Zealand
  • Found near the coast and in deep oceanic waters
  • Grow slowly only becoming mature after 10 years (males) and 15 years (females)
  • Live for more than 60 years
  • Reproduce slowly with litters of 2 - 10 baby sharks, called pups
  • Gestation is thought to be over 12 months
  • Give birth to live young (viviparous)Each pup is between 1.2 - 1.7 meters long when it is born
  • There is no parental care
  • World's largest predatory shark/fish growing up to 6.1 metres
  • Females grow bigger than male 09080224-03-09
  • They weigh over 2000 kgs
  • They have six senses: sight, smell, taste, touch, hearing and electroreception
  • They can see in the day and at night and can see colour
  • They don't have eyelids, but instead roll their eyes back to protect them
  • Sometimes they will stick their heads out of the water which is called spyhopping
  • They have the strongest smell out of all sharks and can smell one drop of blood in a million parts water
  • Man kills over 100 million sharks a year,
  • Sharks cause less than five deaths worldwide per year.
  • Chairs and toasters kill more people than sharks
  • Great White Sharks are Vulnerable to Extinction

 

Published in Sharks
Thursday, 28 February 2019 13:23

10 Amazing Facts About Ocean Animals

With over 72% of the Earth’s surface covered by salt water, the Earth’s oceans are home to 230,000 known species. And that’s with only 5% of the Earth’s oceans considered explored! In celebration of the vast unknown of the ocean, we present our favorite amazing facts about ocean animals: amazing-facts-ocean-animals-blue-whales

amazing-facts-ocean-animals-dolphins-sleep

amazing-facts-ocean-animals-electric-eel

amazing-facts-ocean-animals-jellyfish

amazing-facts-ocean-animals-octopus-hearts

amazing-facts-ocean-animals-oyster-gender

amazing-facts-ocean-animals-seahorses

amazing-facts-ocean-animals-shrimps-heart

amazing-facts-ocean-animals-sponges

amazing-facts-ocean-animals-turtles

Published in Marine Wildlife

THE HATCHFISH

hatchetfish

Given the extreme depths to which scientists must go to find these frightful–and tiny–fish, little is known about the hatchetfish. Making top models around the world jealous, the morose-looking creatures derive their name from how razor-thin they are. Anatomically speaking, the hatchetfish’s thorax is supposed to resemble the blade of the hatchet, and its cold, silver glint the metal. Their name is somewhat deceiving, though; measuring in at a mere one to five inches in length, the hatchetfish is hardly deadly. It’s just, well, pretty terrifying.

THE BLOBFISH

blobfish

More gelatinous than your grandma’s pudding, the blobfish’s strikingly jiggly appearance has captivated the attention of millions for the past several years. So striking is the mass with fins that just this year it was deemed the world’s ugliest animal. Life isn’t all that bad for this Oceania-dwelling creature, though. As the blobfish’s den is primarily near the bottom of the ocean, the water pressure is understandably high, causing the blobfish’s skin to have the approximate density of water. You might think that lack of muscle tissue would prove disadvantageous, but you’d be wrong. All that means is that when it comes time to eat, the blobfish simply opens its mouth while floating merrily above the ocean’s floor. Its lack of density means that it doesn’t have to expend any energy in order to eat. Lazy chefs around the world, direct your ire to the blobfish.

THE FANGTOOTH

-fangtooth-fish-close

Consider the fangtooth fish to be the underwater equivalent of a menacing pitbull with a heart of gold. Despite their threatening appearance, the fangtooth is incredibly benign–especially as its poor eyesight means that if it wants to hunt, the fangtooth quite literally has to bump into its prey in order to find it. Its chompers certainly paint a different portrait, though: protruding from its mouth, in proportion to the fish the fangtooth has the largest teeth of any fish in the ocean. Good luck catching a glimpse of the sharp-mouthed animal: it resides as far as 16,400 feet beneath the sea.

THE SEA CUCUMBER

sea cucumber giant 300x260

These icky echinoderms certainly boggle the mind. Lacking a true brain and any semblance of sensory organs, the sea cucumber boasts about the same mental capacity as the food for which it is named. Nevertheless, the cuke serves as vital part of the oceanic ecosystem, as it recycles nutrients and breaks down detritus that comes its way. Unlike the actual cucumber, the sea cuke’s collagen levels allow it to make some pretty kooky maneuvers: if the sea cucumber needs to wedge itself into a tiny crevice, the collagen will loosen and the sea cucumber will effectively liquify itself to seep into its desired locale.

THE GOBLIN SHARK

goblin-shark

Deemed by some scientists as a “living fossil” and overshadowed by its flashy counterparts, the goblin shark leads a relatively mysterious existence deep below the ocean blue. The only extant survivor of a 125 million-year old family of sharks, the goblin is truly unique…and ugly. Apart from its most salient features (re: its long, flattened snout and protruding jaws), the goblin is relatively unremarkable. Given its flabbiness, most scientists speculate that the goblin shark is sluggish and relatively inactive. It’s highly unlikely you’ll ever see a goblin shark in your lifetime; when one was brought to an aquarium in Japan, it died soon after.

THE ANGLER FISH

angler-fish-bright

The angler fish is perhaps one of the most fascinating and bizarre sea creatures known to man. Not only known for their wily predation techniques (re: having a spine that grows its own fleshy mass that the angler can wiggle about so that it resembles prey, and then devouring its soon-to-be predators in one fell swoop) but also for its mating habits. When scientists first discovered the angler, they noticed that almost all of them were female…and that these specimens had what appeared to be some sort of parasitic growth attached to their lower parts. Turns out that those “parasites” were actually just greatly reduced male angler fish, whose puny size renders their sole objective in life to finding and mating with a female. Once they do find a female partner, the male anglers quickly bite into the female’s skin and thus fuses them together. From this point on, the male’s life literally depends on its female host, as they share a circulatory system. When the female is ready to mate, he pays his dues by providing her with sperm on the spot.

 

 

 

Published in Uncategorized
Thursday, 28 February 2019 12:47

12 Fun Facts About Sea Hawks

Number one: There's no such thing as a "seahawk" You could use the name sea hawk to refer to an osprey (pictured below auger hawk) or a skua (itself a term that covers a group of seven related species of seabirds). Both groups share a number of characteristics, including a fish based diet.

augur_hawk_ 2

1. Ospreys live on every continent besides Antarctica. Although they hunt over water, ospreys generally nest on land, within a few miles of either the ocean or a body of fresh water. Unlike most bird species, they are remarkably widespread, and even more surprising, nearly all these widely dispersed ospreys (with the exception of the eastern osprey, native to Australia) are part of one species. Ospreys that live at temperate latitudes migrate to the tropics for the winter, before heading back to their home area for the summer breeding season. Other ospreys live in the tropics year-round, but also return to the specific nesting grounds (the same ones where they were born) each summer for breeding.

hawk toes

2. Ospreys have reversible toes. Most other hawks and falcons have their talons arranged in a static pattern: three in the front, and one angled towards the back, as shown in the illustration on the left. But ospreys, like owls, have a unique configuration that lets them slide their toes back and forth, so they can create a two-and-two configuration (shown as #2). This helps them more firmly grip tubular-shaped fish as they fly through the air. They also frequently turn the fish to a position parallel to their flying direction, for aerodynamic purposes. 3. Ospreys have closable nostrils. The predatory birds typically fly between 50 and 100 feet above the water before spotting a shallow-swimming fish (such as pike, carp or trout) and diving in for the kill. To avoid getting water up their noses, they have long-slitted nostrils that they can close voluntarily—one of the adaptations that allows them to consume a diet made up of 99 percent fish. 4. Ospreys usually mate for life. After a male osprey reaches the age of three, upon returning to his natal nesting area for the summer breeding season in May, he stakes claim to a spot and begins performing an elaborate flight ritual overhead—often flying in a wave pattern while clutching a fish or nesting material in his talons—to attract a mate. A female responds to his flight by landing at the nesting spot and eating the fish he supplies to her. Afterward, they begin building a nest together out of sticks, twigs, seaweed and other materials. Once bonded, the pair reunites every mating season for the rest of their lives (on average, they live about 30 years), only searching out other mates if one of the birds dies. 5. The osprey species is at least 11 million years old. Fossils found in southern California show that ospreys were around in the Mid-Miocene, which occurred 15 to 11 million years ago. Although the particular species found have since gone extinct, they were recognizably osprey-like and assigned to their genus. 6. In the Middle Ages, people believed ospreys had magical powers. It was widely thought that if a fish looked up at an osprey, it would be somehow mesmerized by the sight of it. This would cause the fish to give itself up to the predator—a belief referenced in Act IV of Shakespeare's Coriolanus: "I think he'll be to Rome/As is the osprey to the fish, who takes it/By sovereignty of nature."

Pomarine Skua

A pomarine skua, frequently called a sea hawk. (Photo by Patrick Coin) 7. Skuas steal much of their food. Unlike ospreys, skuas (the other birds often called "sea hawks") obtain much of their fish diet through a less noble strategy: kleptoparasitism. This means that a skua will wait until a gull, tern or other bird catches a fish, then chase after it and attack it, forcing it to eventually drop its catch so the skua can steal it. They're rather brazen in their extortion attempts—in some cases, they'll successfully steal from a bird three times their weight. During the winter, as much as 95 percent of a skua's diet can be obtained through theft. 8. Some skuas kill other birds, including penguins. Although fish makes up the majority of their diet, some skuas use their aggressiveness to not only steal the catch away from other birds, but occasionally to kill them. South Polar skuas, in particular, are notorious for attacking penguin nesting sites, snapping up penguin chicks and eating them whole:   [youtube]http://www.youtube.com/watch?v=6Xl5GSvyVfU[/youtube] 9. Skuas will attack anything that comes near their nests, including humans.​ The birds are extremely aggressive in defending their young (perhaps from seeing firsthand what happens to less protective parents, like penguins) and will dive at the head of any animal that approaches their nest. This even applies to humans, with skuas occasionally injuring people in the act of defending their chicks. 10. Sometimes, skuas will fake injuries to distract predators. In especially desperate situations, the birds will sometimes resort to a remarkably ingenious tactic: a distraction display, which involves an adult bird luring a predator away from a nest full of vulnerable skua chicks, generally by faking an injury. The predator (often a larger gull, hawk or eagle) follows the seemingly-debilitated skua away from the nest, intent on obtaining a larger meal, and then the skua miraculously flies away at full strength, having saved its offspring along with itself. 11. Skuas are attentive parents. All this aggressiveness has a reasonable justification. Skuas (which mate for life, like ospreys) are attentive parents, guarding their chicks through a 57-day fledging process each year. Fathers, in particular, take on most of the responsibility, obtaining food for the chicks daily (whether by theft or honest hunting) during the entire period. 12. Some skuas migrate from the poles to the equator each year. Among the most remarkable of all skua behaviors is the fact that pomarine skuas, which spend the summer nesting on Arctic tundra North of Russia and Canada, fly all the way down to the tropical waters off Africa and Central America each winter, a journey of several thousand miles. Next time you're judging the birds for their piratical ways, remember that they're fueling up for one of the longest journeys in the animal kingdom. Hermanus Online Website 

Published in Marine Wildlife

More than 70 definitions exist for what makes a species New species of insects, worms and other creepy-crawlers are announced on a monthly basis. Similarly, just last week, two new humpback dolphin species splashed into the headlines. And in October, news broke that early humans may have included fewer species than previously thought. This forces the question: what does it take to be a distinct species?

3_-New-species_dolphin_image_3-small1-1024x477

Name me! Australian humpback dolphins eagerly await their very own scientific name. Photo by Mendez More than 70 official species definitions exist, of which 48 are widely accepted and used by scientists. And there’s no hard rule that scientists must stick to just one definition; some apply a handful of species definitions when approaching the topic. “I personally go to my lab every day and use five species definitions to conduct research,” says Sergios-Orestis Kolokotronis, a molecular ecologist at Fordham University, and co-author of the new dolphin study, published in Molecular Ecology. “And I sleep just fine amidst this uncertainty.” Species definitions oftentimes do not translate from one organism to another. Dolphins may become isolated by distance and behavior that prevents them from reproducing, but in other cases–such as bacteria, which reproduce asexually–these distinguishing markers do not apply. Thus, the definition of what constitutes a species varies depending on whether scientists are studying dolphins, monkeys, insects, jellyfish, plants, fungi, bacteria, viruses or other organisms, Kolokotronis explains. And likewise, methods for investigating those species also vary. In the case of the four dolphin species, each occupy different sections of ocean around the world, including in the Atlantic off West Africa (Sousa teuszii), in the central to western Indo-Pacific (Sousa plumbea), in the eastern Indian and western Pacific (Sousa chinensis) and in northern Australia (researchers are in the process of working on a name for that one–Sousa bazinga, anyone?).

dolphin species 1

Two members of the newly identified Australian dolphin species. Photo by Mendez et. al., Molecular Ecology While the humpback dolphins look quite similar, their genetics tells a different story. Researchers collected 235 tissue samples and 180 skulls throughout the animals’ distribution, representing the biggest dataset assembled to date for the animals. The team analyzed mitochondrial and nuclear DNA from the tissue, which revealed significant variations between those four populations. They also compared the skulls for morphological differences. Although the line between species, sub-species and populations is a blurry one, in this case, the researchers are confident that the four dolphins are divergent enough to warrant the “species” title. The mitochondrial DNA turned up genetic signatures distinct enough to signal a separate species, and likewise, differences in the dolphins skulls supported this divergence. Although the nuclear DNA provided a slightly more confounding picture, it still clearly showed differences between the four species. “We can confidently say that such strong divergence means these populations are demographically and evolutionarily isolated,” says Martin Mendez, a molecular ecologist at the American Museum of Natural History and lead author of the dolphin paper. “The key is that all the evidence–mitochondrial DNA, nuclear DNA and morphology–exhibited concordant patterns of distinct units,” he continues, which are “usually a must for species proposals.” The genetic data the team collected does not have enough resolution to reveal how long ago the humpback dolphins diverged, and the team has yet to examine the drivers that fueled those speciation events. But Mendez and his colleagues have found that, in some dolphin populations, environmental factors such as currents and temperature play a role in separating populations and encouraging speciation. Different behaviors can help reinforce that separation, too. Most likely, however, geographic isolation plays a significant role in this case. “For populations living a couple hundred kilometers from one another, it’s perfectly possible for them to meet,” Mendez says. “But the distance from Africa to Australia is so great, it’s difficult to imagine those populations would ever be linked.” Dolphins, Mendez and his colleagues are finding, evolve relatively quickly once isolated from parent populations. New cryptic–or hidden–species have similarly turned up in waters near South America. There may very well be other species of dolphins–or any type of animal, in fact–lurking undetected within an already-discovered species. ”This really applies to most taxa,” Mendez says. Across the board, “we’re adding many more species by looking at genetic data.” Nonetheless, pondering the speciation of humans in dolphins in light of these two findings raises lots of questions: Are we fractally subdividing genetic information and brain cavity size to group and regroup organisms, or is there vast genetic diversity in even familiar species that we’ve yet to uncover? What does it mean for a species to gain or lose members of its family tree? The world and its organisms await more research. Hermanus Online Website 

Published in Dolphins

 

 

 

 

 

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