January 3, 2012 § Leave a comment
Updated January 03, 2012 20:53:48
More than 50 of the hybrid sharks were found in a 2,000-kilometre stretch of coast.
Marine biologists say they have discovered the world’s first hybrid sharks off Australia’s east coast, a potential sign the predators are adapting to cope with climate change.
They say the mating of the Australian black-tip shark with its global counterpart, the common black-tip, is an unprecedented discovery with implications for the entire shark world.
“It was unprecedented because hybridisation between sharks in the wild has never been reported before in Australia or worldwide,” said Dr Jennifer Ovenden from the Queensland Department of Primary Industries and Fisheries.
The scientists were examining fish stocks when they found 57 of the hybrid sharks in a 2,000-kilometre stretch of coast. They are a cross between two related but genetically different species.
The larger common black-tip shark swims in the colder waters of southern Queensland and northern New South Wales, while the smaller Australian black-tip likes warmer seas.
Dr Ovenden says there is a good reason why these sharks interbreed.
“Species with the smaller body can hybridise with the species with the larger body, allowing that tropical species to move further south,” she said.
“We are thinking that it will provide the sharks with a mechanism to adapt to future environmental change.”
Hybridisation happens among many species in the animal kingdom, including birds and some fish, but until now has been unknown among sharks.
Dr Colin Simpfendorfer, director of the Fishing and Fisheries Research Centre at James Cook University, says the discovery will help expand scientific understanding of sharks.
“It’s obviously a very interesting observation because we’ve never seen hybrid sharks before, and so it’s been hypothesised that it’s possible but we’ve never had any proof that it happens,” he said.
JCU fisheries researcher David Welch says it is a remarkable discovery.
“They actually choose a mate. It’s not like a fish where they actually put eggs and sperm into the water and they can potentially mix,” he said.
“Animal species tend to know their own kind, but in this case there seems to be a high prevalence of them interbreeding.”
The scientists are planning to look for hybridisation in other waters, including the western and northern Australian coasts
Sharks play an important role in the health of the marine environment. Sharks are known for being one of the few animals that never evolved over millions of years as they were perfectly suited to the ocean environment and did not need to adapt. However the new hybrid sharks show that global changes have caused the sharks to begin to process of evolution in order to survive.
June 4, 2010 § Leave a comment
I’ve often thought it was strange that in a highly religious country like Ecuador, there is no controversy over Evolution vs. Creationism. They believe in God, they believe in the bible but they also believe in Evolution. Maybe it is seeing Evolution first hand that makes people more than believe in it but know it as a fact to be true.
Charles Darwin’s the theory of Evolution is based on his works “On the Origin of Species by natural Selection” published in 1859. Darwin spent five years on the HMS Beagle circling the globe and making observations along the way. It is said that while in the Galapagos Islands he collected a number of Finches and on his return to London it was discovered he had found an entirely new group of birds and 12 different species. Thus leading him to his theory of transmutation and evolution.
What if you were to find out it isn’t true? No I don’t think you should have been home schooled so that you avoided hearing about Evolution – but it wasn’t the Finches that inspired Darwin, it was actually the Galapagos Mockingbird – a discovery he made while in Galapagos not while in London that lead him to his theory of evolution…
“The different islands probably have their representative species of races of the Amblyrhynchus, as well as the tortoise. My attention was first thoroughly aroused by comparing together the numerous specimens, short by myself and several other parties on board, of mocking-thrushes, when to my astonishment, I discovered that all those from Charles Island belong to one species (Mimus trifasciatus); all from Albermarle Island to M. parvulus and all from James and Chatham Islands belong to M. melanotis”
The Galapagos Islands are home to four species of Mockingbirds:
- Galapagos Mockingbirds
- Chatham Mockingbirds
- Hood Mockingbirds
- Floreana Mockingbirds
The Galapagos Mockingbirds are the most commonly seen mockingbird in Galapagos. They found on most islands and like other mockingbirds an inquisitive and chatty bird. They are easily recognized with their feathers, which are streaked brown and gray, long tail, and smaller size, and black, angled beak. The bird has a darker color than other mockingbirds.
On the island of San Cristobal the endemic Chatham Mockingbird has an intermediate appearance similar to those on the continent. The best place to see them is at the tortoise reserve in the highlands near Cerro Colorado.
The Hood Mocking endemic to Espanola bird they are the most aggressive of all the Mockingbirds. If you have ever been to Espanola you have probably encountered one as it tried to make it’s way into your daypack or sneak a drink from your water bottle. The Hood Mockingbird has mottled gray and brown plumage with a white underbelly. A long tail and legs give the bird its distinctive appearance. The species has a long, thin beak.
Floreana Mockingbirds were plentiful at the time of Darwin’s voyage and could be found all over the island of Floreana. Identified by their dark-brownish grey upperparts and dull white underparts, with distinct dark patches on the sides of its breast. Its eyes are reddish-brown and its beak, which is long and curved.
As we’ve discussed in other blogs Floreana was a favorite islands of early visitors and settlers, and like the tortoise the mockingbird did not benefit from these visitors. At the end of the 19th century the Floreana Mockingbird became extinct on the island of Floreana. Today they are considered one of the most endangered bird species in the world. The only remaining birds can be found on two rocky formations in front of Floreana —Champion where it is estimated 20-40 live and Gardner where another 60 – 80 are thought to live. Without great preservation efforts it is doubtful these Mockingbirds will survive another 100 years.
However, like the Galapagos Tortoises modern science is working to increase the number of Floreana Mocking birds and to reintroduce them to the main part of the island. Through DNA research the scientists are working to identify which of the mockingbirds are most similar to the original population of the island. As part of the restoration effort the introduced species on Floreana that are a threat to the survival of the Mockingbird are being eradicated. A reforestation project of the Opuntia Cactus a favorite of the Mockingbird has also begun. And once the DNA work is complete park officials and scientists will work to restore numbers and reintroduce them to their native island of Floreana.
May 4, 2010 § Leave a comment
Charles Darwin’s family suffered from the deleterious effects of inbreeding, suggests a new study that serves as ironic punctuation to the evolutionary theorist’s life work.
Pioneer of the theory that genetic traits affect survival of both individual organisms and species, Darwin wondered in his own lifetime if his marriage to first cousin Emma Wedgwood was having “the evil effects of close interbreeding” that he had observed in plants and animals.
Three of their children died before age 10, two from infectious diseases. The survivors were often ill, and out of the six long-term marriages that resulted, only half produced any children. According to researchers at Ohio State University and Spain’s Universidad de Santiago de Compestela, that alone is a “suspicious” sign that the Darwins suffered from reproductive problems.
Inbreeding can cause serious health problems, because it increases the chances of successful gene expression for diseases otherwise rare or muted in an individual’s pedigree.
The new study, detailed in the journal Bioscience, fed genealogical data on the Darwin-Wedgwood link into a specialized computer program, which spit out a “coefficient of inbreeding,” or the probability that an individual received two identical copies of a gene resulting from marriages among relatives. (Some genetic disorders are caused by recessive genes, which means they require two copies of a gene in order for the trait to manifest.)
Results revealed that inbreeding was a possible factor in the offspring’s poor health. Darwin’s children suffered from a “moderate degree” of inbreeding, the researchers concluded. When expanded to other branches of the family tree and four consecutive generations, the analysis found an even stronger association between child mortality and incestuousness.
Darwin’s mother and grandfather were also Wedgwoods, and his mother’s parents were third cousins.
The study relied solely on birth and death records. In the late 19th century it was still fashionable for wealthy families to intermarry over generations. As would be expected of prominent families, their genealogical records were also in excellent condition.
When genealogical records are not available, scientists interested in genetic heritage must rely on DNA and radiological analysis of bone samples — a type of research recently utilized for mummies.
In fact, this past February, an international team announced that a high degree of inbreeding was the likely explanation for boy pharoah King Tutankamun’s early death and frail, club footed frame. And research published last year showed the termination of the Habsburg dynasty that ruled Spain for nearly 200 years may have been a result of frequent inbreeding.
Learn more about Charles Darwin and Evolution
March 19, 2010 § 4 Comments
When you think of Galapagos, the first two thoughts that come to mind are Charles Darwin and giant tortoises. The giant tortoise is the iconic symbol of these islands. The name Galapagos come from a Spanish world for saddle – referring to the shell of these gentle giants. The national park uses an image of the giant tortoise as its logo. Whenever you see information about the Galapagos – you see pictures of the beloved giant tortoise.
The world’s largest tortoises, Galapagos Tortoises have a lengthy 150-year lifespan. Male tortoises are known to grow to be over 600 pounds. The archipelago was never attached to a continent and all the plants and animals, which arrived in the Galapagos, did so by either swimming, flying or floating. The journey across the ocean was too difficult for grazing mammals that dominate the grasslands of other parts of the world, and thus the slow moving tortoise reigned as king for thousands of years.
At the time of Charles Darwin’s visit in 1835, it was thought that 250,000 tortoises and 12 subspecies existed here. It was the comments regarding the tortoises from the local vice-governor, which first dismissed by Darwin, would later come to inspire him:
“I have not as yet noticed by far the most remarkable feature in the natural history of this archipelago; it is, that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the Vice-Governor, Mr. Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought. I did not for some time pay sufficient attention to this statement, and I had already mingled together the collections from two of the islands. I never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under a quite similar climate, rising to a nearly equal height, would have been differently tenanted; but we shall soon see that this is the case. It is the fate of most voyagers, no sooner to discover what is most interesting in any locality, than they are hurried from it; but I ought, perhaps, to be thankful that I obtained sufficient materials to establish this most remarkable fact in the distribution of organic beings.”
Darwin and his shipmates aboard Beagle viewed tortoises much in the same way as the pirates and whalers, tortoises were something to be exploited. The members of the Beagle harvested 30 tortoises from the islands, which they ate on their way home.
Over the past few centuries the systematic harvesting of tortoises for meat, oil, as well as the introduction of new species dwindled the population down some 90% from what it was in during Darwin’s visit. Both the Floreana and Pinta tortoises are noted as extinct and all of the remaining 10 species of Galapagos Tortoise are listed as endangered species.
In 1959, 100 years after the first publishing of Darwin’s On the Origin of Species the Galapagos Islands became as a national park. The park service together with the Darwin Foundation has made remarkable steps over the past 50 years towards the preservation, conservation and restoration of native species.
Perhaps the best example of their efforts is the story of the Espanola tortoise. At one time there were at least 3000 native tortoises on the island of Espanola. However Espanola is one of the flattest and most accessible of the islands, making it a favorite place for passing ships. As a result by 1965 there were just 14 remaining tortoises living on Espanola – 2 males and 12 females. The tortoises were transferred to the Charles Darwin Research Station on Santa Cruz. A third male was then discovered at the San Diego Zoo. In the 1970’s the tortoise-breeding program began. From the brink of extinction, of 15 tortoise the program has been a success and today nearly 1500 Espanola Tortoise have been repatriated to their native island.
With the success of the Espanola program stopping the extinction of other species proved to be more problematic. In 1971, Lonesome George was discovered on the Pinta. He has the unique distinction of being is noted as the last remaining of his species. George was relocated to the Darwin Station and scientists began work on the question how to keep the Pinta Tortoise from becoming extinct. Two females from Wolf Volcano on Isabela were placed in the pin with George. These females were selected as they were found to be the genetically closest relation to George and though any off spring produced would not pureblood – the species would some how continue.
For years George showed little or no interests in these females. But in 2008, the national park announced both of Geroge’s companions laid eggs. The world awaited news if the Pinta race had been saved. At the end of the year it was announced none of the eggs were viable and their search for how to save the species continued.
In 1994 a team of Yale Scientists began the Galapagos Tortoise Genetics Process. The group went to Isabela and took blood samples from 27 tortoises living high on the Wolf Volcano. Some 2000 tortoises are thought to live in and around Wolf. These tortoises are of significant interest, as tortoises here, resemble more than one subspecies. Normally each group of tortoise will either have a domed shaped shell (similar to the tortoises of Alcedo or other parts of Isabela) or a saddleback shaped shell (similar to Lonesome George) depending on the environment where they live. Yet near Wolf, tortoises can be found with both domed and saddleback shells.
Over the next decade the genetics team began collecting DNA samples from the tortoises in not only in Isabela, but also began samples from tortoises at the Darwin Station, around Galapagos, and tortoises held in captivity all over the world. On Pinta they found they took DNA samples from the remains of 15 tortoises and they cataloged the information to gain a better understanding of the species.
As they began to review their database, the impossible seemed to be possible. First they believe they have discovered a second pureblood Pinta tortoise. A Tortoise known as Tony, thought to be approximately 50 years of age is living at the Prague Zoo – from all current data Tony appears to be the same exact subspecies as George.
As they sifted through the DNA information they discovered the reason the Wolf tortoises appeared to resemble more than one subspecies. Isabela and the area near the Wolf Volcano was often the last stop for pirate ships in Galapagos. It appears that these ships collected tortoises on other islands during their stay only to discard them here. When testing the DNA samples, several of the tortoises living on Wolf were found to be first generation hybrid Pinta tortoises – tortoises born to mothers from Isabela and fathers from Pinta. This discovery meant that some of the tortoises living on Wolf were 50% the same genetic subspecies as Lonesome George. This information provided new hope that by further investigation a pureblood or half-blood female Pinta tortoise can be found – and the Pinta race can survive.
The genetic team seemed to have uncovered a miracle – still there were more surprises to realize. The research discovered descendants of the extinct Floreana Tortoise. The Floreana subspecies became extinct during the early 20th century due to human activities, and unlike Lonesome George no known examples were known to have survived. Yet, the DNA research uncovered 9 tortoises with high percentage of Floreana genome (up to 94%) and they believe 1 tortoise may even be pureblood. Of the tortoises identified of being from Floreana 6 are female and 3 are male all of which are currently residing at the breeding center in Santa Cruz.
Drawing from the success of the Espanola breeding program these new findings of the Genetics team, man may now be able to make up for some of their previous wrong doings. What was once extinct may not be extinct in the future. It’s all just a matter of time with the help of science and mother nature.