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Wednesday, August 21, 2019

Turtle and Shark

by Emmanuelle Landais

© Pictures courtesy of The Turtle Rehab Centre - A hawksbill turtle is held just before it’s released
David Robinson and Warren Baverstock examine a baby zebra shark
A baby zebra shark at the rehabilitation centre

Small, friendly and altogether cute, it’s hard not to like turtles. And there’s no doubt the sight of one in its own environment of the Arabian Gulf can be a thrilling experience.

The Arabian Gulf is in fact home to four different species of turtle. The hawksbill, the green, the loggerhead and the olive ridley turtles all have nesting sites along the UAE coastline. So rare are these animals that they’re considered an asset to the region.

Every winter however, sightings of a different nature occur when hundreds of turtles are found washed up on the beaches of the UAE, affected by the drop in sea temperatures common in the last few years. The cold causes the turtles to swim sluggishly and because of their small size they become weighed down by barnacles that clamp to their shells.

The younger ones, or juveniles which are a couple of years old, tend to suffer the most and wildlife conservationists have begun to fear for the future of the species in this part of the world.

However a conservationist programme begun in 2004 – the Dubai Turtle Rehabilitation Project – is aiming to counteract the effects of global warming and save the turtles of the Arabian Gulf. Last year alone, 352 sea turtles were handed into the centre after being picked up along the UAE coastline.

Based in the Burj Al Arab and the Madinat Jumeirah in the Jumeirah area of Dubai which is on the coast, the project is run in collaboration with the Dubai’s Wildlife Protection Office.

Veterinary support at the centre is provided by the Dubai Falcon Clinic and the Central Veterinary Research Laboratory. Costs associated with food for the turtles, husbandry, microchips which are placed under their skin and medicine are all financed by the Jumeirah Group and other funding comes from a number of private associations and people.

The biggest supporters though are the public who through public awareness campaigns have helped to spot injured turtles of every size on the beaches of Dubai and hand them into the centre. The turtles found typically vary in size.

“The greens can vary in weight between 1kg and 150kg, but there is no average size. We also had two loggerhead turtles brought in during 2011, one weighing 65kg and the other 50kg,” explains Warren Baverstock of the Dubai Turtle Rehabilitation Project and the Manager of the Burj Al Arab Aquarium.

“By far the most common species admitted to the centre is the hawksbill turtle,” he adds. “This species is less able to tolerate the colder waters experienced in Dubai over the winter months and this is when they become debilitated.”

According to Baverstock, the largest turtle treated at the centre so far was a green that weighed an impressive 150kg. “She was huge and it took six people just to lift her. We eventually released her with a satellite tag after a few months of rehabilitation. But we’ve also had a huge 95kg loggerhead turtle brought into us this year.”

In 2011 alone, an olive ridley turtle; two loggerheads; 16 greens; and 333 hawksbills were treated at the centre, with some of them remaining there for months at a time.

To date, the project has released over 500 turtles back into the wild and this number looks set to reach approximately 750 by the end of 2012. Each turtle is fitted with a micro-chip when it first arrives so that its progress and growth can be monitored, as well as its ‘return rate’ after it has been released. But so far no turtle has ever returned to the centre, “which is a very good sign,” says Baverstock. “It proves that they have healed satisfactorily.”

This satellite tagging system is also useful to gauge how well the turtles have integrated back into their natural habitat after rehabilitation. According to the project’s preliminary results, rehabilitation is extremely common with one turtle traveling an amazing 8,600km after 18 months in intensive care. The turtle, named Dibba, swam across the Indian Ocean, almost reaching the coast of Thailand. Its progress was monitored all the way – that is until the battery on its tag ran out.

Aside from turtles, the aquarium which is part of the Dubai Turtle Rehabilitation Project houses an impressive array of other marine animals, including zebra sharks which are also an endangered species. Baverstock, and his colleague David Robinson, assistant manager of the Burj Al Arab Aquarium, first discovered eggs laid by a female zebra shark that was later named ‘Zebedee’ in 2007. “The eggs are often laid by females even when there is no male present to fertilise them,” explains Baverstock. “But then they’re usually discarded.”

Parthenogenesis, which comes from the Greek, parthenos, meaning ‘virgin’ and genesis – ‘birth’, takes place when the female’s egg cells double their genome and then split in two.

The lone female shark was able to birth pups because of this process which involves egg cells taking on the role of the male sperm and effectively fertilising the other egg as they merge back together to produce an embryo with two sets of chromosomes from the mother.

Zebedee, who was imported from the Red Sea region, has given birth to 21 pups since 2007, six of which are still alive.

“It was already known that a shark had done this before, but the shark in question was of a totally different lineage than the zebra shark; so, this is very exciting,” explains Robinson. “These are currently the first sharks that are alive and well that have been produced via parthenogenesis” he adds, pointing out that it is quite a coup for the project. In fact the rare birth of these shark pups has been documented in a scientific paper featured in The Journal of Fish Biology.

“Warren and I had read about the first incident with a bonnet-head shark that occurred in 2001 in the US, so we decided to isolate Zebedee’s eggs to see what would happen; three months later we discovered embryos inside some of the eggs which have since hatched.”

Whether Zebedee’s offspring will now be able to produce pups of their own remains unknown, but these sharks are not clones, as they differ genetically from each other and from their mother. They have perfectly formed reproductive systems and so the next stage of research will be to pair them with males to see if they reproduce normally. Robinson adds: “Controlling the number of pups being born is certainly not a concern for us. We can always place our captive-bred zebra sharks with other facilities around the world and this will hopefully help to reduce the number of zebra sharks taken from the wild. It’s also putting us on the global map in terms of marine conservation.”

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Emmanuelle Landais