Original found at http://www.radionetherlands.nl/features/science/salamanders010828.html
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Slippery Salamanders

by Laura Durnford of our Science Unit


A giant Chinese salamander
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It's a Monday afternoon in late August and Dr Willem Schaftenaar is conducting an ultrasound scan on a large, brown, slippery amphibian; a giant Chinese salamander (Andrias davidianus). With her large, powerful jaws and tail, tiny eyes and stumpy legs she weighs in at around 6kg - a miniature compared with the 15kg males that can grow up to 1.5 metres long. Schaftenaar is the zoo's Vet and this salamander is one of six that live in the warm, noisy atmosphere of Rotterdam Zoo's tropical house. This is the only zoo outside China where attempts have been made to assist breeding in these amazing and highly endangered animals.


Andrias davidianus egg with embryo at 6 days of development 

Egg of Andrias davidianus with embryo at 6 days of development. (Courtesy of Willem Schaftenaar)

"I'm looking for the ovaries," explains the Vet, "at this time of year there are dark round spots there which are eggs. When they're completely black they're mature." A computer measures the size of the eggs as they appear in the grainy grey image of the ultrasound scan. A diameter of 5 millimetres suggests the time is right and Schaftenaar injects hormones into the beast, stimulating her to lay her necklace of crystal-ball eggs (15-20mm) within the next three or four days.

Caring, Sharing Male
But it takes two to tango and it seems the male of the species is even more crucial than the female when it comes to the timing of reproductive events. The males here also undergo ultrasound examination and hormone injections. "In salamanders, if the male isn't ready then forget it," says Schaftenaar. "Between July and September he gets a swelling around his cloaca - that's the opening where faeces, urine and semen or eggs leave the body. Only the male gets this. We think he gives off pheromones, kind of hormones, that a female can smell and it stimulates her to ovulate." And getting the female in the mood at the right time is critical for the male salamander. "They produce semen only once per year. This makes them very vulnerable, because in the wild they have to find a female at the right time or wait until the following year to breed!"

sperm of Andrias davidianus 

Sperm of Andrias davidianus (Courtesy of Willem Schaftenaar)

Giant Chinese salamanders are rare even within China. They live in remote streams, hiding in crevices and eating fish, frogs, crustaceans and earthworms. Summer-time melting of mountain snow and ice reduces the water temperature and signals that the breeding season has arrived. The male makes a nest to attract a female to come and spawn. He then releases his semen over the eggs, and as the unusually large sperm hit the water they start moving, actively seeking to fertilise them. In a fascinating twist of behaviour, he even allows other males into his nest to have their way with the precious eggs, before he mounts a guard over them and waits for them to hatch.

High Hopes
It's a process that needs a helping hand in captive salamanders. They've never bred with hormonal assistance in zoos anywhere outside China and it's not known whether anyone there has had any success. In Japan researchers have been breeding the related Japanese species of giant salamander and Willem Schaftenaar has been exchanging information with them. He only discovered that the Chinese salamanders at Blijdorp were physically capable of breeding by conducting extensive studies of ultrasound scans and blood samples from both males and females.


Egg with embryo at 13 days of development. (Courtesy of Willem Schaftenaar)


The age of the creatures is still a mystery as they were all confiscated from a number of smuggled imports about ten years ago. Last year the vet collected sperm by rubbing the males' abdomens and managed to fertilise about 100 eggs, but the embryos died after only two weeks. This year, he's more optimistic.

"Incubation takes exactly 50 days. We'll hang the eggs over bamboo sticks so they get more water and oxygen flowing over them than last year. We don't know how big they'd be when they hatch, but the Japanese species are 8cm long. Once they've hatched they'll have to be fed and that's another thing we don't know - what they eat. We'll have to divide them into groups and try them on different things and hope to find something they like quickly!"


Original found at http://www.radionetherlands.nl/features/science/salamanders010828.html
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