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May 07, 2010

Amazing Amazon mom

Raypup We’ve got lots of moms at Shedd. The biggest is beluga whale Puiji (and her calf was the biggest baby at birth, weighing 164 pounds). The flattest might be the tiger ray in Amazon Rising. Tiger rays (Potamotrygon schroederi) must get their common name from their striped tails, because their disks have a dense pattern of small golden rosettes on a dark brown background.


At 3 feet in diameter, this Amazon mom is the largest of three female tiger rays in the low-water habitat. (Two males also live in the exhibit.) Her third pup—born just last week—is in a pool behind the scenes, but her first offspring (shown at left) is one of the other females on exhibit—and the first tiger ray ever born in a North American aquarium or zoo.

Freshwater rays reproduce by aplacental viviparity. That means the pups—up to three in this species—develop inside the mom’s body, but there is no placenta to provide them with oxygen and nourishment. Instead, each free-swimming embryo starts out with a large yolk sac. But it also gets a significant amount of its nutrition from trophonemata, fingerlike projections in the lining of the uterus that secrete what’s called uterine milk. Biologists are currently studying just how the pups get the milk, and Shedd has contributed sonograms of its pregnant rays to further the research. We still have a lot to discover about these amazing Amazon moms. Be sure to let your mom know how amazing she is on Mother’s Day—this Sunday!

And don't forget to print your Mother's Day buy-one-get-one ticket coupon

Posted by Karen Furnweger, web editor



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