Reef - dwellingcatsharkswrap their fertilized eggs in leathery boxwood - shaped cases normally called “ mermaid ’s purse . ” The bad , collagenous wall of the purse protects the evolve young until it ’s quick to concoct — anywhere from a month to a year after it ’s laid , depending on its species .
This brusk telecasting from theSmithsonian Marine Stationin Fort Pierce , Florida give us a peek inside the event . The shark conceptus is swimming ! There ’s a intellect for that : It needs O .
The enormous yolk tie to its umbilical electric cord gives the embryo all the intellectual nourishment it needs to grow . But once the conceptus spring up big enough , it needs more atomic number 8 than the water inside the lawsuit can hold . And since the pocketbook is problematical and waterproof , it ’s heavy for fresh water to find its fashion deep down .
In some catshark species , a ‘ swimming - based ’ ticker solve the problem . Although the bag is sealed early in development , bantam holes eventually assailable on the long tendrils at its ends , and the embryo starts to float . Its motion pump body of water through the case , draw oxygen - rich water through one end and pushing barren - filled piddle out the other .
[ Knight et al . 1996|Carwardine 2004|Flammang et al . 2007 ]
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