How do female whale sharks meet their perfect mates and go on to create offspring? While little is known about the reproductive behavior of those ocean-roaming giants, a newly published analysis led by University of Illinois at Chicago biologist Jennifer Schmidt reveals new information about the mating habits of this elusive, difficult-to-study fish.
The pregnant shark carried a amazingly many embryos — 304 — still in the uterus and representing a spectrum of age and development phases ranging from being still egg-encased to developed, near-term animals.
“These differently aged embryos — itself unusual across animal species — had the same father,” Schmidt said. “We have to be very cautious in drawing conclusions from a single litter, but the data suggest female whale sharks store sperm after a single mating event, and subsequently fertilize their own eggs as they are produced.”
Whale shark. UIC researcher Jennifer Schmidt, associate professor of biological sciences, studies the large mammals.
In case the finding can be supported from examination of other whale shark litters, Schmidt said, “it would suggest that there is no whale shark breeding ground where large numbers of animals meet to mate, but rather that mating occurs as an isolated event.”
“Protections for whale sharks have increased in many parts around the globe, yet shark numbers appear to be declining, and the average size is getting smaller,” said Mark Meekan, principal research scientist with the Australian Institute of Marine Sciences.
The findings are reported in the journal Endangered Species Research, published online Aug. 4. Other authors include Meekan; Joung and Chien-Chi Chen of the National Taiwan Ocean University; Saad I. Sheikh, formerly of UIC; and Bradley Norman of ECOCEAN Inc.
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