‘Jet packs’ and ultrasounds could reveal secrets of pregnant whale sharks

How have you learnt if the world’s largest dwelling fish is anticipating infants? Not by her bulging stomach, it seems.

Scientists thought that an enlarged space on the undersides of feminine whale sharks was an indication of being pregnant. However a method used for the primary time on free-swimming animals confirmed solely pores and skin and muscle. These humps may as a substitute be a secondary intercourse attribute on mature females, like breasts on people, researchers report within the March 23 Endangered Species Analysis.

The ultrasound is a part of a collection of recent strategies together with underwater “jet packs” and blood exams that scientists hope might unlock secrets and techniques about this creature’s copy.

Whale sharks (Rhincodon typus) are labeled as globally endangered by the Worldwide Union for Conservation of Nature. There are solely an estimated 100,000 to 238,000 people left worldwide, which is greater than a 50 % decline within the final 75 years.

Partially as a result of whale sharks are comparatively uncommon, their reproductive biology is usually a thriller (SN: 8/1/22). Practically all the pieces biologists suppose they know is predicated on the examination of 1 pregnant feminine caught by a business fishing boat in 1995.

“Defending organisms with out understanding about their biology is like making an attempt to catch a fly with our eyes closed,” says Rui Matsumoto, a fisheries biologist with the Okinawa Churashima Basis in Japan. The group researches subtropical animals and vegetation to take care of or enhance pure sources in nationwide parks.

To be taught extra about these mild giants, Matsumoto and shark biologist Kiyomi Murakumo of Japan’s Okinawa Churaumi Aquarium had to determine how you can sustain with them. Like superheroes in a comic book e-book, the biologists used underwater jet packs — propellers hooked up to their scuba tanks — to swim alongside the fish, which common 12 meters in size and transfer about 5 kilometers per hour.

Then the researchers needed to maneuver a 17-kilogram briefcase containing a water-proof ultrasound wand on the undersides of twenty-two females swimming close to the Galápagos Islands and draw blood with syringes from their fins. Till this research, the ultrasound wand had by no means been used exterior of an aquarium on free-swimming wildlife.

Performing these two exams on whale sharks is very difficult, says research coauthor Simon Pierce, a whale shark ecologist with the Marine Megafauna Basis, a nonprofit group that makes use of analysis to drive marine conservation.  The fish “have a number of the thickest pores and skin of any animal — as much as about 30 centimeters thick.”

One other problem is the seawater itself, which may contaminate blood samples. The researchers developed a two-syringe system, the place the primary syringe creates a vacuum and permits the second syringe to attract solely blood. 

Again within the lab, the blood plasma from six of the females confirmed hormone ranges much like ranges obtained from a captive immature feminine in an aquarium, indicating these wild females weren’t sufficiently old to breed.

Ultrasound imagery confirmed egg follicles in two of the 22 feminine sharks, which means these females had been mature sufficient to breed however not pregnant. The biologists didn’t find a pregnant whale shark.

Pioneering these noninvasive strategies on whale sharks has opened the door to probably studying extra about different endangered marine animals, too. Waterproof ultrasound wands mounted on a pole, Pierce says, are actually getting used on tiger sharks in locations the place the predators are drawn in by bait.

Rachel Graham agrees creating these underwater sampling strategies is an “astounding feat.” However the marine conservation scientist and founding father of MarAlliance, a marine wildlife conservation nonprofit, doubts whether or not most free-ranging wild marine animals, significantly faster-swimming sharks or marine mammals, would tolerate comparable exams.

“What makes whale sharks pretty distinctive … is that they transfer comparatively slowly at occasions, have the power to stay stationary, and so they tolerate the presence of different animals — reminiscent of us — close by,” says Graham, who has studied shark species around the globe and was not concerned within the new research.

Coupled with satellite tv for pc monitoring, the brand new strategies, might ultimately present us the place whale sharks give delivery, Pierce says. Little is understood about whale shark pups, together with whether or not they’re born in shallow or deep water, and whether or not pups are born one-at-a-time or if moms collect to offer delivery collectively. “Assuming they do have some type of breeding or pelagic nursery space we are able to establish … then that clearly goes fairly a great distance in the direction of conserving the inhabitants.”