MS TU Shot of young girl pouring water on two horseshoe crabs on beach / St Simon's Island, Georgia, United States

WS Shot over horseshoe crab moving on beach / St Simon's Island, Georgia, United States

WS Shot over young girl watching two horseshoe crabs on beach / St Simon's Island, Georgia, United States

MS TU Shot of young girl pouring water on two horseshoe crabs on beach / St Simon's Island, Georgia, United States

MS Shot of horseshoe crab moving on beach / St Simon's Island, Georgia, United States

WS PAN Shot of young girl dragging two horseshoe crabs to beach / St Simon's Island, Georgia, United States

TIME LAPSE: Pacific Sea nettle jellyfish are displayed at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Pacific Sea nettle jellyfish are displayed at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

TIME LAPSE: Pacific Sea nettle jellyfish are displayed at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

HYPERLAPSE, PAN: Tourists visit the touch pool featuring stingrays and horseshoe crabs at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

HYPERLAPSE, PAN: Pacific Sea nettle jellyfish are displayed at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

HYPERLAPSE, ZOOM IN: Sharks, turtles and other marine animals swim at the 1.3-million-gallon Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

HYPERLAPSE, PAN: Pacific Sea nettle jellyfish are displayed at the Shark Reef Aquarium at the Mandalay Bay Resort and Casino on October 22, 2013 in Las Vegas, Nevada. (Footage by: Ethan Miller/Getty Images)

Horseshoe crab shell

Jun.24 -- The horseshoe crab is a living fossil that's called Earth its home for almost half a billion years. And if you’ve ever had a vaccine, injection, or a medical implant, then you might not know that you’ve been relying on this...

Every May and June, hundreds of thousands of horseshoe crabs — a species with 10 eyes predating dinosaurs and related to scorpions and spiders — come ashore in the Delaware Bay, on the East Coast of the United States, to spawn at high...