Doug Wechsler / Horseshoe crab (Limulus polyphemus) embryos, Delaware Bay, New Jersey, USA, June.

Jurgen Freund / Horsehoe crab (Tachypleus gigas) underside, Palawan, Philippines

Jurgen Freund / Horsehoe crab (Tachypleus gigas) swimming on its back with gills creating the propulsion, Palawan, Philippines. Did you know? Horseshoe crabs are more closely related to spiders than crabs.

Steve Nicholls / Horseshoe crabs (Limulus polyphemus) spawning at low tide, Slaughter Beach, Delaware, USA, May

Ingo Arndt / Rear view of Horseshoe crab (Limulus polyphemus) with trail in sand, Delaware Bay, Delaware, USA, May

Shane Gross / Horseshoe crab (Limulus polyphemus) pair mating in Turtlegrass (Thalassia testudinum) bed. Florida Keys, Florida, USA.

Sirachai Arunrugstitchai / Indo-Pacific horseshoe crabs (Tachypleus gigas) mate in the sandy substrate, Satun province, Thailand.

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) juvenile aged two years, in fifth instar, beside 5 Yen coin for scale. Endangered species due to habitat loss and over-harvesting for food and biochem...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) juvenile aged two years, in fifth instar. Endangered species due to habitat loss and over-harvesting for food and biochemical industry. Yamaguchi Pref...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Female searching for location to spawn, male clasped onto rear of female will fertilise eggs once deposited. Yamaguchi Pre...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) male fertilising eggs deposited by female in substrate. Female crab buried on sea floor beneath male. Yamaguchi Prefecture, Honshu, Japan. July.

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Female digging into substrate before depositing eggs, male clasped onto rear of female to fertilise eggs once deposited. Y...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Female digging into substrate before depositing eggs, male clasped onto rear of female to fertilise eggs once deposited. Y...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Male clasped onto rear of female, male fertilising eggs female has deposited in substrate. Yamaguchi Prefecture, Honshu, J...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Female digging before depositing eggs, disturbance releases air bubbles from substrate. Male clasped onto rear of female w...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair walking across sea floor at night. Female searching for location to spawn, male clasped onto rear of female to fertilise eggs once deposited. Sna...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair on sea floor at night. Female digging before depositing eggs, disturbance releases air bubbles from substrate. Male clasped onto rear of female w...

Tony Wu / Tri-spine horseshoe crab (Tachypleus tridentatus) pair walking across sea floor at night. Female searching for location to spawn, male clasped onto rear of female to fertilise eggs once deposited. Yam...

Wayne Wu Ying / Wild Wonders of China / Man holding Horseshoe crab (Tachypleus tridentatus) at Horseshoe crab release event oragnized by Ocean Park Conservation Foundation, Hak Pak Nai beach, Yue Long, Hong Kong, China

Wayne Wu Ying / Wild Wonders of China / Person taking picture of Horseshoe crab (Tachypleus tridentatus) release event oragnized by Ocean Park Conservation Foundation, Hak Pak Nai beach, Yue Long, Hong Kong, China

Wayne Wu Ying / Wild Wonders of China / Horseshoe crab (Tachypleus tridentatus) measured at release event organized by Ocean Park Conservation Foundation, Hak Pak Nai beach, Yue Long, Hong Kong, China

Wayne Wu Ying / Wild Wonders of China / Horseshoe crab (Tachypleus tridentatus) release event oragnized by Ocean Park Conservation Foundation, Hak Pak Nai beach, Yue Long, Hong Kong, China

Doug Wechsler / Stranded horseshoe crabs (Limulus polyphemus) at sunset; Delaware Bay, New Jersey, USA, June.

Doug Wechsler / Horseshoe crab (Limulus polyphemus) at sunset; Delaware Bay, New Jersey, USA, June.

Magnus Lundgren / Wild Wonders of China / Shells fron the Chinese horseshoe crab, (Tachypleus tridentatus) Ha Pak Nai Wetlands, Yuen Long, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai Wetlands, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Chinese horseshoe crab (Tachypleus tridentatus) juvenile, Ha Pak Nai is a wetlands, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Joe Cheung from the Ocean Park Conservation Foundation Hong Kong , showing students juvenile Chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai Wetlands, Hong Kong, China. June, 2016.

Magnus Lundgren / Wild Wonders of China / Secondary school student shows post cards they have made at the release event of juvenile Horseshoe crab ( Tachypleus tridentatus) artificially-bred by City University of Hong Kong. Ha Pak Nai Wetland...

Magnus Lundgren / Wild Wonders of China / Scients measuring Chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai Wetlands, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Transpond reader (receiver) used to find the juvenile Chinese horseshoe crabs (Tachypleus tridentatus) before the release. Ha Pak Nai, Yuen Long District, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Small transponder (sender) injected into the juvenile Chinese horseshoe crab (Tachypleus tridentatus) before the release. Ha Pak Nai, Yuen Long, Hong Kong, China

Magnus Lundgren / Wild Wonders of China / A small transponder (sender) injected into the juvenile Chinese horseshoe crab (Tachypleus tridentatus) before the release. Ha Pak Nai, Yuen Long District, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Small transponder (sender) to be injected into the juvenile Chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai, Yuen Long Districts, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Secondary school student interviewed by TV channel about the release of juvenile Chinese horseshoe crabs (Tachypleus tridentatus) that have been artificially-bred by City University of Hong Kong, and...

Magnus Lundgren / Wild Wonders of China / Joe Cheung, Ocean Park Conservation Foundation Hong Kong , teaching secondary school students about Chinese horseshoe crab (Tachypleus tridentatus) Yuen Long District facing DHa Pak Nai, Yuen Long, Ho...

Magnus Lundgren / Wild Wonders of China / Secondary school students releasing juvenile Chinese horseshoe crabs (Tachypleus tridentatus) that has been bred by City University of Hong Kong, Ha Pak Nai wetlands, Yuen Long District, Hong Kong, Ch...

Magnus Lundgren / Wild Wonders of China / Secondary school students release a juvenile Chinese horseshoe crab (Tachypleus tridentatus) that has been artificially-bred by City University of Hong Kong, and collectively releasing them into the w...

Magnus Lundgren / Wild Wonders of China / Chinese horseshoe crab (Tachypleus tridentatus) tiny juvenile to be raised by the secondary school students and released into the wild. Ha Pak Nai wetlands, Yuen Long District, Hong Kong, China

Magnus Lundgren / Wild Wonders of China / Secondary school students release a juvenile, age six months, Chinese horseshoe crab (Tachypleus tridentatus) that has been bred by City University of Hong Kong, Ha Pak Nai wetlands area Yuen Long Dis...

Magnus Lundgren / Wild Wonders of China / Staff from Ocean Park Conservation Fund, OPCF, and students visit Ha Pak Nai to see the juvenile Chinese horseshoe crabs, (Tachypleus tridentatus) Yuen Long District, New territories, Hong Kong, China...

Magnus Lundgren / Wild Wonders of China / Staff from Ocean Park Conservation Fund, OPCF, and students visit Ha Pak Nai to see the juvenile chinese horseshoe crabs (Tachypleus tridentatus) in a mudflats, Yuen Long District, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Juvenile chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai wetlands, Yuen Long District, Hong Kong, China.

Magnus Lundgren / Wild Wonders of China / Chinese horseshoe crab (Tachypleus tridentatus) juvenile, at Ha Pak Nai wetlands, Yuen Long District, Hong Kong, China. June, 2016.

Magnus Lundgren / Wild Wonders of China / Chinese horseshoe crab (Tachypleus tridentatus) juvenile held upside down in human hand, Ha Pak Nai wetlands, Yuen Long District, Hong Kong, China. June, 2016.

Magnus Lundgren / Wild Wonders of China / Old shells of Chinese horseshoe crab (Tachypleus tridentatus) Ha Pak Nai, Yuen Long District, Hong Kong, China.

Alex Mustard / Toddler watching a pair of Horseshoe crabs (Limulus polyphemus) spawning in shallow water. Larger female and smaller male. Indian River, North Atlantic Ocean. Titusville, Merrit Island, Florida, USA....

Alex Mustard / Horseshoe crab (Limulus polyphemus) pair, larger female and smaller male, spawning in shallow water. Indian River, North Atlantic Ocean. Titusville, Merrit Island, Florida, USA. February.