In mid-June of 2017,  a small cluster of newly fertilized eggs harvested from a nest on a Cape Cod beach by the Museum aquarium staff and volunteers and were placed in a saltwater tank and monitored. By early July, juvenile horseshoe crabs emerged, active, free swimming and hungry. They were tiny replicas of their parents, minus tails which grew very quickly. Every four to six weeks more horseshoe crabs appeared. Horseshoe crab eggs are genetically wired for some not to develop, to over winter and emerge the following year. Should one year’s juveniles all die, the species survival is guaranteed. For nearly half a billion years this has worked successfully.

Horseshoe crabs have exoskeletons needing to shed them (molt) to order to grow. Molts were regularly observed month after month. Additional tanks were required to accommodate the growing juveniles and their increasing numbers. In the spring of 2018 horseshoe crabs, scientific interest began with visits from a Woods Hole Marine Biological Laboratory researcher and a New England Aquarium Veterinarian. Rutgers University Horseshoe Crab Hatchery Program in New Jersey extended an invitation to collaborate in a research study. Local, national, and Canadian newspapers found the program noteworthy and there was plenty of Facebook activity.

As the program’s first anniversary approached, horseshoe crab counts were conducted. What had been an unknown number of eggs at the start had given rise to over one thousand active juveniles of varying sizes. In nature, only 10 in 100,000 eggs will survive to adulthood making the Museum’s first horseshoe head start journey an amazing success and a valuable head start experience. Some of the original juveniles remained at the museum on display while most were returned to their original nesting site. 2022 marked the first year horseshoe crab eggs were harvested on Wing Island. This year those juveniles will be retuned there.

For Museum visitors and staff this ongoing program, which has head started over a thousand horseshoe crabs, has provided unique firsthand learning experiences and ongoing opportunities to observe the early life stages of a rare “living fossil”, Cod Cod’s ancient mariner, Limulus polyphemus. 

As part of the Museum's continued its commitment to this flagship species for coastal conservation we celebrate International Horseshoe Crab Day (June 20th), on the third Monday in June. Join us this year to learn more about this fascinating marine animal, evolutionary superstar, and everyday superhero!