Horseshoe Crabs: The Living Fossil You’ve Probably Never Heard Of!

Having been around for over 300 million years, horseshoe crabs are often dubbed as living fossils. They provide critical ecosystem services, even serving as keystone species in some corners of the world.

Unfortunately, very little is known, much less understood, about these elusive animals despite their decreasing population.

As such, the Indonesia Horseshoe Crab Project is an effort to catalyse conservation and research efforts in Indonesia by conducting socio-ecological surveys coupled with a rigorous community outreach program to not only gain a much deeper understanding of these endangered creatures, but to also initiate a paradigm shift amongst locals to recognise the crucial importance of the horseshoe crabs to their surrounding ecosystem, whilst taking into account the species cultural and socio-economic significance amongst locals.

In celebrating the launch of our project, here are some fun facts about our favourite living fossil we’d like to share with you!


1. They Are Not Crabs!

Despite their name, horseshoe crabs are actually not crabs at all!

They are, in fact, part of the arachnid family (spiders, scorpions, etc.) [1].

The horseshoe crab refers to four different species, namely: American Horseshoe Crab (Limulus Polyphemus), Tri-spine horseshoe crab (Tachypleus tridentatus), Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda), and the Indo-Pacific Horseshoe Crab (Tachypleus gigas). Except for the American Horseshoe Crab, all horseshoe crabs are found in Indonesia.


2. A Symbol of Love in Indonesian Culture

Uniquely enough, the horseshoe crab has established itself as an important part of Indonesian culture.

Due to their monogamist tendencies, they are perceived as the ultimate manifestation of true love and loyalty in Javanese mythology, deriving the name “Mimi” for male horseshoe crabs and “Mintuno” for female horseshoe crabs. As such, it is common to congratulate newly-weds with the saying, “may your relationship always be as harmonious as Mimi and Mintuno’s.”


3. They Are Considered a Highly Sought-after Commodity

Unfortunately, while they are cultural icons, they are also highly valued economically – caught, smuggled, and consumed in various places across Indonesia.

Horseshoe crabs are highly sought after for their cerulean (blue) blood, which contains a substance used by pharmaceutical companies to detect contaminants in vaccines, drugs, and other pharmaceutical products [2].

Further, in Indonesia and other places in Asia, they are caught and consumed along with their eggs. As a result, they have been smuggled multiple times out of Indonesia for consumption and trade in other Asian countries [3,4,5].


4. They Are Often Caught Tangled In Fishers’ Nets

Horseshoe crabs also face threats from capture fisheries due to entanglement in fishermens nets and subsequently retained as bycatch, including in East Borneo where they have also been known to be bycaught in local, artisanal fishers, although very little is known regarding the specific amount.


5. You Can Help Them!

To protect these species, we need your help!

If you or your friends encounter a horseshoe crab, do report it to us or other horseshoe crab projects in your area. Your data is especially beneficial in helping us map out their distribution and therefore, better strategise what we can do to protect the horseshoe crabs from extinction.

For more information about our project, visit us on our Instagram at @horseshoecrabproject


Written by Hanifa Miranda (@hanifamrnd)


I am an aspiring marine conservationist from Indonesia, and I graduated with a marine science degree from Bali's Udayana University.

I am especially passionate about using science communication to translate scientific data into strong, impactful actions and policies for the benefit of both humans and species.

Currently, I am the project leader of the Indonesia Horseshoe Crab Project, working to establish a socio-ecological database of horseshoe crabs in East Borneo, Indonesia.



[1] Tyrell, K.A. 2019. Study confirms horseshoe crabs are really relatives of spiders, scorpions.

[2] Arnold, C. 2020. Horseshoe crab blood is key to making a COVID-19 vaccine – but the ecosystem may suffer.

[3] Leandha, M. 2019. Gagal Diselundupkan ke Thailand, Ribuan Belangkas Dikubur.

[4] Karokaro, A.S. 2019. Penyelundupan 7 ribu ekor belangkas ke Thailand digagalkan, tiga pelaku ditangkap.

[5] Warsito, B. 2019. Diduga hendak jual 332 belangkas, 3 warga sumut ditangkap polisi.

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