Wild Estuaries: Horseshoe Crabs

My husband and I volunteer to survey and tag horseshoe crabs, and I have to admit the first time I held one, it was really strange. But once the initial creepiness of holding something that looks like it came out of a sci-fi movie faded, I soon came to realized that they are amongst some of the most interesting and fascinating marine creatures swimming in the coastal waters.

Horseshoe crabs are a gentle creature and an essential part of the estuarine habitat. Their life cycle is so simple, just like any wildlife species. They eat, sleep, breed, and live out their lives as freely as possible. 

What’s cool about horseshoe crabs is that they are related to spiders and scorpions because they miss mandibles and antennas.

Horseshoe crabs also molt-meaning they will shed their shell. Many may think that if they see a horseshoe crab’s shell, it may be considered dead, but in actuality, it just sheds its older shell and produces a new one. They will go through a molting process throughout their life span. Their molting season occurs in July and August. 

But that’s not the coolest thing about horseshoe crabs, it’s their eyes, all ten of them. They have ten eyes; all of them serve for different functions for light and sight. The two large compound eyes (lateral eyes) located on each side of the shell have over 1,000 facets (receptors). There is also another eye situated next to each of the compound eyes. Three eyes in the very front (median eyes) may help enhance the adaptation to see in the dark, two eyes near the mouth, and a very complex eye (photoreceptors) on the tail. 

Horesecrabs depend on their eyes to navigate to the shore for successful breeding. Even though research suggests mating takes place during either a new moon or full moon during high tide, you can see them during the day as well. If you do see horseshoe crabs, please be mindful and respect their space. 

They will feast on worms and other small crustaceans as well as algae. Since they don’t have teeth or mandibles (jawbone), they have to crush up their food with their legs. Underneath the body, right in the center is their mouth, which is surrounded by ten legs. The hind legs crush and pass the food to the front appendages (smaller legs called chelicera) to place the food into its mouth. To help the horseshoe crab digest food, they have gizzards to ensure that the food is reduced to finer particles before reaching its stomach. 

Unfortunately, their population has declined due to habitat loss, overharvesting, and public recreational activities on beaches, which can crush them and destroy their nesting areas. 


Links of Interest:

USFWS- Horseshoe Crabs

The Horseshoe Crab

FWC-Horseshoe Crab

NOAA- Hooray for Horseshoe Crabs Teachers Guide

UF|IFAS- Horseshoe Crab Watch

There are hundreds of species to discover in estuarine habitats, and can take many years to document and research them all, which I think would be pretty cool to do. However, September has ended, and it’s time to move to next month’s issue.

October Issue

I will be working on this issue during my spare time to give you the best creepy content nature naturally provides.
The Creepy Critter Project I made up while on a photographing a Green Lynx spider. I hope to be able to photograph those strange adaptations insects have to help them survive in the wild.
Sounds of the night, taking a closer look at those creatures of the night.
And finally, Creepy Captures of Nature Photography. We all know how beautiful the Roseate Spoonbill is, but just sometimes, when you press that shutter release button, you can capture some zombie-like photos.
Have fun exploring, and as always, be safe!

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