---
title: "What the sources say about the Atlantic Horseshoe Crab | AnimalTracks.wiki"
description: "44 claims from the Atlantic Horseshoe Crab profile, each beside the words of the source that backs it."
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---

# What the sources say about the Atlantic Horseshoe Crab (*Limulus polyphemus*)

> 44 claims from the Atlantic Horseshoe Crab profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Atlantic Horseshoe Crab](https://animaltracks.wiki/animals/atlantic-horseshoe-crab/)

## Atlantic Horseshoe Crab. Marine Biological Laboratory, University of Chicago.

https://www.mbl.edu/research/research-organisms/atlantic-horseshoe-crab

| The page says | The source says |
| :--- | :--- |
| A blue-blooded cousin of spiders and scorpions | We call them crabs, but Atlantic horseshoe crabs (Limulus polyphemus) are more closely related to spiders and scorpions than true crabs. |
| blood that clots when it meets certain bacteria | These amebocytes cause the horseshoe crab blood to clot when it encounters potentially harmful gram-negative bacteria. (note: 'meets' glosses 'encounters'; 'certain bacteria' stands for 'gram-negative bacteria') |
| Shallow coastal waters on sandy or muddy bottoms | Habitat: Shallow, coastal waters on sandy or muddy bottoms |
| Worms, bivalves, and other small bottom-dwelling organisms | Diet : Carnivore: worms, bivalves, and other small bottom-dwelling organisms |
| Blue blood that clots when it meets certain bacteria, which labs use to test medicines and medical devices for endotoxins | The blood of Limulus polyphemus is used in biomedical research to test pharmaceuticals and medical devices for potentially deadly endotoxins. ... These amebocytes cause the horseshoe crab blood to clot when it encounters potentially harmful gram-negative bacteria. (note: 'medicines' glosses 'pharmaceuticals'; 'meets' glosses 'encounters'; 'certain bacteria' stands for 'gram-negative bacteria') |
| The blue comes from hemocyanin, a copper-rich protein, where our red blood uses iron-based hemoglobin | This is because of the protein hemocyanin which is copper-rich vs human’s red blood which has the iron-based hemoglobin protein. |
| The blood carries cells called amebocytes, which make it clot when it meets potentially harmful gram-negative bacteria | Horseshoe crab blood contains amebocytes, which play a similar role to the white blood cells of vertebrates in defending the organism against pathogens. These amebocytes cause the horseshoe crab blood to clot when it encounters potentially harmful gram-negative bacteria. |
| Labs use that reaction in the Limulus Amebocyte Lysate (LAL) test, which checks pharmaceuticals and medical devices for potentially deadly endotoxins | The blood of Limulus polyphemus is used in biomedical research to test pharmaceuticals and medical devices for potentially deadly endotoxins. This test, called Limulus Amebocyte Lysate (LAL), takes advantage of the horseshoe crab’s primitive immune system. |
| Each year, the medical industry catches around half a million horseshoe crabs just to harvest their blood | Each year, the medical industry catches around half a million horseshoe crabs just to harvest their blood |
| A synthetic alternative is slowly replacing it | but a synthetic alternative is slowly replacing this practice. |
| Atlantic horseshoe crabs are more closely related to spiders and scorpions than to true crabs | We call them crabs, but Atlantic horseshoe crabs (Limulus polyphemus) are more closely related to spiders and scorpions than true crabs. |
| Their body has three parts: the prosoma (the front shell shaped like a horseshoe), the opisthosoma (the back section) and the telson, the tail | Their bodies are composed of three parts: the prosoma (head / front shell), the opisthosoma (body / back shell), and the telson (tail). The name “horseshoe crab” comes from the prosoma, which resembles a horseshoe. |
| spiky tail | Limulus use their spikey tails to help right themselves if they are flipped over. |
| Adults are up to 2 feet long including the tail and weigh 3 to 4 pounds | Size: up to 2 ft long (including tail) Weight : 3 – 4 pounds |
| In the wild they live 20 to 40 years | Life Span in the Wild: 20 – 40 years |
| Their rods and cones, the cells that detect light, are the largest of any known animal | the largest rods and cones (the cells responsible for vision) of any known animal |
| The species lives in shallow coastal waters on sandy or muddy bottoms | Habitat: Shallow, coastal waters on sandy or muddy bottoms |
| It eats worms, bivalves and other small bottom-dwelling organisms | Diet : Carnivore: worms, bivalves, and other small bottom-dwelling organisms |
| In the spring, crabs come ashore during the new and full moons to spawn | They come ashore during the new and full moons in the spring to spawn |
| she can lay 100,000 eggs over a few nights | females can lay 100,000 eggs over the course of a few nights |
| The eggs are a critical food source for the red knot, a migratory bird with one of the longest known migration ranges, 9,000 miles | These eggs are a critical food source for the red knot, a migratory bird with one of the longest known migration ranges—9,000 miles! |
| In the spring, crabs come ashore during the new and full moons to spawn | They come ashore during the new and full moons in the spring to spawn (note: vibe.reason; same quote as the body claim) |

## Atlantic Horseshoe Crab (Limulus polyphemus). U.S. Fish & Wildlife Service.

https://www.fws.gov/species/atlantic-horseshoe-crab-limulus-polyphemus

| The page says | The source says |
| :--- | :--- |
| on the Atlantic coast from Maine to the Yucatan Peninsula | ranges on the Atlantic coast from Maine to the Yucatan Peninsula |
| Horseshoe crab blood is straw-colored and turns blue when it meets high levels of oxygen | The straw-colored, copper-based blood turns blue when exposed to high concentrations of oxygen. (note: reviewer: MBL's bare 'blue blood' replaced by FWS's fuller statement) |
| It helps the crab flip itself over if waves on the beach turn it over | The telson helps the crab to flip itself over if waves on the beach turn it over. |
| This design has stayed relatively unchanged in appearance for 350 million years | Horseshoe crabs are evolutionary survivors that have remained relatively unchanged in appearance for 350 million years. |
| The largest crabs are found on the Georgia coast, where mature females grow to about 11 pounds (4.8 kg) | the largest individuals can be found along the Georgia coast with mature females grows to about 11 pounds (4.8 kg) |
| Males are typically 25 to 30% smaller than females | Males are typically 25 to 30% smaller than females. |
| on the Atlantic coast from Maine to the Yucatan Peninsula | ranges on the Atlantic coast from Maine to the Yucatan Peninsula |
| A female drags a male clasped to her shell | The male clasps onto the female’s shell with a modified pair of claws. The female drags him around during the spawning process. |
| No | they are completely harmless. (note: FAQ answer opener) |
| It looks prehistoric and menacing, with many legs and a tail that looks like a stinger, but the U.S. Fish & Wildlife Service says it is completely harmless | look prehistoric and menacing with their multiple legs and long tail that looks like a stinger, they are completely harmless. |

## Northeast Coastal and Barrier Network Species Spotlight: Atlantic Horseshoe Crab. National Park Service.

https://www.nps.gov/articles/ncbn-species-spotlight-atlantic-horseshoe-crab.htm

| The page says | The source says |
| :--- | :--- |
| ten eyes | Out of the horseshoe crabs 10 total eyes |
| The spiky tail is usually mistaken for a weapon, but it is harmless | Usually mistaken for a weapon, the telson (tail) of the horseshoe is harmless |
| They have ten eyes | Out of the horseshoe crabs 10 total eyes |
| the two large compound eyes on the sides are mainly used to locate a mate | These are called the compound eyes and their main function is to locate a mate during mating season. |
| Ten | Out of the horseshoe crabs 10 total eyes |
| Two large compound eyes sit on the sides of the shell, and the National Park Service says their main job is finding a mate | These are called the compound eyes and their main function is to locate a mate during mating season. |
| Eight other light-sensitive eyes are scattered over the body, shell and even the tail, and they help the crab stay oriented | Scattered around the rest of the body, shell, and even the tail, are eight other eyes which are very light-sensitive and keep the crab oriented while moving or swimming around. |

## Krisfalusi-Gannon et al. (2018). The Role of Horseshoe Crabs in the Biomedical Industry and Recent Trends Impacting Species Sustainability. Frontiers in Marine Science.

https://doi.org/10.3389/fmars.2018.00185

| The page says | The source says |
| :--- | :--- |
| a type of germ that carries endotoxins in its cell walls | endotoxin or 1,3ß-D-glucan (present in the cell walls of Gram-negative bacteria and fungi, respectively) |
| A review of the practice reports that mortality after harvest ranges from 10 to 30% | Horseshoe crab mortality rates following such harvesting range from 10 to 30% |
| A review reports a 30% death rate after bleeding female horseshoe crabs and 8% after bleeding males | the high mortality rate of 30% following the bleeding of female horseshoe crabs regardless of pre- or post-spawning phases (Leschen and Correia, 2010 ); whereas, bleeding male horseshoe crabs has demonstrated a mortality rate of 8% |
| it notes that reported figures leave out later trauma once the crabs are returned to the ocean | these figures do not account for any further trauma and/or detrimental behavioral changes once the animals are returned to the ocean |

## Smith et al. (2016). Limulus polyphemus. The IUCN Red List of Threatened Species 2016: e.T11987A80159830.

https://doi.org/10.2305/iucn.uk.2016-1.rlts.t11987a80159830.en

| The page says | The source says |
| :--- | :--- |
| Vulnerable | IUCN Red List category: Vulnerable (VU). (note: Red List 2016 assessment; category read through GBIF's copy, quote is from that cached page) |