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What the sources say

Atlantic Horseshoe CrabLimulus polyphemus

Every figure, record and mechanism on the Atlantic Horseshoe Crab profile was written from a source, and this is the working table behind it: 44 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Marine Biological Laboratory, University of Chicago

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

The page saysA blue-blooded cousin of spiders and scorpions
The source saysWe call them crabs, but Atlantic horseshoe crabs (Limulus polyphemus) are more closely related to spiders and scorpions than true crabs.
The page saysblood that clots when it meets certain bacteria
The source saysThese 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'
The page saysShallow coastal waters on sandy or muddy bottoms
The source saysHabitat: Shallow, coastal waters on sandy or muddy bottoms
The page saysWorms, bivalves, and other small bottom-dwelling organisms
The source saysDiet : Carnivore: worms, bivalves, and other small bottom-dwelling organisms
The page saysBlue blood that clots when it meets certain bacteria, which labs use to test medicines and medical devices for endotoxins
The source saysThe 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 page saysThe blue comes from hemocyanin, a copper-rich protein, where our red blood uses iron-based hemoglobin
The source saysThis is because of the protein hemocyanin which is copper-rich vs human’s red blood which has the iron-based hemoglobin protein.
The page saysThe blood carries cells called amebocytes, which make it clot when it meets potentially harmful gram-negative bacteria
The source saysHorseshoe 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.
The page saysLabs use that reaction in the Limulus Amebocyte Lysate (LAL) test, which checks pharmaceuticals and medical devices for potentially deadly endotoxins
The source saysThe 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.
The page saysEach year, the medical industry catches around half a million horseshoe crabs just to harvest their blood
The source saysEach year, the medical industry catches around half a million horseshoe crabs just to harvest their blood
The page saysA synthetic alternative is slowly replacing it
The source saysbut a synthetic alternative is slowly replacing this practice.
The page saysAtlantic horseshoe crabs are more closely related to spiders and scorpions than to true crabs
The source saysWe call them crabs, but Atlantic horseshoe crabs (Limulus polyphemus) are more closely related to spiders and scorpions than true crabs.
The page saysTheir body has three parts: the prosoma (the front shell shaped like a horseshoe), the opisthosoma (the back section) and the telson, the tail
The source saysTheir 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.
The page saysspiky tail
The source saysLimulus use their spikey tails to help right themselves if they are flipped over.
The page saysAdults are up to 2 feet long including the tail and weigh 3 to 4 pounds
The source saysSize: up to 2 ft long (including tail) Weight : 3 – 4 pounds
The page saysIn the wild they live 20 to 40 years
The source saysLife Span in the Wild: 20 – 40 years
The page saysTheir rods and cones, the cells that detect light, are the largest of any known animal
The source saysthe largest rods and cones (the cells responsible for vision) of any known animal
The page saysThe species lives in shallow coastal waters on sandy or muddy bottoms
The source saysHabitat: Shallow, coastal waters on sandy or muddy bottoms
The page saysIt eats worms, bivalves and other small bottom-dwelling organisms
The source saysDiet : Carnivore: worms, bivalves, and other small bottom-dwelling organisms
The page saysIn the spring, crabs come ashore during the new and full moons to spawn
The source saysThey come ashore during the new and full moons in the spring to spawn
The page saysshe can lay 100,000 eggs over a few nights
The source saysfemales can lay 100,000 eggs over the course of a few nights
The page saysThe eggs are a critical food source for the red knot, a migratory bird with one of the longest known migration ranges, 9,000 miles
The source saysThese eggs are a critical food source for the red knot, a migratory bird with one of the longest known migration ranges—9,000 miles!
The page saysIn the spring, crabs come ashore during the new and full moons to spawn
The source saysThey come ashore during the new and full moons in the spring to spawnNote: vibe.reason; same quote as the body claim

Source
02

U.S. Fish & Wildlife Service

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

The page sayson the Atlantic coast from Maine to the Yucatan Peninsula
The source saysranges on the Atlantic coast from Maine to the Yucatan Peninsula
The page saysHorseshoe crab blood is straw-colored and turns blue when it meets high levels of oxygen
The source saysThe 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
The page saysIt helps the crab flip itself over if waves on the beach turn it over
The source saysThe telson helps the crab to flip itself over if waves on the beach turn it over.
The page saysThis design has stayed relatively unchanged in appearance for 350 million years
The source saysHorseshoe crabs are evolutionary survivors that have remained relatively unchanged in appearance for 350 million years.
The page saysThe largest crabs are found on the Georgia coast, where mature females grow to about 11 pounds (4.8 kg)
The source saysthe largest individuals can be found along the Georgia coast with mature females grows to about 11 pounds (4.8 kg)
The page saysMales are typically 25 to 30% smaller than females
The source saysMales are typically 25 to 30% smaller than females.
The page sayson the Atlantic coast from Maine to the Yucatan Peninsula
The source saysranges on the Atlantic coast from Maine to the Yucatan Peninsula
The page saysA female drags a male clasped to her shell
The source saysThe male clasps onto the female’s shell with a modified pair of claws. The female drags him around during the spawning process.
The page saysNo
The source saysthey are completely harmless.Note: FAQ answer opener
The page saysIt 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
The source sayslook prehistoric and menacing with their multiple legs and long tail that looks like a stinger, they are completely harmless.

Source
03

National Park Service

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

The page saysten eyes
The source saysOut of the horseshoe crabs 10 total eyes
The page saysThe spiky tail is usually mistaken for a weapon, but it is harmless
The source saysUsually mistaken for a weapon, the telson (tail) of the horseshoe is harmless
The page saysThey have ten eyes
The source saysOut of the horseshoe crabs 10 total eyes
The page saysthe two large compound eyes on the sides are mainly used to locate a mate
The source saysThese are called the compound eyes and their main function is to locate a mate during mating season.
The page saysTen
The source saysOut of the horseshoe crabs 10 total eyes
The page saysTwo large compound eyes sit on the sides of the shell, and the National Park Service says their main job is finding a mate
The source saysThese are called the compound eyes and their main function is to locate a mate during mating season.
The page saysEight other light-sensitive eyes are scattered over the body, shell and even the tail, and they help the crab stay oriented
The source saysScattered 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.

Source
04

Krisfalusi-Gannon et al. 2018

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

The page saysa type of germ that carries endotoxins in its cell walls
The source saysendotoxin or 1,3ß-D-glucan (present in the cell walls of Gram-negative bacteria and fungi, respectively)
The page saysA review of the practice reports that mortality after harvest ranges from 10 to 30%
The source saysHorseshoe crab mortality rates following such harvesting range from 10 to 30%
The page saysA review reports a 30% death rate after bleeding female horseshoe crabs and 8% after bleeding males
The source saysthe 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%
The page saysit notes that reported figures leave out later trauma once the crabs are returned to the ocean
The source saysthese figures do not account for any further trauma and/or detrimental behavioral changes once the animals are returned to the ocean

Source
05

Smith et al. 2016

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

The page saysVulnerable
The source saysIUCN Red List category: Vulnerable (VU).Note: Red List 2016 assessment; category read through GBIF's copy, quote is from that cached page

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.