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The smallest species is the mangrove horseshoe crab (C. rotundicauda) and the largest is the tri-spine horseshoe crab (T. tridentatus). [ 44 ] On average, males of C. rotundicauda are about 30 centimeters (12 inches) long, including a telson that is about 15 cm (6 in), and a carapace about 15 cm (6 in) wide. [ 45 ]
Atlantic horseshoe crab on the shore at Brighton Beach, New York City. The Atlantic horseshoe crab (Limulus polyphemus), also known as the American horseshoe crab, is a species of horseshoe crab, a kind of marine and brackish chelicerate arthropod. [1] It is found in the Gulf of Mexico and along the Atlantic coast of North America. [1]
The horseshoe crab has traditionally been used in investigations into the eye, because it has relatively large ommatidia with large nerve fibres (making them easy to experiment on). It also falls near the base of the chelicerates ; its eyes are believed to represent the ancestral condition because they have changed so little over evolutionary time.
Both the common name tri-spine horseshoe crab and the scientific name tridentatus refer to the three small spiny processes on the rear part of the opisthosoma (one spine in the middle above the tail and one on either side), while other species only have a single spine (in the middle).
The group has hardly changed in appearance in hundreds of millions of years; the modern horseshoe crabs look almost identical to prehistoric genera and are considered to be living fossils. The most notable difference between ancient and modern forms is that the abdominal segments in present species are fused into a single unit in adults.
According to the department, a horseshoe crab's blood has a blue to blue-green color when exposed to the air. The blood is blue because it contains a copper-based respiratory pigment called ...
The name "Merostomata" derives from the Greek roots μηρός (meros, "thigh") and στόμα (stoma, "mouth"), in reference to the animals' possession of appendages which are mouthparts at their proximal end, but swimming legs at their distal end.
The federal government is shutting down the harvest of a species of marine invertebrate in a national wildlife refuge during the spawning season to try to give the animal a chance to reproduce.