Glossary of Terms

A Horseshoe Crab Glossary

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  • Arthropods (ar-throw-pods) Animals that have jointed legs, a body divided into two or more parts, and a skeleton on the outside of its body; all arthropods lack a backbone; horseshoe crabs are members of this group.This phylum also includes insects, crustaceans, and spiders.
  • Annelid (an - uh - lid) A generic term to refer to animals belonging to the phylum Annelida, which includes earthworms and leeches. Adult horseshoe crabs eat annelids.

  • ASMFC The Atlantic States Marine Fisheries Commission. The ASMFC is a compact of the fifteen Atlantic Coast states created to promote better utilization of the fisheries of the Atlantic seaboard. The ASMFC develops management plans for the various fishery resources within state and federal waters. Once plans are completed and approved, ASMFC states are obliged to implement its mandatory requirements. All ASMFC management plans must include specific measurable standards to improve the status of the stock and to determine whether or not a state is in compliance with those standards. If a state does not comply, the US Secretary of Commerce can lawfully impose a moratorium in that stateís fishery.

  • Benthic (ben-thick) Living on the bottom of a sea or lake

  • Bivalve (buy - valv) A mollusk whose shell is two pieces joined by a muscular hinge. Clams and oysters are bivalves.

  • Carapace (kar - uh - pace) A chitinous or bony shield covering all or part of certain animals. On horseshoe crabs, it is the hard outer shell that covers the top of the animal.

  • Cephalothorax (sef - uh - low - thor - aks) The front body segment consisting of a fused head and thorax; on horseshoe crabs, it's the part that looks like a horseshoe.

  • Chelicerae (kih - lis- er - ay) The first pair of two-jointed appendages, near the mouth, used for feeding.

  • Chelicerate: The Cheliceramorpha includes spiders and scorpions, mites and ticks, horseshoe crabs, and extinct "sea-scorpions", to name a few. It is the second most prominent order of terrestrial arthropods. Most of its marine representatives are extinct.

  • Chitin (kite - in) A protein material, similar to fingernails, that provides a protective covering for the horseshoe crab. The horseshoe crabís carapace is made of chitin.

  • Clutch (kluch) The number of eggs produced or incubated at one time. Horseshoe crab clutches may contain as many as 4,000 eggs.

  • Compound eye An eye that consists of many visual units, each having its own lens. Messages received from the different units together produce a large field of view that is not sharp in detail. Insects and crustaceans have compound eyes.

  • Continental shelf The part of the sea floor that gradually descends from the coastline to depths of about 600 feet (182 meters); from there, the bottom drops down sharply, forming the continental slope to the great depths of the ocean.

  • Crustacean (kruh - stay- shun) Crustaceans are aquatic arthropods that are characterized by a segmented body, chitinous exoskeleton, and paired, jointed limbs. Lobsters, crabs, and shrimp are all crustaceans. Horseshoe crabs are not crustaceans ñ they have their own class grouping ñ Merostomata.

  • Cyanobacteria (sigh - an- o - bak - teer - ee - uh) Blue-green algae; there are over 7,500 species of cyanobacteria and they are found in many environments: damp soil and rocks, fresh water, and salt water.

  • Decapod (de - kah - pod) Having ten feet. This term usually refers to members of the order Decapoda, e. g., lobsters and shrimp.

  • Ectocommensal (ek - to - co - men - sul) A commensal organism that lives on the outer body surface of another organism. Commensal organisms live in close association; one of the organisms may benefit from the other, but neither does harm to the other or is parasitic.

  • Embryo (em - bree - oh) A young organism in early stages of development.

  • Endotoxin (en - do - tok - sin) A large toxic molecule derived from the outer cell wall of Gram-negative bacteria. Endotoxin is a complex molecule of polysaccharide, lipid A, and other cell wall components.

  • Endotoxin limit The maximum amount of endotoxin allowed in a parenteral product or medical device. The endotoxin limit set by the FDA for drugs is 5.0 EU/kg/hr or 0.2 EU/kg/hr for intrathecal products. The limit for devices is 0.5 EU/mL, based on a 40 mL rinse or 0.06 EU/mL for intrathecal devices.

  • Estuary (ess - choo - air - ee) The part of the wide lower course of a river where its current is met by the tides.

  • Exoskeleton (ek - soh - skel - i - ton) An external protective or supportive covering of many invertebrates, including horseshoe crabs. The carapace forms part of the horseshoe crabís exoskeleton.

  • FDA The U.S. Food and Drug Administration

  • Gastropod( gas - troh - pod) A generic term for animals belonging to the class Gastropoda. A single coiled shell and a single muscle mass for locomotion characterize them. Snails and slugs are gastropods.

  • Gill book Horseshoe crab gills look like books with many "pages" that collect oxygen from the water. Each "page" is called a lamella (plural: lamellae). Horseshoe crabs have six pairs of gill books. The movement of the gills acts as a paddle when horseshoe crabs are swimming.

  • Gnathobase (nath - oh - base) The expanded and hardened base of the appendage of many arthropods, notably trilobites, crustaceans, and marine cheliceramorphs. Used to macerate food items before ingestion.

  • Gravid (grav - id) Pregnant or carrying eggs or embryos. When female horseshoe crabs are gravid, eggs fill the space between the walls of the carapace.

  • Hemolymph (hee - mo - limf) The circulatory fluid of various invertebrate animals that is functionally comparable to the blood and lymph of vertebrates.

  • Hyperoxia (high - per - ox - ee - uh) An excess in the amount of oxygen reaching bodily tissues.

  • Hypoxia (high - pok - see - uh) A deficiency in the amount of oxygen reaching bodily tissues.

  • Instar (in - star) An arthropod between molts. Some species may go through a series of instars before reaching the adult size or form.

  • Integument (in - teg - yoo - ment) Something that covers or encloses; an enveloping layer. For example, the skin of an animal, the covering of a seed, or the feathers on a bird.

  • Intertidal zone The area of the beach between the high and low tide waterlines.

  • Intrathecal (in - tra - thee- cal) Introduced into or occurring in the space under the arachnoid membrane of the brain or spinal cord.

  • Lamellae (lah - mel- ee) In horseshoe crabs, they are the thin layers or ìpagesî in a gill book. The exchange of oxygen and carbon dioxide occur across the thin membranes of the lamellae.

  • Larva (lar - vuh) The newly-hatched, earliest stage of horseshoe crabs (and other animals that undergo one or more molts before becoming adults). Larva usually do not resemble the adult form.

  • Lateral (lat - er - ul) Pertaining to or on the side.

  • Limulus Amebocyte Lysate (LAL) (lim- yoo - lus- ah - mee- bo - site lie - sate) An aqueous extract of the circulating blood cells (amebocytes) of the American horseshoe crab, Limulus polyphemus.

  • Macro-invertebrate (mak - row - in - ver - tuh - brit) Invertebrates large enough to be seen by the naked eye (as opposed to micro-invertebrates, which must be viewed with the aid of magnification).

  • Merostomata (mer - oh -stow - ma -tuh) Legs attached to the mouth. The class of Arthropods to which all four remaining horseshoe crab species belong.

    • Metacercaria (met - uh -sir - kare- ee - uh) The larval stage of a parasitic flatworm (trematodes). They are an internal parasite of adult horseshoe crabs.

    • Mollusc (or mollusk) (mol - usk) A marine invertebrate that creates and lives in a calcareous shell. Clams, snails, oysters, and whelks are all mollusks.

    • Molt (as a verb) To shed fur, feathers, or a shell before they are replaced with new growth. Horseshoe crabs molt their chitin shells 16 to 17 times before they reach adulthood. Once they are adults, they cease to molt.

    • Neap tide A tide of the lowest range that occurs when the sun and moon form a 90 degree angle with the Earth.

    • Nematode (ne- mah - toad) A type of roundworm; members of this phylum are often parasitic. Horseshoe crab larvae feed on nematodes.

    • Nemertean (ne - mer - tee - un) A type of marine worm; adult horseshoe crabs feed on nemerteans.

    • Nereis (near - ee - is) A type of marine flatworm (there are many species in the genus Nereis). Horseshoe crabs larvae eat nereis.

    • NMFS National Marine Fisheries Service

    • Operculum (oh - perk - yoo - lum) In Horseshoe crabs, it is the first of six pairs of gill books. Serves as a cover for the other five pairs. Houses the opening of the genital pores through which eggs and sperm are released from the body.

    • Opisthosoma (op - iss - tho - so -mah) Portion of the body posterior to the legs. In horseshoe crabs, it is the pentagon-like region behind the "horseshoe."

    • Parenteral drug (pah - ren - ter - ul) This is a term to describe drugs that are given by hypodermic injection (intravenous, subcutaneous, intraosseous, or intramuscular). All parenteral drugs require endotoxin testing.

    • Pedipalps (ped - ee - palps) In horseshoe crabs, this refers to their jointed walking legs (five pairs), each ending in a claw.

    • Photoreceptors (foh -toh -ree - sep - torz) Light-sensitive cells that may occur alone or grouped together. Horseshoe crabs have photoreceptors on the dorsal surface of their carapace.

    • Polychaete (pol- i - kee)t A type of marine worm and a food source for the larval stage of horseshoe crabs.

    • Posterior( poh -steer- ee - ur) Pertaining to the ìtail endî of an animal

    • Prosoma (proh - soh - ma) In horseshoe crabs, this is the front portion of the body (the "horseshoe" part). One component of the data gathered about horseshoe crabs during population surveys is the prosomal width of individual animals.

    • Salinity (sah - lin - i - tee) The amount or percentage of salt in water. Horseshoe crabs require a certain salinity; they cannot survive in freshwater.

    • Sessile (sess - u)l Permanently attached or fixed; not free-moving.

    • Simple eye An eye that has a single lens. Simple eyes can be as small as a horseshoe crabís or as large as a whaleís.

    • Spawn (v) 1. to deposit eggs 2. to produce young in large numbers

    • Telson(tel - sun) In horseshoe crabs, the telson is the tail.

    • Trilobite( tri - loh - bite) An early stage in horseshoe crab development; it is the stage after hatching and before the first molt. This stage is so named because it resembles trilobites, an extinct ancient animal related to the horseshoe crab.

    • Univalve (yoo - ni - valv) A mollusk whose shell is one piece. Whelks and snails are univalves.

    • USFWS The U.S. Fish and Wildlife Service

    • Ventral (ven - trul) Pertaining to or situated on lower or abdominal surface.