Barnacles, Crabs & Lobsters, and Horseshoe "Crabs"
(Fr-bernacle, crabe, homard; Ger- Entenmuschel/Seepocken-?, Krebbe, Hummer;
-andeskjell, krepsdyr, hummer; Rus-щипцы, краб, рак)


A. Barnacles. Relatively large one (height - 3.3 cm), upon which others have been deposited, found on beach at Port Aransas, Texas.  (© photo by  Dick Dietrich)

B. Crab. "This crab [size not indicated] was collected from deep in the ocean.  The red color helps protect it from predators."  (NOAA as the source Ocean explorer)  (photo from National Oceanic and Atmospheric Administration, U.S. Department of Commerce,      

C. Lobster replica (length ~ 4.5 cm). “hand-painted pewter ... [to] use as a pin, tie tack, hat pin or lapel pin.”  Fashioned in Washington and Idaho by a team of U.S. artists.  (© photo courtesy of  Sheryl Todd )

D. Horseshoe "crabs."  Bottom (length ~18cm) and top of skeletons, collected by Iona Whitley from shore of Delaware Bay.  (© photo courtesy Patricia A. Weeg,

DESCRIPTION:  Phylum, Arthropoda; class, Crustacea: This class includes barnacles (subclass Cirripedia), the hard parts of which comprise several calcite (CaCO3) plates, and crabs and lobsters (both subclass, Malacostraca), the exoskeletons of which are chitin.  In addition, this entry includes horseshoe "crabs" (Limulus polyphemus Linnaeus, 1758) -- Phylum, Arthorpoda;  class, Merostomata;  subclass, Xiphosura -- which have keratinous exoskeletons.  
    Colors - BarnaclesWhite, gray, brown, reddish, purplish.   Crabsdiverse hues of red, orange, yellow, green, blue and purple and/or white, tan or brown;  most have skeletons with different colors typical of different sections, and some have, for example, some multicolored and/or patterned (e.g., streaked and/or spotted) surfaces.   Lobsters: "A live lobster is greenish-black on top and orange below, with accents of blue on the joints of its claws. That is because a lobster's shell is composed of three pigments: red, blue, and yellow. ¶ When one or more of these pigments are missing at birth, a lobster may be red, blue, albino (white), or calico (dark with yellow spots). ...  Except for albinos, all the color variations of lobsters turn red when they are cooked." (Gulf of Maine Aquarium, 1997) -- So much for the analogy "red as a lobster."   Horseshoe "crabs": carapaces tend to be dark to light brown or greenish.     
Barnacles:  ~3.  Others:  ~2½ <<  an example of plate-like keratin-rich material.
    S.G.   Barnacles2.65 - 2.84.    Others:  ~1.29 <<  an example of plate-like keratin-rich material.
   Light transmission -
Barnacles: semitranslucent to opaque.  Others -  transparent to semitranslucent  
    Luster - Barnacles: dull to pearly.  Others: outside, subvitreous to waxy; inside, dull to porcelaneous
    Breakage - irregular (brittle)
    Miscellaneousbarnacles' hard parts consist of six or more relatively thick plates, the overall arrangement of which roughly resembles a volcano (i.e., a truncated cone), and they commonly have macroscopically visible growth bands more-or-less parallel to the base (Figure A);  the plates, which consist largely of calcite, effervesce with dilute HCl.

OTHER NAMES:  Many scientists consider it necessary to enclose crab in quotation marks when referring to horseshoe crabs -- see first paragraph of REMARKS. 
USES: Barnacles of the acorn type have found use as decorative accessories (in some cases dyed) in aquaria.  Exoskeletons of crabs, lobsters and horseshoe "crabs" are frequently used as decorative pieces in, for example, restaurants that feature seafood.

The California spiny lobster Panulirus interruptus (J.W. Randall, 1840) of the eastern Pacific -- range, San Luis Obispo, California to Rosalia Bay, Baja California -- and the American lobster (Homarus americanus H. Milne-Edwards, 1837) of New England and the Canadian maritime provinces, though having quite different appearances are both used as decorations in restaurants that feature their meat.  Among other things, spiny lobsters lack the large claws that are characteristic of the American lobster, and, as their common name indicates, they have scattered spines over much of their bodies.  The appearance of the spiny lobster (see Colla, 2006), however, appears to have led to its less widespread use as a decoration in the decorative arts and crafts as well as in restaurants;  this despite the fact that, at least in my opinion, both lobsters are equally tasty.  Whatever, both of these lobsters and horseshoe "crabs" have found widespread use as decorations.

Not a decorative but nonetheless a noteworth use:  "Limulus [the horseshoe "crab"] was well-known to American Indians;  coastal tribes used the long serrated telson as a fish-spearhead."  (Shuster, 1979, p. 3)

OCCURRENCES & NOTEWORTHY LOCALITIES:    Barnacles live attached to hard surfaces such as rocks, docks, ship hulls, etc. at virtually all latitudes and at depths ranging from intertidal flats to deep sea zones. Crabs, if one considers all the numerous species, have a nearly worldwide distribution with their habitats including diverse marine, freshwater and semi-terrestrial environments. Lobsters are benthic (bottom-dwelling) and live in marine waters that have certain temperature ranges here and there around the world;  an example is the North American Atlantic coastal area from North Carolina north to the Strait of Belle Isle between Newfoundland and the mainland, with the greatest abundance apparently within the Gulf of Maine (Maine, New Brunswick and Nova Scotia production accounts for a large percentage of marketed lobsters). Horseshoe "crabs" are benthic, with Limulus polyphemus  Linnaeus, 1758  described as "an estuarine species with anadromous tendencies ... [that] as they grow larger ... move further and further away from their natal area into deeper water, many going out onto the continental shelf" (Shuster, 1979, p.30);  they occur sporadically on the continental shelf and in estuaries along the western Atlantic coast  from the Yucatán peninsula northward to Taunton Bay, which is north of Mt. Desert Island, Maine,  and "In May and June, the beaches of Delaware Bay are visited by the largest spawning population of Limulus along the Atlantic coast." (op. cit., p.20)An outline map showing the general distribution of the three western Pacific-Indian Ocean species as well as the western Atlantic horseshoe "crabs" is given by Sekiguchi and Nakamura (1979, p.39).

REMARKS: . Application of the word barnacle to these crustaceans appears to have an origin that is analogous to the old poser "which came first the chicken or the egg?".  Harper provides the following:  "... Often [suggested as] derived from a Celtic source (cf. Bret[on?]). bernik 'kind of shellfish'), but the application to the goose predates that of the shellfish in Eng[lish]. The goose nests in the Arctic in summer and returns to Europe in the winter, hence the mystery surrounding its reproduction. It was believed in ancient superstition to hatch from barnacle's shell, possibly because the crustacean's feathery stalks resemble goose down." (Harper, 2001).   Crab appears to be from Old English crabba with possible roots to Low Germ Krabben (to scratch or claw)?   Lobster is thought to come from Middle English lopster, perhaps via Old English lobbe (spider) and/or Latin locusta (locust) -- both possible roots, if pertinent, are hypothesized to be based on physical resemblances.  The designation horseshoe crab is considered by many professional biologists to be misleading because the animal is not a crustacean and consequently they contend not a crab (although crab is a common rather than a scientific name);  indeed, when using the common name, they use horseshoe "crab."  That "problem" notwithstanding, the horseshoe designation is based on the shape of the animal's shell. 

The importance of the horseshoe "crab" so far as medical research involving eyes is well known because of H.K. Hartline's work that led to his receiving the Nobel Prize in the late 1960s.  (Hartline began the investigations that led to his understanding of vision systems by studying the nerves that carry impulses from horseshoe crabs' eyes to their brains;  the fact that those nerves are relatively large in horseshoe crabs meant that they could be manipulated macroscopically; ...)  In addition, though not as widely known, "[t]he blood of the horseshoe crab provides a valuable medical product critical to maintaining the safety of many drugs and devices used in medical care. A protein in the blood called Limulus Amebocyte Lysate (LAL) is used by pharmaceutical and medical device manufacturers to test their products for the presence of endotoxins, bacterial substances that can cause fevers and even be fatal to humans." (Maryland DNR, 1995-2005).

 “Commercial interest in chitin has slowly increased in the past several years because chitin is strong, nonallergenic, and biodegradable.  Chitin can, for example, be solubilized and then reformed into fibers, which can then be used in making fabrics and surgical sutures." (Pechenik, 2005, p.330).

One of the 12 signs of the zodiac has a crustacean as its sign: Cancer, a crab, for June 22 through July 22;  another has
Scorpio, the scorpion, for October 24 through November 22, which is not a crustacean but is of the same subphylum (Chaliceriformes) as the horseshoe crabs.

-- An aside:  Although the lyrics of  "Barnacle Bill the sailor man" seem hardly worth a thought, here or elsewhere, as a fan of Bix Beiderbecke's cornet artistry, I cannot pass up this chance to mention his solo
on this tune with the Hoagy Carmichael group. -- It was one of Bix's last recorded solos (May 21, 1930).  As Sudhalter and Evans (1947, p.304) note: "[Bix] turns on the old fire for a 20-bar, up-tempo outburst on 'Barnacle Bill.'"

SIMULANTS:    None so far as I know. 

REPLICAS:  Diminutive and/or large replicas (an admitted oxymoronic phrase) of crabs, lobsters and horseshoe "crabs," many of which are stylized, have been used as functional things -- e.g., can openers, Christmas tree ornaments, "collectibles," jewelry boxes, lamps, paper weights and salt and pepper shakers -- as well as in jewelry.  Most of these consist largely of some ceramic, glass,  gold, silver (including sterling), steel, brass, pewter, an unidentified metal or alloy, OR some combination of two or more of these materials;  some are bejeweled and/or enameled or even painted or otherwise colored to resemble the animal more closely (Figure C).  In addition, larger-than-life-size replicas, commonly fashoined from bronze, have been produced and are marketed for placing in homes or gardens.

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R.V. Dietrich © 2015
Last update:  28 January 2014
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