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Barnacle

2007 Schools Wikipedia Selection. Related subjects: Organisms

                                iBarnacle
   "Cirripedia" from Ernst Haeckel's Kunstformen der Natur (1904). The
   crab at the centre is nursing the externa of the parasitic cirripede
   Sacculina
   "Cirripedia" from Ernst Haeckel's Kunstformen der Natur (1904). The
   crab at the centre is nursing the externa of the parasitic cirripede
   Sacculina
                        Scientific classification

   Kingdom:    Animalia
   Phylum:     Arthropoda
   Subphylum:  Crustacea
   Class:      Maxillopoda
   Subclass:   Thecostraca
   Infraclass: Cirripedia
               Burmeister, 1834

                                 Superorders

   Acrothoracica
   Thoracica
   Rhizocephala

   A barnacle is a type of arthropod belonging to infraclass Cirripedia in
   the subphylum Crustacea and is hence distantly related to crabs and
   lobsters. Some authorities regard Cirripedia as a full class or
   subclass, and the orders listed at right are sometimes treated as
   superorders. Around 1,220 barnacle species are currently known. The
   name "Cirripedia" means "curl-footed".

   Barnacles were first fully studied and classified by Charles Darwin, at
   the suggestion of his friend Joseph Dalton Hooker, in his quest to
   further his ongoing development of the theory of evolution and natural
   selection.

Life cycle

   Barnacles have two larval stages. The first is called the nauplius,
   which spends its time as part of the plankton, floating wherever the
   wind, waves, currents, and tides may take it, whilst eating and
   molting. This lasts for about two weeks until the second stage is
   reached. At this point the nauplius metamorphoses into a non-feeding,
   more strongly swimming cyprid larva. The cyprids settle down in an area
   where environmental cues indicate a safe and productive environment. If
   they don't, the larvae will die.
   Balanus balanoides
   Enlarge
   Balanus balanoides

   When an appropriate place is found, the cyprid larva cements itself
   headfirst to the surface and then undergoes metamorphosis into a
   juvenile barnacle. Typical barnacles develop six hard armor plates to
   surround and protect their bodies. For the rest of their lives they are
   cemented to the ground, using their feathery legs to capture plankton
   and gametes when spawning. They are usually found in the intertidal
   zone.

   Once metamorphosis is over and they have reached their adult form,
   barnacles will continue to grow, but not molt. Instead, they grow by
   adding new material to the ends of their heavily calcified plates.

   Like many invertebrates, barnacles are hermaphroditic and alternate
   male and female roles over time. Barnacles have the longest penis in
   the animal kingdom, in proportion to their body length .

   Barnacles often attach themselves to man-made structures, sometimes to
   the structure's detriment. Particularly in the case of ships, they are
   classified as fouling organisms.

   However, some members of the class have quite a different mode of life.
   For example, members of the genus Sacculina are parasitic on crabs.

   The Barnacle Goose gets its name from the ancient European belief that
   it grew from the gooseneck barnacle, Pollicipes polymerus; eggs and
   goslings of this bird were never seen because it bred in the remote
   Arctic. Since barnacles are seafood, the Barnacle Goose was counted as
   a fish, and could be eaten by Catholics on Fridays, when meat used to
   be forbidden.

Classification

   Balanidae, Mission Beach National Park, Queensland, Australia, 2002
   Enlarge
   Balanidae, Mission Beach National Park, Queensland, Australia, 2002
   Corrosion caused partly by barnacles
   Enlarge
   Corrosion caused partly by barnacles

   This article follows Martin and Davis in placing Cirripedia as an
   infraorder of Thecostraca and in the following classification of
   cirripedes down to the level of orders:

   Infraclass Cirripedia Burmeister, 1834
     * Superorder Acrothoracica Gruvel, 1905
          + Order Pygophora Berndt, 1907
          + Order Apygophora Berndt, 1907
     * Superorder Rhizocephala Müller, 1862
          + Order Kentrogonida Delage, 1884
          + Order Akentrogonida Häfele, 1911
     * Superorder Thoracica Darwin, 1854
          + Order Pedunculata Lamarck, 1818
          + Order Sessilia Lamarck, 1818

Synonyms

   Other names for this group of crustaceans include Thyrostraca,
   Cirrhopoda (meaning "tawny-footed"), Cirrhipoda, and Cirrhipedia.
   Retrieved from " http://en.wikipedia.org/wiki/Barnacle"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
