The pea crab, Pinnotheres pisum, is a small crab that lives symbiotically in oyster and mussel shells. They are about the size of a pea but can be up to the size of a small walnut. It is also commonly called the oyster crab. They have a large tail flap that is used to cover eggs under the body when they are breeding, adding to the spherical appearance. Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms. ... Phyla Subregnum Parazoa Porifera Subregnum Agnotozoa Placozoa Orthonectida Rhombozoa Subregnum Eumetazoa Radiata (unranked) Ctenophora Cnidaria Bilateria (unranked) Acoelomorpha Myxozoa Superphylum Deuterostomia Chordata Hemichordata Echinodermata Chaetognatha Superphylum Ecdysozoa Kinorhyncha Loricifera Priapulida Nematoda Nematomorpha Onychophora Tardigrada Arthropoda Superphylum Platyzoa Platyhelminthes Gastrotricha Rotifera Acanthocephala Gnathostomulida Micrognathozoa Cycliophora Superphylum Lophotrochozoa Sipuncula Nemertea Phoronida Bryozoa... Subphyla and Classes Subphylum Trilobitomorpha Trilobita - trilobites (extinct) Subphylum Chelicerata Arachnida - spiders,scorpions, etc. ... Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The crustaceans (Crustacea) are a large group of arthropods (55,000 species), usually treated as a subphylum [1]. They include organisms such as lobsters, crabs, shrimp and barnacles. ... Subclasses Eumalacostraca Hoplocarida Phyllocarida See text for orders. ... Suborders and Infraorders Dendrobranchiata Pleocyemata Caridea Stenopodidea Reptantia, comprising: Eryonoidea Achelata Astacidea Glypheidea Thalassinidea Anomala Brachyura The decapods or Decapoda are a group of crustaceans within the class Malacostraca, including many familiar groups of crustaceans, such as crabs, lobsters and shrimp, but also some families that are less well known. ... Infraorders Caridea Stenopodidea Reptantia, divided into: Polychelida Achelata Glypheoidea Astacidea Thalassinidea Anomala Brachyura Pleocyemata is a sub-order of decapod crustaceans, erected by Martin Burkenroad in 1963. ... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ... Genera and species See text Pinnotheridae is a family of pea crabs. ... Genera and species See text Pinnotheridae is a family of pea crabs. ... In biology, binomial nomenclature is the formal method of naming species. ... Carolus Linnaeus, also known after his ennoblement as  , (May 23, 1707 – January 10, 1778), was a Swedish botanist, physician and zoologist[1] who laid the foundations for the modern scheme of nomenclature. ... Superfamilies Dromiacea Homolodromioidea Dromioidea Homoloidea Eubrachyura Raninoidea Cyclodorippoidea Dorippoidea Calappoidea Leucosioidea Majoidea Hymenosomatoidea Parthenopoidea Retroplumoidea Cancroidea Portunoidea Bythograeoidea Xanthoidea Bellioidea Potamoidea Pseudothelphusoidea Gecarcinucoidea Cryptochiroidea Pinnotheroidea * Ocypodoidea * Grapsoidea * An asterisk (*) marks the crabs included in the clade Thoracotremata. ... Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron Crassostrea gigas, Marennes-Oléron, opened The name oyster is used for a number of different groups of mollusks which grow for the most part in marine or brackish water. ... Subclasses Pteriomorpha (marine mussels) Palaeoheterodonta (freshwater mussels) Heterodonta (zebra mussels) The term mussel is used for several families of bivalve mollusks inhabiting lakes, rivers, and creeks, as well as intertidal areas along coastlines worldwide. ... Binomial name Pisum sativum L. A pea is the small, edible round green bean which grows in a pod on the leguminous vine Pisum sativum, or in some cases to the immature pods. ... Species See text The walnuts (genus Juglans) are plants in the walnut family Juglandaceae. ...

It is found from southern Scandinavia to western Africa, and throughout the Mediterranean in the mantle cavity of such bivalve molluscs as mussels, and inside ascidians. Scandinavia is a region in Northern Europe. ... A world map showing the continent of Africa. ... The Mediterranean Sea is an intercontinental sea positioned between Europe to the north, Africa to the south and Asia to the east, covering an approximate area of 2. ... Orders Subclass Protobranchia Solemyoida Nuculoida Subclass Pteriomorphia - oysters Arcoida Mytiloida Pterioida Subclass Paleoheterodonta - mussels Trigoinoida Unionoida Subclass Heterodonta - clams, zebra mussels Veneroida Myoida Subclass Anomalosdesmata Pholadomyoida Animals of the Class Bivalvia are known as bivalves because they typically have two-part shells, with both parts being more or less symmetrical. ... Classes Caudofoveata Aplacophora Polyplacophora - Chitons Monoplacophora Bivalvia - Bivalves Scaphopoda - Tusk shells Gastropoda - Snails and Slugs Cephalopoda - Squids, Octopuses, etc. ... Orders Aplousobranchia Enterogona Phlebobranchia Pleurogona Stolidobranchia Ascidiacea (commonly known as the ascidians) is an order in the Urochordata subphylum of sac-like marine filter feeders. ...

Although researchers once thought that pea crabs were not harmful to their hosts, they have found that their activities do cause damage to the delicate gills of bivalves; the crabs are now considered parasites. gills of a Smooth Newt Gills inside of a tuna head In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ...

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