Arthropods
    (Phylum Arthropoda)



  • Amphipods

  • Cladocerans

  • Crab larvae

  • Copepods

  • Mysids

  • Ostracods

  • Shrimp larvae

    The phylum Arthropoda includes insects, spiders, millipedes, centipedes and crustaceans. Marine arthropods are characterized by a hard chitinized exoskeleton, segmented body with many paired appendages, planktonic larval stage and often with external gills. Crustaceans are the dominant marine arthropods which include water fleas (cladocerans), copepods, ostracods (seed shrimp), amphipods (scuds), mysids (opposum shrimp), crabs, lobsters and shrimp. Copepods and sometimes cladocerans are the most abundant holoplankton in estuarine and coastal waters.

    • Amphipods

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      These have bodies that are crescent-shaped and laterally compressed.




    • Hyperiid amphipod

      Cladocerans

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      Cladocerans comprise a small (ca. 700 exant specie) order of crustaceans and are thus related, albeit distantly, to other crustacean arthropods such as copepods, shrimp and crabs. Daphnia are a familiar genus of freshwater cladocerans. Read more about cladocerans on Wikipedia. Below are some cladocerans common in the plankton assemblages of Mid-Atlantic coastal waters.


      Cladocerans w/ rounded bodies and hemispherical carapace valves



    • Pseudevadne tergestina

      .


    • Podon intermedius


    • Pleopsis polyphemoides

      Cladocerans w/ pointed bodies and pointed carapace valves




    • Evadne nordmanni


    • Evadne spinifera

      Cladocerans w/ large, open carapace valves and posterior spines




    • Penilia avirostris

    • Crab larvae

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      These have 4 long spines: 1 top, 1 bottom, and 1 on either side.




    • Crab larvae (various species)

      Copepods

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      Copepods comprise a diverse assemblage of some 13,000 extant, mostly marine species. Read more about copepods on Wikipedia. Below are some copepods common in the plankton assemblages of Mid-Atlantic coastal waters.




    • Euterpina acutifrons
      (a harpacticoid copepod)


    • Centropages typicus
      (a calanoid copepod)
      female


    • Temora longicornis
      (a calanoid copepod)
      female



    • Oithona simils
      (a cyclopoid copepod)
      female


    • Oithona simils
      (a cyclopoid copepod)
      female w/ eggs


    • Oithona simils
      (a cyclopoid copepod)
      male

    • Mysids

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      These are shrimp-like in appearance. They have 2 spherical statocysts at the base of their uropods.


    • Mysids

    • Ostracods

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      Ostracods consist of some 13,000 extant species comprising several taxonomic orders of crustaceans. They are small (typically about 1 mm in size) and are characterized by isolaterally flattened bodies protected by a bivalve-like "shell."


    • Ostracods

    • Shrimp larvae

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      Shrimp larvae are widespread and abundant. They can be confused with mysids and amphipods.


    • Shrimp larvae