Phyla Arthropoda

    (Jointed Foot)

Arthropods are the largest animal phylum on the planet with more than a million species

    -3 out of 4 animals on the planet are arthropods

    -The largest group of arthropods are the insects yet there are not many insects in the sea

    -The largest group of arthropods in the oceans are the crustaceans

    Arthropod Characteristics

        -Segmented body

        -Bilaterally symmetrical

        -Jointed appendages

        -Exoskeleton- made of chitin

            -Molt their exoskeleton to grow

Sub Phyla Crustaceans

    -68,000 known species but maybe as many as 150,000 undescribed species

        -Most are marine

    -Crustaceans have two pairs of antennae, most have gills, their chitinous exoskeleton is usually hardened with calcium carbonate, and they have many legs.

Crustaceans have many different types of appendages

        -It is best to familiarize yourself with these terms now because they will be present throughout the arthropod phylum

    -Cephalon - Head (has the maxillae)

        -Maxillipeds - Feeding legs

    -Thorax - Holds arms and legs also known as Pereon

        -Pereiopods - Walking legs

    -Abdomen - Back end of body also known as Pleon

        -Pleopods - Swimming legs

    -Uropods - Tail Legs

    -Telson - Paddle like tail

    Crustacean Classes

Most crustacean classes are organized by their segments. For example their Cephalic segments (head), their Thoracic segments (Body), Abdominal segments (tail end). Also their feeding legs, maxillae, are used to categorize them. 

    Class Maxillopoda (Feed with their Maxillae)

    -Maxillopods have

        -5 Cephalic segments

        -6 Thoracic segments

        -4 Abdominal segments followed by a telson

        Subclass: Copepoda (Oar Feet)

            -Copepods are extremely abundant. One of the most abundant animals on earth

            -Considered Plankton

            -Use their mouth parts to filter food from water

            -Can use their first pair of antennae to swim so they do not sink

            -Some species are parasitic

    Infraclass: Cirripedia (Curly Foot)

   Common Name: Barnacles

            -Are sessile

            -Filter Feeders

            -Live on rocks, whales, and crabs

            -Many are very specific about the type of surface they live on

            -Inclosed by heavy calcateous plates and can be easily confused for mussels

            -Have Cirri- feathery filtering appendages

    Class Malacostraca

                   Malacostracans have 20 body segments...there are a couple that have 21...but most of them, 20 BODY SEGMENTS!

        Order: Amphipoda (Two Legs)

            -Sometimes known as water fleas

            -Can jump

                -Beach hoppers

                -Live on the sand eating dead seaweed

            -There are freshwater and saltwater species

            -Most of them are very tiny

                -very hard to see

            -Have sideways flattened bodies

            -Some are parasitic

                -Whale lice burrow into the skin of whales

            -Over 5,000 species

        Order: Isopoda (Same Legs)

            -Are usually dorsoventrally flattened

            -Pill bugs are common land isopods

            -Most isopods are very small but there are some giant isopods in the ocean

            -Legs that are similar to each other

            -The sea louse or sea roach (not a roach) lives on shore and eats decaying seaweed

            -There are also parasitic isopods

                -Fish lice- Will eat the tongue of fish and replace it with themselves sharing the food that the fish eats

 Order: Krill

        (Order Euphausiids)

            -Plankton

            -Head is fused to some of the body segments forming a distinctive carapace

            -Filter feeders

            -Arctic

            -Primary food for many whales, penguins, and some fish

    -Krill vs shrimp. Krill and shrimp look very similar. One of the main differences is that Krill usually have 3 body segments and shrimp have only two body segments.

            -Krill are not decapods because their 10 Pereiopods are not functional for walking. This is because most krill live in open water. They never land or stand on something. They spend their whole life swimming. Unlike shrimp who mostly live near reefs or coastlines where they walk around on the sandy or rocky floor. 

  Order: Stomatopoda (Mouth Foot)

-Common Name: Mantis Shrimp

            (Not a true shrimp)

        Order: Decapoda

Shrimp, Lobsters, and Crabs

           -More than 10,000 species

            -Largest group of crustaceans

            -5 pairs of legs (Pereiopods) this is where their get their name decapod (10 legs)

                -First pair are usually claws or used for feeding

            -3 pairs of maxillipeds for feeding

            -Cephalothorax and abdomen

Some common Decapods:

Common Name: Shrimp 

        Common Name: Lobsters (Has two very large claws)

        Common Name: Spiny Lobster (Does not have front two claws, instead has spines)

        Common Name: Crabs (Tail is sealed or tucked under thorax)