Arthropoda

(Jointed Foot)

Arthropod Hunt Sheet

Arthropods are the largest animal phylum on the planet with more than a million species named and recient studies suggest there might be between 30 and 50 million species on the planet

-3 out of 4 animals on the planet are arthropods

-The largest group of arthropods are the insects

Arthropod Characteristics

-Segmented body/ Metamerism modified by specialization of body regions for specific function (tagmatization)

-Bilaterally symmetrical

-Ventral nervous system

-Coelom reduced to only surrounding the gonads

-Open circulatory system

-Complete digestive tract

-Paired Jointed appendages

-Exoskeleton- made of chitin

-Molt their exoskeleton to grow

-Metamorphosis often present (helps reduce competition between immature and adult stages

Because Arthropoda is so large their are many classes and subphyla

Here are the ones we will study

Subphylum Trilobitomorpha

-Trilobites- Extinct

Subphyla Chelicerata

They all have chelicerae which are fangs that can move

Class Arachnida

-Greek Arachne- Spider

-Have book lungs

-Four pair of walking legs

-Spiders, scorpions, ticks, mites, harvestmen

Order Araneae (Spiders &Tarantulas)

-Latin - spider

-True spiders - over 40,000 species

-Have a cephalothorax and abdomen

-Make many different types of web

-Males use pedipalps to pass a spermatophore or sperm sac to the female

Curly Hair Tarantula

Order Scorpiones (Scorpionodea) (Scorpions)

-Over 2,000 species

-Have pincher pedipalps

-Prosoma is what the legs are attached to

-Preabdomen (body)

-Postabdomen (tail)

-Abdomenal sting (Stinger)

-Males lay down a spermatophore and position females over it

There are some other orders of arachnids that have an appearance somewhere in between that of a scorpion and that of a spider. Because each of these orders does not have that many species or we do not normal encounter them we do not have to learn them. But they have fascinating behaviors and body structures.

Order Thelyphonida (Uropygid)

-Greek Uropygid - Oura - Tail and puge - rump

-Whipscorpions Also called Vinegaroons

Order Amblypygi

-Greek - Blunt Rump

-Tailless whipscorpions or whip spiders )Commonly called cave spiders or cave scorpions

Order Pseudoscorpionida

-Very small

-Harmless to humans but beneficial since they eat cloths moths, mites, and ants

Order Solifugae

-Latin sol - sun and fugere flee

-1,000 species

-The sun spiders and camel spiders

Order Acarina (Ticks & Mites)

-Greek Akari - mite

-50,000 species

Order Opiliones (Harvestmen)

-6,300 species

-No venom glands

-No silk glands

-Are omnivores

-These are the real "daddy long legs" the spider that Californians call "daddy long legs" is really a cellar spider

Subphyla Crustacea

-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.

Crustacean Classes

In marine biology we focused on crustaceans, so in Zoology we will only study one class of Crustacean

Class Malacostraca (Pill bugs, crabs, lobsters, shrimp, etc.)

Order Isopods

-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

Order Decapods (A type of Malacostraca)

Shrimp, Lobsters, and Crabs

-More than 10,000 species

-Largest group of crustaceans

-5 pairs of legs (Pereopods)

-First pair are usually claws or used for feeding

-3 pairs of maxillipeds for feeding

-Cephalothorax and abdomen

Shrimp

Lobsters

Crabs

Crabs have some of the most complicated gestures for an invertebrate

-Crabs use a large variety of hand signals and often communicate using signals

-Crabs argue and settle disputes using leg gestures

-They also have matting dances

-crabs also have some neat use of tools

The worlds largest land Arthropod

The Coconut Crab (A giant hermit crab)