Phylum Arthropoda Copy this organization down. Can you give the common name for each group listed? Kingdom Animalia Phylum Arthropoda Subphylum Crustacea Class Cirripedia Class Copepoda Class Malacostraca Order Decapoda Order Euphausiacea Subphylum Chelicerata Class Merostomata Class Pycnogonida

Arthropods Largest phylum of animals 1 million species (some estimates say up to 20 million) Includes mainly terrestrial bugs 3 out of every 4 animals are arthropods

General Characteristics of Arthropods Segmented body Bilateral Symmetry Jointed appendages Chitinous exoskeleton

Sub Phylum Crustacea Includes: Shrimp Crabs Lobsters Barnacles

General Characteristics of Crustaceans Two pairs of antennae Mandibles for chewing Pair of appendages on each body segment Gills for oxygen

Molting To grow, arthropods must molt their exoskeleton

Digestion Smaller crustaceans are filter feeders, catching particles in bristles on their appendages Some have specialized appendages that push food towards their mouths Nutrients passed to an open circulatory system

Nervous System Can vary from simple ladder-like to centralized nervous systems Most have compound eyes Keen sense of smell Communicate with each other via body postures

Compound Eyes Bundles of up to 14,000 light sensitive units grouped together

Reproduction Separate sexes Mating usually takes place immediately after female molts Some carry eggs in appendages under the body Planktonic larvae (number of stages varies from group to group

Class Cirripedia Filter feeders Cirri – feathery like appendages (actually legs) sweep water Attached to surfaces including living ones Calcareous plates/shells (look like mollusks)

Class Copepoda Abundant and important in the role of plankton Can use their antennae to swim “Sea Monkeys”

Importance of Copepods Most numerous multi-cellular animals on Earth Eat the tiniest plankton and are in turned eaten by fish & krill Nutrient cycling

Order Decapoda “ten legs” Largest crustaceans in terms of size Extended carapace Shrimp, lobsters, and crabs

Order Decapoda Five pairs of walking legs (pereopods) of which one is usually heavier (claws) Carapace encloses the cephlalothorax with the rest of the body being the abdomen

Order Decapoda Shrimp and lobsters can range from scavengers to parasite removers Crabs tend to be scavengers

Order Euphausiacea Krill Planktonic Shrimp-like Filter feeders (eat diatoms) Head fused with body pieces to form a unique carapace Major food source for larger organisms (whales, seals, penguins, etc.) Very common in polar waters

Sub Phylum Chelicerata Includes Horseshoe crabs, spiders, mites Chelicerae are the only small appendages before the mouth Range from small pinchers to venomous fangs

Class Merostomata Horseshoe Crabs Not true crabs and have not evolved for millions of years Six pairs of appendages No mandible jaw Chelicerae, Walking Legs, four pairs of Pushing Legs Telson or tail used for steering and flipping itself right side up.

Class Pycnogonida Sea Spiders Have four or more pairs of legs A large proboscis with a mouth on the tip allows it to feed on soft invertebrates No respiratory system as gases diffuse through body Tiny muscles consist of one cell covered with connective tissue