Phylum Arthropoda “jointed” “foot” 80% of all animals are arthropods….. 76% of those are insects…..

Major Classes of Arthropods Above left: Subphylum Myriapoda, Class Chilipoda: includes the centipedes Lower Right: Subphylum Hexapoda, Class Insecta: includes all 6 legged insects Above: Subphylum Myriapoda, Class Diplopoda: includes the millipedes

Above Left: Subphylum Chelicerata Class Arachnida: includes the spiders, mites and scorpions Lower right: Subphylum Crustacea, Class Malacostraca: includes the lobsters, crab and shrimp Above: Subphylum Crustacea, Class Maxillopoda: includes the barnacles

Shared characteristics of Arthropods Coelomate and bilaterally symmetrical Jointed appendages Exoskeleton of chitin secreted by the epidermis 3 body regions (head, thorax, and abdomen) Respiration by body surface, gills, trachea, or book lungs Open circulatory system Sensory organs are well-developed: compound eyes, tympanum (drum-like ear) antenna (touch, smell, chemical reception) Complete digestive systems with mouth, specialized organs and anus Dioecious: fertilization is usually internal Developed nervous system with dorsal brain connected by a ring and double ventral nerve cords Found in marine, freshwater, terrestrial and aerial environments

Let’s take a closer look at a few different Classes of Arthropods Class Insecta Exoskeleton made of chitin Have a head segmented into 6 with sensory antennae and compound eyes Have a thorax with attached segmented legs and possibly wings Have an abdomen with 11 segments which houses most of the digestive, respiratory, excretory and reproductive systems

Insects respire through a system of internal tubes and sacs that lie directly next to the circulatory system,therefore the circulatory system does not need closed vessels Most insects hatch from eggs which are fertilized by sexual reproduction (see ladybugs at top right) Insects molt as they grow in size (undergo metamorphosis)

Class Maxillopoda : The Barnacles The Barnacle Life Cycle Includes 2 larval stages 1. NAUPILUS spend their time floating around in the current, eating and molting last approx. 2 weeks 2. CYPRID strong swimmer Settles in a safe, productive environment Cements itself headfirst to surface and undergoes metamorphosis into a barnacle

As the cyprid metamorphosizes it develops 6 hard armor plates around its body The adult barnacle has feathery legs that protrude to capture food and gametes when spawning Barnacles are hermaphroditic Famous Barnacle Fact: Barnacles have the largest penis to body size ratio of any species in the animal kingdom

Class Malacostraca : The Crustaceans Head and thorax are often fused into cephalothorax Head includes 6 segments with antennules, antennae and mouthparts with appendages called maxillipeds 8 thoracic segments Cephalothorax is almost completely covered by a carapace 6 abdominal segments often used for swimming

Eyes are compound stalked or sessile (stalked eyes allow the crustacean to pull them in for protection or see in many different directions) 5 pairs of walking legs, some with modified pincers 2-chambered stomach Centralized nervous system Spiny King Crab Hermit Crab

Above: Pacific White Cleaner Shrimp Left: Decorator Crab: will cover its body in algae etc. in order to camouflage itself with its surroundings Above: Lobster

Pair of LobsterPrawn Spiny LobsterHermit Crab

Ecological Roles of Arthropods Pollination Production of honey, wax, and silk Recycle biological materials to aid in producing topsoil Form symbiotic relationships with other organisms (see left) Part of food chain Burrowing shrimp and Goby fish living in Symbiosis shrimp cleans and digs a burrow where they both live When danger approaches, the goby fish touches the shrimp with its tail to warn it (shrimp is blind) and both hide in the burrow

The Largest living Arthropod! is the Japanese Spider Crab with a leg span of 4 meters and a weight of 20kg. This crab has a life expectancy of 100 years.