Phylum Arthropoda “jointed foot” “jointed appendages” the arthropods Things that creep around on the ocean bottom (some don’t really creep!); also crustaceans and other stuff

General Characteristics –The largest phylum of animals on earth – three out of four animals on earth are arthropods –Include marine barnacles, shrimp and lobsters as well as all insects –Have a segmented body –Bilateral symmetry –Jointed appendages –Hard exoskeleton made of chitin Tough and non-living Tough and non-living Covers all parts of the animal Covers all parts of the animal Shed when the animal grows – “molting” Shed when the animal grows – “molting” Limits size of the animal because it becomes too heavy in larger animals to allow movement Limits size of the animal because it becomes too heavy in larger animals to allow movement

Feeding and Digestion Because of the mandibles and specialized legs, arthropods have the ability to eat almost anything Because of the mandibles and specialized legs, arthropods have the ability to eat almost anything Fill all niches of ecology – carnivores, filter feeders, herbivores and parasites Fill all niches of ecology – carnivores, filter feeders, herbivores and parasites Many marine species use their mouthparts or legs to filter the water Many marine species use their mouthparts or legs to filter the water Parasitic crustaceans have their appendages specialized for sticking onto another organism Parasitic crustaceans have their appendages specialized for sticking onto another organism The mouth of these organism have the first real teeth like structures made of chitin The mouth of these organism have the first real teeth like structures made of chitin They have a two chambered stomach connected to digestive glands which release enzymes to aide in digestion They have a two chambered stomach connected to digestive glands which release enzymes to aide in digestion Digestion is extracellular and waste is sent out through the anus Digestion is extracellular and waste is sent out through the anus

Respiration Arthropods use gills that resemble feathers located just under their exoskeleton Arthropods use gills that resemble feathers located just under their exoskeleton Movement of the mouthparts keeps water moving in a steady stream over the gills Movement of the mouthparts keeps water moving in a steady stream over the gills Land crabs also have gills for respiration – the gills are kept wet with body fluids and air is passed over the moistened gills for oxygen absorption Land crabs also have gills for respiration – the gills are kept wet with body fluids and air is passed over the moistened gills for oxygen absorption

Behavior and Response Crustaceans have a small and simple brain Crustaceans have a small and simple brain Most members of this phylum have well defined sense organs Most members of this phylum have well defined sense organs –Compound eyes – a bundle of light sensitive units grouped together at the end of a stalk like antennae –Sense of smell – very sensitive to chemicals in water Very complex communication is possible between members through movement Very complex communication is possible between members through movement –Used for courtship and territory protection

Reproduction Separate male and female individuals Separate male and female individuals Internal fertilization occurs Internal fertilization occurs Females can store sperm for long periods of time before they use it to fertilize their eggs Females can store sperm for long periods of time before they use it to fertilize their eggs Females tend to carry the eggs until they hatch Females tend to carry the eggs until they hatch The young are larvae that are plankton-like and very rarely resemble the adults The young are larvae that are plankton-like and very rarely resemble the adults

Class Trilobites Oldest class from which the rest of the phylum evolved Oldest class from which the rest of the phylum evolved Lived in all the ancient seas. Is now the most common fossil. Distinguishes the areas that were occupied by the organism Lived in all the ancient seas. Is now the most common fossil. Distinguishes the areas that were occupied by the organism All members of this class are now extinct All members of this class are now extinct

Class Crustaceans Specialized for life in the ocean – all members have gills for respiration and appendages specialized for swimming Specialized for life in the ocean – all members have gills for respiration and appendages specialized for swimming Over 35,000 species exist Over 35,000 species exist Generally characterized by a hard exoskeleton, two pairs of antennae and mouth parts called mandibles Generally characterized by a hard exoskeleton, two pairs of antennae and mouth parts called mandibles Have two pair of antennae that are specialize for sensing the environment Have two pair of antennae that are specialize for sensing the environment The mandibles are generally short, heavy and specialized for feeding The mandibles are generally short, heavy and specialized for feeding Vary in size between microscopic plankton to large lobsters Vary in size between microscopic plankton to large lobsters Main body plan is a head, thorax (area behind the head) and abdomen (the tail end of the animal) Main body plan is a head, thorax (area behind the head) and abdomen (the tail end of the animal)

Class Crustaceans Barnacles are part of this class even though they look like mollusks Barnacles are part of this class even though they look like mollusks –The legs that stick out of the volcano shaped exoskeleton capture plankton to eat Shrimp, lobsters and crabs belong to a group called decapods have 10 legs Shrimp, lobsters and crabs belong to a group called decapods have 10 legs –Prized for food –Two pairs of the legs are often specialized into claws for feeding purposes –Tend to be scavengers

Other Arthropods –Horseshoe crabs – still the same after thousands of years, are called living fossils –Sea Spiders – resemble land spiders, most common in cold waters and large –Insects – have only three pairs of legs as adults, not aquatic but worth mentioning Largest and most diverse group on earth; may be as many as 1-3 million species Largest and most diverse group on earth; may be as many as 1-3 million species Can live at the sea’s edge scavenging on seaweed and barnacles Can live at the sea’s edge scavenging on seaweed and barnacles