Photo credits: www.wikipedia.org Phylum Arthropoda Photo credits: www.wikipedia.org

Arthropod Characteristics More than 1 million species known, mostly marine Most marine species are subphylum Crustacea (shrimp, lobster, crab, barnacles, etc) Coral crustaceans California crustaceans About 75% of all animals on earth are arthropods Chitin exoskeleton - hard, but light and moderately flexible Must molt to grow (Video: molting)

Arthropod Characteristics Jointed appendages Many divided into sections called head, thorax and abdomen Specialized segmentation- segments combined for specific functions Simple brain but specialized eye & sensory organs Specialized respiratory structures, gills, used for gas exchange Some are filter feeders, some scavengers, others carnivores

Arthropod Reproduction Male transfers sperm directly to female to ensure reproductive success In some species, female will house eggs for a time until they are further developed Females can store sperm for fertilization at a later time Many arthropods have complex behaviors including mating rituals (lobsters); mating rituals (crabs) Baby Crabs 6th show videos

Planktonic larvae to Adult organism

Subphylum Crustacea 68,000 species 2 pairs antennae Gills for respiration Head and thorax fused into a single unit called a cephalothorax; entire external body is called the carapace Large array of appendages specialized for different functions; ex: pinchers on crabs, swimmerettes on the underside of shrimp hold developing eggs, etc. Types of crustaceans – copepods, barnacles, amphipods, isopods, crabs, shrimp, lobsters, etc.

Copeopod Amphipod Isopod Curved and flattened sideways, ~2cm. Orchestoidea – beach hopper First antennae – Specialized for swimming Curved and flattened sideways, ~2cm. Planktonic, extremely abundant. Isopod Ligia oceanica – sea louse Dorsoventrally flattened, commonly parasites, ~2cm.

Cirri are modified legs Barnacles Cirri are modified legs Reproduction

Decopods Largest group of crustaceans with ~10,000 species Largest crustaceans 10 legs Shrimp, lobster, and crabs Carcinus maenas

American Lobster Homarus americanus

Caribbean Spiny Lobster Panulirus argus

Class Merostomata Horseshoe crabs- 5 pairs of legs, first pair modified in males for reproduction Females larger than males Mating pairs come onto beaches each spring to breed and lay their eggs in wet sand Among the oldest creatures on earth – they have remained virtually unchanged for millions of years They live and borrow in soft sediments, normally near shore where they feed on other invertebrates and scavenge. Valuable blood

Class Pycnogonida Sea Spiders: Four of more pairs of jointed legs Not insects or true spiders Possess a mouth and proboscis for feeding Mainly feed on sea anemones and hydrozoans (they are voracious predators!) More common in cold waters, but can be found worldwide

Sea spiders

Class Insecta Insects: Very few marine insects exist Many insects feed in the intertidal zone at low tide, but these are just temporary visitors

Phylum Chordata Characteristics: Notochord – flexible support rod between nerve cord and gut Tubular nerve cord Muscular pharynx (gut) Gill slits Post-Anal Tail Ventral heart Note: no backbone. In vertebrates, notochord is surrounded or replaced by the vertebral column.

Invertebrate Chordates Tunicates – Subphylum Urochordata, Class Ascidiacea Characteristics: Commonly called “sea squirts” because most filter feed via an incurrent siphon and “squirt” water out an excurrent siphon after the water has been filtered (Exception: Predatory tunicate) Larvae has chordate characteristics that are not seen in adults- only pharynx remains Called tunicates because of thick outer covering called a tunic Larvae are free swimming after fertilization occurs in open water- mass reproduction - see Fig. 7.51 Adults normally live attached to boats, docks, reefs, or other hard substrate All 3000 known species are marine

Tunicates A A B Figure 7.51 A. Clavelina picta, colonial ascidian. B. tadpole larva of ascidians exhibits all the distinguishing characteristics of chordates.

B A Figure 7.52 A. Cliona intestinalis, shallow water sea squirt. B. Adult tunicate