Subphylum Crustaceans Phylum Arthropoda

Characteristics 67,000 species Lobsters, crabs, crayfish, shrimp Also known as “insects of the sea” Mainly marine Only arthropods with two pairs of antennae Also have one pair of mandibles and two pairs of maxillae Have a pair of appendages on each body segment Most have between 16-20 segments, but some can have as many as 60 or more.

Characteristics Three Tagmata: Head Thorax Some crustaceans have fused the head and thoracic segments together to form the Cephalothorax Abdomen Some have a carapace-the dorsal cuticle of the head may extend posteriorly and around the sides to cover the abdomen and thoracic segments (ex. a lobster shell)

Characteristics Bodies are covered with a secreted cuticle composed of chitin, protein, and calcareous material The harder, heavy plates of larger crustaceans contain large portions of calcareous deposits Provides a hard protective covering Soft and thin at the joints Will have a telson, which will bear the anus

Muscular System Striated muscles Flexors- draw a part toward the body Extensors- extend a part outward

Circulatory System Open circulatory system No veins No separation of blood from interstitial fluid Hemolymph (blood) enters the dorsal heart (single-chambered sac of striated muscle) from the surrounding hemocoel (space in the coelom containing blood) The hemolymph will enter sinuses (spaces that serve as veins) Sinuses contain valves that prevent backflow into the heart The hemolymph will travel through the sinus to different organs such as the gills for oxygen and carbon dioxide exchange

Circulatory System Hemolymph may be colorless, reddish or bluish Hemocyanin (a copper-containing respiratory pigment) and Hemoglobin (an iron-containing pigment) may be present in the solution. This helps give the hemolymph the property of clotting, which prevents its loss in minor injuries.

Respiratory System Use gills for respiration Gills- delicate, featherlike projections with a very thin cuticle used for gas exchange

Nervous System Have a well developed sense organ Advance eyes Tactile hairs- cover mouthparts, cuticle and telson Chemical senses for taste and smell can reside in receptors on antennae, mouthparts etc.

Reproduction Most crustaceans are dioecious

Crustacean Evolution

Classes Class Remipedia Class Cephalocarida Class Branchiopoda Class Ostracoda Class Maxillopoda Class Malacostraca

Class Remipedia Very small class of crustacea Live in caves 25-38 trunk segments Have swimming appendages

Class Cephalocarida Small group- 9 species known 2-3mm long Live in the bottom sediments of the intertidal zone of coasts No eyes No carapace No abdominal appendages True hermaphrodites Unique because they are the only arthropod that discharges both eggs and sperm into a common duct

Class Branchiopoda 10,000 species 3 orders: Anostraca- fairy shrimp Notostraca- tadpole shrimp Diplostraca- water fleas Have phyllopodia – legs that serve as chief respiratory organs Water fleas (cladocerans) will often produce only females in the summer, by parthenogensis (unisexual reproduction of a female) increasing the population. When conditions are unfavorable, some males will be produced, and eggs that must be fertilized are produced by normal meiosis Fertilized eggs are highly resistant to cold weather

Class Ostracoda Enclosed in a bivalved carapace, encloses the body but not the head Mussel shrimp or seed shrimp Development is gradual by metamorphosis

Class Maxillopoda 6 subclasses: Subclass Mystacocarida Subclass Copepoda Subclass Tantulocarida Subclass Branchiura Subclass Pentastomida Subclass Cirripedia

Subclass Mystacocarida Tiny crustaceans Live in interstitial water between sand grains of marine beaches Only 10 species

Subclass Copepoda Small Lack carapace Antennules are often longer than other appendages and used for swimming

Subclass Tantulocarida 12 species known No head appendages except for one pair of antennae on sexual females Parathenogenetic Lose their abdomen and all thoracic limbs during metamorphosis

Subclass Branchiura Small group of fish ectoparasites Mouthparts are modified for sucking- second maxillae have been modified as suction cups 5-10mm long Broad shield-like carapace Unsegmented abdomen Fish heavily infected with these crustaceans can get infections and die

Subclass pentastomida Tongue worms 130 species Wormlike parasites of the respiratory system of vertebrates Adults live mostly in lungs of reptiles (snakes, lizards and crocodiles Intermediate hosts may consist of fish or other reptiles, sometimes mammals 1-13cm Females are larger than males Females may produce several million eggs

Subclass Cirripedia Barnacles Enclosed in a shell of calcareous plates Sessile as adults No abdomen Thoracic legs are long Nonparasitic barnacles are hermaphroditic Can have bivalve carapace

Class Malacostraca 20,000 species Largest class with great diversity 3 subclasses, 14 orders and many suborders 4 orders we will discuss: Order Isopoda Order Amphipoda Order Euphausiacea Order Decapoda

Order Isopoda Truly terrestrial Dorsoventrally flattened Lack a carapace Psuedotracheae- abdominal appendages bearing gills Can roll into tight ball for protection Ex. Pill bugs (Rolly Pollies)

Order Amphipoda Lack carapace Compressed laterally Appendages can be used for different functions Ex. One pair used for swimming, one pair for jumping

Order Euphausia Krill 90 species 3-6cm long Most are bioluminescent- contain a photophore organ which will produce light Food for many whale and fish species

Order Decopoda Lobsters, crabs, crayfishes and “true” shrimp 18,000 species Very diverse order 5 pairs of walking legs May have first pair of walking legs are modified to form chelae (pinchers) Economically important because they are used as food.