Arthropods

http://www.iteachbio.com/Marine-Biology/Crustacians.mov

Subphylum Crustacea Over 67,000 species Primarily aquatic Lobsters, crayfishes, shrimp, crabs, water fleas, copepods, barnacles Primarily aquatic Mostly marine but some freshwater Only arthropods with 2 pairs of antennae Mandible 2 pairs of maxillae

Lobsters

Crayfish

Shrimp

Shrimp

Crabs

Water Fleas

Water Fleas

Copepods

Copepods

Barnacles

Barnacles

Subphylum Crustacea Major tagmata Carapace Head, thorax, abdomen A hard outer covering or shell made of chitin

Subphylum Crustacea Form & Function Appendages Swimmerets (abdominal appendages) Endopod & exopod (inner & outer branches) Attached to one or more basal segments (protopod)

Subphylum Crustacea General – Majority are free swimming Very important components of aquatic ecosystems Have two pairs of antennae (only arthropods with these) Most have between 16 and 20 segments Compound eyes (detects motion) Crabs & crayfish are on the ends of movable eyestalks

Subphylum Crustacea Ecdysis Feeding Habits (ekdysis = strip off) Periodic shedding of old cuticle for a larger one Feeding Habits Suspension feeders Plankton, detritus, bacteria Predators Larvae, worms, crustaceans, snails, fishes Scavengers Dead animals & plant matter

Subphylum Crustacea Class Branchiopoda branchia – gills, podos – foot Four orders are recognized: Anostraca – fairy shrimp and brine shrimp Notostraca – tadpole shrimp (Triops) Conchostraca – clam shrimp (Lynceus) Cladocera – water fleas (Daphnia) Have reduced first antennae and second maxillae Legs are flattened and leaflike (phyllopodia) chief respiratory organs

Subphylum Crustacea Class Maxillopoda include barnacles, copepods, ostracods, and related groups. Most are small Most feed by means of their maxillae Barnacles are an exception Barnacles feed with thoracic appendages, but in a way that is unique among crustaceans. basic plan of 5 head and 10 trunk segments (6 thoracic and usually 4 abdominal) The abdominal segments typically lack appendages; appendages elsewhere on the body are usually biramous.

Subphylum Crustacea Class Maxillopoda Subclass Ostracoda Enclosed in a bivalve carapace (resemble tiny clams; 0.25- 8 mm long) Fusion of trunk segments; scavenge food, feed on detritus, or collect particles from water Subclase Copepoda Small, elongated, lack carapace and retain simple, median nauplius eye in adults (kōpē – oar, podos – foot)

Ostracoda Copepoda

Subphylum Crustacea Class Maxillopoda Subclass Branchiura Branchia – gills, ura – tail Primarily fish parasites (despite name, has no gills) Broad, sheildlike carapace, compound eyes, 4 biramous thoracic appendages & short abdomen Subclass Cirripedia Cirrus – curl of hair, pedis – foot Includes barnacles, as well as smaller orders of burrowing or parasitic forms Barnacles are sessile as adults Attach to their substrate by stalk (gooseneck barnacles) Attach directly (acorn barnacles) Typically, a carapace (mantle) surrounds their body and secretes a shell Head is reduced, abdomen is absent, and thoracic legs are long, many-jointed cirri with hairlike setae

Subphylum Crustacea Class Malacostraca (malakos – soft, ostrakon – shell) Largest Crustacae class Trunk usually has 8 thoracic and 6 abdominal segments each with a pair of appendages Many marine &freshwater species Includes krill, sow bugs, lobsters, crayfish, shrimp, and crabs

Isopoda (Class Malacostraca) (isos – equal, podos – foot) Commonly dorsoventrally flattened, lack a carapace, and have sessile compound eyes Abdominal appendages bear gills Common land forms are sow bugs (pill bugs)

Amphipoda (Class Malacostraca) (amphis – on both sides, podos – foot) Resemble isopods in that members have no carapace and have sessile compound eyes However, they are usually compressed laterally and their gills are in the thoracic position

Euphausiacea (Class Malacostraca) (eu – well, phausi – shining bright, acea – pertaining to) Group of about 90 species Important as oceanic plankton known as “krill” Occur in great oceanic swarms Eaten by baleen whales and many fish

Krill

Krill

Krill

Whale eating Krill

Decapoda (Class Malacostraca) (deka – ten, podos – foot) five pairs of walking legs First is often modified to form pincers (chelae) Lobsters, crayfish, shrimp, and crabs

Lobsters

Crayfish

Crabs