ARTHROPODS

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

SUBPHYLUM CRUSTACEA Over 67,000 species

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

Major tagmata Head, thorax, abdomen

Carapace 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 (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

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 CRUSTACEACLASS BRANCHIOPODA

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 CRUSTACEACLASS 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)

SUBPHYLUM CRUSTACEACLASS MAXILLOPODA

OSTRACODA

COPEPODA

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 CRUSTACEACLASS MAXILLOPODA

(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

SUBPHYLUM CRUSTACEACLASS MALACOSTRACA

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