ARTHROPODS

“Jointed Feet”

GENERAL CHARACTERISTICS

Arthropods are the most SUCCESSFUL animals on earth. (Species = 1 million)

Include insects, spiders, scorpions, centipedes, and millipedes on land; crabs, crayfish, shrimp, lobsters, and barnacles in water.

Found in every environment including the ocean.

Arthropods are great recyclers and decomposers and they are a super food source.

EXOSKELETON

Composed of CHITIN.

Divided into segments: (pg. 247)

HEAD

THORAX

ABDOMEN

In some arthropods, the head and thorax are fused into what is called the CEPHALOTHORAX. (Example: Crabs, Shrimp, and Lobster)

Function of Exoskeleton:

PROTECTION

MOVEMENT – MUSCLES ARE ATTACHED TO THE INNER SURFACE OF EXOSKELETON

MOLTING – SHEDDING OF EXOSKELETON PERIODICALLY IN ORDER TO GROW

SYMMETRY AND RESPIRATION

BILATERAL symmetry.

Respiration –

GILLS – ORGAN WHOSE FUNCTION IS TO EXTRACT OXYGEN FROM WATER

LUNGS – ESSENTIAL ORGAN IN AIR-BREATHING ANIMALS

TRACHEA – AN ELABORATE SYSTEM OF SMALL, BRANCHING TUBES THAT CARRY OXYGEN TO INDIVIVDUAL BODY CELLS

DIGESTIVE AND CIRCULATORY SYSTEM

COMPLETE digestive system.

(Mouth Digestive tube Anus)

Open Circulatory System –

NUTRIENTS AND WASTES ARE MOVED THROUGH

THE BODY WITH THE ASSISTANCE OF A FLUID

WHICH FLOWS FREELY THROUGH THE BODY

CAVITY, RATHER THAN BEING CONTAINED IN VEINS

NERVOUS AND REPRODUCTIVE SYSTEM

Ladder-like – made up of a series of ganglia,

connected by a ventral nerve cord made up of two

parallel connectives running along the length of the

belly

Compound Eye – well-developed sensory organ

containing thousands of individual photoreceptor

units called “Ommatidia” (Detect fast movement and

have large view angle)

REPRODUCTION

Dioecious – HAVING THE MALE AND FEMALE

ORGANS IN SEPARATE DISTINCT INDIVIDUALS;

SEPARATE SEXES

Fertilization – INTERNAL; SPERM DEPOSITED

NEAR FEMALE’S OVIDUCTS

CLASSIFICATION

Superclass Crustacea

Examples: CRABS, SHRIMP, LOBSTERS, AND CRAYFISH

Order Decapoda “Ten Footed”

8 pairs of feathery gills

Green Glands – USED FOR THE COLLECTION AND

EXCRETION OF URINE; FILTER OUT WASTE MATERIALS

(SIMILAR FUNCTION AS OUR KIDNEYS)

Crustacean Body Parts and Function

Rostrum• Sharp anterior projection of head region

• Located medially to eyes

• Protects brain

Cephalothorax

• Fused head and thorax

• Contains vital organs

Heavy shield covering the cephalothorax

Protects vital organs

Carapace

Telson

• Median, last abdominal segment

• Has anal opening

Uropods

• Lateral, paddle-like appendages of telson

• Used for swimming

Antenna

• Longest pair of antennae

• Touch and tastes

• Unbranched

Antennules

• Branched

• Shortest pair of antennae

• Touch, taste

• Statocyst at base

Mandibles • Jaws

• Used for crushing food

• Move laterally (opens side to side)

high

• Food handling mouth parts

Maxillipeds

Walking legs

Swimmerets

• Used to held eggs by female

• =

Subphylum Crustacean

• Divided into 3 classes:

– Class Branchiopoda (fairy shrimp, water fleas, etc.)

– Class Malacostraca (crabs, lobsters, shrimp)

– Class Maxillipoda (ostracods, copepods, barnacles)

Class Branchiopoda

• Primarily freshwater

• Resemble shrimp

• Example: Artemia (brine shrimp); Daphnia (water flea);

• Have curved legs (feathery food-catching appendages)

Class Malacostraca

• The most important group from the commercial industry point of view.

• Orders: Isopoda, Stomatopoda, Amphipoda Decapoda.

• ~ 2/3 of all crustacean species

Order Decapoda

• Largest group of crustaceans, (~ 8,500 known species)

• Most marine, few freshwater species (crayfish - Astacus sp.)

• two groups:

– Those which swim, including the shrimps

– Those which crawl, including the lobsters and crabs

Class Maxillipoda

• Example: copepods, branchiurans, barnacles and ostracods

Ex: Copepod

• free-living, symbiotic, or internal or external parasites on almost every phylum of animals in water.

• Ecologically important:

– Dominant members of zooplankton

– Major food source for small fish, whales, seabirds, and other crustaceans.

Ex: Branchiurans

• flattened crustaceans which are temporary parasites on fish

• Example: carp lice (Argulus).

Ex. Barnacles• Attach to hard substratum

• Filter feeders

• Found in the intertidal region

– pressure is high from predation, desiccation, wave action, and competition for space.

Ex. Ostracods

• One of the most successful crustacean groups– ~ 8000 living species.

Subphylum: Chelicerata

• Class Pycnogonida (sea spiders)

• Class Merostomata (horseshoe crabs)

Class Pycnogonida

• Sea Spiders

http://www.youtube.com/watch?v=SV4SYSsnMug

CLASSIFICATION

Class Merostomata

Example: HORSESHOE CRAB

There are only 4 extant species.

Shallow water; marine/brackish

Large dorsal CARAPACE (EXOSKELETON SHIELD COVERING THE HEAD, THORAX AND GILL CHAMBER)

Long TELSON (TAIL-LIKE EXTENSION; USED IN BACKWARD SWIMMING)

Breathe with BOOK GILLS

HORSESHOE CRAB

The horseshoe crab plays a vital, if little-known, role in the life of anyone who has

received an injectable medication. An extract of the horseshoe crab's blood is

used by the pharmaceutical and medical device industries to ensure that their

products, e.g., intravenous drugs, vaccines, and medical devices, are free of

bacterial contamination. No other test works as easily or reliably for this purpose.

Used as bait for eels.

Use hemocyanin to carry oxygen throughout their bodies so blood is blue!

CLASSIFICATION

Class Copepoda

Largest part of marine PRODUCTIVITY.

Link SMALLEST plankton to LARGEST filter feeders

in marine food webs.