PHYLUM ARTHROPODA

Subphylum Crustacea: Aquatic Mandibulates

Diversity Over 67,000 species worldwide

Live in aquatic environments (both ocean and freshwater)

Can burrow, creep on bottom of ocean floor Some are sessile/permanently fixed

(barnacles) Examples include: crabs, crayfish,

lobster, shrimp, water fleas, brine shrimp, barnacle, daphnia, fish louse (parasite), krill, pill bugs (rollie pollies)

Called crustaceans

Diversity Some are edible (lobster, shrimp,

crayfish, crabs) Others are parasites to other ocean-

going organisms Fill a wide range of ecological roles and

have enormous variationFood, bioindicators, etc

Called Mandibulates Why? Because of the many pairs of sensory,

chewing, food-handling appendages

Characteristics of Aquatic Mandibulates

Most have two body regions: ○1) Abdomen

Long narrow Tail regionIncludes the telson and uropod

Most have two body regions: ○ 2) Cephalothorax

fused head and thorax—chest region, appendages attached to this segmentcovered by a carapace - Def: a cuticle composed of chitin, protein and calcareous material- Used for protection but is very flexible- Carapace covers most of the cephalothorax

Characteristics of Aquatic Mandibulates

Appendages○ All appendages are biramous (two

main branches)○ First two pair:

Antennae (2 pair – this distinguishes them from all other arthropods)

○Next pair:Jaw-like mandibles Used to chew and crush food

○Next pair:Maxillae Used to hold food

Characteristics of Aquatic Mandibulates

Appendages, cont. ○ Three pairs of jaw feet called

maxillipedsUsed to touch, taste and handle food

○Claws for catching food○One pair of walking legs for each

segment (four pairs total)○ Swimmerets on the abdomen

Used for swimming and to catch sperm

Characteristics of Aquatic Mandibulates

Respiration○ Gills (if present)○ Some use diffusion for respiration

Segments○ Most have 16-20 segments (some have

more)Nervous System○ Nerve cord on ventral side that swells to

gangliaDigestive system○ Digestive gland mixes food with digestive

enzyme○ Stomach, intestines, anus

Characteristics of Aquatic Mandibulates

Characteristics of Aquatic Mandibulates

Excretory system○Green gland—regulates amount of salt

in bodyReproduction○Gonopores—pores that release

reproductive cellsThe position of these varies according to sexLocation: at the base of a pair of swimmerets

or on segments without legs

Classification Subphylum Crustacea

Class RemipediaClass CephalocaridaClass Branchiopoda○ Orders: Anostraca (Fairy Shrimp, Brine

Shrimp), Notostraca (tadpole shrimp), Diplostraca (water fleas, clam shrimp)

Fairy shrimp

Brine shrimp Tadpole shrimp Water flea

Classification Subphylum Crustacea,

cont. Class OstracodaClass Maxillopoda○ Subclasses: Copepoda,

Tantulocarida, Branchiura (fish lice), Cerripedia (barnacles)

Class Malocostraca○ Orders: Isopoda (pill bug),

Amphipoda, Euphasiacea (krill), Decapoda (shrimps, crabs, lobsters)

Fish lice

Copepods

Classification Decapods (Order

Decapoda)Crayfish, lobsters,

shrimp, crabs10 walking legsCarnivoresEyes on stalksfirst three pairs of

appendages modified for eating

Isopods (Order Isopoda)Pill bugs, sow bugsFeed on dead,

decaying matterObtain oxygen

from air/moist soilno carapaceeyes are not

stalkedgills on

appendages

Classification

Cerripeds (Subclass Cerripedia)BarnaclesShelled, sessileNo eyes, gills, heart

or blood vessels

Classification

Giant Barnacles

Copepods○ Smallest in

size○ Plankton, Krill○ Feed on algae○No gills or

abdominal appendages

Classification

Crayfish External Dissection

Crayfish Characteristics

General Characteristics○ freshwater aquatic invertebrate ○ typically 6 to 8 cm in length, may

be as long as 12 cm ○ jointed exoskeleton ○ body consists of cephalothorax and abdomen

Crayfish Characteristics

General Characteristics, cont. ○ paired, jointed appendages ○ head has 2 pairs of antennae, 1

pair of mandibles, and 2 pairs of maxillae

○ undergoes ecdysis (shedding of the exoskeleton to accomplish an increase in body size)

Digestive System○ The digestive tract consists of:

1) the foregut, - includes an enlarged stomach (grinding)

2) the midgut3) the hindgut (functions in water and salt)

regulation. 4) anus5) digestive gland - secretes digestive enzymes and aids in the absorption of the products of digestion.

Crayfish Characteristics

Excretory System○ Excretory organs are called the

antennal glands ○ They excrete the waste products of

blood filtration; ○ Ammonia is the primary waste

product. Ammonia is also excreted across the gill

surfaces and by diffusion across thin parts of the exoskeleton.

Crayfish Characteristics

Respiratory System○Use gills

The gills are located in between the carapace (the exoskeleton of the cephalothorax) and the body wall.

Circulatory System○ The circulatory system of the

crayfish is centered around a muscular heart

Crayfish Characteristics

Nervous System○ The crayfish nervous system is

composed of a ventral nerve cord ○Concentrated ganglia (anterior end)○Giant neurons in the ventral nerve

cord function in escape responses.

Crayfish Characteristics

Endocrine System○ The endocrine glands

Release hormones into the blood

○ The hormones control functions, such as ecdysis, sex determination, color change and regulation of heart rate

Crayfish Characteristics

Sensory Structures○ Chemoreceptors ○ Tactile receptors

function in equilibrium, balance, and position senses

○ Statocysts functions in movement and orientation

○ Ocelli (simple eye)allows larvae to go toward or away from lightdoes not form images

○ Compound eyes mounted on moveable eyestalks lens system made of 14,000 individual receptors

Crayfish Characteristics

Sexual Characteristics and Reproduction○Crayfish have separate sexes.○Mating occurs just after the female has

molted (usually in the spring). ○Once they leave their mother, they

begin an adult life and reach maturity in anywhere from a few months to a year.

○ The average life span for a crayfish is two to three years.

Crayfish Characteristics

Crayfish Internal DissectionAnother dissection

Predator / Prey Relationships○ Feed on living animals and plants, ○ Also consume a fair amount of

dead plants, dead or dying animals, and detritus.

○Crayfish are omnivores. ○Crayfish do not prey on larger

animals, such as fish

Crayfish Characteristics

PHYLUM ARTHROPODA

Terrestrial Mandibulates: Spiders and Insects

CharacteristicsSegmented bodies Jointed appendages ○ Specialized for eating, sensing,

reproduction, defense and movementExoskeleton○ Hard covering on the outside of the animal○ Limits the growth of the organism (must

shed)○ Muscles are attached to this layer○ Secreted by underlying epidermis ○ Shed (molted) at intervals

Bilateral symmetry Muscular system ○ Complex ○ Contains two types of muscles

Body cavity ○ Coelom is smaller in size  ○ Most of body cavity consists of

hemocoel (sinuses, or spaces, in the tissues)

○ Filled with blood

Characteristics

Digestion ○Complete digestive system 

Esophagus, crop, gizzard, midgut, hindgut and anus

○Mouthparts modified from appendages and adapted for different methods of feeding

Circulatory System○Open system○Dorsal contractile heart, arteries

Characteristics

Respiration○Obtain oxygen through:

1) body surface (diffusion), 2) gills, 3) tracheal (air tubes) – carry oxygen to muscles4) book lungs

○ Spiracles—small openings in the exoskeleton through which air opens

Characteristics

Water retention—3 structures ○ 1) Malpighian tubules—

excretory structures that remove metabolic wastes from blood and return water to the cells

○ 2) Exoskeleton—prevents water evaporation

○ 3) Book Lungs—gas exchange without water loss (also used in

respiration)

Characteristics

Excretory system○ Paired excretory glands in some ○ Same as the nephridial system of

annelids ○ Some with other excretory organs,

called Malpighian tubules

Characteristics

Nervous system○Contains same system of annelid

(with dorsal brain connected by a double nerve chain)

○ Fusion of ganglia in some species  ○Well-developed sensory organs

Compounds eyes with many lenses (can see motion and color)

Characteristics

Reproduction○ Sexes usually separate, ○ Paired reproductive organs and

ducts;  ○Usually internal fertilization; ○ often go through metamorphosis

(change in body form larva to adult)

Characteristics

Classification Phylum Arthropoda (most diverse

phylum)Subgroups of Terrestrial Arthropods: ○ Subphylum Chelicerata –

Characteristics of all:- six pairs of appendages that include - a pair of chelicerae, - a pair of pedipalps, and - 4 pairs of walking legs - No mandibles and no antennae.  - Suck up liquid food from their prey.- Two body segments (abdomen and cephalothorax)

Class Merostomata – ○ Horseshoe crabs are

practically unchanged ○ Have an unsegmented,

horseshoe-shaped carapace, and a broad abdomen, which has a long spine like telson.

○ Book gills are exposed.  ○ They feed at night on worms

and small mollusks and are harmless to humans.

○ Include horseshoe crabs

Classification

Class Arachnida – ○ over 50,000 species ○ Body organization:

cephalothorax, abdomen○ Examples: Spiders (35,000

species), scorpions, ticks, mites

Classification

Spiders: - hunt using strong legs and good eyes; weave silk for web (hunt and reproduction); fangs are modified chelicerae (liquefy prey with venom)

Scorpions:- long, segmented abdomen with a stinger;

Mites and Ticks: - mites have one body segment, eat bacteria or skin cells of humans; ticks are mostly parasitic, require blood before molting and can cause Rocky Mtn spotted fever

Classification

○Subphylum Uniramia – Characteristics:- Appendages are unbranched.  - Includes the insects and the myriapods (centipedes and millipedes). - Heads resemble the crustacean head but have only one pair of antennae, instead of two. - Also have a tympanic membrane for sound 

- Have mandibles and two pairs of maxillae- Respiration is by body surface and tracheal systems, - Although juveniles, if aquatic, may have gills.

Classification

○Class Chilopoda - They are active predators with a

preference for moist places such as under logs or stones, where they feed on earthworms, insects, etc.  

Each segment (they have between 10 and 70), except the one behind the head and the last two, bears one pair of appendages.

Include: centipedes

Classification

○Class Diplopoda – Include Millipedes Have cylindrical bodies made up of 25

to 100 segments. Abdominal segments each have two

pairs.Millipedes are less active than

centipedes Generally herbivorous, living on

decayed plant and animal matter

Classification

○Class Insecta – Most numerous and diverse of all

arthropods. - (There are more species of insects than species in all the other classes of animals combined!!)

Have three pairs of legs Usually have two pairs of wings (although

some have one pair of wings, or none)  Body organization: head, thorax, and

abdomen.- The head usually bears a pair of large compound eyes, a pair of antennae, and usually three ocelli.  

Classification