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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
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