Transcript 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 variation

 Food, 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 region
 Includes the telson and uropod
Characteristics of Aquatic
Mandibulates
 Most have two body regions:
○ 2) Cephalothorax
 fused head and thorax—chest region,
 appendages attached to this
segment
 covered 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 maxillipeds
 Used 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 ganglia
 Digestive system
○ Digestive gland mixes food with digestive enzyme
○ Stomach, intestines, anus
Characteristics of Aquatic
Mandibulates
 Excretory system
○ Green gland—regulates amount of salt in
body
 Reproduction
○ Gonopores—pores that release reproductive
cells
 The position of these varies according to sex
 Location: at the base of a pair of swimmerets or
on segments without legs
Classification

Subphylum Crustacea
 Class Remipedia
Fairy shrimp
 Class Cephalocarida
 Class Branchiopoda
○ Orders: Anostraca (Fairy Shrimp, Brine Shrimp),
Notostraca (tadpole shrimp), Diplostraca (water
fleas, clam shrimp)
Tadpole shrimp
Water flea
Brine shrimp
Classification

Subphylum Crustacea, cont.
 Class Ostracoda
Fish lice
 Class Maxillopoda
○ Subclasses: Copepoda, Tantulocarida,
Branchiura (fish lice), Cerripedia
(barnacles)
 Class Malocostraca
○ Orders: Isopoda (pill bug),
Amphipoda, Euphasiacea (krill),
Decapoda (shrimps, crabs, lobsters)
Copepods
Classification
 Decapods
(Order
Decapoda)
 Crayfish, lobsters,
shrimp, crabs
 10 walking legs
 Carnivores
 Eyes on stalks
 first three pairs of
appendages
modified for eating
Classification
 Isopods
(Order
Isopoda)
 Pill bugs, sow bugs
 Feed on dead,
decaying matter
 Obtain oxygen from
air/moist soil
 no carapace
 eyes are not stalked
 gills on appendages
Classification
 Cerripeds
(Subclass
Cerripedia)
 Barnacles
 Shelled, sessile
 No eyes, gills, heart
or blood vessels
Giant Barnacles
Classification
 Copepods
○ Smallest in size
○ Plankton, Krill
○ Feed on algae
○ No gills or
abdominal
appendages
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)
Crayfish Characteristics
 Digestive System
○ The digestive tract consists of:
 1) the foregut,
- includes an enlarged stomach (grinding)
 2) the midgut
 3) the hindgut (functions in water and salt)
regulation.
 4) anus
 5) 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 light
 does 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 Internal Dissection
Another dissection
Crayfish Characteristics
 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
Terrestrial Mandibulates: Spiders and Insects
Characteristics
 Segmented bodies
 Jointed appendages
○ Specialized for eating, sensing, reproduction,
defense and movement
 Exoskeleton
○ 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
Characteristics
 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 muscles
 4) 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)
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)
Classification
 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.