Phylum Arthropoda, Phylum Echinodermata

Phylum Arthropoda
-Largest group- more than all other animals combined
-Includes: spiders, scorpions, ticks, mites, crustaceans, millipedes, centipedes, and insects.
1. Used for food, pollination, dyes, produce silk, honey, beeswax, spread diseases, yield drugs, medicine, etc.
2. Found in all types of environments; parasitize plants and animals.
3. They are carnivores, herbivores, omnivores, symbiotic.
-Most are herbivores
4. Diversity among this phylum has no equal

A. External Features of Arthropods
1. Bilateral symmetry, a metameric body
-Larvae shows all segments
-Tagmata (tagma singular) which are segments fused into functional groups such as head and thorax
-This becomes the cephalothorax
-Occurs during the process of molting
2. Jointed Appendages; new to animals
-Helps them become more successful in adaptation
-Often specialized for walking, swimming, jumping, flying, eating
-Appendages can be modified into antennae, mouth parts, legs, etc., but not wings
3. Exoskeleton: new to animals
-Keeps animals small; larger exoskeletons mean more weight. It would have to be excessively thick for the muscles to work. This leads to lack of mobility.
- Metamorphosis is the term used that encompasses an arthropod’s stages from egg to adult
4. Compound eye- corneal lens at top
-Ommatidia- visual unit
-Rhabdom- light sensitive core
-Surrounding rhabdom are 8 retinal cells

TYPES OF COMPOUND EYES
1. Appositional eyes- results in an inverted image
-Pigment cells; bees

2. Superposition
-Give right side up image
-No pigment cells; moths

3. Simple eye or ocelli
-Distinguishes light from dark


B. Internal Features
-Reduced coelom
-No cilia
-Tubular gut, mouth- anus

1. Nervous system
a. Double chain of unsegmented ganglion
b. Most control is in the ventral ganglia
c. Brain: 3 fused pairs of dorsal ganglia at anterior end
-Act as an inhibitor; will stop a reaction
-Ex: copulation, eating etc.

2. Respiratory system
a. No major respiratory organs
b. Trachea: small cuticle-lined air ducts
-Tracheoles- branches of trachea
*for gas exchange
c. Spiracles- opening to outside- prevents water loss
-Have a valve to open/close
d. In chelicerates (some spiders) have book lungs- leaf like plates, w/ a chamber in which air can be drawn in or out
-Found in aquatic arthropods such as horse shoe crab

3. Circulatory system
a. Open
b. Heart is a longitudinal vessel

4. Excretory system- terrestrial arthropods
a. Malpighian Tubules- between hind and gut
-A way of concentrating waste; helps send nitrogenous waste to hind gut

5. Reproduction
a. Sexes are usually separate
b. Mostly internal fertilization
-Oviparous-eggs released, developed outside female
-Ovoviviparous- eggs developed inside the female

C. Subphylum Chelicerata

Class Arachnida
a. Spiders, ticks, daddy long legs, mites, scorpions, etc.
b. Terrestrial- most are harmless or beneficial
c. 6 pairs of appendages
-1 pair of chelicerae instead of jaws
a. Used for capturing and paralyzing their victims
b. Fanglike or pincers
-1 pair of pedipoles (male spiders use as copulatory organ)
-Many spiders have mating dance-specific movement- and make a noise by vibrating the abdomen
-4 pairs of walking legs
d. Most are carnivores except mites (this will be on the test)
e. Most have external digestion
-Turn solid food into liquid by enzyme
f. Breathe by trachea, book lungs, or both
g. 8 simple eyes used for detecting moving objects
-Eyesight considered poor
-Uses sensory setae to sample environment (hairs on legs)
h. Web-spinning behavior
-Dependant on silk glands which produce a protein secretion- very strong substance
i. Excretory- waste is mostly uric acid
-Dangerous- black widows and brown recluse spiders
-Ticks- blood eating external parasites of mammals, birds, and reptiles throughout the world (so scary!)

- Class Merostomata- horseshoe crab
a. Genus limulus
b. Ancient - 500 million yrs old
c. One pair of chelicera
d. 5 pairs of walking legs
-Last pair have leaf-like plates at tip for digging and locomotion
e. Book gills for gas exchange
f. Covered by carapace- hard plate over cephalothorax
g. Long spine like telson- tail piece
h. Scavenge muddy/sandy substrates for annelids, small mollusks, and other invertebrates
i. Dioecious male and female


D. Subphylum Crustacea
-Crabs, shrimp, lobsters, crayfish, barnacles, pillbugs, waterfleas, etc.
a. Barnacles used to be in the Phylum Echinodermata; they are now part of sessile crustaceans
b. Mainly marines- some freshwater
c. Only arthropods with two pairs of antennae
d. Some have carapace (shield on dorsal side) over the cephalothorax
(lobster crayfish...)
-Swimmerettes (5 pairs) are primarily swimming legs
-First pair used for brooding eggs (female) or copulation (male)
-Uropods-either side of telson, flipper like-used for steering
e. Some have various number of pairs of legs on abdomen and thorax
-Biramous (double branched) appendages have a leg/gill structure with a common root at the body segment
f. Compound eyes
g. Respiration: gas exchange takes place through the gills or cuticle
h. Excretory- have green glands (located in head) instead of malpighian tubules
i. Reproduction: most sexes are separate except barnacles which are hermaphroditic
-Majority of crustaceans produce a larvae called naupilus- ancient form

E. Subphylum Myriapoda
-Millipedes, centipedes
a. Uniramous legs

Class Chilopoda- centipedes
a. Predators; found in moist places; feed on insects
b. Head region then the body consist of numerous segments
c. One pair of legs per segment
-First pair has changed into poison claws (fangs to kill prey)

Class Diplopoda -millipedes
a. Most herbivores- found in decaying vegetation
b. Head region and body with numerous segments
c. 2 pairs of legs per segment
(Really 2 segments fused together)
d. Defense, foul fluid or gas

Subphylum Hexapoda

Class Insecta
1. Largest group of organisms on earth, either number of individuals or number of species
2. Study of insects: entomology
3. Found in all habitats; few aquatic
- Wide distribution due to wings
4. Morphologically more closely related to crustaceans.

A. External Features
-Tagmata found in head, thorax, abdomen
-Cuticle composed of 4 plates called sclerites

1. Head
a. Large pair of compound eyes
b. One pair of antennae
c. Three ocelli (simple eye)
d. Mouth Parts
-Determines how the insect feeds
-Review Figure 12.144, page 242

2. Thorax
a. Three parts- each with a pair of legs
-Prothorax, Mesothorax, Metathorax
b. Wings – 2 pairs
-One pair attached to the mesothorax
-Other pair to metathorax
-If only one pair, attached to the mesothorax
c. Filled with muscles to operate wings (analogous to bird and mammal wings, not homologous)

B. Internal Features:
1. Respiration
a. Trachea extends throughout the body
b. Spiracles
-Located between segments of thorax and abdomen

2. Digestion
a. Takes place in a coiled tube – digestive tract
-Found in midgut- called stomach

3. Excretion
a. Is facilitated by the malpighian tubules
b. Helps the insect with water and electrolyte balance
c. Waste empties into hindgut

4. Sensory Receptors
a. In addition to eyes
b. Sensory hairs – sensitive to touch
c. Taste organs on mouthparts
d. Smell- Located on antennae
e. Hearing – tympanal organs
f. Chemoreceptors help detect pheromones

5. Reproduction
a. Dioecious
b. Fertilization is internal
c. Sperm goes into female at time of copulation
d. Usually only one mate, one time
e. Lay a large number of eggs
f. Show some sexual dimorphism (sexes different sizes, female usually larger than male)

6. Life Histories of Insects
a. Ecdysis (molt) – Goes through 4 to 7 times
b. Metamorphosis – Change from egg to adult form
-Two types of Metamorphosis:
1. Simple: All immature forms look like adult
-These stages are called nymphs
-Think of dragonfly nymphs
2. Complete: Immature form looks different from adult
-These immature forms are called larvae
- Think of the butterfly
c. Start with egg  Larvae (wormlike, segmented)  Developmental stage, sometimes several, called pupa  (molt) Adult
d. Larvae could be: 1st instar larvae, 2nd instar larvae, etc. (stage between molts)


ECHINODERMS AND LESSER DEUTEROSTOMES

Phylum Echinodermata
a. All are marine forms
b. Sea stars (starfish), brittle stars, sea urchins, sand dollars, and sea cucumbers
-Belong to the deuterostome branch of the animal kingdom, and are coelomates. (Only major invertebrates that show an affinity to lower vertebrates)
c. All radially symmetrical as adults, but with a 5 part body plan in most
d. Bilateral as larvae – free swimming
e. Water vascular system: madreporite in most (opening on top)
-How it works, Example: Sea Star:
-Water enters madreporite, goes down tube to stone canal, to ring canal which gives rise to radial canal
-Responsible for movement – forces water into tube feet
-Ampulla – Sac that pushes water into tube foot and blocks it from coming back to radial canal
f. No head or brain
g. Nervous system – Central nerve ring with branches – primitive
h. Endoskeleton is of dermal calcareous ossicles (plates) with spines covered by epidermis.
-Name derived from this feature (Greek = spiny skin)
i. Locomotion is by tube feet or by movement from arms which project from central disc of body
j. Respiration and excretion is handled by skin gills located in between spines
k. Has ability to regenerate lost parts; cut arms off or break in half
l. Reproduction – Some by regeneration
-Most by sexual reproduction
-Most have separate sexes
-Fertilization is external; Larvae free swimming
-Larvae different than trocophore larvae of mollusks

A. Class Crinoidea
1. Sea lilies and feather stars
2. Mouth and anus on upper surfaces of disk (oral side)
3. Filter feeders; mostly sessile (Figures14.18, 14.19)
4. 5 radial arms branch into other arms that support pinnules (feather-like structures)
5. Body Plans:
-Stalks – Attached organism to substrate (sea lilies)
-Claw-like structure- Anchors to substrate (feather stars)
6. Fertilization is external
-Female shelters larvae (brooding)

B. Class Asteroidia
1. True sea stars or starfish (some have more than 5 arms)
-Epidermis has pigment
-These are most familiar to us
-Found shallow to very deep
2. Important marine predators
-Help keep things in balance
3. Mouth is on lower surface
4. Can extrude the stomach through their mouth, killing and partially digesting their prey outside their body
5. Lab: Asterias

C. Class Ophiuroidea:
1. Brittle star
2. Have slender branched arms
-Which are brittle with spines
-Number of spines depends on species
-Arms move from side-to-side – Like rowing a boat
3. Feed on microplankton; many are scavengers and will eat just about anything
4. Lab: Ophiura

D. Class Echinoidea
1. Sea urchins, sand dollars, sea biscuits (page 283, Figure 14.14)
2. No distinct arms; have 5 part body plan
3. Move with tube feet with suckers
-Some have moveable spines
4. Feed on algae or planktonic organisms
5. Lab: Arbacia

E. Class Holothuroidea:
1. Sea cucumbers (delicacy)
2. Elongated, leather body (the prettier they are, the more toxic they are)
3. No arms, spines absent
4. Microscopic ossicles (plates) embedded in thick, muscular walls
-Ossicles – calcareous material
5. Used in the orient as a food and for medicinal value
-Helps heal wounds more quickly and reduces scarring.