Ch. 17: 321-348; RQ-17: 2, 5, 6, 8, 9, 11, 13
See hand-out lecture notes from class
Ch. 18: 350-357, 366-368; RQ-18: 1, 5-6, 8, 12
Ch. 19: 369-381; RQ-19: 1-6, 9
Ch. 20: 384-392, 399-403; RQ-20: 1, 4-9
Ch. 21: 404-421, 426-429; RQ-21: 1-4, 6, 7, 9, 10, 18
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Ch. 18 Lecture notes:
Annelida (about 15,000 species) Ð "many little rings"
Most diverse are polychaete annelids Ð "many setae"
These include all annelids except "clitellate" annelids
Clitellates have a clitellum used in reproduction
Clitellates include earthworms and leeches
(see cladogram on p. 366, will cover in lab)
Polychaetes are diverse, mostly marine, annelids
Two ways to characterize polychaete diversity:
1) crawlers vs. burrowers vs. tube-builders
Example of crawler: Nereis (Fig. 18-3, 18-7)
crawlers use setae on ventral parapodia (lateral lobes) neuropodia
setae supported by acicula (rods)
paired coeloms in each segment acts as hydrostatic skeleton
coeloms separated by mesentery tissue (Fig. 18.1)
surrounded by longitudinal and circular muscles
dorsal parapodia are used as gills (notopodia)
"head" is made up of prostomium (eyes, brain, sensory palps) and peristomium (jaws, surrounds mouth)
2) Burrowers emphasize hydrostatic skeleton
Examples: Amphitrite (Fig. 18-4), Arenicola (18-5), earthworm (p. 634)
3) Tube-builders live in blind tube (a sanitation problem for a bilateral animal)
Usually feed with tentacles
Another way to contrast polychaetes:
1) macrofeeders (e.g., Nereis feeds on worms)
2) tentaculate detritus feeders
Example: Arenicola, Amphitrite
tentacles u-shaped in cross-section
cilia in food groove bring particles to animal
cilia outside of groove move tentacle away
3) tentaculate suspension feeders
Example: Sabella (Fig. 18-10)
Review Questions for Arthropods (Chs. 19-21):
What are important distinguishing features of arthropods? (RQ 19: 1)
What are important differences in the body plans of the following main groups of arthropods?
Chelicerates
Myriapods
Crustaceans
Insects
What appendages are characteristic of each of the above?
Contrast an arthropod with an annelid?
Similarities?
Differences?
Contrast segmentation in an annelid and an arthropod.
What is tagmatization?
What are the tagmata and the appendages on the head of a crustacean?
What is serial homology?
How is an arthropod exoskeleton formed?
The cuticle is made up of what layers?
Describe the molting process.
What is the role of ecdysone?
What are the X- and Y-organs of a crayfish?
How does ecdysone interact with brain and juvenile hormones in insects?
Where are each of these produced?
Are you familiar with the underlined groups in the arthropod classification handout?
Specifically, are you familiar with the following taxa?
onychophoran
trilobite
horseshoe crab
scorpion
mite
arachnid
Remipedia (remipedes)
Cephalocarida (cephalocarids)
Branchiopoda (incl. brine shrimps)
Maxillopoda (incl. copepods and barnacles)
Malacostraca (incl. isopods and decapods)
bristletails, springtails (wingless insects)
mayflies, dragonflies, grasshoppers, etc. (hemimetabolous winged insects)
beetles, flies, butterflies and moths, ants bees and wasps, etc. (holometabolous winged insects)
What is a hemocoel and which animals have one?
How is this different from a coelom?
How does a crayfish respire?
What is the function of antennal (green) glands in crustaceans?
Describe the components that make up a compound eye.
How does the compound eye adjust to varying light levels?
What groups of crustaceans have a nauplius?
What are some other crustacean larval stages?
What is caridoid facies?
What is an example of a myriapod?
What are Diplopodans and Chilopodans?
Describe the sensory receptors on insect antennae.
How does an insect walk?
Why do indirect flight muscles beat much more rapidly than direct flight muscles?
What are halteres?
Which arthropods have trachea?
Which insects have tracheal gills?
What are spiracles?
Contrast hemi- and holometabolous insects.
Give some examples of insect sensory organs and describe their function.
What were the main points made in the guest lecture on insects?
May get to this in lecture: Contrast the Eutrochozoa and Articulata phylogenetic hypotheses.
What other phyla, besides molluscs and annelds, does Eutrochozoa include?
From an earlier lecture, what is Ecdysozoa, and what features do ecdysozoans share?
What are the closest living outgroups for arthropods?
Which groups (orders) of insects have the most species?
Why is there such a great diversity of insect species?
Lecture Notes for Monday 4/3/00
Introduction to Insects
Ch. 21: 404-421, 426-429; RQ-21: 1-4, 6, 7, 9, 10, 18
Terms for today
o homeotic genes
o wingless vs. winged insects
o incomplete vs. complete metamorphosis
o hemimetabolous vs. holometabolous
o insect anatomy
o tracheae, tracheal gills, spiracles
o malpighian tubules, uric acid
o sensilla
o endo- vs. ectognathous mouthparts
Over 1 million species arthropods described
Mostly insects
Mostly beetles, flies, moths, wasps
Estimated 10 to 100 million undescribed
Why so many?
1) Long evolutionary history (540+ My)
2) broad size range/habitat utilization
3) metameric body plan/rigid exoskeleton
4) profound influence of homeotic genes (read pp. 115-116)
5) co-evolution with plants/algae
6) evolution of flight
Insect Diversity
29 orders total
o 4 wingless (apterygotes) - examples: bristletails, springtails
o 16 hemimetabolous winged (exopterygotes) (incomplete metamorphosis)
examples: mayflies, dragonflies, grasshoppers, stick insects, earwigs, roaches, termites, true bugs
o 9 holometabolous winged (endopterygotes) (complete metamorphosis)
examples: lacewings, fleas, beetles, flies, butterflies and moths, caddis flies, ants bees and wasps
Most insect species are holometabolous
Could have something to do with mixed life cycle: offspring are ecologically different from adults
Most insect biomass is from ants and termites:
Each represents about 10% of all animal biomass
Insect Anatomy (Head Ð Thorax Ð Abdomen)
Head Ð bears eyes (usually compound), antennae, mouthparts
Mouthparts Ð chewing (grasshoppers), sucking with stylet (bugs & aphids), sucking with coiled tongue (butterflies), etc.
Antennae Ð used to detect odors or as tactile organs
Thorax Ð 3 segments, with 3 prs. legs, winged insects normally have 2 pairs of wings
Legs Ð 6 legs (Hexapoda)
Each thoracic segment supports 1 pr.
Legs are segmented
Last segment often bears small claw
Some have legs specialized for jumping
Wings Ð probably arose once in common ancestor
Most insects have two pairs
Flies have 1 pr. (front pr. modified as halteres)
Most membranous Ð some leathery or hard
Sometimes wings bear hairs or scales
Abdomen Ð 11 segments
Bears external genitalia (e.g., ovipositor)
Gas Exchange
Insect cuticle highly resistant to water loss
This presents challenge for gas exchange
Problem solved with tracheal system
Tracheae are highly-branched cuticular tubes
Open to outside through spiracles
Taper down from 1+ mm to 0.0001 mm
Can provide oxygen directly where it is needed
Aquatic insects have tracheal gills
Excretion/Water Balance
Insects/spiders have malpighian tubules
Potasium, other solutes, secreted into tubules
Secreted as uric acid
See Fig. 21-18 (wasp)
Sense Organs
mechanical, auditory, chemical, visual, other
mechanoreception Ð sensilla
auditory Ð setae or tympanal organs
chemoreception Ð taste, smell
visual Ð simple or compound
Reproduction
Separate sexes attract each other
Internal fertilization Ð sperm or sperm packets
Females copulate 1 to many times
Eggs laid where some cue guides female
Most insects undergo change in form in life
Insect between each molt is instar
Metamorphosis can be incomplete or complete
Hemimetabolous insects: incomplete
egg Ð> nymphs Ð> adult
nymphs have external wing pads
Holometabolous insects: complete
egg Ð> larva Ð> pupa Ð> adult
wing pads internal in larvae
Hormones regulate metamorphosis (see p. 743)
brain (intercerebral) Ð> brain hormone
prothoracic glands Ð> molting hormone (ecdysone)
corpora allata Ð> juvenile hormone (delays adulthood)
Lecture on Locomotion and Support
See Ch. 32 but some only in lecture notes
(see Web site)
Skeletons
- Metazoans all depend on a skeleton
- Particularly important for locomotion
Animals
dramatic size increase
single- to multicellular
directed movement
Evolution of mutual systems
locomotion and support
Four locomotory patterns
ameboid
ciliary/flagellar
hydrostatic
limb
Most animals live in water
move through water
or move water over body
Face problems of fluid dynamics
solid body with surrounding liquid
The size of an animal can dramatically affect its locomotion in water
Reynolds Number (Re)
dimensionless ratio:
inertial forces/viscous forces
(body size)(fluid speed)
ÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ
(kinematic viscosity)
Useful for characterizing organismÕs life:
size: small <-> large
Re: low <-> high
fluid viscosity: high <-> low
inertia: low <-> high
currents: laminar <-> turbulent
Animals swimming through water behave differently:
Large "nekton" (inertial forces dominate)
Large whale (v = 10 m/sec)
Re = 300,000,000
Tuna (v = 10 m/sec)
Re = 30,000,000
- viscosity unimportant
- inertia carries animal forward
- flow of water becomes turbulent
Small "plankton" (viscosity dominates)
Copepod (v = 20 cm/sec)
Re = 300
Typical metazoan larva (v = 1 mm/sec)
Re = 0.3
Sperm (v = 0.2 mm/sec)
Re = 0.03
- inertia/turbulence nonexistent
- like swimming through liquid tar
- start/stop instantaneously
Scale effects in terrestrial animals
- surface increases as square while
volume increases as cube
- big animals require greater
respiration
circulation
thermal regulation (cooling off)
support from legs (fig. 32-8, p. 630)
- muscles of small and large animals
same force per x-sectional area
grasshopper carries 50x its weight
leap many times their height
horse could not carry its own weight
chipmunks run in crouched posture
elephants need their legs underneath
largest dinosaurs had fat legs
Ameboid locomotion
- many protists
- internal ameboid cells
Gel-like ectoplasm
surrounded by
more fluid endoplasm
pseudopodia develop
endoplasm flows in
becomes semi-rigid ectoplasm at tip
involves actin/myosin/ATP
similar to muscle contraction
Cilia and flagella
- ultrastructure identical
- cilia short and in clusters
- flagella long and single or paired
- found in all animals except arthropods
- can move animal through water
- or move water over animal
- but always at low Re
Fluid (hydrostatic) skeleton
- most widespread type
- fluid is sealed within tissues
- tissues can also be used for skeletons
- total volume must remain constant
- reduction in one region causes a
compensatory enlargement
- usually two or more layers of muscles
at different orientations
Rigid skeleton
- complement/replace fluid skeletons
- durable, strong, fossilize easily
- exoskeletons - secreted by ectoderm
- endoskeletons - secreted by mesoderm
- can be entirely organic -
chitin is a tough polysaccharide
can be cross-linked with proteins
- others mineralized
calcium carbonate - molluscs, etc.
calcium phosphate - vertebrates
Rigid skeleton (limbs)
- muscles act against skeleton
- this action converted to movement
- restretched by antagonistic forces
- others use elastic structures
- most muscles have discrete origin
e.g., biceps - on scapula
- most muscles have an insertion
e.g., biceps - on radius
flexors and extensors
extend across joint
protractors and retractors
ant./post. movement of limb
adductors and abductors
part moved toward/away
- other muscles interlaced
e.g., snail foot, gut wall muscles
- some muscles "quick"
e.g., rapid shell closing in clams
- others "catch"
e.g., used for holding shell closed
© D. J. Eernisse
These notes may not be reposted or used for any commercial purpose without the written permission of Prof. Eernisse (deernisse@fullerton.edu).