Following pages and RQs refer to 11th Edition.
Ch. 15 ("pseudocoelomates"): 304-317, 320-323; RQ-15: 1-6, 11-14, 20
Ch. 16 (Molluscs): All; RQ-16: 2, 5, 6, 8, 9, 11, 13
Ch. 17 (Annelids): 356-364, 371-374; RQ-17: 1, 5-6, 8, 12
Ch. 18 (Arthropods) (All); RQ-18: 1-6, 9
Ch. 19 (Arthropods): 389-399, 406-409; RQ-19: 1, 4-9
Ch. 20 (Arthropods): 411-427, 432-437; RQ-20: 1-4, 6, 7, 9, 10, 18
Ch. 32: reference for lecture on support and locomotion
Here are corresponding pages in 10th Edition.
(10th - Ch. 16 ("pseudocoelomates"): 301-313, 317-319; RQ-16: 1-6, 11-14, 20*, hand-out xerox of 11th Ed. p. 320)
*different RQ#20: If rotifers and gastrotrichs are lophotrochozoans and nematodes, nematomorphs, priapulids, and kinorhynchs are ecdysozoans, what is the effect on a taxon called Aschelminthes? Why?)
(10th - Ch. 17 (Molluscs): All; RQ-17: 2, 5, 6, 8, 9, 11, 13)
(10th - Ch. 18 (Annelids): 350-357, 366-368; RQ-18: 1, 5-6, 8, 12)
(10th - Ch. 19 (Arthropods) (All); RQ-19: 1-6, 9)
(10th - Ch. 20 (Arthropods): 383-392, 399-403; RQ-20: 1, 4-9)
(10th - Ch. 21 (Arthropods): 404-421, 426-429; RQ-21: 1-4, 6, 7, 9, 10, 18)
(10th - Ch. 32: reference for lecture on support and locomotion)
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Notes for Pseudocoelomate Lecture:
Terms
pseudocoelom (from embryonic blastocoel)
tube-within-a-tube
cuticle (often made of chitin)
molting
eutely (nuclear constancy)
Concepts
two views of bilaterian ancestor
pseudocoelomates are polyphyletic
common traits of tiny animals
alternate asexual/sexual reproduction in rotifers
Micrometazoans
1. Minute animals
2. Copulate
3. Eutely (cell or nuclear constancy)
4. Body does not divide asexually
5. Little or no regeneration
6. Presence of anus (some reduced)
7. body cavity modified
(pseudocoelom with more or less
fluid depending on whether or not
there is eversible organ present)
Pseudocoelomate phyla:
Priapulida (actually quite large worms)
Kinorhyncha (kinorhynchs)
Loricifera (loriciferans, only discovered in 1970s)
Gastrotricha (gastrotrichs)
Nematoda (some of parasitic members get very large)
Nematomorpha (horsehair worms)
Rotifera (rotifers)
Acanthocephala (these are probably a derived type of rotifer)
Tardigrada (water bears)
We will emphasize rotifers and nematodes
Nematoda (nematodes)
Enormous number of species
- Ranks 3rd after arthropods and molluscs (number of described species)
- Probably should be 1st (Not enough nematode taxonomists)
Every conceivable habitat on Earth
- Enormous numbers
- Many are free-living
- Also important animal/plant parasites
- Parasites resemble flatworms in adaptations
Extremely important as model system - C. elegans ("the worm") is nematode lab rat
Rotifers
- feed with ciliated crown, the corona
- "chew" with mastax
- hang on with pedal glands
- about 1,800 species, mostly in freshwater
- show nuclear constancy (eutely)
- can often endure prolonged desiccation
- "just add water" for resumed activity
- usually large females and small males
- the bdelloids have only females
- these females are parthenogens (asexual)
- the monogononts alternate between asexual and sexual reproduction (Fig. 15-4)
- haploid egg + sperm = dormant zygote
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Mollusca ("molluscs" or "mollusks")
Terms
radula
mantle
mantle cavity
ctenidium
foot
coiling vs. torsion
siphuncle
Classification based on Fig. 16-42 (10th- 17-42)
Mollusca (> 100,000 species - esp. snails) **Caudofoveata (burrowers) **Solenogasters (cnidarian-feeders) **Testaria (shelled molluscs) ****Polyplacophora (chitons) ****Conchifera (discrete shell gland; includes snails, squids, clams, etc.)
Note: Testaria and Conchifera are not labeled in Fig. 16-42 (10th: 17-42) - Can you find them?
Common molluscan features (none in all)
- radula
- muscular creeping foot
- visceral mass (gut, blood, gonads)
- mantle
- shell
- mantle cavity
- ctenidia (gills)
- trochophore larva
- spiral cleavage
- coelomic heart cavity
- hemocyanin blood pigments
"aplacophorans" (did not cover in lecture)
- mostly in deep sea and poorly known
- lack shell but have spicules in mantle, like a chiton
- with or without foot groove
- with or without gill (ctenidium)
- have radula (secondarily lost in some)
- little evidence of serial repetition
chitons
- eight shell plates
- repeated gills, shell muscles
- creeping foot
- radula like a limpet/monoplacophoran
- teeth mineralized with magnetite (iron)
- many sensory organs in shells and girdle
- serial repetition (ancestral or derived?)
conchiferans (all molluscs except chitons and aplacophorans)
- single shell, discrete shell gland
- periostracum
- prismatic and nacreous shell layers
- mantle margin with three folds
- crystalline style
- no spicules in mantle
- some have serial repetition (monoplacophorans, Nautilus)
Molluscs and Humans
1. Positive aspects
- Food (e.g., oyster farm produces 20 times meat/acre as a cattle farm)
- Rich cultural history, inspirations in art
- Currency (NW Native Americans used scaphopods - "wompom")
2. Negative aspects
- Introduced pests
slugs
carnivorous snails in Pacific islands
Corbicula - a clam introduced "for fish bait" from Asia, clogs dams
zebra mussel - larvae transported in bilge water to Great Lakes - huge ecological and financial impact
- Bankia - bivalve "shipworm" bores into wood, tremendous destruction
- Schistosomiasis flatworm parasite uses snails for intermediate host - widespread in tropical areas with primitive sewage treatment
- venomous - snail Conus and blue-ringed octopus can be deadly
Gastropods (snails, slugs: >> 50,000 species)
"prosobranchs" are all snails except the
clade of opisthobranchs + pulmonates
About half of all snail species
Includes, limpets, abalones, keyholes,
diverse marine snails including trochaceans, neogastropods
Opisthobranchs -diverse but few species
-shell internal or absent
-includes Aplysia, nudibranchs
Pulmonates -half of all snail species -
-lungs instead of gills
-lining of mantle cavity takes over
-coincide with invasion of land
Evolutionary Trends in Gastropod Gills: (see Fig. 16-17; 10th: 17-17)
"prosobranchs"
two gills (abalone, key hole limpets)
reduce right gill
loss of right gill (limpets)
monopectinate gill fused to mantle
opisthobranchs -secondary gill
pulmonates - lungs
Gastropod Features:
1. Torsion - important synapomorphy (does not = coiling)
upper part is twisted nearly 180¡ from lower part (See Fig. 16-13; 10th: 17-13)
mantle cavity moves from back to front
hypotheses:
- helps larval "veliger" pull its head inside its shell (Walter Garstang)
- helps the adult carry weight of shell
2. Coiling
snails protect themselves:
clamping, withdrawing, locomotion
coiling helps a high uncoiled shell would be hard to carry - high center of gravity, frontal cross-section great
shell is usually tilted (See Fig. 16-14; 10th: 17-14)
most shells coil to right (dextral)
some coil to left (sinistral)
Parameters of coiling - see p. 334 (10th-329):
amount of translation (T)
- isotrophic (T = 0) [planispiral]
- orthostrophic (T is negative)
- hyperstrophic (T is positive)
whorl expansion rate (W)
- long pointed shells (W is low)
- broad shells (W is high)
distance from axis of coiling (D)
- hollow center as D increases
Of possible combinations of T, W, D snail examples for many but not all
Cephalopods
have large head like their snail relatives
all predators
use muscles, not cilia, for locomotion (siphon)
synapomorphy is siphuncle, but this is lost as shell is internalized, reduced
Nautilus -> Spirula -> Sepia -> Loligo
Nautilus has eyes like pinhole cameras
Squids have much more complex eyes (direct, not indirect as in vertebrates)
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Annelid Lecture notes:
Annelida (about 15,000 species) - "many little rings"
Most diverse are polychaete annelids - "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. 372 (366 in 10th)
Note that the clitellum is a synapomorphy uniting earthworms and leeches (Clitellata)
Polychaetes are diverse, mostly marine, annelids
Two ways to characterize polychaete diversity:
1) crawlers vs. burrowers vs. tube-builders
Example of crawler: Nereis - Fig. 17-3, 17-7 (10th - 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. 17.1)
surrounded by longitudinal and circular muscles
dorsal parapodia are used as gills (notopodia)
"head" is made up of two parts: -prostomium (eyes, brain, sensory palps)
-peristomium (jaws, surrounds mouth)
2) Burrowers emphasize hydrostatic skeleton
Examples: Amphitrite (Fig. 17-4; 10th: 18-4), Arenicola (17-5; 10th: 18-5), earthworm (17-12; 31-5 on p. 647; 10th: 18-12, 32-4 p. 634)
3) Tube-builders live in blind tube (a sanitation problem for a bilateral animal)
Usually feed with tentacles (see fig. 17-2, 17-10; 10th - 18-2, 18-10)
Another way to contrast polychaetes:
1) macrofeeders (e.g., Nereis feeds on worms)
2) tentaculate detritus feeders
Example: Amphitrite
tentacles u-shaped in cross-section (Fig. 17-4a-d; 10th - 18-4a-d)
cilia in food groove bring particles to animal
cilia outside of groove move tentacle away
3) tentaculate suspension feeders
Example: Sabella (Fig. 17-10; 10th-18-10)
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Review Questions for Arthropods (Chs. 18-20; 10th: Chs. 19-21):
What are important distinguishing features of arthropods? (RQ 18: 1; 10th: 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? (Monday before Exam 2)
According to new views of animal relationships based on ribosomal DNA sequence comparsons:
-Are arthropods members of Ecdysozoa or Lophotrochozoa?
-Are annelids members of Ecdysozoa or Lophotrochozoa?
-Are molluscs members of Ecdysozoa or Lophotrochozoa?
-Which "pseudocoelomate" groups are members of Ecdysozoa?
From an earlier lecture, 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 Insects
Introduction to Insects
Terms for today
o homeotic genes (covered earlier in semester - see Figs. 8-16, 8-17; 10th- 7-17, 7-18)
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) co-evolution with plants
5) evolution of flight
Insect Diversity
29 orders total
- 4 wingless (apterygotes) - examples: bristletails, springtails
- 16 hemimetabolous winged (exopterygotes) (incomplete metamorphosis)
examples: mayflies, dragonflies, grasshoppers, stick insects, earwigs, roaches, termites, true bugs
- 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 - Thorax - Abdomen)
Head - bears eyes (usually compound), antennae, mouthparts
Mouthparts - chewing (grasshoppers), sucking with stylet (bugs & aphids), sucking with coiled tongue (butterflies), etc.
Antennae - used to detect odors or as tactile organs
Thorax - 3 segments, with 3 prs. legs, winged insects normally have 2 pairs of wings
Legs - 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 - probably arose once in common ancestor
Most insects have two pairs
Flies have 1 pr. (front pr. modified as halteres)
Most membranous - some leathery or hard
Sometimes wings bear hairs or scales
Direct vs. indirect flight muscles (see Fig. 20-12; 10th- 21-12)
Abdomen - 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. 20-20 (wasp) (10th- 21-18)
Sense Organs
mechanical, auditory, chemical, visual, other
mechanoreception - sensilla
auditory - setae or tympanal organs
chemoreception - taste, smell
visual - simple or compound
Reproduction
Separate sexes attract each other
Internal fertilization - 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 -> nymphs -> adult
nymphs have external wing pads
Holometabolous insects: complete
egg -> larva -> pupa -> adult
wing pads internal in larvae
Hormones regulate metamorphosis (see pp. 425-426, 755; 10th- pp. 417-419, p. 743)
brain (intercerebral) -> brain hormone
prothoracic glands -> molting hormone (ecdysone)
corpora allata -> juvenile hormone (delays adulthood)
Lecture on Locomotion and Support
See Ch. 31 (10th-32) but some only in lecture notes
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)
------------------------
(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. 31-10, p. 652; 10th- p. 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 (see Fig. 31-12, p. 654; 10th- 32-10, p. 641)
- 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 (see Fig. 31-5, 31-6; 10th- 32-4, 32-5)
- 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).