Laboratory 10
Zoology 1121
Phylum Arthropoda
Quiz
I. Background
1. most species in world belong to this group…very diverse
2. arthropod means “jointed foot”…great way to classify this phylum
is to look at their legs and think “do
they have bendable joints”
3. also have an exoskeleton, which is a secretion from the epidermis
cell (outermost cells)
4. These can ditch their exoskeleton in order to get a bigger one in
a process called “molting”
II. Evolution
1. Most think they had split-off from annelids (earthworms) at some
point in the past. They are actually related to mollusca
as well. Both arthropods
and mollusca have an open circulation system for example, but unlike mollusca
(and like
annelid) the arthropods
are segmented.
2. This phylum has spread into all different kinds of environments.
As such, an important concept arises. This is the notion
of “adaptive radiation”
3. AR- carries the general idea of moving into new, unexploited habitats
in order to survive. Think, finding a new niche
4. Additionally, expect to see a redesigning of some similar structures
now modified to suit the new environment. For
example, the foot of the
P. Bivalvia versus the foot modifies into tentacles in P. Cephalopoda
5. Another idea, less stressed at this point, is they idea of “co-evolution”….
this is where we see two distinct life-forms
evolving in conjunction
together.
III. Phylum Classification –
- First time we see Sub-Phylum
classification
- All species in phylum
will share these characteristics.
I. Phylum Arthropoda
1. jointed appendages
2. presence of exoskeleton
3. segmented body plan
4. open circulatory system – note, blood and cavity fluid freely mix
together
5. Subphylum are basically based on antenna (no pairs, one pair, two
pairs)
II. Subphylum Trilobitomormpha
1. Extinct marine arthropods – look very similar to horseshoe crabs
and are found fossilized into rocks.
IV. Subphylum Chelicerata
1. No antennae present
2. First pair of appendages are specialized into pincers or fangs (called
chelicerae)
3. Two classes
a. 6 pairs of appendages
(5 of which are gills). . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . .C. Merostomata
b. Fused Cephalothorax with
6 types appendages on it as well (1 for fangs, 1 pedipalp,
& 4 for walking) . . . . . . . . . . C. Arachnida
V. Subphylum Uniramia
1. 1 pair antenna
2. Three Classes
a. Poison claws, one pair
legs per trunk segment . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . Class Chilopoda
b. No poison claws, 2 pair
legs per trunk segment . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . Class Diplopoda
c. Three pairs walking legs
per trunk segment, usually winged at some point in life . . . . .
. . . . . . . . Class Hexapoda
VI. Subphylum Crustacea
1. two pair of antennae on head
2. also, one pair mandibles and two pairs of maxillae
3. One class we have to know
a. 8 segments in thorax, 14 segments to trunk, abdominal
appendages used for:
feeding, walking, swimming . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Class Malacostraca
VII. Class Merostomata
1. common name is horseshoe crab
2. tough leathery exoskeleton
3. 2 segments, 1 fused cephalothorax and an abdomen
4. has great ocular system, rich area for scientific study
5. has 6 pairs of spines along sides
6. has a long, spike for a telson
7. 6 pairs of ventral appendages on both cephalothorax and abdomen
(12 total)
8. chelicerae very first at head and used to hold, catch prey, next
five are for walking
VIII. Class Arachnida
1. common name for spiders, scorpions, mites, and ticks
2. have 2 segments: 1 fused cephalothorax and 1 abdomen
3. 6 pairs on cephalothorax with first being chelicerae
4. second pair are modified into “pedipalps”, used in mating or fighting
5. rest of 4 are for walking
6. abdomen is specialized and has no appendages (hence, difference
between this class and C. Merostomata)
7. Spiders have slits in abdomen, which contain parts of the respiratory
system.
8. Called “book-lungs” since find many folds within the body wall that
make look like a stack of papers
9. One side of “page” open to air and the other washed in blood
10. Other in class have a tracheal system for respiration
IX. Class Chilopoda
1. common name is centipedes
2. have one pair antennae
3. long, cylindrical bodies divided into 2 segments ; 1 head and 1
trunk
4. each trunk segment has 2 legs (i.e., one pair of jointed appendages)
5. has mandible appendages on head segment
6. 1st pair of appendages on 1st trunk segment modified into “maxilliped”
that usually has poison tipped fangs
7. carnivorous
8. ocelli – are primitive eyes with eyespots
X. Class Diplopoda
1. common name are the millipedes
2. superficially look like centipedes
3. herbivorous
4. lack the poison fangs of centipedes
5. fusion of 2 trunk segments into one thus making 2 pairs of leg appendages
per trunk
6. have ocelli – which are primitive eyes
XI. Class Hexapoda
1. common name for whole range of organisms known primarily as “insects”
- flies, crickets, grasshoppers,
butterflies, bees, fleas, cockroaches, and beetles
2. Largest class of in phylum
3. Majority are Uniramians
a. single pair of antennae
b. three pairs walking legs
c. three distinct segments:
head, thorax, and abdomen
4. Has tracheal system (TS) for respiration, which are highly branched
network of tubes that invades all the tissues
of the body.
5. TS not only in hexapods, also seen in C. Chilopoda, Diplopoda, and
some Arachnida
6. Exoskeletons –a chitinous covering, usually patterned or colored
7. Insects grow by shedding of the old exoskeleton to new, soft exoskeleton
that will harden in process called molting.
[Read how this is done pg.
112, 3rd paragraph]
8. Many species have wings for flight, 1st time to ever see this adaptive
radiation
9. Three main divisions: head, thorax, abdomen
10. Remember, the word hexapod means “six feet”, that is, 3 pairs of
appendages but also in addition has 1 pair of antennae
11. Two distinct Growth Patterns
a. Hatch from eggs as miniature
adults, never change appearance afterwards
b. Hatch into one stage
(in some species called a nymph, others just a larva) then metamorphosis
after they molt (best
example species are butterflies)
12. Growth under control of hormones from an endocrine system
a. Remember: hormones are
internal signals, pheromones are external signals
b. The nervous system actually
controls and regulates the endocrine system.
c. Conceptually, the endocrine
system is like a motor effector system. The nervous system detects
incoming sensory
cues and translates (interprets) those cues by releasing hormones into
the circulatory system.
d. For example, some hormones
will elicit the physical changes of molting for example, not just in metamorphisizing
species as well.
e. But hormones not just
related to molting, they function in an amazing amount of situations.
Another example is
fine-tuning of metabolism. Try and think up many others as well.
f. Humans have hormonal
signals as well, menstrual cycles in females for example.
XII Grasshopper External Anatomy
1. Grasshopper (Romalea microptera)
2. Two types of photoreceptors
a. compound eye – large
pair
b. ocelli – small pair anterior
to compound eye
3. two dorsal antennae on head segment : sensory organs for touch,
taste, and smell
4. ventral mouth parts on the head segment
5. two pairs appendages on thorax for flight:
a. forewings
b. hindwings
6. Spiracles [not spicules] – located posteriorly on abdomen. These
are the openings to the tracheal respiratory system
XII. Grasshopper Internal Anatomy
1. Respiratory system
a. Spiracles on outside
connected to highly branched tubules called tracheal
b. Tracheal distribute oxygen
to all parts of body
2. Circulatory system
a. open circulatory system
b. only blood vessels found
in body is the dorsal blood vessel which also serves as the Heart, which
has holes in it
called “ostia”
c. Ostia allow the blood
fluid to flow back into system in order to be pumped out the d.b.v.
3. Digestive System
a. mouth – on ventral head
b. mouth – esophagus – crop
– stomach – gastric cecae (assist in extracellular digestion) – intestine
– rectum (vital for
H2O re-absorption) – anus
4. Excretory System
a. Malpighian tube system
– comprised of filamentous, blind-ended tubules to rid itself of metabolic
(nitrogenous)
wastes
b. Found along lateral sides
of abdomen
c. Connected to anterior
portion of intestine but absorb stuff from the surrounding blood, and concentrates
it to be
deposited into the intestines to be eliminated with the feces
5. Nervous System
a. Dorsal brain in head
segment (i.e., cephalization)
b. Ventral nerve cord
c. Ganglia – enlargements
of the v.n.c.
XIV Subphylum Crustacea
Class Malacostraca
I. External Anatomy of Crayfish
1. Crayfish (Cambarus species)
2. Fused head and thorax region called cephalothorax
3. Abdomen
4. Exoskeleton – comprised of calcium
5. Rostrum (beak) – extends forward, out from head
6. Compound eyes – under rostrum, eyes are on stalks
7. Two pairs of antenna – chemo- and tactile sensory decoders
a. smaller of two called
“antennules”
8. serial homology – appendages are derived from precursor appendages
that were essential identical
a. anatomical structures
are said to be homologous if they have a similar embryonic origin or were
derived from a
common ancestral structure
b. Analogy – different that
homology – mean similar function but different evolutionary / ancestral
origins. Example,
bat wing versus a bird wing.
9. Appendages
a. Five on head segment
1. antennae
2. antennules
3. mandibles
4. 2 maxilla
b. Eight on Thorax
1. 3 maxilliped (holds food)
2. 5 walking
a. first walking leg has special name – cheliped – used in catching food
and defense
c. 5 Swimmerets on abdomen
1. uropod – last two aid in swimming backwards
10. Swimmerets – are “biramous” – meaning having two branches
11. Biramous is a specific characteristic of Subphylum Crustacea
12. Male Crayfish – 1st set of swimmerets modified into “claspers”
to hold onto female during copulation
13. Female Crayfish – no claspers
a. but have setae
(hairs) on swimmerets to attach eggs
b. lay eggs through a pore
by the 3rd walking leg
14. Gills – housed in two small chambers on side
15. The portion of the exoskeleton that covers the gills is not attached
to the ventral edge
16. Gills – are very feather-like (i.e., filamentous)
II. Internal Anatomy of Crayfish
1. Epidermis secretes the exoskeleton
2. Muscular System
a. Mandibular muscles –
attached to stomach
b. Extensor muscles -
either side of thorax – pass posteriorly into abdomen, cause abdomen to
straighten
c. Flexor muscles – found
in abdomen – cause abdomen to flex ventrally
d. Both flexors and extensor
used for quick escape response
3. Circulatory system
a. heart – located mid-dorsally
and posterior in cephalothorax
b. ostia – 3 holes found
within the heart – to draw in blood
c. ophthalmic artery – vessel
running to the eyes from heart
d. two antenna arteries
e. dorsal abdominal artery
– runs posteriorly from heart into abdomen, lied dorsal to intestines
f. two hepatic arteries
– to to digestive gland
g. sternal artery –
h. ventral thoracic
artery
i. ventral abdominal artery
j. hemocyanin – blood pigment
containing copper (instead of iron)
k. amoboecytes – the actual
blood cells
1. phagocytitic
2. store glycogen
4. Reproductive system
a. gonads – paired ventral
to heart, but dorsal to digestive gland
b. narrow and long
c. testes – usually small
and whitish
d. sperm duct – opens to
outside at 5th leg
e. ovary – larger than testes,
pale yellow to orange-brown: change color depending on in breed season
or not
f. oviducts – open to outside
at base of 3rd walking leg
5. Digestive system
a. mouth – surrounded by
2 heavy toothed mouth-parts
b. esophagus
c. stomach – lies immediately
posteriorly to rostrum, 2 parts
1. cardiac stomach – contain gastric mill for grinding
2. pyloric stomach
d. gastroliths – sites of
calcium storage, used in exoskeleton construction
e. intestines – after pyloric
stomach
f. digestive gland – produces
digestive enzymes into the pyloric stomach via a small duct
g. anus
5. Excretory system
a. green glands – paired
located anterior part of cephalothorax
1. many tubules
a. end sac
b. labyrinth
c. convoluted tubules
– urine passes through here and chloride ions reabsorbed
d. bladder
e. excretory duct – opening
to outside at base of antennae
6. Nervous system – [know fig. 10-10 page 119]
a. similar to annelids
b. brain – anteriorly fused
ganglia from first 3 ganglia from first three segments
c. stellate appearance to
nerve cells
d. circumesophageal connectives
– circle the esophagus
e. subesophagael ganglion
– fusion of the 5 pairs of thoracic and head ganglion
7. Endocrine system
a. specialized nerve cells
produce hormones
b. hormones released directly
into blood
c. neurohormones – technical
name for neurons that produce hormones
d. hormones – for both long-
and short-term information transfer
e. produced in:
1. eyestalk ganglia
2. brain
3. subesophogeal ganglion
f . x-
organ – in eyestalk – meet up in sinus gland, which is directly posterior
to compound eye
g. x-organ continued – several
different neurohormones produced here
1. one controls levels of sugar in blood
2. another controls osmotic concentration in blood another controls color
changes
h. arthropods use two types
of endocrine control
1. non-nervous gland produces “ecdysone”, a steroid hormone, for growth
and development
2. produced in “y-organ”
3. y-organ located above mandibles attached to the body wall
XIV Hormonal Control of Color Change
1. epidermis has specialized cells for color change
2. these highly branched cells called chromatophores
3. chromatophores contain pigment granules
4. pigment granules concentrated near center of cell or dispersed into
branched processes of the cell
5. depending on the color of the pigment, dispersal through branches
causes a lightening or a darkening of the animal
6. movement of color caused by neurohormones from x-organ from eyestalk
and released into sinus gland
XV Genetic Control of Eye Color in Drosphila
1. Common name for Drosphila melanogaster is the fruit fly (Class Hexapoda)
2. color of eyes under genetic control (as in humans as well) and is
a heritable trait
3. wild-type – the normal color found in the wild
4. mutants – other than the wild-type, different eye-color than find
in nature
5. ry mutant – a mutant with rosy eye-color
6. ry gene locus a structural gene on 3rd chromosome
7. xanthine dehydrogenase [XDH] – name of enzyme coded by gene
8. enzyme involved in metabolism of one set of eye pigments called
pteridines
9. pteridines are reddish pigments derived from purine
10. mutants lack certain enzymes that act upon 2-amino-4-hydroxypteridine
11. wild-types have all enzymes
12. XHD – responsible for conversion of 2-a-4-h into isoxanthopterin
13. Flies that are homozygous for the ry allele produce no XHD and
lack the violet component of the wild-type eye
14. Wild-type eyes are bright red, homozygous rosy eyes are brown
15. Pteridines are organic solvents and it is possible to extract the
pigments from the entire head of a fruit fly
16. Use a chromatograph to separate the individual pigments
17. This process is called pigment profiling of the wild-type
18. Chromatography – technique used to separate mixtures of compounds
based on chemical properties of the compounds
being separated
19. Involves movement of a solid called the mobile phase (cause it’s
moving) through an immobile medium ( cause it ain’t
moving)
20. Because of the differences in the size, molecular structures, and
charges of the compounds the mixture will move at
different rates
21. The components of the mixture will be separated on the basis of
the rates of movement
22. TLC- thin layer chromatography
23. Immobile phase is composed of silica gel
24. silica gel coated on glass slide
25. mobile phase is the solvent
26. Not only does it separate but can be used to identify the compounds
being separated
27. Migration patterns of identical compounds are identical
28. Ratio of the distance a compound moves to the distance that the
solvent front moves is called the “ratio-to-front” value
or Rf value
29. Rf == distance of pigment spot from origin divided by the distance
of solvent front from origin
30. Codominant – heterozygotes have a phenotype that is intermediate
between the homozygous parental phenotypes
IMPORTANT TERMS:
DNA
mRNA
tRNA
rRNA
Genes
proteins
alleles
locus
transcription
translation
"onegene one protein"
phenotype, genotype
homozygous
heterozygous
codominan
Drosophila melanogaster
wild-type
mutants
rosy
sepia
pteridines
isoxanthopterin
xanthopterin
biopterin
drosopterin
sepiapterin
isosepiapterin
xanthine dehydrogenase
TLC
mobile phase
immobile phase
ratio to front
Rf, silica gel plate
solvent
solvent front.