Biol 212 Zoology
Lab 08: Phylum Arthropoda and Phylum Onychophora
(20 points)
Introduction
With over a million describes species, 89% of which are insects (see Lab 9), the
arthropods make up the largest phylum of animals. A brief summary of the systematics of the
major groups of the phylum covered in this lab and the next, along with common names, is as
follows:
Phylum Arthropoda
Subphylum Trilobitamorpha (extinct)
Subphylum Cheliceriformes
Class Chelicerata
Subclass Merostomata (horseshoe crabs)
Subclass Arachnida (spiders, scorpions)
Class Pycnogonida (sea spiders)
Subphylum Myriopoda
Class Chelopoda (centipedes)
Class Diplopoda (millipedes)
Class Pauropoda
Class Symphyla
Subphylum Pancrustacea (crustaceans + insects)
Class Ostracoda (ostracods)
Class Hexanaupli
Subclass Copepoda (copepods)
Subclass Thecostrata (barnacles)
Class Malacostraca
Order Isopoda (sowbugs, pillbugs, sea slaters)
Order Amphipoda (amphipods)
Order Decapoda (crabs, lobsters, shrimp)
Class Cephalocarida
Class Branchiopoda
Class Remipedia
Clade Hexapoda (insects)
Phylum Onychophora
Perusing the above systematics, you can see
that arthropods include insects, spiders, scorpions,
barnacles, shrimp, crabs, lobsters, horseshoe crabs—
and all their relatives. What do these animals have in
common? One characteristic they all have is
Fig. 8.1. Class Myriopoda.
Metamerization in a centipede.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 1
metamerization, the serial repetition of body segments called metamers, also seen in annelids;
metamerization is especially obvious in the myriopods (Fig. 8.1). It was once thought that
metamerization was a synapomorphy, a characteristic that linked annelid worms, arthropods and
others together; based on molecular evidence, we now think that metamerization evolved more
than once, and that annelids are not closely related to arthropods.
As arthropods become evolutionarily more advanced, metamers fuse and specialize to
form two to three tagmata, body regions. Primitive arthropods such as myriopods (centipedes
and millipeds) do not have tagmata, but trilobites, cheliceriformes (spiders and their relatives)
and crustaceans have two tagmata, a cephalothorax and abdomen, called the prosoma and
opisthoma in arachnids, and hexapods (insects) have three tagmata, a head, thorax and
Fig. 8.2. Tagmata in arachnid (left), crustacean (middle) and hexapod (right). Ex. Kozloff.
abdomen (Fig. 8.2). Note that the cephalothorax of crustaceans is usually covered by a shell
called the carapace (Fig. 8.3).
Arthropods all have jointed legs, hence the origin of the taxon, “Arthropoda,” which
means, “jointed legs”; this is certainly a definitive, apomorphic characteristic of the phylum. The
body and jointed legs are covered by a cuticle, which usually forms a hard exoskeleton, except
where the joints must articulate. When the animal needs to grow, the exoskeleton splits and the
soft-shelled animal crawls out, a process known as ecdysis; this is what soft-shelled crabs are.
Once out, the arthropod puffs itself up with fluids so that the new exoskeleton hardens a size
larger than its immediate needs so that it can grow into its new shell. The cast-off exoskeleton is
called the exuvia.
Arthropod appendages are specialized structures that allow the animal to move through,
sense and manipulate their environment. Antennae are major sense organs and are attached to
the head. The cheliceriformes (spiders, horseshoe crabs) have no antennae; myriopods and
hexapods have one pair of antennae, whereas the crustaceans generally have two pairs of
antennae, one pair smaller than the other (Fig. 9.2). Appendages around the mouth may include
chelicera, the first pair of appendage of the Chelicerata, modified for tearing or piercing, like the
fangs of spiders; chewing, biting, piercing or sucking mouthparts as in the myriopoda and
Putman/Pierce College Biol 212 Lab 08/20160424/Page 2
Fig. 8.3. Cambaris (crayfish) external anatomy. Ex. Van De Graaf and Crawley.
hexapoda; or a pair of mandibles, immediately to either side of the mouth, with two pairs of
maxilla also attached to the head and assisting in gathering food.
Appendages attached to the thorax may include three sets of walking legs, as in the
hexapoda, or four sets of walking legs, as in the arachnids. In the decapods crustaceans,
including the crabs, lobsters and crayfish, there are ten pairs of
appendages attached to the thorax, the first three pair being
maxillipeds, which assist in food handling, the last eight pair of
thorax appeandages are called pereopods. The first pereopods,
which have the big nippers, arecalled chelipods. The nippers
are termed chelae.
Most often, appendages are not attached to the
abdomen—except in the Crustacea. In crustaceans, there may
be ten pairs of abdominal legs called pleopods. Pleopods are
generally used to maintain respiratory currents and for holding
eggs, in females.
At the end of the abdomen in crustaceans is a central
segment called the telson; the telson bears the anus ventrally.
To either side of the telson are the uropods, which fan out,
allowing the animal to move backwards quickly.
The nervous system of arthropods is virtually identical
to that of annelids (Fig. 8.4). It consists of a circumenteric
ganglion (brain), with a ventral nerve cord; at each metamer
there is a ganglionic swelling, with paired nerves extending
laterally. In primitive arthropods, as in primitive annelids, the
initial portion of the ventral nerve cord may be paired,
exhibiting remnants of a ladder-like nerve cord, similar to that
found in the platyhelminthes.
Fig. 8.4. Generalized arthropod
Most arthropods have a definitive, compound eye
nervous system.
made up of individual light-receptor units called
ommatidia (Fig. 8.5). This gives trilobites, crustaceans
Putman/Pierce College Biol 212 Lab 08/20160424/Page 3
and insects their unique eyes, which are
very easy to observe under the dissecting
microscope.
Arthropods have a complete gut,
but variations on the specifics of the gut
exist. The gut of a crustacean, which we’ll
use as an example, begins with the
mouth. A short esophagus conveys food
from the mouth to the stomach. The
stomach is large, with two chambers; the
first, the cardiac chamber, has
specialized structures that mechanically
digest food; the second, the pyloric
chamber, is a complicated structure that
sorts and filters food so that only liquid
and very fine particles enter into the
Fig. 8.5. Arthropod compound eye made
intestine; everything else must be regurgitated out
up of ommatidia. The labeled structures
of the mouth.
describe one ommatidium. Ex. Brusca
The huge digestive glands open just
and Brusca.
posterior to the stomach into the intestine (Fig.
8.9). They function to secrete digestive enzymes into the intestine and to absorb digestive
nutrients. The intestine serves to compact material into feces and to absorb water; the other parts
of the digestive tract absorb water as well. Feces are moved through the rectum, then into the
environment through the anus.
Respiration in arthropods
presents a unique problem. Most
organisms exchange oxygen and
carbon dioxide through their
epidermis; however, the arthropod
epidermis is covered by an air-tight
cuticle. So, specialized structures
are necessary that involve creating
holes in the exoskeleton and
pumping air, or oxygen-containing
water, in and out of the animal.
Terrestrial arthropods, such as
Fig. 8.6. Arachnid respiratory and circulatory
insects, have special tracheal systems
system.
for breathing that we’ll look at in the
next lab. Other terrestrials, such as
spiders, possess a set of internal, gill-like structures called the book lung (Fig. 8.6). Aquatic
arthropods have gills beneath their carapace and use their pleopods to vent their gill chambers.
Dedicated blood vessels are present that carry oxygenated blood from the respiratory structures
directly to the heart for quick distribution to the tissues.
Arthropods have an open circulatory system, with the spacious body cavity being a
hemocoel, which bathes the tissues directly. The heart is contained in a pericardial cavity and is
a rather unique structure in that it contains holes called ostia. Blood is brought into the
Putman/Pierce College Biol 212 Lab 08/20160424/Page 4
pericardial cavity from the respiratory structures by special veins or percolates into the
pericardial cavity from the hemocoel. From there, blood enters the heart via the ostia. The heart
beats as the ostia close, pumping blood anteriorly and posteriorly through arteries to the tissues.
The excretory systems of arthropods are quite varied. In terrestrial arthropods, including
arachnids (spiders and scorpions), myriopods (centipedes and millipedes) and hexapods (insects),
there is a series of fine ducts called Malpighian tubules, which collect wastes from the tissues
and deposit them where they connect into the intestine. We’ll be looking at these in the next lab.
In aquatics, such as crustaceans, there is a specialized nephridium called the antennal gland or
green gland, which opens at the base of the second antennae (antennules). Fluids diffuse into the
gland from the hemocoel and materials that are needed by the body are then reabsorbed by the
tubules of the gland, leaving wastes that are excreted form the animal.
Fig. 8.7. Sexual dimorphism in Cambarus, subphylum Pancrustacea. Note the copulatory
swimmerets in the male, and the lack of copulatory swimmerets in the female.
Arthropods are generally gonochoristic (dioecious), with separate sexes, and there is
usually sufficient sexual dimorphism present to enable us to differentiate between males and
females. In the Cheliceriformes, females are most often larger than males; in the Crustacea,
females generally have a wider abdomen than males, males usually have large chelae that are
used in sexual displays, and males may have specialized structures used in copulation (Fig. 8.7).
Although arthropods have a true coelom during development, a schizocoel, it is generally
limited to forming excretory organs, the gonads and genital ducts. The spacious body cavity of
arthropods is a hemocoel, not a true coelom, unlike the body cavity of annelids, which is a
schizocoel—a true coelom.
The purpose of this lab is to introduce you to the phylum Arthropoda and four of its
subphyla; we’ll also take a look at the group from which the arthropods may have evolved, the
phylum Onychorphora.
For the Lab Report:
*On the upper, right-hand corner of your lab report, print your name, Biol 212, Lab 8: Phylum
Arthropoda and Phylum Onychophora, and the date you did this lab.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 5
Introductory Objectives
Objective 1: Be able to outline the systematic of the phylum Arthropoda, as given in the
introduction to this lab.
Objective 2: State the trend in tagmata formation in the arthropods.
Objective 3: Define ecdysis and exuvia.
Objective 4: Give the number of antennae, thoracic and abdominal appendages in the
cheliceriformes, myriopods, crustaceans and hexapods.
Objective 5: Name the head, thoracic and abdominal appendages of crustaceans.
Objective 6: State how the arthropod nervous system compares to that of annelids and
platyhelminthians.
Objective 7: Briefly describe the structure and functional units of arthropod compound eyes.
Objective 8: Describe the components of an arthropod gut.
Objective 9: Recognize the problem to respiration of having an exoskeleton, and state how
terrestrial and aquatic arthropods have overcome this problem.
Objective 10: Describe the circulatory system of a typical arthropod.
Objective 11: Explain the excretory system of terrestrial and aquatic arthropods, describing the
function of Malpighian tubules and the antenna/green gland.
Objective 12: Be able to list the major features of the phylum Arthropoda.
For the Lab Report:
Write out these questions then answer them:
1. Write out the systematic of the phylum Arthropoda as given in the introduction to this lab.
Give a common name for each taxon, if you can!
2. What is the difference between a metamer and a tagma?
3. Describe the tagmata in the Myriopods, Cheliceriformes, Crustacea and Hexapoda.
4. Complete the following chart of the numbers of appendages in each tagma in the following
subphyla:
# Antennae
Thorax
Abdomen
Cheliceriformes
Myriopoda
Crustacea
Hexapoda
5. How is the arthropod nervous system like the nervous system of annelids and
platyhelminthes?
6. What are ommatidia?
7. What are the components of an arthropod (crustacean) gut?
8. What is the general problem to respiration of having an exoskeleton, and how have terrestrial
and aquatic arthropods solved this problem?
9. What is unique about the circulatory system of arthropods? Briefly describe or outline the
circulatory system of a typical arthropod.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 6
For the Lab Report:
Write out these questions then answer them:
10. Describe the excretory system of aquatic arthropods such as crustaceans. What is the
antenna/green gland?
11. List at least three characteristics of the phylum Arthropoda!
12. Why is the hemocoel of arthropods not a true coelom? Where is the true coelom?
Exercise 8.1: Phylum Onychophora
Introduction
Onychophorans are common members of the forest floors of the humid tropics. They
share many features of both annelid worms and arthropods, and were thought to be the “missing
link” between these two groups. Although their relationship to the annelids is in question, it is
thought that they may, indeed, be the animals from which arthropods evolved.
Note that onychophorans look at bit like centipedes. Their legs are, however, unjointed.
Onychophorans do exhibit ecdysis and they are members of the clade Ecdysozoa. Peripatus is a
common onychophora genus.
Objectives
Objective 13: Identify a member of the phylum Onychophora from a preserved specimen or
photograph.
Objective 14: State the number of antennae onychohorans have and whether or not the legs are
jointed.
Materials and Methods
*Preserved or Plastomount onychophoran for observation (not dissection)
1. Examine the onychophoran on display. Note the structures that are arthropod-like and those
that are not; answer the questions in the For the Lab Report box below.
For the Lab Report:
Write out these questions then answer them:
13. What morphological structures (visible structures that you see) does the onychophoran on
display have that are arthropod-like? Which structures are not arthropod-like?
14. How many antennae do onychophorans have?
15. Are onychophoran legs jointed?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 7
Exercise 8.2: Phylum Arthropoda, Subphylum Trilobitamorpha
Introduction
Unfortunately, trilobites are extinct. They lived in the marine environment some 600 to
300 million years ago. They can now be commonly found in the fossil record, in Cambrian to
Carboniferous rock strata.
We can infer quite a bit about the ecology of trilobites, based on their external
morphology. Animals that live in low-light conditions usually have large eyes to gather enough
light to see; thus, trilobites with large eyes were probably either nocturnal, or lived in deep water.
Animals that are diurnal and live in shallow depths have moderate-sized eyes; thus, trilobites
with moderate eyes probably lived in shallow seas. In conditions with no light, as in the deepest
depths of the sea, eyes are not needed, so are very small or vestigial; trilobites with eyes reduced
or absent probably lived in very deep water.
The placement of the eyes and overall body morphology gives us clues as to where the
animal lived. Eyes that are placed dorsally or dorso-laterally, along with a flattened body,
suggest an animal that lived benthically, on the bottom, probably in a mud or sand substrate.
Dorsally or dorso-laterally placed eyes, along with an elevated body, not so flattened, suggest an
animal that lived benthically, but amongst rocks. Eyes that are placed laterally or ventro-laterally
are positioned to look down; these animals also usually have a laterlly-compresseed body
adapted for swimming within the pelagic or open-sea realm.
Animals with a lot of predators tend to develop strategies to survive. Such strategies often
include thick shells or shells with spikes. This suggests that trilobites with thick shell or spikes
probably had to deal with considerable predation.
The importance of trilobites is that they provide direct evidence of what early arthropods
looked like and possible ancestors of modern arthropods.
Objectives
Objective 15: Identify a member of the subphylum Trilobitamorpha to phylum and subphylum
from either a specimen or photograph.
Objective 16: State what kind of eyes trilobites had.
Objective 17: Discuss the ecology of the trilobite, based on external morphology.
Materials and Methods
*Trilobite fossils or photographs
1. Please don’t touch the trilobite on display unless you are given permission; they are very
fragile!
2. Examine the trilobite on display under the dissection microscope and answer the questions in
the For the Lab Report box below.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 8
For the Lab Report:
Write out these questions then answer them:
16. What kind of eyes does the trilobite have?
17. Where are the eyes of the trilobite located? (dorsum, lateral, dorso-lateral, ventro-lateral)
18. Is the trilobite dorso-ventrally flattened, laterally flattened, or in between?
19. Does the carapace of the trilobite have spikes or is it without spikes?
20. Describe the probable habitat and ecology of the trilobite you observed. (pelagic, benthic;
high-light conditions, low-light conditions; area of high predation, area of low predation;
rocky bottom, muddy bottom) What evidence do you have to support your conclusion?
Exercise 8.3: Phylum Arthropoda, Subphylum Cheliceriformes, Class
Chelicerata, Subclass Merostomata
Introduction
The arthropod subphylum Cheliceriformes is currently divided into two classes: class
Chelicerata, with subclass Merostomata and subclass Arachnida, and class Pycnogonida. The
Merostomata, represented by only five species, includes the horseshoe crab, Limulus
polyphemus, which lives on the East coast of North America and is especially common off the
beaches of Virginia in the spring. The other four species live in Southeast Asia.
The dorsum of Limulus polyphemus is dominanted by the large frontal shield, the
prosoma. Posterior to and hinged to the prosoma is the opisthoma. The long spike is part of the
opisthoma and is termed the telson. The telson is used defensively, and for helping the animal
turn over, should it find itself upside down. Mid laterally on the prosoma are the compound
eyes. Medially, and to the anterior, is a singular, small triangular patch of ocelli, the median or
simple eyes; these are a little more difficult to spot than the large compound eyes.
Ventrally, surrounding the mouth, six pairs of appendages can be easily spotted. The first
two appendages are associated with feeding, the chelicerae and the pedipalps. The nexst four
sets of legs are walking legs; note that spiders, close relates of the merostomata, also have four
sets of walking legs. Further, the legs are uniramous, meaning they don’t have secondary
appendages coming off of them.
Posterior to the legs are book gills, covered by places called gill opercula. The anus is at
the base of the telson.
Objectives
Objective 18: Identify Limulus polyphemus, to phylum, subphylum, class, genus and species,
from preserved specimens or photographs.
Objective 19: Identify the following structures on a preserved Limulus polyphemus: prosoma,
opisthoma, telson, compound eyes, simple eyes, mouth, chelicerae, pedipalps, walking legs,
book gills, gill opercula and anus.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 9
Materials and Methods
*Preserved or dry Limulus polyphemus (horseshoe crab) for demo (not dissection)
-Dissection pan and forceps, if crabs are wet-preserved
1. If available, obtain a preserved Limulus polyphemus and place it in a dissection pan, if it is
wet. Otherwise, carefully obtain a dried horseshoe crab.
2. Draw the dorsal aspect of the crab and label it as per the For the Lab Report box below.
For the Lab Report:
21. Write out, “21. Phylum Arthropoda, subphylum Cheliceriformes, class Chelicerata, subclass
Merostomata, Limulus polyphemus, dorsum.” Draw the dorsal anatomy of the horseshoe
crab. Identify and label the prosoma, opisthoma, telson, compound eyes and simple eyes.
Include an accurate size rule in centimeters next to your drawing. No credit for drawings
without accurate size rules. To the right of your drawing, include how big the size rule is (for
example, “Size rule = ___cm.” Also, include any notes that might help you to identify the
organism on the lab practical! Have your instructor check and initial your drawings for
credit; all drawings must be completed in lab and signed by your instructor for credit!
3. Turn the Limulus polyphemus over. Draw the ventral aspect—to save time, you need only
draw the legs on one side. Identify and label it as per the For the Lab Report Box below.
4. When finished, please carefully return the horseshoe crab to the demo table.
For the Lab Report:
22. Write out, “22. Phylum Arthropoda, subphylum Cheliceriformes, class Chelicerata, subclass
Merostomata, Limulus polyphemus, ventrum.” Draw the ventral anatomy of the horseshoe
crab. Identify and label the mouth, chelicerae, pedipalps, walking legs, book gills, gill
opercula and anus. Include an accurate size rule in centimeters next to your drawing. No
credit for drawings without accurate size rules. To the right of your drawing, include how big
the size rule is (for example, “Size rule = ___cm.” Also, include any notes that might help
you to identify the organism on the lab practical! Have your instructor check and initial your
drawings for credit; all drawings must be completed in lab and signed by your instructor for
credit!
For the Lab Report:
Write out these questions then answer them:
23. How many pairs of appendages does Limulus polyphemus have total?
24. How many pairs of walking legs does the horseshoe crab have?
25. What kind(s) of eyes does Limulus polyphemus have?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 10
Exercise 8.4: Phylum Arthropoda, Subphylum Cheliceriformes, Class
Chelicerata, Subclass Arachnida
Introduction
The subclass Arachnida includes the spiders, scorpions, ticks, mites, chiggers, and their
relatives. Like the merostomata, arachnids have two body segments, the prosoma
(cephalothorax) and the opisthoma (abdomen). They have six pairs of appendages attached to
the prosoma, like the horseshoe crabs. The first pair of appendages is the chelicerae, which are
often massive and modified into fangs with associated poison glands. The second pair is the
pedipalps, which help in feeding and, in males, in the transferring of sperm packets,
spermatophores, to the female; in scorpions, the pedipalps terminate in chelae, used to seize
and tear food apart. Pairs three through six constitute walking legs one through four. All the legs
are uniramous, without appendages. In the order Araneae, the spiders, at the end of the
opisthoma are the silk glands and specialized appendages called spinnerets which spin silk into
webs, silk that is up to five times stronger than steel!
The eyes of arachnids vary in number and structure from simple ocelli to eyes with lenses
and retinas; some arachnids have no eyes and are blind.
The subclass Arachnida is large, with over 60,000 described species living in virtually all
terrestrial habitats imaginable, as well as a few species living under water, even though they all
must breathe air to survive! (Arachnids that live under water go to the surface and trap bubbles
of air, then dive back down to their dens with the air to breathe.)
Objectives
Objective 20: Identify representatives of the arthropod subphylum Cheliceriformes, class
Chelicerata, subclass Arachnida from living or preserved specimens, or photographs; be able to
give the phylum, subphylum, class and subclass.
Objective 21: identify the following structures on a preserved or photograph of a spider:
prosoma, opisthoma, chelicera (with fangs), pedipalp, walking legs, eyes.
Materials and Methods
*Preserved or plastomount of arachnid(s) for demo (not dissection)
-Dissecting microscope, dissection pan, forceps
1. Obtain a preserved or plastomount of an arachnid (spider or scorpion). Place it under a
dissecting microscope. Examine the dosum. Accurately draw and label the dorsal region as
per the For the Lab Report box below.
2. Make sure you draw the head region accurately, including the number of eyes!
Putman/Pierce College Biol 212 Lab 08/20160424/Page 11
For the Lab Report:
26. Write out, “26. Phylum Arthropoda, subphylum Cheliceriformes, class Chelicerata, subclass
Arachnida, spider (or scorpion), dorsum.” [If the genus of the animal is known, replace the
word “spider or scorpion” with the genus.] Accurately draw the dorsum of the representative
arachnid. Identify, draw and label the eyes, chelicerae with fangs (if apparent), pedipalps,
prosoma and opisthoma; for this drawing, you do not need to draw the legs. Include an
accurate size rule in millimeters next to your drawing. No credit for drawings without
accurate size rules. To the right of your drawing, include how big the size rule is (for
example, “Size rule = ___mm.” Also, include any notes that might help you to identify the
organism on the lab practical! Have your instructor check and initial your drawings for
credit; all drawings must be completed in lab and signed by your instructor for credit!
3. Now examine the ventral aspect of the arachnid. Accurately draw the body of the arachnid
and at least half of the appendages. Label it as per the For the Lab Report box below.
For the Lab Report:
27. Write out, “27. Phylum Arthropoda, subphylum Cheliceriformes, class Chelicerata, subclass
Arachnida, spider (or scorpion), ventrum.” [If the genus of the animal is known, replace the
word “spider or scorpion” with the genus.] Draw the ventral region of the representative
arachnid. Identify, draw and label the prosoma, opisthoma, chelicerae (with fangs),
pedipalps, and at least half of the walking legs; also identify, draw and label the spinnerets, if
apparent. Include an accurate size rule in millimeters next to your drawing. No credit for
drawings without accurate size rules. To the right of your drawing, include how big the size
rule is (for example, “Size rule = ___mm.” Also, include any notes that might help you to
identify the organism on the lab practical! Have your instructor check and initial your
drawings for credit; all drawings must be completed in lab and signed by your instructor for
credit!
For the Lab Report:
Write out these questions then answer them:
28. How many eyes did your representative arachnid have?
29. How do the chelicerae of the subclass Merostomata differ from those of the subclass
Arachnida?
30. How do the walking legs of the subclass Merostomata differ from those of the subclass
Arachnida?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 12
Exercise 8.5: Phylum Arthropoda, Subphylum Cheliceriformes, Class
Pycnogonida
Introduction
Pycnogonids, also called “sea spiders,” occur only in the oceans, found within the
intertidal down to a depth of about 7,000 m, where they can have leg spans of over 60 cm,
though most pycnogonids are small, a centimeter or two across. They occur on seaweeds, sea
anemones, hydroids, bryozoans, tunicates, and even within the bells of jellyfish. They are placed
within the subphylum Cheliceriformes for several reasons, including having ten pairs of
appendages, the first two associated with the mouth, the final four pairs being walking legs.
Further, all of the walking legs of the subphylum Cheliceriformes are uniramous, without
branches or secondary extensions, similar to those in the rest of the subphylum.
The body of pycnogonids is divided into several slender body segments. A proboscis,
completely unique to the pycnogonids, extends from the head between the two chelifores
(chelicerae). Gonads are carried outside the body on or between the legs, the male serving to
brood masses of fertilized eggs, carrying them on ovigers—specialized appendages between the
pedipalps and the first walking legs. Another distinctive feature of pycnogonids is they have four
simple eyes clustered medially on the head (cephalon).
Objectives
Objective 22: Identify a representative of the class Pycnogonida to phylum, subphylum and
class, from living or preserved specimens, or photograph.
Objective 23: State what unites pycnogonids with other Cheliceriformes and what makes them
unique.
Materials and Methods
*Preserved or plastomounts of representative pycnogonids
1. Examine a pycnogonid under a dissection microscope. Note the proboscis, peculiar
segmentation of the body, and the ten pairs of appendages, including eight pairs of walking
legs. See if there are ovigers just anterior to the first walking legs. Note the location of the
eyes.
2. Make a sketch of at least half of the pycnogonid as per the For the Lab Report Box below.
For the Lab Report:
31. Write out, “27. Phylum Arthropoda, subphylum Cheliceriformes, class Pycnogonida,
ventrum.” Draw the ventral region of the representative pycnogonid. Identify, draw and label
the proboscis, chelifores, and oviger, if apparent; draw at least half of the walking legs.
Include an accurate size rule in millimeters next to your drawing. No credit for drawings
without accurate size rules. To the right of your drawing, include how big the size rule is (for
example, “Size rule = ___mm.” Also, include any notes that might help you to identify the
organism on the lab practical! Have your instructor check and initial your drawings for
credit; all drawings must be completed in lab and signed by your instructor for credit!
Putman/Pierce College Biol 212 Lab 08/20160424/Page 13
3. Measure the maximum leg span of the pycnogonid and record it.
For the Lab Report:
Write out these questions then answer them:
32. How many pairs of walking legs do pycnogonids have?
33. What morphological characteristics did you actually observe that unite the pycnogonids with
the other Cheliceriformes?
34. What morphological differences did you actually observe that appear to be unique to the
class Pycnogonida?
35. What was the maximum leg span of the pycnogonid you observed?
Exercise 8.6: Phylum Arthropoda, Subphylum Myriopoda
Introduction
The subphylum Myriopoda (“many feet”) is divided into several classes, two of which
are the classes Chilopoda and Diplopoda. Myriopods are vermiform (worm-like), with multiple
segments. Chilopods, the centipedes, have 15-193 segments and usually have a single pair of
legs per segment. Diplopods, the millipedes, have 11-192 segments, and usually have two pairs
of legs per segment (hence their scientific name). The other two classes, not studied in this lab,
are the Pauropoda and Symphyla. The pauropods are very small, less than 1.5 mm in length, with
12 segments and 9 to 11 pairs of legs. They are found worldwide in decaying leaf litter on forest
floors. Also found in decaying vegetation, sometimes in gardens, are the symphylids, which are
up to 8 mm in length, with 15 to 22 segments and 12 pairs of legs.
Myriopods are considered as having two tagmata, a head and a trunk made of segments.
They have a single pair of antennae, like the hexapods, and have three sets of head appendages
surrounding the mouth: a pair of mandibles and two pairs of maxillae, all modified for feeding,
being very similar to the mouthparts of the typical crustacean or hexapod. The first body segment
contributes a fourth pair of mouth-related feeding appendages, the maxillipeds, which bears
fangs with associated poison glands.
Unlike hexapods, myriopods do not have compound eyes; rather, they have relatively
simple ocelli.
Objective
Objective 24: Identify representatives of the myriopod classes Chilopoda and diplopoda to
phylum, subphylum and class, from living or preserved specimens, or photographs.
Materials and Methods
*Preserved or Plastomount specimen of a chilopod (centipede)
*Preserved or Plastomount specimen of a diplopod (millipede)
Putman/Pierce College Biol 212 Lab 08/20160424/Page 14
1. Examine the chilopod on display. Identify the ocelli and maxillipeds with fangs, and note the
number of antennae.
2. Examine the diplopod on display. Identify the ocelli and maxillipeds with fangs, and note the
number of antennae.
For the Lab Report:
Write out these questions then answer them:
36. What characteristics can be used to differentiate between members of the myriopod classes
Chilopoda and Diplopoda?
37. Myriopods look a lot like polychaetes (phylum Annelida) and onychophorans. How can you
easily tell the difference between these three groups?
Exercise 8.7: Phylum Arthropoda, Subphylum Pancrustacea, Class
Ostracoda
Introduction
Members of the class Ostracoda have a single eye and reduced numbers of appendages.
They also have a bivalve shell, like clams, and live on the bottom of marine habitats, within the
benthos. They are not sessile, like the theostrata (barnacles), and can move about freely.
Objective
Objective 25: Identify an ostracod as to phylum, subphylum and class, from a living or preserved
specimen, or photograph.
Materials and Methods
*Microscope slides of ostracods
-Compound microscope
1. Obtain your compound microscope. Examine a representative of the class Ostracoda. Note
the bivalve shell. Estimate the length of the ostracod, in m. Answer the questions in the For
the Lab Report box below.
For the Lab Report:
Write out these questions then answer them:
38. How long was your ostracod?
39. What characteristics could you use to easily differentiate an ostracod from other crustaceans
or small clams?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 15
Exercise 8.8: Phylum Arthropoda, Subphylum Pancrustacea, Class
Hexanaupli, Subclass Copepoda
Introduction
Probably the most abundant animals on the planet Earth are copepods, particularly
members of the genus Calanus. They make up much of the marine plankton of cold to temperate
waters, feeding on diatoms and other photoautotrophs, then becoming food for other planktonic
animals such as larval fishes; they are, in fact, the primary herbivores of cold and temperate
marine waters. Without copepods, most of the food webs of the global sea would collapse. They
are also found in freshwater environments.
Copepods are generally easy to identify, with their single, red eye and often very long
antennae that project out from their heads. They average about 1 mm (1000 m) in length.
Objectives
Objective 26: Identify a copepod as to phylum subphylum, class and subclass, from a preserved
specimen (microscope slide), living specimens or photographs.
Materials and Methods
*Microscope slides or photographs, or living specimens of calanoid copepods.
-Compound microscope
1. Obtain a slide of a copepod. Examine the specimen and draw it, as per the For the Lab Report
box below.
2. Answer the questions in the For the Lab Report box below!
For the Lab Report:
40. Write out, “40. Phylum Arthropoda, subphylum Pancrustacea, Class Hexanaupli, Subclass
Copepoda, Calanus.” Draw a representative calanoid copepod. Include an accurate size rule
in micrometers next to your drawing. No credit for drawings without accurate size rules. To
the right of your drawing, include how big the size rule is (for example, “Size rule = ___m.”
Also, include any notes that might help you to identify the organism on the lab practical!
Have your instructor check and initial your drawings for credit; all drawings must be
completed in lab and signed by your instructor for credit!
For the Lab Report:
Write out these questions then answer them:
41. What characteristics could you use to easily identify a copepod?
42. What is the importance of copepods to global ecology?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 16
Exercise 8.9: Phylum Arthropoda, Subclass Pancrustacea, Class
Hexanaupli, subclass Thecostraca
Introduction
Barnacles belong to the subclass Thecostraca. They are strictly marine and sessile, being
attached to hard substrates like rocks and the hulls of ships, either directly or by stalks; some
even attaching themselves to the hides of whales. We think one reason whales breech is to
dislodge attached barnacles! Larval barnacles settle down on hard substrates and form durable,
calcium carbonate shells. To feed, it kicks out its legs, called cirri, bringing water, oxygen and
food into its shell.
A common intertidal genus of barnacle off the West Coast is Balanus.
Objective
Objective 27: Identify a barnacle to phylum, subphylum, class and subclass, from a preserved
specimen, shell, photograph or living specimen. Identify the genus Balanus.
Materials and Methods
*Preserved barnacles or barnacles shells, photographs of barnacles, or living barnacles
1. On display, you should find preserved specimens, shells, photographs or living
representatives of the subclass Cirripedia. The genus Balanus should be identified. Answer
the questions in the For the Lab Report Box below.
For the Lab Report:
Write out these questions then answer them:
43. What characteristics could you use to easily identify a barnacle in the field?
44. One barnacle belonging to the genus Sacoglossa does not form a hard shell. It is, in fact, a
parasite of crabs. How do you suppose it was identified as a barnacle? (The answer is in your
lecture notes!)
Exercise 9.10: Phylum Arthropoda, Subphylum Pancrustacea, Class
Malacostraca, Order Isopoda
Introduction
Sowbugs and pillbugs are common terrestrial isopods. Isopods are doso-ventrally
flattened crustaceans with seven pairs of identical walking legs. Most species are marine, living
between rocks and holding onto kelp. Deep-sea isopods may reach over 2/3 of a meter in length.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 17
Objective
Objective 28: Identify an isopod to phylum, subphylum, class and subclass, from a preserved
specimen, living specimen or photograph.
Materials and Methods
*Preserved, plastomount or living isopods
1. On display, you should find representatives of the order Isopoda. Examine a specimen and
answer the questions in the For the Lab Report box below.
For the Lab Report:
Write out these questions then answer them:
45. What characteristics could you use to easily identify an isopod in the field?
46. How many antennae does the isopod have?
47. How many walking legs does the isopod have? Are the legs uniform or specialized for
various functions?
Exercise 9.11: Phylum Arthropoda, Subclass Pancrustacea, Class
Malacostraca, Order Amphipoda
Introduction
Amphipods are very common members of the benthos of the sea, living amongst algae
and kelp, where they serve as food for many organisms. Like isopods, they also have seven
walking legs, but unlike isopods, are laterally flattened. Further, whereas isopods have
undifferentiated legs, isopod legs are differentiated for various functions.
Objective
Objective 29: Identify an amphipod as to phylum, subphylum, class and subclass, from a
preserved specimen, microscope slide, or photograph.
Materials and Methods
*Preserved (or microscope slides of) amphipods
1. On display, you should find preserved or commercially-prepared microscope slides of
amphipods. With your compound or dissecting microscope, examine a specimen and answer
the questions in the For the Lab Report box below.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 18
For the Lab Report:
Write out these questions then answer them:
48. What characteristics could you use to easily identify an amphipod in the field?
49. How many antennae does the amphipod have?
50. Are the legs of the amphipod relatively uniform or do they appear to be specialized?
Exercise 8.12: Phylum Arthropoda, Subphylum Pancrustacea, Class
Malacostraca, Order Decapoda
Introduction
The decapods crustaceans include the crabs, lobsters, crayfish, shrimps and a few other
groups, many of which are of considerable commercial importance. The order name,
“decapoda,” means “ten legs.” All members of the order Decapoda have ten thoracic walking
legs called pereopods.
Using the crayfish Cambaris as an example (Fig. 8.3), the typical crustacean has a “nose”
called the rostrum. To either side of the rostrum, decapods crustaceans have compound eyes on
stalks, The head is solidly fused with the thorax into the cephalothorax, which is covered by the
carapace. To either side of the carapace are wide extensions or flaps called brachiostegites,
which cover the gills, water being drawn in ventrally. Posterior and attached to the cephalothorax
is the articulated and freely movable abdomen. Attached to the head are two antennae, the
Fig. 8.8. Mouthparts of Cambarus, subphylum Crustacea.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 19
antenna proper (first antenna) and the smaller antennules (second antenna), as well as a pair of
mandibles, which define the entrance into the mouth, and two pairs of maxillae also associated
with the mouth (Fig. 8.8). Also associated with the mouth but attached to the thorax, are three
pairs of appendages that help the animal taste and handle food, the first, second and third
maxillipeds. Attached to the thorax are the five pairs of pereopods, the first of which is usually
modified into the large nippers or chelipeds. Attached to the abdomen then are five pairs of
pleopods, also called swimmerets. The abdomen terminates with the central telson and uropods
attached to either side, forming a fan-shaped backwards swimming mechanism.
Decapods are common in both marine and freshwater, with many crab species living on
land, climbing trees and living in burrows. In the Puget Sound area, the most important
commercial crustacean is the dunginess crab, genus Cancer. There are about 14,000 described
species of decapods crustaceans named.
Objectives
Objective 30: Identify a crayfish, crab, lobster or shrimp to phylum, subphylum, class and order.
Objective 31: Identify a Cambaris crayfish to phylum, subphylum, class, order and genus.
Objective 32: Identify the following structures on the external anatomy of Cambaris: carapace,
brachiostegites, cephalothorax, rostrum, eye, antenna (first antenna), antennules (second
antenna), chelicerae, mandibles, maxilla, maxillipeds, pereopods, chelipeds, chelae, abdomen,
pleopods, telson and uropods.
Objective 33: Differentiate between a male and female Cambaris. Identify the following
structures in crayfish of the appropriate sex: copulatory swimmeret, opening of vas deferens,
opening of oviduct, seminal receptacle.
Objective 34: Objective 36: identify the following structures on the internal anatomy of
Cambaris: epidermis, esophagus, cardiac stomach, pyloric stomach, hepatopancreas (digestive
gland), intestine, pericardium, pericardial sinus, heart, ostia in heart, ophthalmic artery, antennal
arteries, dorsal abdominal artery, testes, ovaries, esophagus, antenna/green gland, circumenteric
ganglia (brain) and ventral nerve cord.
Materials and Methods
*Preserved crayfish, Cambaris, for dissection
-Dissection pans and dissection tools
-Dissection tools: maul probe, needle probe, forceps, fine-point scissors, scalpel, dissection pins
1. Obtain a dissection pan, dissection equipment, and a preserved Cambaris. Accurately draw
the dorsal aspect of the crayfish, excluding the legs, if you wish. Label it as per the For the
Lab Report box below, using the written descriptions and diagrams in the introduction to this
lab to help you identify the parts.
2. Turn your Cambaris over. Accurately draw the ventral aspect, drawing only the insertions of
the legs, if you wish. Identify and label the parts listed in the For the Lab Report box below.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 20
For the Lab Report:
51. Write out, “51. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, dorsum.” Draw the dorsal aspect of the crayfish, excluding the legs, if
you wish. Identify and label the carapace, brachiostegites, cephalothorax, rostrum, eye,
antenna (first antenna), antennules (second antenna), chelicerae, mandibles, maxilla,
maxillipeds, pereopods, chelipeds, chelae, abdomen, pleopods, telson and uropods. Include
an accurate size rule next to your drawing—use a centimeter rule to measure the specimen
and make your size rule. No credit for drawings without accurate size rules. To the right of
your drawing, include how big the size rule is (for example, “Size rule = ___cm.” Also,
include any notes that might help you to identify the organism on the lab practical! Have
your instructor check and initial your drawings for credit; all drawings must be completed in
lab and signed by your instructor for credit!
For the Lab Report:
52. Write out, “52. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, ventrum.” Draw the ventral aspect of the crayfish, drawing only where
the legs insert, if you wish. Identify and label the brachiostegites, abdomen, telson, uropods,
antenna, antennules, rostrum, first to fifth pereopods, pleopods, mouth and anus. Include an
accurate size rule next to your drawing—use a centimeter rule to measure the specimen and
make your size rule. No credit for drawings without accurate size rules. To the right of your
drawing, include how big the size rule is (for example, “Size rule = ___cm.” Also, include
any notes that might help you to identify the organism on the lab practical! Have your
instructor check and initial your drawings for credit; all drawings must be completed in lab
and signed by your instructor for credit!
3. Now, from around the mouth, and from one side of the animal only, carefully remove the
mandible, the first maxilla and the second maxilla. Place them in order on a piece of paper.
From the same side of the body, remove the first maxilliped, second maxilliped and third
maxilliped. Then remove the first walking leg (cheliped, with the chelae), and second
through fourth walking legs, arranging them, in order, on the paper. Once they are arranged,
accurately sketch them. (If time is of a premium in lab, you may tape them to the piece of
paper, have your instructor initial your lab report, #52, and complete this part of the lab at
home.)
For the Lab Report:
53. Write out, “53. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, appendages.” Draw and label the disarticulated appendages of the
crayfish. Include an accurate size rule next to your drawing. No credit for drawings without
an accurate size rule. To the right of your drawing, include how big the size rule. Also,
include any notes that might help you to identify the organism on the lab practical! Have
your instructor check and initial your drawings for credit; all drawings must be completed in
lab and signed by your instructor for credit!
Putman/Pierce College Biol 212 Lab 08/20160424/Page 21
4. Examine the reproductive organs of your crayfish. Determine the sex. Make detailed
drawings of the reproductive organs of your crayfish, then examine a different-sex crayfish
of another student and draw its reproductive organs. Label the drawings as to sex. Label the
male drawing with the following: copulatory swimmeret, opening of vas deferens. Label the
female drawing with the following: opening of oviduct, seminal receptacle. See Fig. 8.7 to
help you with your identifications.
For the Lab Report:
54. Write out, “54. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, reproductive organs.” Draw and label the reproductive organs of a
male and female crayfish. Label the drawings as to sex. Label the male drawing with the
following: copulatory swimmeret, opening of vas deferens. Label the female drawing with
the following: opening of oviduct, seminal receptacle. Include an accurate size rule next to
your drawing. No credit for drawings without an accurate size rule. To the right of your
drawing, include how big the size rule. Also, include any notes that might help you to
identify the organism on the lab practical! Have your instructor check and initial your
drawings for credit; all drawings must be completed in lab and signed by your instructor for
credit!
5. Don’t begin to dissect your crayfish until you have asked the class if anyone needs to draw
and label the sex organs of your crayfish!
6. Place the Cambaris on its side. With a pair of forceps, lift up a brachiostegite. Observe the
gills. Using a pair of sharp, fine-tip scissors, remove the brachiostegite. Sketch the gills and
the surrounding tissue as per the For the Lab Report box below.
For the Lab Report:
55. Write out, “55. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, gill chamber.” Draw and label the gill chamber of the crayfish with the
brachiostegite removed. Include an accurate size rule next to your drawing. No credit for
drawings without an accurate size rule. To the right of your drawing, include how big the size
rule. Also, include any notes that might help you to identify the organism on the lab
practical! Have your instructor check and initial your drawings for credit; all drawings must
be completed in lab and signed by your instructor for credit!
7. Turn the crayfish ventral side down. Begin your dissection at the dorsal surface. Using a finepoint pair of dissection scissors, insert the sharp point into the right posterior edge of the
carapace and cut just under the surface toward the head, being careful not to damage
underlying tissues; stop just before reaching the eye. Make the same cut on the other side.
Beginning at the posterior edge, carefully lift the carapace up, being careful not to pull the
underlying epidermis and attached muscles up with the carapace. With your scissors,
carefully cut away the carapace where it attaches to the head.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 22
8. Now with your scissors,
carefully remove the
epidermis.
9. Draw the internal anatomy that
you exposed by carefully
removing the epidermis.
Identify, draw and label the
cardiac stomach, pyloric
stomach, the hepatopancreas
(digestive gland), and the
intestine; also, identify, draw
and label the pericardium
(membrane surrounding heart),
pericardial sinus (space in
which th heart resides), heart,
ostia in heart, the ophthalmic
artery, antennal arteries, and
dorsal abdominal artery. See
Figs. 8.9 and 8.10 to help you
identify internal structures.
Fig. 8.9: Cambaris internal
anatomy, dorsal view. Ex. Hickman
and Katz.
For the Lab Report:
56. Write out, “56. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, internal anatomy.” Draw the internal anatomy that you exposed and
label the cardiac stomach, pyloric stomach, hepatopancreas, intestine, pericardium,
pericardial sinus, heart, ostia in heart, ophthalmic artery, antennal arteries, and dorsal
abdominal artery. Include an accurate size rule next to your drawing. No credit for drawings
without an accurate size rule. To the right of your drawing, include how big the size rule.
Also, include any notes that might help you to identify the organism on the lab practical!
Have your instructor check and initial your drawings for credit; all drawings must be
completed in lab and signed by your instructor for credit!
Putman/Pierce College Biol 212 Lab 08/20160424/Page 23
Fig. 8.10: Cambaris internal anatomy, lateral view. Ex. Hickman and Katz.
10. Carefully remove the heart. Identify, draw and label the gonads. Note the color of the gonads;
if you have a male, they should be white—label them testes; if you have a female, they
should be pinkish to orange (not white), so label them as ovaries. Identify, draw and label the
gonoducts (sperm duct or oviduct), if you can find them. Note: this drawing does not have to
be of the entire crayfish, only of the organs in question and the surrounding structures.
For the Lab Report:
57. Write out, “57. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, internal anatomy.” Draw the internal anatomy that you exposed and
label the gonads (testes or ovaries), gonoducts (sperm duct or oviduct). Include an accurate
size rule next to your drawing. No credit for drawings without an accurate size rule. To the
right of your drawing, include how big the size rule. Also, include any notes that might help
you to identify the organism on the lab practical! Have your instructor check and initial your
drawings for credit; all drawings must be completed in lab and signed by your instructor for
credit!
11. Remove the hepatopancreas and the stomach carefully. Identify, draw and label the
esophagus and antenna glands/green glands. Again, this drawing does not have to be of the
entire crayfish, only of the organs in question and the surrounding structures.
Putman/Pierce College Biol 212 Lab 08/20160424/Page 24
For the Lab Report:
58. Write out, “58. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, esophagus and antenna gland.” Draw and label the esophagus and
antenna gland. Include an accurate size rule next to your drawing. No credit for drawings
without an accurate size rule. To the right of your drawing, include how big the size rule.
Also, include any notes that might help you to identify the organism on the lab practical!
Have your instructor check and initial your drawings for credit; all drawings must be
completed in lab and signed by your instructor for credit!
12. Finally, isolate the brain. Carefully remove all of the internal organs, washing away excess
tissues with a squirt bottle of water. Identify, draw and label the esophagus, the circumenteric
ganglia, which surrounds the esophagus, and the ventral nerve cord.
For the Lab Report:
59. Write out, “59. Phylum Arthropoda, subphylum Pancrustaces, Class Malacostraca, order
Decapoda, Cambaris, nervous system.” Draw and label the esophagus, circumenteric ganglia
(brain) and the ventral nerve cord. Include an accurate size rule next to your drawing. No
credit for drawings without an accurate size rule. To the right of your drawing, include how
big the size rule. Also, include any notes that might help you to identify the organism on the
lab practical! Have your instructor check and initial your drawings for credit; all drawings
must be completed in lab and signed by your instructor for credit!
13. Ask your instructor if he would like to see your dissection! Once he has examined it, please
wrap the animal parts in a couple of paper towels and dispose of into the animal waste bin.
Please rinse off all dissection tools with soap and water, dry and return to the cart.
For the Lab Report:
Write out these questions then answer them:
60. Assuming that your Cambaris is a typical decapod crustacean (it is), what characteristics
could you use to quickly differentiate a member of the order Decapoda from other
crustaceans?
61. Externally, how can you tell the difference between a male and female Cambaris?
~When you’re finished, help clean up!
1. Is your lab bench clean and wiped down with antiseptic solution?
2. Are all materials returned to their proper place?
3. Is the oil immersion objective of your microscope clean?
4. Is the lowest-power objective of your microscope positioned down?
5. Is the power cord draped loosely about one of the oculars?
6. Is your microscope put away?
7. Is all refuse disposed of properly?
8. Is the lab generally in order?
Putman/Pierce College Biol 212 Lab 08/20160424/Page 25