FOR YOUR JOURNAL, this week, we are expecting the following.
1 and 2. Photographs of external and internal shrimp anatomy. Include in your journal
observation a list of internal structures you have located.
3. Movie showing beating heart and if at all possible, following one artery away from the heart
until it ends.
4. Movie of barnacle feeding (and mating if possible). If specimens are available, photographs
of barnacle larvae
5 - 6. Movie of two model crustaceans moving. These are an important movie. It will serve as
your model that you use next week for comparative locomotory studies in crustaceans. If
skeletal shrimp are available please use these.
Movies of skeletal shrimp feeding and moving. Please also include some photos of the
shrimp’s habitat.
7. Observations of a horseshoe crab.
8. Barnacles and hydroids (skeletal shrimp were shipped attached to these) become habitat
for numerous species. Your laboratory instructor will show you a few we found last night.
You should always record what other types of animals are found with specimens examined.
These species are important clues as to the niche occupied by the animal of interest. We also
cannot order many species. Most supply companies will not collect sea spiders or flatworms
for classes. Therefore when we do get lucky to get a specimen that is not typically available I
want the class to examine it, whether we are focusing on that group in lab or not. If you find
specimens that might be of interest to the class, please share your observations with the
instructor and the class. Some of the species you will come across will look like something
out of a fantasy novel. Please again share your observations; this may be the only time in
their lifetime that your classmates and instructor will be able to observe these specimens. Dr.
Feaver saw a worm last night that she had never seen before. It had crazy red stripes on it
and very peculiar feeding tentacles. It disappeared before she could photograph it, but if you
find interesting critters, please film them. I always encourage instructors at course’s end or
for individual labs to give a few points for this extra effort.
Today we will try to begin to build a picture of the “typical” arthropod. In some sense such a creature
does not exist, yet all arthropods do share several features in common.
We will be using as the grass shrimp as our model. This species is relatively large and transparent,
so that most of its organs can be seen using the stereoscope. You may try feeding it some fish food.
Just use a pinch so water does not become contaminated. For a side view, try giving it a small rock
or piece of vegetation to hang on to. Often you can tilt the vegetation for a better view of side view of
some important organs such as the bill.
1, External anatomy. Try to identify the different segments of the body, cephalothorax (carapace),
and abdomen. Try to count the number of abdominal segments, legs, and walking legs. Do they
match the number in the picture below, which is a diagram of a large commercial shrimp cultivated for
food? RECORD YOUR OBSERVATIONS IN YOUR JOURNAL
2. Internal anatomy: Below is a diagram of a female crayfish.
The reproductive organs of the male appear as smaller but similar sac like structures. You will
probably be able to easily distinguish the heart, gills (need side view), stomach and intestine. Feed
you animal some colored fish food and if it is cooperative, you should be able to trace the movement
of the food down the digestive track. Can you describe how the mouthparts move while the shrimp is
feeding?
Gills are located just below the heart.
Make a list of organs you can see in your journal.
3. Open circulatory system.
Take a short video of the beating heart. Can you trace the flow of hemolymph out of the heart
into the major arteries? RECORD YOUR OBSERVATIONS IN YOUR JOURNAL. Below are some
diagrams to help you.
The first is of a lobster. Crayfish and shrimp are smaller and to not have veins. It is a very good
diagram of the relationship of the gills to the major vessels and heart.
Diagram of heart showing relative placement of ostia in shrimp and crayfish.
You should try
following the
anterior median
artery since it will
not be as
obscured by other
organs as the
dorsal artery.
You probably will not be able to see ostia in these small shrimp, but check out the movie below of
a dissection in a large crayfish that shows the ostia closing and opening.
http://www2.gsu.edu/~bioasx/heartbeat.html
4. Barnacles We have the common purple striped barnacle, Balanus amphitrite and an unidentified
species (probably another species of Balanus). We also received this year a tiny species,
Chthamalus fragilis that lives on Spartina grass. Sometimes keeping these overnight in dishes in the
dark will produce larvae, but don’t spend a lot of time looking for them. Some years the dishes are
full of them, in others we don’t see any. I always order barnacles for this first lab so you have enough
time to watch and film them.
Examine the diagram below of a barnacle. The barnacle feeds with its legs.
a. You are to film and describe feeding in a barnacle.
Obtain a dish of barnacles or if all are in one dish simply gently scoot a barnacle or two into a smaller
container. Make sure the smaller container can hold enough water to cover the barnacle. While
you are waiting for the animal to adjust to its new surroundings, document any animals that are using
the barnacle as habitat. Those students obtaining the dish containing the larger colony should share
their observations with the class. In a large colony, you should be able to see most of the major
groups of animals we have been discussing in lecture.
Good reference for barnacle behavior. http://creaturecast.org/archives/490-mating-when-you-arestuck-to-a-rock
(Hint: Patience is the key here to good filming.)
Focus and adjust your lighting using the empty container that will house your barnacle. Place your
barnacle under the stereoscope, lights off and wait for it to become adjusted to its new surroundings.
If you barnacle does not feed after it is set and left alone in its new container for a few minutes, you
can try feeding it macro zooplankton or if that does not work phytoplankton. Simply use a small
pipette to obtain some food to add to your dish containing the barnacle. Is there evidence of mating?
If so, please film mating in these animals.
b. Types of barnacle larvae. The diagram below shows the Cyprid larvae attaching to the substrate
to assume the sessile lifestyle of the adult.
b. If larvae are produced during the night, they will be visible as small objects darting around in these
dishes. Use a small pipette to obtain some of these if you see them, place in the smallest dish
available, and observe how they move under the stereoscope. Identify if they are nauplius or cyprid
larvae. Record your observations, obtaining photographs whenever possible.
5. Check with your instructor if marine Caprellid or skeleton shrimp survived the night. These are
truly spectacular creatures to watch feed and move. a. If so, please obtain a film of their l feeding
behavior. b. You should also be able to obtain photographs of overall structure to label. Label
antennae and peropods at least in photographs. If not, we will try to order these again.
.
6. You are to obtain a movie of model locomotion in two crustaceans. These movies will serve
as the model to which you will compare locomotion in a variety of crustaceans, so you want to make
sure that you can clearly see how the legs or other appendages are used in locomotion. You can
use your movie of Caprellids if you wish. Then simply watch locomotion in the glass shrimp or sexy
shrimp in the tank. All these species are large so it is very easy to see how the appendages move.
If the Caprellids did not survive the trip, I have also ordered cultures of some fresh water forms. Your
instructor will give you more instructions on how to work with these. Unfortunately we move quickly
from the large Caprellids and shrimp to species that need to be examined under the stereoscope.
Their size and quickness will provide a bit of a challenge for good observation of how appendages
are used.
7. You will be examining arthropod diversity next week. This week however we are fortunate enough
to have received two Limulus or horseshoe crabs in with the barnacle order. They are too expensive
to ship by themselves. So please watch the one that survived move in the dish and then examine
the ventral surface of the one who tried unsuccessfully to molt during shipment. Count the number of
legs and see if you can identify the gnathobase or grinding organ. Food often encased in a hard shell
or exoskeleton is guided by the chiliarium through the legs and to the gnathobase. After being
ground here, the chelicerae are used to place it in the mouth.
Can you locate the book gills, which serve as respiratory organs?