Laboratory two:
This week in lab we will begin our look at arthropod diversity by focusing on
variation in overall body plan and movement within the group.
1. The simplest case for tagmata, a head and the “rest”
Obtain a millipede.
Lab journal notes:
a. Count the number of legs found per segment.
b. Observe locomotion in the millipede. How much of the body moves as a
unit when moving forward? When turning?
c. Transfer your millipede to a wet but firm sand surface. What type of tracks
are left by the moving millipede? Are they impressions of appendages on or
body segments dragged through the sand?
d. Which of the following tracks do they most resemble?
Millipede track one
Millipede track two
e. Draw as best you can in Photoshop, the tracks left behind. You can simply ask for
a new file, specifying one about 6 by 6 inches. Then use a small sized paintbrush in
any color you wish to draw your tracks.
See example below.
Crustaceans, “let’s talk about warping bodies and legs”. Next week you will
conduct a more intensive investigation of variation in crustaceans. This week we will
simply look at some extremes.
2. Those of you who have taken Bio 181 recently have worked with pillbugs. We will
use the pill bug as our model for crustaceans, comparing their morphology to two
more common and then unusual crustaceans. Next week you will be comparing other
crustaceans to these models. The diagram below indicates the types of diagrams or
labeled photographs that should accompany descriptions in your journal.
Examine the pill bugs or land isopods available.
Journal notes
a. Compare the morphology of the pillbug to that of the millipede. How it have
more or less tagmata or specialized groups of segments.
b. Compare how it uses its legs to walk with that of the millipede
c. Also in your lab journal, compare the patterns of segmentation observed in pill
bugs with those observed in Daphnia, another crustacean, last week.
Compare locomotion in the two organisms living in two very different
environments.
3 and 4. More common crustaceans crabs and shrimp.
3. We will attempt to set up colonies of Geosesarma or vampire crabs. The most
popular species is red and black, but there are now purple and black or ivory and black
species available. I have no idea what is being shipped. If successful, we should be
able to observe mating behavior and development in this group.
a. For this lab, simply diagram their overall structure and make a few
observations (try not to disturb them too much) on their locomotion.
4. Brazilian yellow-bellied shrimp. Similar to the shrimp you may have viewed in
introductory biology, but hardier and so more expensive. Again we will try to get a
colony of these going. In the meantime we will use these to review what you have
should have learned before about arthropod structure.
Journal notes:
a. Obtain photographs of these shrimp tagmata. Label structures similar to
those labeled in the diagram of the sowbug.
b. Locate and make a short video of the beating heart in these shrimp.
Can you trace the flow of hemolymph out of the heart into the major arteries?
At higher magnification see if you can see the ostia or openings by way,
hemolymph returns to the heart.
5-7: The more unusual.
5. Your next examination should be of barnacles. We have the purple striped
barnacle, Balanus amphitrite and an unidentified species (probably another species of
Balanus) that can reproduce in shipment. That means you may be able to see living
larvae of this species.
Examine the diagram below of a barnacle. The barnacle feeds with its legs.
Lab notes:
a. You are to film and describe feeding in a barnacle.
Obtain a barnacle from the dish containing them, by gently scooting a barnacle into a
smaller container. Make sure the smaller container can hold enough water to cover
the barnacle. Good filming.
(Hint: Patience is the key here. 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 shrimp larvae (Your instructor will provide directions). Simply use a
small pipette to obtain some larvae to add to your dish containing the barnacle. They
are gold objects swimming after you remove the top of the container. Do not place
these larvae back in the barnacle dish with the barnacle. You will have to lift
the barnacle and quickly place it back in the container. We do not want to mix
shrimp larvae with barnacle larvae.
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 survive the night, they will be visible as small objects darting around in
these dishes. Use a small pipette to obtain some of these, place in the smallest dish
available and observe how they move under the stereoscope. Add some food shrimp
larvae to the container and compare movement and form. The take a small sample of
both forms and adds to a drop or grid slide to observe under the light microscope.
Record your observations, obtaining photographs whenever possible.
6. Check with your instructor if marine Caprellid or skeleton shrimp were shipped.
These are truly spectacular creatures to watch feed and move. a. If so, please obtain
a film of their locomotion and/or feeding behavior. b. You should also be able to
obtain photograph of overall structure to label.
7. Fish lice:
These are crustaceans modified for a parasitic life style. a. Obtain a photograph
if you can. b. Compare the morphology of a fish louse to that of a shrimp and sowbug.
The photographs below show a louse on a tail of a goldfish and a more magnified shot
of the louse’s ventral surface.