Name: _____________________________

Fish 310 Spring 2015

Animals needed:
 
- Representatives of 5 classes of molluscs—can be **LIVE** or preserved, as appropriate (animals A-E)
- Polyplacophora (chiton) **LIVE**
- Cephalopoda (squid, octopus or cuttlefish)
- Scaphopoda (tusk shell)
- Bivalvia **LIVE**
- Gastropoda **LIVE**
- Additional gastropods, bivalves and cephalopods to examine  (can be others, as available, alive or preserved, as appropriate)
- True limpet **LIVE**
- Moon snail **LIVE**
- Clam **LIVE**
- Dog whelk 
- Nudibranch **LIVE**
- Squid (B)
- Chiton (3 species) **LIVE**
- Molluscs to observe pedal morphology
- Giant chiton
- Clam
- Squid
- Nudibranch
- Limpet
- Moonsnail

Equipment needed:

- Dissecting Scopes

**Agenda**

- Quick Presentation
- Station Rotation
- Class Discussion
- 
#Introduction to the Phylum Mollusca 

The phylum Mollusca is a highly diverse group of animals found in marine, terrestrial, and freshwater ecosystems. The diversity of this group, which includes land snails, geoduck clams, and octopuses, can make it difficult to identify features common to the entire phylum. Today you will examine a number of interesting molluscs, look at the features that unite them and some of their adaptations, and learn to identify the major groups of molluscs. You will examine individuals from 5 of the 7 Molluscan classes.  

Generally molluscs are bilaterally symmetrical, which means there is only one plane along which the body can be divided into equal halves (which are mirror images of one another).  However, there are many exceptions where molluscs are secondarily asymmetrical, and no longer retain bilateral symmetry as adults.  

###Using information from lecture and the pre-lab talk 
1. **Assign each of the animals labeled A – E to a Class**
1. **Sketch each below**
1. **Draw a dashed line to indicate the plane along which each organism is symmetric**
 

 

 

 

 


A. Class : __________________________
 

 

 

 

 


B. Class : __________________________
 

 

 

 

 


C. Class : __________________________
 

 

 

 

 


D. Class : __________________________

 

 

 

 

 

E. Class : __________________________
 

 

 

 

 

#####Which two Molluscan classes are NOT represented here? 
 

 

 

 

 

Another feature that most molluscs share is a radula.  Radulas are a kind of toothed – tongue, used to rasp away at food.  Radulas come in many forms, and range from long, wide radulas with many rows of teeth (typical of algae grazers), to short narrow ones with only a few rows of teeth (commonly found in predatory molluscs). As a general rule of thumb, the fewer radular teeth an animal has, the more evolved (derived) the animal is; in the very advanced cone shells there is only a single tooth.


####Draw the gastropod radula (under the compound scope) and the chiton radula (under the dissecting scope.  Based on the radula structure, what do you think these animals eat?  
 

 

 

 

 
####Sketch the dorsal and ventral view of a chiton. Label the following parts: Anterior end, posterior end, mouth, foot, mantle, valves, girdle, ctenidia (gills). 
 

 

 

 

 

In a chiton, the anus discharges into the mantle cavity.  Further forward there is a pair of excretory pores and in front of that a pair of reproductive pores; both also empty into the mantle cavity.  


####What is a disadvantage to this body layout? 
 

 

 

 

 

####Examine the different species of chitons that are available. List three different characteristics that you could use to distinguish among them. 
 

 

 

 

 

Many molluscs have a large, broad, muscular foot. In some classes the foot is used for locomotion, in others it is used to anchor the animal in the sediment, and in some groups the foot has been reduced (and is not often used) or has been combined with the head and no longer is recognizable.  

####Observe the following organisms and their ‘feet’ and fill in the table below 

| Animal | Common name | Class | Footshape | Purpose/Use of the foot |
|--------|-------------|-------|-----------|-------------------------|
| F      |             |       |           |                         |
| G      |             |       |           |                         |
| H      |             |       |           |                         |
| I      |             |       |           |                         |
| J      |             |       |           |                         |

 

####Develop a dichotomous key using external features for the animals listed below.  

In those cases where there’s more than one example in a particular Class (for example, mussels and cockles are both in the Class Bivalvia), construct the key so both are separated from the rest at the class level first, and then separated from each other.  You may want to start on scratch paper and wait to record your final key here.  If you have questions, please ask!

Scaphopoda

Chiton

Squid 

Octopus

Mussel

Cockle

True Limpet

Keyhole Limpet

Moonsnail 

Nudibranch