Be sure to write about what you are learning in the lab section of your notebook. You will be expected to answer questions about the lab activity during the lab self test and lab quiz. It helps to have your text and coloring books open beside you for support.

Predators

Predators are animals which capture, kill and consume other organisms which are called prey. The prey organism can be of any type. Predators are classified by the type of prey they cconsume.

Herbivores

Predators that eat plants, seaweeds and algae are called herbivores. There are two types of herbivores: macrophagous and microphagous. Macrophagous herbivores eat large plants and seaweeds or parts of large plants and seaweeds. Microphagous herbivores eat small algae and seaweeds which they must gather in large numbers. Microphagous herbivores collect their food in different ways. Some are grazers that scrape algae from surfaces and some are filter-feeders that filter it out of the water.

Top Snails
Top snails are microphagous herbivores. They are grazers that collect their food by scraping it from rocks with a special chitinous "tongue" called a radula. The radula is a file-like structure that has many rows of teeth. The radula is extended through the mouth and applied to the rock and then retracted back into the mouth. On the return trip the teeth of the radula scrape algae into the mouth.
Experimental Set Up:  We filled a small glass bowl with seawater and placed Top Snails in it. We placed the bowl under the dissecting microscope and focused on the the snails. We adjusted the magnification and position of the bowl until the snail filled the field. We video taped the snails moving around the bowl. Then we placed a Top Snail on a glass slide and waited until it started to crawl on the glass. Then we turned the slide over with the snail adhering to it. We placed the slide onto a watchglass filled with seawater without trapping any air so that the upside down snail was completely submerged. We placed the watchglass under the dissecting microscope and focused on the underside of the snail. We adjusted the magnification and position of the watchglass until the snail filled the field. We photographed the snail moving on the slide watching for the action of the radula as the snail attempted to scrape algae off the watchglass.
Observations: How do you think the top snail fed? Why is the radula an efficient tool for scraping up food?	Examine the photograph of the Top Snail and note the radula in it's mouth.

Snail Radula
The teeth on the radula of a snail are specific for the type of food it eats. In fact the radulae of different snail species are structurely so different that they can be used to identify the snails.
Experimental Set Up:  We obtained a prepared slide of a snail radula. We examined the slide with a compound microscope and photographed the radula at 400X magnification.
Observations: Describe the structure of the radula. How is the radula adapted for scraping?	Examine the photograph of the snail radula and note the arrangement of its teeth.	Examine the photograph of the snail radula and note the arrangement of its teeth.

Acorn Barnacles
Acorn Barnacles are microphagous herbivores that collect their food by filtering it out of the water using their cirri (legs). The cirri are held together in the shape of a basket as they are swept through the water. Algal cells are captured on the cirri and are transferred to the mouth at the base of the basket.
Experimental Set Up:  We filled a watchglass with seawater and placed two clusters of barnacles in it. We made sure that they were completely submerged. We placed the watchglass under the dissecting microscope and focused on the barnacles. We adjusted the magnification and positioned the watchglass until the bodies of the barnacles filled the field. We photographed the cirri as the barnacles attempted to filter algae from the water.
Observations: How do you think the barnacle fed? How does the action of it's cirri enable them to filter feed?	Examine the photograph of the Acorn Barnacles and note the cirri extending from one's shell.

Stalked Barnacles
Stalked barnacles are stalked barnacles that feed in the same way as acorn barnacles. They are easier to examine and photograph than acorn barnacles because of their larger size and the arrangement of their shell plates and soft parts.
Experimental Set Up:  We obtained a live specimen of a stalked barnacle and photographed it feeding.
Observations: How many cirri does the goose-neck barnacle have? Why are the cirri a good tool for filtering food?	Examine the photograph of the stalked barnacle and carefully observe the cirri.

 

Mussels
Mussels are microphagous herbivores that collect their food by filtering it out of the water using their gills. Water is pumped into the cavity inside the shell by the beating of many tiny, hair-like cilia on the gills and the thin, fleshy mantle that lines the shell. The water passes through the gills and exits from the shell cavity. Algae is filtered from the water by the gill and is conducted by cilia along the gill toward the mouth. At the top of the gill a set of small labial palps pass the food from the gill to the mouth.
Experimental Set Up: We obtained a live mussel and placed it in a small glass bowl. We cut through the adductor muscles that hold the shells together using a scalpel. We opened the shell and examined the internal anatomy of the mussel. We located the gills and labial palps. We sprinkled a small amount of red carmine powder on the gills. We photographed the mussel as it moved the carmine powder down its gills.
Observations: How did the mussel move the carmine particles? Compare the gill of the mussel to the cirri of the barnacle. How is each structure used to solve the problem of filtering?	Carefully observe the action of the gills as it moves the carmine particles.