Instructions

Class Period One:

1) Divide students into groups of four to six.

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2) Give each group a set of cards, paper, and marking pens.

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3) Have students follow the instructions on the Student Page “Living and Eating on the Web” to create one or more marine food chains (15 minutes).

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4) Have each group present its food chain to the whole class, allowing each group two minutes to present.

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5) Have students follow the instructions on the student activity sheet to create a marine food web, using all of the cards in the set. NOTE: Groups may want to tape the two remaining sheets of paper together for their food web, since it will be larger than the food chain (20 minutes).

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6) Have each group present its food web to the class, allowing each group two minutes to present. If there is time at the end of the class, discuss questions and observations from the activity.

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7) Keep the food webs intact for the next class period.

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8) As homework, assign the Student Page “Poison Pathways.”

Class Period Two:

1) Divide the class into the same groups as in the previous class. Have each group add to its food web to show how ciguatoxin is transferred between organisms and bioaccumulates in the food chain until it reaches humans. Groups should show how people could get ciguatera poisoning from eating herbivorous fishes as well as from carnivorous fishes. They will need to use information from the Marine Food Chains and Webs Cards as well as the Student Page “Poison Pathways” and will need to draw additional species onto their food webs to illustrate the transfer of ciguatoxin.

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2) When groups have finished their work, have each present its results to the class.

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3) Discuss student responses to and questions about the homework assignment.

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4) As a wrap-up to the “Poison Pathways” activity, share with students the following information from J. L. Shirai, L. K. Shirai, and Y. Hokama, Seafood Poisoning: Ciguatera, Yosh Hokama Family Trust, Gardena, California, 1991. This passage provides some insight into the third homework question, which asked students to hypothesize about how ʻūʻū or soldierfish might be implicated in cases of ciguatera poisoning:

Examination of the clinical symptoms in patients with pufferfish, shellfish (red tide due to dinoflagellates) and polyether type toxin (ciguatoxin, okadaic acid, brevetoxin and other polyether) poisonings shows that the symptoms overlap and the causative toxins can’t be distinguished. In other words, there is no unique feature that separates the clinical effect. The temperature reversal was supposedly unique for ciguatoxin. This is no longer the case as…okadaic adid, palytoxin, brevetoxin and other ciguatoxin-like compounds including organophosphates and botulism toxin can produce this clinical effect (p. 9).