Aliens in Our Oceans: Cephalopods
Aliens… or Masters of Disguise - created by Faye Josephson

Key Concept
Synopsis
Background
Into Activity
Through Activity
Assessment
Extensions
Resources
References

Enduring Idea/ Concept:

Adaptations that improve the survival of these (mostly) unarmored animals in an unforgiving and highly competitive environment. These animals as a group exhibit numerous means of evasive behaviors for escape: rapid swimming ability, jetting away from predators, ink emission, wrestling with predators and camouflage, since all but the nautilus have no external armor to protect them. Although most cephalopods have beaks to grind shells, they are embedded within the arms, and are not practical for defense.

Synopsis of Lesson:

Students will research and report on the myriad ways that cephalopods behave for survival:

• Some are very rapid swimmers and escape using that mode
• Some emit jets of water to escape, and use that ability in other ways ( see Octopuses Are Smart Suckers; www.manandmollusc.net for other applications of this ability)
• Some use clouds of ink to frighten and confuse predators: see www.tonmo.com/articles/octopusink.php
• Some are capable of attacking prey much larger than they are, and even fight off predators.
• Some may change color, change shape or apparent size, and some can even change the texture of their skin to disappear in order to escape predators: why is this so effective for this class of animals? See: http://is.dal.ca/~ceph/TCP/chroma2.html and http://is.dal.ca/~ceph/TCP/chroma3.html

Students will explore how this class of animals performs these amazing feats and prepare presentations:

1. Have students separate into groups by the topic they want to explore.
2. Have each group articulate which strategies they will focus on (some strategies are shared by more than one order of cephalopod; divide the tasks as evenly as possible.
3. Allow 2-5 days for exploration, and 2 days to prepare the presentations. It takes one day for 2 presentations, usually. (15 minutes each, plus discussion)
4. Students can prepare PowerPoint Presentations, since they lend themselves to use of photos, video and documentation.

ALL students will explore the form and function of the chromatophore in the Into Activity. This is an amazing structure that is as useful as it is rare, being dominant in this class of animals. Students will discuss how the brain and nervous system must coordinate the function of these structures to create the visual changes within the skin of these animals that allows the wide range of color change exhibited by these animals. Students will make mental connections between the habitat and habits for this class of animals.

Background Information:

Cephalopods possess an unusual mechanism for camouflage: the chromatophore, elastic sacs just beneath the surface of the skin, filled with chemicals that react to electrical impulses sent through the nervous system of these animals. All they need to do is ‘think change’ and the chromatophores respond by changing shape under the skin, which influences the way that light is reflected from the skin surface, and influencing the apparent color of the animal. These animals can change color rapidly when they need to escape a predator (many cuttlefish and some octopuses, example of species), or they ease through a range of color as they glide over a rocky, intertidal area in shallow water (many octopuses, example species).

Some cephalopods actually exhibit outrageous colors and do not employ camouflage: how do they defend themselves? Why can they survive if they “standout in a crowd”? Think Blue-ring Octopus (spp. Haplolochlaena lunalata) and some of the cuttlefish…see CephBase for photos. Have students speculate how these features assure survival in a harsh and inhospitable environment. (Bright colors in nature are usually a warning signal or mimicry)

This lesson is designed for independent study by students employing a WebQuest-like format. Teachers may elect to truncate or expand the assignment depending on grade level, technology available and time dedicated to this unit.

Into Activity:

Ask the students questions to elicit prior knowledge and connect to the previous lessons in this unit:
Have them explain and extend as much as possible to allow them to fully engage the topic.

• How do terrestrial animals usually defend themselves?
• How do marine animals usually defend themselves?
• If these animals have no armor and no teeth to use defensively, how do they defend themselves from predators cruising the same areas?
• Post the speculative answers on the board or on paper to refer to later.

Then have the class explore the following information before the activity: http://is.dal.ca/~ceph/TCP/chroma2.html
and http://is.dal.ca/~ceph/TCP/chroma3.html

Have students paraphrase what they read in small groups for 5 minutes, then openly discuss with the entire class until the material has been thoroughly reviewed and restated by the students.

Activity: Using balloons as models to demonstrate the action of chromatophores.

1. Student will take three latex balloon each, different colors AND sizes
2. Inflate the balloons partially, NOT completely, and tie off to seal them. Students need to be able to manipulate the balloons and squeeze them between their fingers. The balloons should NOT be the same size.
3. Use one rubber band to tie each student’s three balloons together in a bundle at the opening/neck of the balloons.
4. Each student should place the bundle in the palm of the hand, wrap the fingers around the balloons, but keep the fingers separated.
5. Squeeze gently until some of the inflated balloons squeeze through the separated fingers in different places, exposing just a small area of the colored balloon between the open fingers. Repeat, changing the area of the ‘bundle’ that squeezes through the areas between the fingers.
6. This exposure of different areas of the balloons models how cephalopods change the color of their skin by exposing different portions of the chromatophores, and they do it by just thinking about it!

Materials:
Supply of latex balloons, various colors and sizes (mostly small ones)
Enough for each student to have at least three, different colors.
Rubber bands to tie the three balloons together

Through Activity:

Students will research survival strategies as exhibited by this class of animals via bookmarked websites and text-based resources. This activity is based on the WebQuest format, but may be adjusted as necessary to make the lesson more or less in depth or challenging.

Teachers can bookmark preselected websites for research, based on the list enclosed, and add resources as required.

Assessment:

Devise a rubric for the research project:

• Decide the main categories to assess: the big ideas associated with camouflage for these animals

Deeper Depths/Extensions:

Students can research cephalopods regarding what part of the ocean they usually inhabit. Each of the four types of cephalopods use somewhat different forms of camouflage: how is that influenced by the part of the ocean they choose to call home? Whether they inhabit shallow areas, mid-ocean or deeper depths, is there any correlation to their dominant form of camouflage? Or are they influenced by other factors, such as geology, temperature, season, or water composition? This will be a very challenging research project, but students typically do well and enjoy the freedom to explore widely.

Possible research questions to explore:

• Do all cephalopods possess and employ the same mechanisms for escape?
• Do they all employ those mechanisms in the same manner?
• Why do some cephalopods exploit one main form of escape strategy, and some employ an array of strategies?
• Consider predator/prey relationships and the influence they exert on the physical characteristics of these animals: do these factors influence the number or type of escape strategies?
• Consider where these animals live: how does habitat influence escape strategies?
• Consider the influence of intellect on escape strategies: how do these animals outsmart predators when escape strategies are not working?

Major Resources

General Cephalopod Information: including measurement, drawings and descriptions.http://www.fao.org/docrep/t0726e/t0726e0c.htm#cephalopods

Chromatophores: http://is.dal.ca/~ceph/TCP/chroma1.html
and http://is.dal.ca/~ceph/TCP/chroma2.html
and http://is.dal.ca/~ceph/TCP/chroma3.html

Man & Mollusc: http://www.manandmollusc.net

National Resource Center for Cephalopods: http://www.nrcc.utmb.edu/

TONMO: Everything Cephalopod http://www.tonmo.com/

More References

Text & video of new species recently found ‘Mystery Squid’: http://www.mnh.si.edu/cephs/vetal01/vetal01.html

Cephalopod Husbandry: http://www.nrcc.utmb.edu/cephhusbguid.htm

Learn about raising cuttlefish: Start here and follow the links to 3 more articles: http://is.dal.ca/~ceph/TCP/cuttle1.html

Obtaining Live Cephalopods: http://www.nrcc.utmb.edu/LiveAnimRes.htm

Cuttlefish Capital of the world: http://www.cuttlefishcapital.com.au/

Environmental Enrichment for captive Octopus: http://www.enrichment.org/articles/83octopus.pdf

Octopus Ink: http://www.tonmo.com/articles/octopusink.php

Cephalopod Myths:
Norse folktales http://www.tonmo.com/articles/midgard.php

Models of Cephalopods/other resources: http://www.leaveonlybubbles.com/

Visit NRCC and view Dr. Woods’ toy cephalopod collection: http://www.tonmo.com/articles/nrcc.php