Investigating a Deep Sea Mystery Author: Jennifer Collins, Science Education Specialist

Investigating a Deep Sea Mystery is based on Deep-sea mystery solved: astonishing larval transformation and extreme sexual dimorphism unite three fish families by Johnson, et al. (2009)* published in Biology Letters, Royal Society. The deep sea fishes at the heart of the investigation and this activity were historically classified into three families or clades based on the obvious morphological differences between the members of each group. Over time, as new data was accumulated, a new hypothesis was generated; the three fish clades were really one. Johnson, et al. found patterns in collection data that supported an alternative relationship; that they are the males, females, and larvae of a single family or clade, and that the morphological differences are the result of extreme ontogenetic (developmental) metamorphosis and sexual dimorphism. In this activity students follow the steps of the science team to unravel the mystery of the fishes' classification by analyzing some of the same morphological and phylogenetic data as the science team.

* Dave Johnson (National Museum of Natural History, Smithsonian Institution), John Paxton (Australian Museum, Sydney), Tracey Sutton (Virginia Institute of Marine Science, Virginia), Takashi Satoh and Mutsumi Nishida (Ocean Research Institute-University of Tokyo), and Tetsuya Sado and Masaki Miya (Natural History Museum and Institute in Chiba, Japan)

Deep Sea Mystery Teacher Guide (pdf)

Grades: 9–12

Objectives: Students will:

• use external morphology to classify a group of deep sea fishes
• analyze data to examine alternative hypotheses about the classification and evolutionary relationships of the organisms
• use multiple lines of morphological and phylogenetic data to make inferences about the function of different features and test alternative hypotheses
• learn how science is an ongoing and dynamic process of discovery

The activity is divided into six parts that should be completed in order. Below is a brief description, recommended time commitment, and list of related documents and other materials needed for each section.

Activity Sections and Materials

I. Introduction - What is a Fish? (45 minutes) — Students devise their own definition of what makes an organism a fish, then test their ideas by reading about how scientists define "fish."

Materials:

Student Research Notes KEY (pdf) Student Research Notes, page 1 (pdf) Fish Resource Guide (pdf)

II. Classifying Some Unusual Fishes (30 minutes) — To become familiar with the fishes in this activity, students sort a set of specimen cards into three clades based on their external morphology. This hypothesis will be referred to as the Three Clade Hypothesis. Students then check their classification scheme with the scheme historically proposed by ichthyologists. This will represent the first of two hypotheses that they will later test.

Materials:

Student Research Notes, page 2 (pdf) Deep Sea Fish Specimen Cards (pdf) Deep Sea Fish Specimen Key (pdf; also to be used for Parts IV and V)

III. Looking for Patterns in Collection Data (45-60 minutes) — Students look for patterns in data pertaining to the sex, collection depth, and stage of development that were compiled by Johnson et. al. From this data students will work through the alternative hypothesis the scientists came up with to explain the patterns they see. Students will refer to this as the Single Clade Hypothesis.

Materials:

Student Research Notes, pages 3-4 (pdf)

IV. Testing Hypotheses - Using Morphology (60 minutes) — Students test the alternative hypotheses by making observations of three sets of morphological features used by Johnson et al. For each morphological feature, students make inferences about the function of the features and how that might support or refute each hypothesis.

Materials:

Student Research Notes, pages 5-8 (pdf) Deep Sea Fish Specimen Key (pdf; from Part II) Morphology Cards (pdf; Gut, Muscle, Gill A&B)

V. Testing Hypotheses - Using Phylogenetic Trees (30 minutes) — Students practice their skills at distinguishing how the topology of different phylogenetic trees support different hypotheses, then test the Single and Three Clade Hypotheses using one of the phylogenetic trees Johnson et al. referenced.

Materials:

Student Research Notes, pages 9-10 (pdf) Deep Sea Fish Specimen Key (pdf; from Part II) Colored pencils, so each student or group has three distinct colors

VI. Wrapping it up (30 minutes) — Students compile what they learned from the morphological and phylogenetic data to summarize which of the two hypotheses best represents the relatedness and classification of these fish. Students also generate new questions to investigate.

Materials:

Student Research Notes, page 11 (pdf)

National Science Education Standards:

Life Science:
	Molecular basis of heredity Biological evolution
Science as Inquiry

Prerequisites and Recommended Resources
Below is a list of student prerequisites along with resources that provide background information and/or classroom activities that address each prerequisite.

Students should:

• understand that a phylogeny, or evolutionary tree, represents the evolutionary relationships among a set of organisms or groups of organisms
  — The Tree Room - What is an evolutionary tree?
• have a basic understanding of how to read and make inferences from phylogenetic trees, including an understanding of shared characters
  — The Tree Room - Primer on Trees
  — What Did T-Rex Taste Like?
  — An Exercise in Tree Interpretation, Page 9 of the Student Research Notes
• understand that a clade is a group of organisms that includes an ancestor and all descendants of that ancestor
  —The Tree Room - Primer on Trees
• have a basic understanding of how organisms are classified into clades
  — Understanding Evolution - Using Trees for Classification

Other Recommended Resources

• About the Johnson et al. research
  — Deep-sea mystery solved: astonishing larval transformations and extreme sexual dimorphism unite three fish families
  — Museum Collections Solve Whalefish Mystery
  — An Overdue Family Reunion
• More about how science really works
  — Understanding Science

Preparation:
Prior to starting the activity, the teacher should:

• become familiar with the research of Johnson, et al. using the resources listed in the Recommended Resources section
• determine student research teams (recommended groups of 3-4 students/team)
• photocopy 1 per group of the following
  — Deep Sea Fish Specimen Cards (pdf; these will need to be cut in advance)
  — Fish Resource Guide (pdf)
  — Deep Sea Fish Specimen Key (pdf)
  — Morphology Cards (pdf; Gut, Muscle, Gill A, Gill B)
  — Student Research Notes (pdf; one per student)
• prepare 1 set of 3 different colored pencils or highlighters per group

Acknowledgements

Dave Johnson, National Museum of Natural History, Smithsonian Institution
Ed Wiley, University of Kansas Biodiversity Institute
Teresa MacDonald, University of Kansas Natural History Museum
Judy Scotchmoor, University of California, Berkeley Museum of Paleontology
Anna Thanukos, University of California, Berkeley Museum of Paleontology
Kathryn Mickle, University of Kansas Biodiversity Institute

Reviewers
Bekkah Lampe, University of Kansas Natural History Museum
Mark Terry, Northwest School

Photo and Illustration Credit
Dave Johnson, National Museum of Natural History, Smithsonian Institution
Bekkah Lampe, University of Kansas Natural History Museum
Chris Kenaley, University of Washington
Kathryn Mickle, University of Kansas Biodiversity Institute
Sandra Raredon, National Museum of Natural History, Smithsonian Institution
Bruce Robison, Monterey Bay Aquarium Research Institute

Deep Sea Mystery home

Activity 1

Activity 2

Activity 3

Activity 4

Activity 5

Activity 6