Environmental Sex Determination in Ferns

Environmental Sex Determination in Ferns



Next spring, I will be using CREATE in a course (BIOL 2040 Fundamentals of Biological Investigation, 2 credits) designed to offer experience in hands-on research and scientific writing that is a requirement for all of our biology majors. The class meets once a week for two hours and 52 minutes and is capped at 16 students. In the first half of the semester, students work together as a class to design and carry out an independent research investigation within a topic or system selected by the instructor. In my section of the course, the model organism that the students use for their research is either Ceratopteris richardii (C-Fern®) or C. thalictroides (C-Fern Express™). In the second half of the semester, students work in teams of four to write and extensively revise a formal paper written in the style required for publication in the American Journal of Botany.


The papers in this module focus on the topic of environmental control of post-fertilization sexual development in ferns, the last two specifically in Ceratopteris. The papers come from two different labs and provide a basis for understanding of the interaction of environmental variables and antheridiogen, the hormone responsible for sex determination in some ferns, as well as basic experimental design using ferns.

Applicable for Courses:

Fundamentals of Biological Investigation

Educational Level:

lower-mid level

Roadmap Objectives:

    • Article: Quintanilla, L.G., L. DeSoto, A. Jiménez and M. Méndez. 2007. Do antheridiogens act via gametophyte size? A study of Woodwardia radicans (Blechnaceae). American Journal of Botany 94: 986-990.
    • Content area/major concepts: I chose this paper as the starting point for this module because it has a brief explanation of environmental sex determination and introduces competing hypotheses explaining the relationships among antheridiogen, gametophyte size and maleness. It also serves as an introduction to basic methodology in studying fern gametophytes.

      mechanisms of sex determination, natural selection, pheromones, antheridiogen, competing hypotheses, cost of sexual reproduction
    • Methods or technology used to obtain data: plant collection in the field, sterile technique, establishing and growing fern cultures on artificial medium, techniques of identification of gametophyte sex and measurement, image capture, image analysis using ImageTool, statistical tests
    • How the CREATE strategy was used:
    • Biggest teaching challenge: jargon, unfamiliar methods and statistics
    • Article: DeSoto, L., L.G. Quintanilla, and M. Méndez. 2008. Environmental sex determination in ferns: effects of nutrient availability and individual density in Woodwardia radicans. Journal of Ecology 96: 1319-1327.
    • Content area/major concepts: The second paper in the series is a continuation of the work from the Méndez lab, building on the results of the first study and adding the component of the effects of nutrient availability on sex expression.

      environmental sex determination, mate competition, nutrient availability, homosporous ferns, gametophyte generation, sporophyte generation, pheromones, density effects on development
    • Methods or technology used to obtain data: Serial dilution, specimen fixation, slide preparation, image analysis using ImageJ (Note: this program is used in the class), statistics
    • How the CREATE strategy was used:
    • Biggest teaching challenge: jargon of plant life cycle and morphology, scientific names, unfamiliar statistics, includes several experiments
    • Article: Ayrapetov, A. and M. T. Ganger. 2009. Nutrient levels do not affect male gametophyte induction by antheridiogen in Ceratopteris richardii. American Fern Journal 99: 273-278.
    • Content area/major concepts: The third paper focuses specifically on Ceratopteris (C-Fern®), providing results in this model organism that contradict the findings of Paper 2.

      sexual dimorphism, C-Fern® biology and life history characteristics, antheridiogen, regression analysis
    • Methods or technology used to obtain data: introduces standard methodology established for C-Fern® cultures
    • How the CREATE strategy was used:
    • Biggest teaching challenge: not a lot of evidence provided, no acknowledgement of the work of the Méndez lab.
    • Article: Students will each select the final paper of the series individually, with instructor approval prior to starting a CREATE analysis. This should encourage each group to obtain four additional papers that they will use as sources in their own manuscript.
    • Content area/major concepts:
    • Methods or technology used to obtain data:
    • How the CREATE strategy was used:
    • Biggest teaching challenge:

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