INNOVATIONS - The Use of Kryptolebias marmoratus Eggs as an Educational Tool for Embryology Education

Oct 15, 2026

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Plastic embryological models lack the excitement of observing real, live embryos, and traditional chick embryo demonstrations require sacrificing organisms. Kryptolebias marmoratus embryos are large enough to be viewed with a light microscope without harming the organism, and eggs are easy to obtain from captive fish. Key early developmental traits are readily visible, and classroom use is rewarding, increasing student engagement with embryology and chordate evolution.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages6

Reading Time15 min

AccessFree to download

Abstract

Introduction

Methods

Acquisition of fish

Fish Maintenance

Collecting eggs

INNOVATIONS The Use ofKryptolebias marmoratus Eggs as an Educational Tool for Embryology Education Tyrone Genade Current address: Department of Biology, Northwestern College, Iowa, 51041 Department of Human Biology, Faculty of Health Sciences, University of Cape Town, South Africa Corresponding Author: [tyrone.genade@gmail.com](tyrone.genade@gmail.com) Abstract: Plastic embryological models lack the excitement of seeing real, live embryos. Chick embryos are often used to demonstrate embryological development and blood circulation to students but this necessitates the death of the organism. Kryptolebias marmoratus embryos are large and can be viewed by means of a light microscope without need to harm the organism. Eggs are easily obtained from captive fish; and are easy to display to students. Embryological features common to early human development are readily visible in the K. marmoratus embryos: early brain development, eye development, somites, limb buds, blood circulation and pigment cell migration. Embryos also twitch when exposed to light and the beating heart is readily viewable. Use of the embryos in a classroom has proven rewarding, students marvel at observing embryological development and are more eager to consider the common embryology and evolution of chordates. Key Words: Kryptolebias, embryos, gastrula, vitelline artery, melanophore, erythrophore, somites INTRODUCTION Kryptolebias marmoratus (Poey, 1880) are small hermaphrodite fish found in mangrove swamps along the shoreline of the Gulf of Mexico and the Caribbean (Taylor, 2012). These fish lay large, 2 mm diameter eggs (Huber, 2015) and are easy to care for in captivity where they will breed freely. The eggs are clear and the developing embryo can be easily observed by aid of a dissecting microscope, which make this fish an interesting and useful educational tool for use in both anatomy and embryology courses. In spite of its self-fertilizing biology and relatively low genetic diversity (Tatarenkov et al., 2015), K. marmoratus remains phenotypically plastic. It survives in a wide range of water conditions, from soft acidic water to full strength sea water and can tolerate temperatures from 18 °C to 38 °C (Huber, 2015). It can survive long periods (days) immersed so long as it remains moist (Wright, 2012), and is often encountered in large numbers hiding above the water level, beneath bark and under logs in mangrove swamps (Taylor, 2012) . This hardiness facilitates uncomplicated captive maintenance. K. marmotatus reaches a maximum size of 75 mm (Huber, 2015) and requires little space per individual fish meaning large colonies can be maintained without the need for large aquaria. More interesting still is that these fish, having lived as self-fertilizing hermaphrodites for much of their lives, can change into fully functional males that are able to spawn with and fertilize the eggs of hermaphrodite fish. Environmental conditions (such as temperature stress) can stimulate the development of males from eggs (Turner et al., 2006) . As the large eggs develop and without killing the organism, students can use a dissecting microscope to observe gastrulation, the development of the neural tube, somites and the circulation of blood. The embryos twitch when exposed to light, which means they can be used to facilitate a discussion of motor system synapse formation. A detailed study ofK. marmoratus embryology has been published by Mourabit et al. (2011) as well as a means to manipulate the embryos for microscopic studies (Mourabit & Kudoh, 2012) . The current article discusses the basic care ofK. marmoratus in the teaching lab and presents micrographs of observations made using a dissecting microscope. METHODS Acquisition of fish Fish were obtained from hobbyists within the American Killifish Association ([http://www.aka.org](http://www.aka.org)) but they are also available from research labs such as my own or others such as Dr. Ryan

FAQs

Why are Kryptolebias marmoratus embryos suggested instead of chick embryos?

Chick embryo demonstrations typically require killing the organism, while K. marmoratus embryos can be viewed under a light microscope without harming the organism.

What developmental features of early human development are visible in K. marmoratus embryos?

Early brain development, eye development, somites, limb buds, blood circulation, and pigment cell migration are described as readily visible.

How are the eggs collected and incubated for classroom use?

Fish spawn daily on acrylic yarn mops; eggs are removed for incubation, handled carefully, placed on damp cotton wool or in petri dishes with salt solution, and infertile eggs are removed when they appear murky white.

Oct 15, 2026

Upload by Ben