Model organisms are plants, animals, and microorganisms that we study in order to understand biological phenomena. Common model organisms that you may have heard of – or even worked with – are the mouse, rat, fruit fly, nematode C. elegans, plant Arabidopsis, and bacteria E. coli.
When researchers choose a model organism, they consider factors like size, generation time, accessibility, conservation of mechanisms, economic costs/benefits, and genetics. New biotechnologies like genomic sequencing and CRISPR have enabled researchers to assume that most organisms have readily available molecular biology resources. This allows scientists to focus on a wider cast of organisms and pick a species whose behavior, physiology, or genome structure is particularly suited for examining their research questions.
Here are four lesser-known model organisms that are helping scientists tackle big questions.
Arbacia punctulata: For over a century, this purple sea urchin found in the Atlantic Ocean has been central to the study of reproduction and development. Its eggs are transparent and easy to fertilize AND its embryos develop rapidly and synchronously. These four qualities make these urchins-to-be a great model organism for embryological studies. Such studies helped researchers formulate the theory of heredity, understand parthenogenesis and fertilization, and determine the importance of centrosomes and microtubules! Today they are helping researchers examine the roles of mRNA and actin within cells as well as the causes of many birth defects.
Gasterosteus aculeatus: This fish species, more commonly known as the three spine stickleback, is small (3-4 cm), easy to raise, morphologically variable, and found throughout much of North America. Early ecologists were able to collect and compare multiple populations of this fish from a variety of habitats. As a result they quickly became the go-to organism for studying how environment shapes evolution and vice versa. Today three spin sticklebacks are a key model organism to understand climate change adaption. They’re also a model organism for studying host-parasite interactions, sensory physiology, reproductive physiology, environmental genomics, and endocrinology.
Nothobranchius furzeri: This killifish species is the fastest maturing vertebrate on earth. They have to be because they live in the emphermal pools of Zimbabwe and Mozambique. They’ve evolved eggs that can survive a year without water, a natural life span that lasts only a few months, and a two-week childhood! Their rapid growth, early sexual maturation, and natural variation in life spans has made them a popular model organism in the study of aging.
Neurospospora crassa: This red bread mold was first identified in France 1843 where it was a pest to local bakers. One hundred years later scientists Edward Tatum and George Beadle decided to use the mold to study the relationship between DNA and enzymes. That because red bread mold is easy to grow, has a haploid life cycle (easy to induce and track mutations), and has a simple seven chromosome genome. Tatum’s and Beadle’s work resulted in the “one gene one enzyme hypothesis” that earned them the Noble Prize in Medicine in 1958. Today this organism continues to be used to study molecular and cell biology topics like gene silencing, epigenetics, circadian rhythms, cell polarity, and cell fusion.
There are many model organisms out there! Interested in learning more? Listen to this 4 minute NPR story on the Octopus as a model organism, read or listen to this article from Quanta Magazine about the search for new models, or simply scroll through Wikipedia’s extensive List of Model Organisms.