Biology of the Family Chiaceae (Chia Pets)

Biology of the Family Chiaceae (Chia Pets)

by Eric J. Weissberger
Institute of Marine and Coastal Sciences
Rutgers University
New Brunswick, New Jersey

Members of the family Chiaceae, popularly known as Chia pets (Figures 1 and 2), are common organisms, frequently found in the same habitat as humans. Although widespread, very little is known about the biology of Chias. The field of Chia research is wide open, and provides many opportunities for fascinating research.
Chia Sheep
Figures 1 and 2. Chia sheep (Figure 1) and chia frog (Figure 2) are two common members of the family Chiaceae. Each species is shown here in its both its animal phase (1a, 2a) and its plant phase (1b, 2b).
Chia Frog

First, Chias are a missing link between plants and animals. Until this time, the only known motile, photosynthetic organisms were certain types of algae and protists. Chias are the first truly photosynthetic animals to be discovered.
Generalized Chia Life Cycle
Figure 3. Generalized Chia life cycle.
Second, the Chia life cycle (Figure 3) is complex. The Chia's mating call is usually heard in early November, a melodic ch-ch-ch-chia (whence this group gets its name). This call is usually broadcast over television airwaves. How Chias have adapted so quickly to use human produced electromagnetic radiation remains a mystery. After being born, juvenile Chias begin life in a purely animal phase, inside a plain cardboard cocoon. These cocoons are usually found in large aggregations in stores such as K-Mart and Target around late November. The cardboard cocoon is then transported via a human host to a location underneath a coniferous tree. The cocoon at this point usually becomes decorated with bright papers and ribbons, not unlike a decorator crab's shell. In an amazing display of synchrony, all Chias hatch on the morning of December 25, and migrate to windowsills, where the plant phase begins to grow. How the Chias return to K-Mart to complete the life cycle is open to debate.
Two possible evolutionary trees for Chias
Figure 4. Two possible evolutionary trees for Chias: monophyletic (all Chias closely related) and polyphyletic (Chias distantly related but appear similar because of convergent evolution).
Third, the evolutionary history of Chias is unclear. I propose two possible hypotheses to explain Chia evolution (Figure 4). First, Chias may represent a monophyletic group, meaning they are descended from a common ancestor. If this were so, then all Chias are closely related, but have evolved to mimic other animals. For example, the Chia sheep is more closely related to the Chia frog than to an actual sheep. This would be similar to the case of marsupials, which are all closely related, but appear similar to many types of placental mammals. The alternative hypothesis is that Chias are polyphyletic, meaning that they are not really related evolutionarily, but appear similar because of convergent evolution (adaptation to similar environments). In this case, the Chia sheep is more closely related to an actual sheep than it is to the Chia frog. If this hypothesis were true, it would imply that Chiaism has arisen independently many times.

Some researchers claim that Chias are not one organism, but two distinct organisms living together symbiotically. Some support is given to this hypothesis with the recent discovery of the Chia herb garden, which has no known animal host.

Finally, and most controversially, Chias may be close relatives of humans. With the discovery of the so-called "Chia professor" (Figure 5), the importance of Chia research in learning about our own evolutionary history is more germane than ever.
Chia Professor
Figure 5. The so-called Chia professor, shown here in both its animal phase (5a) and its plant phase (5b), may be the missing link between humans and photosynthetic animals.


Thanks to Lee Kerkhof, David Scala, Judy Grassle, Chris Gregg, and Jeanine Bayus for helpful comments on the manuscript

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