Growing Camouflage

 A garden on the back of a weevil living a humid Chilean rainforest.

A garden on the back of a weevil living a humid Chilean rainforest.

Lots of us will be familiar with organisms like decorator crabs that utilize bits and pieces of their environment, especially living sea anemones, as a form of camouflage and protection. Examples of terrestrial insects attaching bits and pieces of lichens to their body are not unheard of either. However, there are at least two groups of arthropods that take their camouflage to a whole new level by actively growing miniature gardens on their bodies.

Little is known about these garden-growing arthropods. To date, these miniature gardens have only been reported on a few species of weevil in the genus Gymnopholus as well as a species of millipede called Psammodesmus bryophorus. Coined epizoic symbiosis, it is thought that these gardens serve as a form of protection by camouflaging the gardeners against the backdrop of their environment.

 Bryophytes on a  Psammodesmus bryophorus  male.

Bryophytes on a Psammodesmus bryophorus male.

Indeed, both groups of arthropods frequent exposed areas. What is most remarkable about this relationship is that these plants were not placed on the carapace from elsewhere in the environment. Instead, they have been actively growing there from the beginning. Closer inspection of the cuticle of these arthropods reveals unique structural adaptations like pits and hairs that provide favorable microclimates for spores to germinate and grow.

The plant communities largely consist of mosses and liverworts. At least 5 different liverwort families are represented and at least one family of moss. Even more remarkable is the fact that even these small botanical communities are enough to support a miniature ecosystem of their own. Researchers have found numerous algae such as diatoms, lichens, and a variety of fungi growing amidst the mosses and liverworts. These in turn support small communities of mites. It appears that an entire unknown ecosystem lives on the backs of these mysterious arthropods.

 FIGURE 39. Elytral base of Gymnopholus (Niphetoscapha) nitidus with exudates. FIGURES 40a–b. Gymnopholus (Niphetoscapha) inexspectatus sp. n., live specimen with incrustrations of algae and lichens; photographs M. Wild, Mokndoma.  [SOURCE]

FIGURE 39. Elytral base of Gymnopholus (Niphetoscapha) nitidus with exudates. FIGURES 40a–b. Gymnopholus (Niphetoscapha) inexspectatus sp. n., live specimen with incrustrations of algae and lichens; photographs M. Wild, Mokndoma. [SOURCE]

There is still much to be learned about this symbiotic relationship. Although camouflage is the leading hypothesis, no work has been done to actually investigate the benefits these arthropods receive from actively growing these miniature gardens on their backs. Mysteries still abound. For instance, in the case of the millipede, gardens are found more frequently on the backs of males than on the backs of females. Could it be that males spend more time searching their environment and thus benefit from the added camouflage? Only further research will tell.

Photo Credits: [1] [2] [3]

Further Reading: [1] [2] [3]

Yeast in Lichens

Quite possibly one of the oldest symbiotic relationships on Earth has been hiding in plain sight all this time. Lichens have long been regarded as the poster child for symbiotic relationships. Certain species of fungi team up with specific algae and/or cyanobacteria in a sort of "you scratch my back and I'll scratch yours" type of relationship. In return for room and board the photosynthetic partner feeds the fungus. There are many variations on this theme which translates into the myriad shapes and colors of lichen species around the globe. For 150 years we have been operating under the assumption that there is only ever one species of fungus (in the phylum Ascomycota) for any given lichen. We were wrong. 

Originally thought to be contamination, researchers at the University of Montana and Perdue found gene expression belonging to the other major fungal phyla, Basidiomycota. The research team soon realized that they had uncovered something quite monumental. Lichens were harboring a partner we never knew existed. These newly discovered fungi are an entirely new lineage of yeast. What's more, this relationship has been documented in upwards of 52 other lichen genera worldwide! 

This discovery has led to another major breakthrough in lichen biology, their bizarre variety. The exact same species of fungus and alga can produce completely different lichens with wildly different attributes. Take the example of Bryoria torturosa and B. fremontii. They were thought to share the same partners and yet one is yellow and toxic whereas the other is brown and innocuous. Knowing what to look for, however, has revealed that their yeast partners are entirely different. The yeast is thought to be a sort of shield for the lichen, producing noxious acids that deter infections and predation. 

Almost overnight a new light has been shown on our lichen neighbors. These newly discovered partners aren't a recent evolutionary development. This trifecta likely stems back to the early days when little else lived on land. It just goes to show you how much we still do not know about our planet. It's nice to be reminded of this. 

Further Reading:

http://bit.ly/29WWZ2z