The natural world has been creating light for over 400 million years through chemical reactions. In the ocean, more than 90% of species use bioluminescence to light up their lives, however, did you know bioluminescence has evolved in some land species too. Fireflies, fungi and even snails use light to survive. The amazing skills these species possess can even aid in medical research!
Luminescence in the sea is much more common than on land. It is not fully understood why this is but there are conditions in the sea which make it much more favourable for bioluminescence to evolve. Many parts of the deep ocean receive no light at all meaning many prey species contain a molecule called luciferin, giving them the ability of bioluminescence and allowing them to be responsible for most light production in the ocean. Recent research has started to focus on tropical forest species that obtain the ability to bio illuminate using this same mechanisms.
Fireflies are among the species that illuminate tropical rainforests. Interesting research has brought light to why they do this. Biologists investigated 26 Brazilian firefly species, which are found in tropical forest as well as open fields surrounding them. The firefly species found in the forest emitted bioluminescence on the green light spectrum. The field fireflies were emitting light on the yellow spectrum and with more flashing patterns of light. The results suggest an adaptation for attracting mates in different types of habitat and the different colours may be potentially due to defense against predators. Scientists investigating the species suggest the light displays a colour that some animals may see as untasteful and avoid eating.This defense tactic has also been observed in the larvae of many insects and adds light to the dark, Brazilian rainforest at night.
Light may be defensive but it also attracts attention. Recently discovered fire beetle larvae (Pyrophorus nyctophanus) have been seen illuminating termite mounds in Emas National Park, Brazil. The green glows, in this case, are for a predatory reason. The larvae stick their heads out of holes in the mounds to attract prey like ants and flying termites, which cannot resist a bright light. The larvae have glands that produce luciferin, the molecule used in marine species to glow and attract prey .
Luciferin was also found to allow bioluminescence in tropical fungi species. The variety of fungi in the tropics is immense with many new species discovered every year. No surprise as estimates of the number of fungal species range from 1.5 million to 5.1million and there are currently only 100,000 classified species. As far as we know, only 71 of these species are capable of bioluminescence.
Studying fungi could be the key to understanding bioluminescence on land. A study carried out by the Brazil’s Instituto de Química-Universidade de São Paulo and Dartmouth’s Geisel School of Medicine last year, identified fungal bioluminescence is controlled by a circadian clock in Neonothopanus gardneri. A circadian clock is an organisms internal alarm clock, responding to environmental queues for certain metabolic processes in a 24 hour period and throughout seasons in the year. In this case, temperature controls the light emitted, suggesting the fungi have adapted to emitting more light in the nighttime to attract more insects and lower wind speeds, both which aid in spore dispersal and therefore reproduction.
There is so much more to explore in the tropical rain forest, with potential new bioluminescent species to be discovered every year. The application of new species to medicine is an often repeated argument for conserving the rainforest. Scientists are now trying to identify the genes responsible for the interactions between bioluminescence and the circadian clock in fungi, in order to shed light on the way our own circadian clocks function. Let’s hope this fungus and potential others can show us the light in understanding bioluminescence on land.
By Meike Simms - Online Media Intern