Deep Water Rave: Biofluorescence in Fish

From the magical glow of fireflies at night, to the mesmerizing orb of the deep sea angler fish designed to lure prey, most people are familiar with nature’s glowing creatures. This is due to a process called bioluminescence. These animals create their own light by producing a chemical called luciferin, which chemically reacts with oxygen to release energy in the form of light.

A similar process called biofluorescence occurs when one wavelength of light is absorbed, and then converted into a lower energy and higher wavelength, resulting in a different color of light. Recently, it was found that  more than 180 species of biofluorescent fish swimming in the waters. Fishes from the Cayman Islands, the Bahamas, and the Solomon Islands were imaged and scanned for fluorescence using special LED light sources and filters, and the results presented a wide variety of patterns and colors.

Diversity of fluorescent patterns and colors in marine fishes. A, swell shark (Cephaloscyllium ventriosum); B, ray (Urobatis jamaicensis); C, sole (Soleichthys heterorhinos); D, flathead (Cociella hutchinsi); E, lizardfish (Synodus dermatogenys); F, frogfish (Antennarius maculatus); G, false stonefish (Scorpaenopsis diabolus); H, false moray eel (Kaupichthys brachychirus); I, false moray eel (Kaupichthys nuchalis); J, pipefish (Corythoichthys haematopterus); K, sand stargazer (Gillellus uranidea); L, goby (Eviota sp.); M, goby (Eviota atriventris); N, surgeonfish (Acanthurus coeruleus, larval); O, threadfin bream (Scolopsis bilineata). doi:10.1371/journal.pone.0083259.g001

In deep sea waters, red, yellow, orange, and green light gets filtered out, leaving only the wavelength of light that we perceive as blue light. Using biofluorescence, these fish species absorb the blue light, and convert it back to a lower energy of light, thus re-emmiting the red, yellow, orange, and green colors seen above.

Scientists are currently studying this broad diversity of biofluorescence to determine it’s evolutionary advantages and adaptations to marine life. One hypothesis is that the variations of color and patterns may be used to attract a mate, similar to the way a male peacock will flash his patterned feathers at a female. Another possibility is that different colors and patterns are suited for camouflage within biofluorescent coral reefs. There have also been studies about using biofluorescence as a type of “hidden communication” between the species; they flash their light to one another to signal that a predator is nearby. This silent communication is possible because the light emitted is at a wavelength that the predator itself can’t see.

While most of us will never get to see these beautiful creatures for ourselves, we can close our eyes and envision ourselves swimming in the dark surrounded by glowing flashes of reds, yellows, and greens – nature’s version of a dance rave in your imagination!

Dogs poop in alignment with Earth’s magnetic field

Call me crazy, but I think watching my dogs poop is hilarious. The way they sniff about, scurry and circle around the perfect spot, to finally awkwardly hunker down into position. A recent study suggests that there may be a method to this madness, and the explanation is magnetism.

70 dogs of varying breeds, age, and sex were observed for two years while they took care of business (defecation and urination). The alignment of their body axis was analyzed in conjunction with the magnetic field conditions of Earth during the observation period. Geomagnetic conditions fluctuate depending on time and location, and magnetic declination occurs when magnetic north is deviates from true north (the physical direction moving towards the North pole). When magnetic declination is at 0%, compass north and true north are the same and the condition of the magnetic field is considered stable. When there is deviation from true north, the magnetic field is considered unstable. What researchers found was that under stable “calm magnetic conditions”, dogs preferred to align themselves with the north-south axis when dropping a deuce.

It is still unclear exactly why this response occurs only when the geomagnetic conditions are stable and why the dogs assumed a north-south alignment (as opposed to the east-west direction). The study also mentions that female dogs assumed this alignment while urinating as well, whereas male dogs aligned themselves slightly angled at north-west, possibly due to the “leg lift” position. Domesticated dogs are also dependent on their owner’s calls and commands, which may have an influence on responding to natural instincts and sensitivities to their surroundings.

The subject matter may be strange and begs the question, “WHY?” Yet, the implications may lead to further understanding on how geomagnetic sensitivity affects animal behavior. Similar studies have also been researched in other mammals, such as deer, cattle, and foxes, in regards to grazing/feeding, hunting, homing, and other navigational behaviors in the wild.

Just the other day, I observed both my dogs doing their thing while facing toward the same direction. Is it because of their innate sensitivity to the Earth’s magnetic field or just pure coincidence? I should invest in a good compass to figure it out.