When humans fall ill, we can go to the doctor to receive a diagnosis and treatment. We have a form of communication, and our body has good indicators that can help the doctor diagnose the problem. But what happens when we are trying to diagnose organisms that have no way to tell us what is wrong, and no way of knowing how badly they are affected? For instance, in the case of many marine organisms, illness is being caused by humans. We have used our oceans such that they now contain areas with little to no oxygen, where life is barely sustainable. How does this, combined with ongoing pollution and human activities, stress marine life?

Researchers at the College of Charleston recently faced this problem, and have developed a method of “talking” to crustaceans such as shrimp and blue crabs through motor physiology. Karen and Louis Burnett have created an underwater treadmill to determine vital signs as a measure of stress. The study organisms are infected with bacteria, and water conditions on the treadmill can be regulated to encompass various oxygen levels, pH, and other water quality characteristics. Vital signs such as heart rate and blood pressure from the infected animals can then be compared to those of uninfected animals in the same water conditions (the same vital signs that are used in human stress tests). The studies are also looking at muscle physiology to examine the use of aerobic and anaerobic respiration to molecularly determine how stressed animals are affected. How are abilities necessary for their lives, such as walking and swimming, affected by bacterial infections and water oxygen levels? The Burnetts have found that uninfected animals perform better on the treadmill, and that infected animals have a hard time taking up oxygen due to immune responses. Additionally, the animals’ ability to fight infection is negatively affected by a low oxygen supply in the water. Continual study to answer questions such as these will help assess what we can change in our use of natural resources.

See an interview with the Burnetts here.

And just for fun…here’s shrimp on a treadmill!

Reference:
Energy metabolism and metabolic depression during exercise in Callinectes sapidus,
the Atlantic blue crab: effects of the bacterial pathogen Vibrio campbellii – The Journal of Experimental Biology

The mantis shrimp diverged evolutionarily from the crustacean mainline about 400 years ago and have since developed unique characteristics. Unlike most other crustaceans, they actively hunt prey and kill it with a crushing blow which has been theorized to be strong enough to create bubbles containing gas at temperatures upwards of 2000 Kelvin. This quality, however, is nowhere near as stunning as the mantis shrimp’s most incredible attribute: their eyes. In April 2001, the most comprehensive paper to date describing the mantis shrimp’s visual system was published by Justin Marshall and Thomas Cronin in The Biological Bulletin. In their paper, the authors described the unusual characteristics of the mantis shrimp visual system and hypothesized the applications of this system in the development of machine vision.

Mantis Shrimp Eye via New Scientist

The first moderately unique quality of the mantis shrimp eye is a property which arises simply from the anatomy itself. Each eye is broken up into three distinct areas: two hemispherical regions on either side of a central “midband” area. Interestingly, each ommatidium (photoreceptor) in the hemispherical regions has a corresponding ommatidium in the opposing hemisphere with which it shares a visual field. This characteristic allows for stereoscopic visual perception within each eye. In other words, each eye of the mantis shrimp has the internal ability to produce depth perception and create a three-dimensional representation of the world without input from the other eye. While the eyes of humans have to move in synchrony in order to create depth perception, the eyes of the mantis shrimp can move freely from one another and still possess the ability to model the surrounding world in three dimensions.
The next interesting ability of the mantis shrimp eye that the authors discussed was its ability to qualitatively detect polarized light. Most objects reflect light of a specific wavelength which gives rise to color vision. In a similar fashion, most objects also reflect light with a certain polarization that is characteristic of the material itself and mantis shrimp have the unique ability to detect and distinguish different planes of polarization, allowing them to identify materials at a distance.
On a final but similar note, the authors also suggest that the mantis shrimp eye also might possess the extremely unique ability to make sense of circularly polarized light. Circularly polarized light is an emergent property of the reflected light of some metals and membranes, and the authors seem to believe that the shrimp’s R8 receptor may act as a quarter-wavelength retarder which would allow the animal to convert circularly polarized light into linearly polarized light which they could then sense using their previously described polarized light receptor system.
The most important conclusion the authors suggest can be drawn from this paper is the parallel processing systems used to detect all of these different properties of light. Since most of the shrimp’s ommatidia or photoreceptors are specific for detecting a single light property, little higher level processing of the information is needed. This layout, they say, is a potent model for the creation of machine vision systems as little higher level processing is needed for extremely precise color vision. The authors think that this sort of thinking – drawing ideas for mechanical systems through the design of biological ones - will be increasingly important in the future. That aside, the mantis shrimp is an incredible animal and the inner workings of the eye are still very much a mystery and will require much more research to fully understand.

Parallel Processing and Image Analysis in the Eyes of Mantis Shrimps – The Biological Bulletin

The Art of Thriving -New Scientist