Sea Urchins: The Marine Hedgehogs

Red Sea Urchins in a kelp forest off the coast of British Columbia  (Photo credit: NatGeo)

The sea urchin is a small echinoderm found in marine ecosystems from the very depths of the ocean to the intertidal zone. Feeding primarily on algae and small invertebrates, these spectacular pin-cushions move along the ocean floor using tubular feet powered by a water vasculature system. In 14th century England, the term "urchin" was used to refer to the hedgehog. Thus, when these spiky marine creatures were first described, they were given the name "sea urchin." From kina in New Zealand, to uni in Japan, sea urchin is served in local cuisine all around the world. But perhaps more importantly, this organism has helped better our understanding of animal embryonic development. A dioecious organism, the male and female urchins produce sperm and eggs, respectively. Both gametes are dispersed into the open ocean in synchrony, in order to increase the likelihood of fertilization.

In a recent laboratory exercise, I had the opportunity to collect gametes from live sea urchins of the species Lytechinus variegatus. After observing the sperm and eggs under a microscope, we mixed the two and watched as the eggs were fertilized, began to cleave, and eventually gave rise to motile, feeding plutei. The video below, of a 48 hour pluteus was created by taking a series of images through the larva on Rhode Island College's new Olympus FluoView 1000 confocal laser scanning microscope. The green coloration is the result of autofluorescence.

Thanks to Dr. Thomas Meedel of Rhode Island College for the excellent lab, and Dr. Eric Roberts for his assistance with the confocal microscopy. 

The Namib Desert Beetle: A Recipe for Water

The Namib Desert Beetle laden with water droplets (Photo credit: Solvin Zankl)

As the early morning fog drifts across the Namib Desert of south-west Africa, an army of spindly-legged beetles emerges from the sand. Accustomed to an average annual rainfall of one inch, these critters are eager to employ their water collection apparatus that makes them so unique. The process begins when heat is radiated from the matte black exoskeleton, resulting in a body temperature slightly lower than that of the surrounding air. With the beetle's body held at a 45° angle to the sand, the moist breeze contacts the cool exoskeleton and water condenses into small droplets. This beading effect is facilitated by a series of hydrophilic (water attracting) bumps surrounding by a waxy, hydrophobic (water repelling) surface on the insect's back. The droplets may grow to nearly a quarter of an inch, and then roll down to be gratefully sequestered by the beetle's mouthparts. And then it's back down the dunes and away from the morning sun for these diminutive hydroplants.

A seawater greenhouse in Australia (Read about the exciting initiative here)

Researchers at MIT have used this peculiar water collection mechanism as a model for the synthesis of materials used in a range of innovative research and industrial devices (See the news article here). Among other applications of this mechanism is a seawater greenhouse project designed for arid coastal regions, described by Michael Pawlyn in his presentation entitled "Using nature's genius in architecture" (Available on TED here). These projects represent yet another example of innovation based directly on natural systems observed on this planet - the ultimate design project.

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The beetle's water collection mechanism was first described in the article: Parker, Andrew R., and Lawrence, Chris R. November, 2010 "Water capture by a desert beetle." Nature 414: 33-34. More about this insect, and other biomimicry projects can be explored on AskNature. Watch the BBC wildlife feature on this beetle here.