Biologist studies symbiosis of squids
and their bacterial buddies

Bobtail squids, sea creatures that inhabit shallow tropical waters around the world, have a unique way of eluding their predators on moonlit nights. Their undersides glow - just enough to match the moonlight and make them virtually invisible to eels and big fish below. "If you're a Star Trek fan, you might think of it as a Klingon cloaking device," said NMSU biologist Michele Nishiguchi, who studies the squids and their unusual relationship with the luminous bacteria they use for their protective light. It is a case study in symbiosis - a mutually beneficial association between two different organisms - that has taken Nishiguchi to exotic locations in Hawaii, the Indo-West Pacific and the Mediterranean to collect specimens of the squids and their bacterial buddies. And because both organisms can live independently in a laboratory, unlike those in most marine symbiotic relationships, Nishiguchi can pursue her research at her new home base in southern New Mexico. "My interest is in how bacteria interact with larger animals, including humans," said the evolutionary biologist who joined NMSU's faculty in January. "Humans and bacteria interact all the time, so it's important to understand how bacteria react and adapt, and what kinds of ecological or environmental factors are involved."

Biologist Michele Nishiguchi has traveled to exotic locations in Hawaii, the Indo-West Pacific and the Mediterranean to collect specimens of squids. Photo by Michael Kiernan

She explores these factors by getting up close and personal with bobtail squids, which include a number of closely related species of small squids in the family Sepiolidae.

"These little guys are nocturnal; they bury themselves in the sand during the day and come out to hunt at night," said Nishiguchi. The squids are excellent predators, feeding on shrimp and other small marine life, but they also are vulnerable to larger predators in the clear, shallow waters they inhabit, she said.

From below, the bobtail squid would be easily spotted against the moonlight, if not for its "cloaking device" - a light organ that houses glow-in-the-dark bacteria known by the scientific name of Vibrio fischeri.

Surrounding the light organ is a bilobed ink sac that acts like the diaphragm of a camera, regulating the amount of light that comes out. On the ventral (bottom) side of the light organ is a lens that casts the light downward. On the dorsal (top) side is a reflector.

Using these mechanisms, the squid can let out just the right amount of light to counter the moonlight on any given night. If there is no moonlight, the squid keeps the ink sac contracted so little light gets out. "At dawn the squid vents out about 90 percent of its bacteria," and the remaining 10 percent repopulate the light organ during the day, she said. The bacteria benefit from the association by obtaining nutrients from the squid.

In a juvenile squid, the light organ develops only after it has been infected by the bacteria, and only certain strains of bacteria can get into the organ, Nishiguchi said. Her current laboratory research focuses on the selective mechanisms involved.

"If you have juvenile squids from Hawaii and you compete bacteria strains from Hawaii with Japanese bacteria, the Hawaiian bacteria will always win," she said, even though the squids from different geographic locations are closely related and the bacteria are of the same species.

"Rarely have evolutionary biologists been able to demonstrate this interorganismal fidelity so clearly," the magazine Science noted in an article reporting on Nishiguchi's research.

How and why the squids can be so finicky are questions Nishiguchi is trying to answer now. The answers could have important implications because humans, too, interact with bacteria. For example, some bacteria that live in the human intestinal tract produce vitamins and other nutritional supplements that benefit their hosts.

Karl Hill

AMC builds abrasive block cutter
for Santa Fe company

"Built from scratch" is an apt term to describe one of the Advanced Manufacturing Center's latest creations. It is a machine designed to cut abrasive blocks into sizes small enough to be used around the home.

Staff and students at NMSU's AMC designed and built the device from the ground up for Earthstone International, a Santa Fe company that uses glass to make abrasive blocks. QUIKSAND blocks can be used in place of sandpaper for household jobs such as sanding and paint stripping, or as heavy-duty household cleaners, rust removers or grill cleaners. Cutting the blocks presented a unique challenge, said Steve Haines, Earthstone's research director. Bearings and steel blades on the band saws they used were wearing out due to the harsh material. "It's so abrasive it wears things out, but you can cut it with a pocketknife," he said. So they contacted the AMC, a fully operational manufacturing facility within the College of Engineering that pairs NMSU students with full-time staff. About 17 students and three staff members worked for about nine months to design and build the cutting machine.

Yu-Ping Tang, '97, design engineer for NMSU's Advanced Manufacturing Center, stands in front of the four sections of the abrasive block cutting machine he developed. Photo by Michael Kiernan

Yu-Ping Tang, '97, an NMSU mechanical engineering master's graduate, designed the device, composed of four sections assembled in an L-shape. The machine, using a conveyor belt, propels large blocks through several cutting areas where blades slice them like loaves of bread. The blocks are cut into small, uniform pieces with little waste. To combat worn-out blades, the new machine uses a combination of diamond-cutting blades and carbide inserts, which are much hardier than those used previously.

Earthstone's officials are thrilled with the outcome. "It will increase our production 10-fold, at least, while also reducing labor cost and increasing air quality, safety, efficiency and consistency," Haines said.

"This is exactly the kind of project we want to do more of," said Ed Hensel, '86, AMC director. "The AMC designs and manufactures unique industrial machinery and process automation equipment. This equipment often opens up new market opportunities for New Mexico businesses."

Benjamin Varela, '96, an NMSU mechanical engineering doctoral candidate, served as project manager, overseeing all aspects and coordinating project involvement at the AMC from start to finish. "I had to find materials, work with vendors, develop quotes and job orders for the students in the shop," he said. "I learned a lot from managing this kind of project."

One of his jobs included helping students translate Tang's drawings into a physical product. Mechanical engineering technology student Wes Eaton said that was one of his biggest challenges in building the machine. "We had to try to understand the design, and the way the designer was thinking, to build it," he said. "This project was totally new. You don't know what's going to happen, so you have to try it and go with it. It's just like working in the real world."

Rachel Kendall