Cephalopods
have long been a subject of fascination throughout the world. They have inspired movies, books and legends, and they are now the focus of compelling new research programs at BBSR. The cephalopod group
includes octopuses, squid, cuttlefish and nautiluses, animals that are found in all of the world's oceans, from the tropics to the poles; from the intertidal zone to the abyss of the deep ocean. Unlike many
mollusks, cephalopods have well-developed senses, heads and brains, and lack the hard external shell of most of their less-sophisticated relatives. Cephalopods are thought by many scientists to be the
most intelligent of the invertebrates and have developed a large repertoire of survival tricks over the past several hundred million years to replace the heavy protective shell. They are able to camouflage
almost instantaneously, change texture and shape to blend into the background, and squeeze through the tiniest of crevices. They can disappear from sight in a cloud of "smoke," and escape from predators
using jet propulsion. Until very recently, even the 60-foot giant squid have been able to evade scientists. While most other invertebrates are sessile or slow moving, these animals are quick and are more
like fish than they are like their sluggish mollusk relatives. My doctoral thesis involved studies of the life history, physiology and behavior of one such species of cephalopod, a particular deep-sea
octopus. While completing this research, I leapt at the opportunity to join a team of scientists, graduate students and select undergraduates, led by Dr. Jennifer Mather, on a study of communication among
Caribbean Reef Squid in Bonaire, a small southern Caribbean island. This project spawned numerous additional collaborations and eventually led me to Bermuda. While attending graduate school at Dalhousie
University, I had access to Caribbean Reef Squid and common octopuses for only two or three weeks of the year, during research expeditions to Bonaire. In September 2003, I joined the faculty at BBSR, where
the same species of squid and octopuses are found in abundance year round in Bermuda's readily accessible coral reef and seagrass habitats. My current research includes investigations of octopus camouflage,
tag-and-release growth studies on wild squid, and predator response and signaling in Caribbean Reef Squid. In order to study octopus camouflage in an objective, quantifiable way, volunteer intern
Nancee Kumpfmiller and I use a digital camera to photograph the animals in controlled settings. As digital cameras record each tiny area, or pixel, of an image as a series of numbers that represent the values of red, green and blue present, this method does not rely on human judgment to assess whether or not an octopus is camouflaged. The initial study involved taking a series of images of octopuses on various backgrounds with controlled lighting. The backgrounds consisted of: 12 vinyl panels of uniform color; colored tank gravel inside the aquarium, which allowed the octopuses to touch textured objects; the same gravel outside the glass where the octopuses could not access it; and natural substrates likely to be found in the wild.
Dr. James Wood catches a common octopus for his research on camouflage. |
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We were then able to compare the values of the different backgrounds, in grayscale and in color, to those of the octopuses,
quantifying how well the octopuses matched each background. Our preliminary results show interesting and significant differences between their camouflage ability on these four sets of backgrounds.
My second BBSR research project, initiated in 2004, centers on the tagging of Caribbean Reef Squid. As larger predatory fish are being removed from the marine ecosystem, squid are becoming
an increasingly important part of the world's fisheries. Despite this, very little is known about the life history of squid and how factors such as water temperature and size affect
their growth rates in the wild. When current fisheries models are applied to squid with the assumption that squid grow
like fish, they produce errors as large as 1,000 percent. The objective of our tagging study is to develop a method to measure the growth rates of squid in the wild so biologists and
fisheries managers will have the necessary data to better understand the life history of these fast-growing animals.
Most species of squid live offshore, so the chances of finding the same animal twice are near zero. In contrast, the Caribbean Reef Squid in Bermuda live close to the shore and in
some locations can be consistently recaptured. They are model species for the development of a tagging technique to monitor growth. With Suzanne Replinger, an intern in the 2004 Research Experiences for Undergraduates
program, I developed a tagging technique to directly measure the growth of individual wild squid using newly developed elastomeer tags donated by Northwest Marine Technology. This method can be used over
short periods of time, allowing the effects of seasonally changing environmental factors, such as sea temperature, to be assessed. This year, intern Kim Zeeh and I confirmed that
these tags do not affect the growth rate of the squid. Studies conducted on other marine species have shown that the tags do not affect predation levels either.
In summer 2004, my team began experimenting with visual signaling in Caribbean Reef Squid. Although squid reliably use visual signals, our laboratory experiments indicated that
they also use additional methods of communication, spurring us to further pursue our research in this area. Looking to the future, our initial studies of cephalopods in Bermuda show great potential for
expansion. As is often typical in science, the answers from one set of experiments have led to even more questions about these fascinating residents of the sea. |
