Thursday, September 23, 2010

Otter Cliffs field trip

The class went on a field trip yesterday to my favorite intertidal site on MDI, Otter Cliffs. Everyone saw various species of hydroids and bryozoans in the wild, as well as sponge. The stinkiness of the sponge provided a memorable demonstration of the secondary compounds used by these critters to protect themselves from being eaten. The pungent odor of rotten garlic mingled with gunpowder seems a convincing predator deterrent. We did happily sample the red alga, dulse, for an interesting intertidal snack.

Saturday, September 18, 2010

Communicating Science via Film

I'm currently reading Randy Olson's Don't Be Such a Scientist, hoping to broaden my perspective on effective science communication. The book's subtitle, "talking substance in an age of style," captures what is challenging and aggravating to scientists who encounter resistance to evidence-based, fact-filled explanations about topics such as evolution and climate change.
Dr. Olson, a PhD from Harvard, with a background in evolution and ecology, also has an MFA in fimmaking from USC. He left the narrow arena of peer-reviewed journals and significantly expanded the audience he reaches through his website and films. Next week, he'll be at the University of Maine at Orono for three days, where panel discussions will follow screenings of several of his films, including Flock of Dodos: The Evolution-Intelligent Design Circus, Salt of the Earth: A Journey into the Heart of Maine Lobster Fishermen, and the improbably titled, Sizzle: A Global Warming Comedy. I'm heading up Thursday for Sizzle, leaving the COA campus at 2:30. Students, let me know if you'd like a ride.
He's come a long way as a filmmaker, but Randy Olson's early short, Barnacles Tell No Lies, is still an excellent illustration of the contrast between the accurate, thorough, and fact-filled, yet ultimately unilluminating approach of a college lecture (however unfairly stereotyped) and the power of humor and compelling visuals that film is so good at.

Sunday, September 12, 2010

sponges: simply splendid

Sponges are typically described as the simplest of animals. In some ways, that’s a fair label. Their bodies are composed of only a handful of cell types responsible for all the functions in a living sponge: covering the outside, pumping water through the inside, digesting food, making the skeleton (yes, sponges have skeletons), and making gametes. These processes are all conducted at the cellular level, with no higher organization imposed. In contrast, there are hundreds of unique types of cells in humans, which are arranged into tissues, organs, and systems.
But sponges should not be underestimated; they have some special attributes.
Archaeocytes, a cell type that is dispersed throughout the body of the sponge, are totipotent, meaning they retain the ability to give rise to any type of cell in the sponge. Totipotency is the quality that makes human embryonic stem cells so attractive as a research tool and as a potential therapy for patients with certain types of cell damage due to disease or injury. Actually, embryonic stem cells cannot make the extra-embryonic membranes or placenta, so they are not, strictly speaking, totipotent, and are more precisely defined as pleuripotent. Virtually all animals begin life as a single, totipotent cell, the fertilized egg or zygote. (There are some exceptions to this assertion; can you think of an example?) During development, cell division and differentiation result in an increase in the number of cells and cell types, with various cell lines specialized for different tasks within the organism. Sponges are likely to be the oldest animals. Thus, the retention of a large population of totipotent cells could be an ancestral trait within our kingdom. Amazing regenerative ability and powers of asexual reproduction, which depend on totipotent or pleuripotent stem cells, are widespread among invertebrates. It’s our bad luck as mammals that our cells that are capable of differentiating into all cells in the body are so elusive, found only very early in development, when the embryo is but a tiny ball of cells.

Thursday, September 2, 2010


I'm teaching Invertebrate Zoology again this fall, and I intend to blog regularly throughout the term. For starters when I teach this class, before delving into the morphology, physiology, behavior, and ecology of the various groups, I like to think about the larger context and how invertebrates fit into the big picture of life on Earth. One way to visualize this big picture is in a phylogentic tree, which depicts patterns of evolutionary relationships among the groups represented by branches on the tree. This one includes everything from bacteria to people, although it gives short shrift to some important groups, like the Protists, and inflates others. It's odd that the mere 4500 mammalian species take up such a significant proportion of this figure, which represents tens of millions of species, at least. There are fuller treatments of mammalian phylogenic patterns available. Ignoring the bacteria for the moment, this tree of eukaryotes gives a rather different representation of protist diversity relative to the metazoans, which occupy only a modest corner in the lower right of the figure. The textbook for this class presents multiple versions of metazoan phylogeny, and we'll be discussing evolutionary relationships among animal phyla throughout the term.
I love phylogenetic trees and the evolutionary context they offer for considering life's diversity, although there are clearly others who are more committed to this view of the world than I am. This image is from Carl Zimmer's Science Tattoo Emporium, and if you're really excited about scientists acknowledging their passions in ink on their skins, you'll be happy to know there is a book coming out soon.