A long absence

Last Saturday I got back from a fascinating (albeit ecologically depressing) trip to the Austral Islands and to Raiatea. I will talk more about these islands in later blog posts and put up albums on Picasa hopefully soon. Things have changed a bit at the Gump Station since I got back, with the arrival of 22 Berkeley undergrads, three grad student instructors (including my friend Erica), and two Berkeley professors to teach the infamous "Biology and Geomorphology of Tropical Islands" field course. The extremely excitable undergrads will be here on Mo'orea for two months, and this past week I accompanied them on an extended ecological tour of the island to teach them everything I knew about the natural history of Polynesia. I tried to get them excited about native plants and fruit flies and leaf-mining moths, but I think the aquatic activities stole their attention. We went snorkeling in the coral reefs of the lagoon, took a boat to the offshore islet Motu Moea, swam with stingrays and sharks, saw loads of enormous freshwater eels being fed (YouTube video coming soon), collected shrimp and snails from the pool at the base of a waterfall, and harassed a lot of sea cucumbers until they eviscerated (ejected their internal organs as a defensive measure). To top it all off, I picked up a strange marine mollusk (Lima sp.) and its tentacles broke off and stuck to my hand, which prompted someone to say, "David, you aren't allowed to pick things up anymore". They came off after rubbing with sand.

Some things I learned over the past week that I thought were cool:

- On the origins of freshwater snails: On Raiatea, I thought the snails I saw in a freshwater stream looked a lot like intertidal (coastal) snails. They had thick, ribbed shells. This makes sense, because when streams start to form on a new volcanic island out in the middle of the ocean, they only organisms available to colonize the new habitat are ones that can either travel through the air or survive in salt water. All the native freshwater fish in French Polynesia either survive in salt water or had ancestors that did, for instance. When the students did their stream transect along the Putoa River on Wednesday, they found tons of freshwater neritid snails that looked for all the world like marine ones. One of the professors told us that indeed, these snails evolved from marine ancestors, and in fact their larvae still live in the ocean.

- Gecko eggs: Yesterday at the Belvédère, a student found a pair of small white eggs, flattened and pressed against the leaf of an 'ie'ie vine (Freycinetia impavida). I figured these must be gecko eggs, and when a student interested in lizards heard about this, he headed back and found not only a bunch more pairs of eggs on the same vine, but an extremely gravid female through whose belly you could see two enormous eggs, like the yolks of a chicken egg held up to the light. The eggs were always laid in pairs, and one side of each egg was flattened and stuck to the leaf.

- Rare introduced plant: On yesterday's hike, we passed a group of Tahitian men, one of whom had a sprig of a vaguely familiar-looking plant stuck in his backpack. He spoke a little bit of English, so he started explaining to the students that it was kava (Piperaceae: Piper methysticum, 'ava in Tahitian), and that he had taken the cutting to plant in his yard. Kava is not native to Tahiti, but was introduced by the ancient Polynesians. The roots are used to make an intoxicating beverage traditionally consumed throughout the tropical Pacific, but missionaries were successful at almost completely eradicating the use of the plant in Tahiti. As a result, although it is an introduced plant, kava is extremely rare now either in the wild or in cultivation in French Polynesia--I've never seen it anywhere, especially not along this trail on Mo'orea. (It looked familiar because it is related to native plants in the genus Macropiper, which I am familiar with.) The man told me that kava was very rare now on the island, and you had to know where to look to find it.