Monday, July 7, 2008
Aliens of the deep
From C.E. Mills:
In general, hydromedusae are small, and either transparent or lightly pigmented, although some of the deep sea species are deeply colored - usually some version of dark red. (Scyphomedusae, in contrast, are usually large and often highly pigmented and are what most people think of when jellyfish are mentioned.) Hydromedusae are often abundant in coastal habitats, but they are usually seasonal, occurring most commonly from late spring into the early fall. Many species live only a few days and never get more than a few millimeters in size, but others are easily visible, reaching a few centimeters and living several months. Few hydromedusae sting, although the few that do may be quite painful. One called Gonionemus in the Russian Far-East can send its human victims to the hospital.
Most coastal hydromedusae are asexually budded off their single-sexed parent hydroids. The female or male medusae then produce eggs and sperm which are free-spawned into the sea; the fertilized eggs develop into new hydroids, which are usually benthic. The hydromedusae therefore represent only part of the life cycle of each animal, and it is important to realize that their usually-attached polyps/hydroids must be considered when one thinks about the ecology of these organisms. Some open ocean hydromedusae also have hydroids, which may live deep on the sea floor, but some of which have found highly specialized substrates to live on, such as little floating clumps of algae, the skin of fishes, or the shells of pelagic snails. Other hydromedusae (typically oceanic or deep water species) do not have a hydroid, but have a life cycle in which the fertilized eggs produced by medusae instead develop directly into the next generation of medusae. Such species are sometimes described as "holoplanktonic" - carrying out their entire life cycle in the plankton.
I've always loved sea creatures, especially beluga whales. And rays. And jellies. Here is a slideshow from National Geographic showcasing only a tiny handful of translucent, colorful creatures of the deep.
Diving certification is expensive in NYC. But worth it - my project for next year.