Wednesday, April 6, 2011

The Things You Don’t See

(Okay, the caption contest will be on hold for just a little while longer—but everything’s all set for it, so don’t worry! And there will be a prize, too… Oh, the suspense!)

I am one of the many people who, when I lived in Boston, would enjoy going to the New England Aquarium and watching the harbor seals in their outdoor (free to the public) tank; I would peer through the glass like everyone else and ooh and aah over the seals’ cuteness, their speed in the water, their ability to close up their nostrils when they dove.

I was also one of the only people who noticed the other residents of the tank—mainly the myriad little snails gripping the inside of the glass and using their tiny little radulae (one radula per snail) to scrape at the algae growing on the tank. On the occasions when I went inside the aquarium, I was one of the few pointing out snails and hermit crabs and mussels in amongst the brightly colored or impressively toothed fishes. The one time I went snorkeling, I exclaimed over the sea urchins.

I still enjoy the seals and fishes, mind you—but it’s fun to discover other animals that no one else seems to notice, as if there’s a separate aquarium, a separate world, just for people like me. That’s how I felt at the zoo a couple of weeks ago when I noticed these hydromedusae all over the walls of the starfish tank:

[this hydromedusa was about 5 mm across]

Hydromedusae are—well, it’s a little complicated. A fair number of animals in the cnidarian (Nye-dARE-eee-ann) phylum—which includes anemones, corals, and jellyfish—have alternating life stages, with a sexual form (usually a “medusa,” or jellyfish-like-form) and an asexual form (a “polyp”—something that looks like an anemone). Hydrozoans are cnidarians that can either have alternating forms (hydroids and hydromedusae) or just a single form (one or the other). The animals I saw in the tank might be hydromedusae that are never polyps, or they might be a species that has hydroid forms, too; any help in their identification would be appreciated.

Either way, I have only two points to make about them: in spite of the fact that there were many of them in the tank, no one else appeared to notice them; and my computer’s spell-checker has had no problem with either “hydroid” or “hydromedusae,” even though it always tries to insist that I don't really want to type my name that way.

{A note: I do write all text and take all pictures. Please do not reproduce either without my permission.}

1 comment:

Anca said...

Wondrous creatures! I'm glad we're able to see them through your eyes (and lens).

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