Monday, May 24, 2010

YPM ICH 8522 & 8524: Fish that hunt birds

Here on Earth, we are used to seeing this:


But in South America's Amazon River Basin, all bets are off. There, under the water's surface, lurk swimming things that hunt flying things.

Meet the arowanas of the genus Osteoglossum. Osteoglossum comprises two species, Osteoglossum ferreirai and Osteoglossum bicirrhosum. They normally feed on insects swimming on top of the water, but they are skilled jumpers and are known to feed on bats, birds, and monkeys resting on low-hanging branches, and even small planes. Just kidding about the small planes. I'm not kidding though that Wikipedia says that they eat small planes! Haha. Here's the screenshot:


(Yesterday, that line read "small birds").

Our collection has quite a few Osteoglossum specimens. Here is ICH 8522, Osteoglossum bicirrhosum, collected in British Guiana on January 31, 1953 by Ed Migdalski:


Osteoglossum's
unique predatory behavior has been observed by many locals, and confirmed via examination of the stomach contents of museum specimens such as this one. Here is a picture of the head of another one of our specimens, ICH 8522, another Osteoglossum bicirrhosum, collected in the same place, at the same time, and by the same guy as ICH 8524:

It's been sagittally sectioned and stained with Alizarin red dye. Alizarin red is used by zoologists to highlight bone in a specimen, so that it can be studied and distinguished from cartilage and muscular tissue. This specimen thus was probably prepared in this way to study some aspect of the fish's cranial osteology.



Below is the external view of the same Alizarin red-dyed specimen. Pretty neat-looking in my opinion.


Here is one more picture from ICH 8524:

These are some of this specimen's gill rakers, which had fallen off and were loose in the jar. Gill rakers (the spikey red projections in the picture) are attached to the inside of a fish's gills, and function to help keep food from escaping through the gill slits.

Lest you think arowanas are boring-looking without a scientific tattoo job, here is a picture of a live arowana (pic from Wikimedia Commons). They are quite majestic fish:

Before signing off, I must direct you to this video, from a National Geographic show. Unfortunately it doesn't show an arowana catching a bird, but it does show footage of one stalking an insect and jumping out of the water to catch it!

5 comments:

  1. Jordan, thanks for sharing your discoveries!

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  2. I love the sneakiness of the arowana! Definitely another awesome fish!

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  3. Thanks for the comments, friends!

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  4. Here are a few videos of a Silver Arowana eating birds. Same Silver in all the videos......different birds.
    http://www.youtube.com/watch?v=g3LWRth9gzs
    http://www.youtube.com/watch?v=klsMGBKtu8I

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  5. Thanks for sharing the info, pictures, and great you tube videos. I'm doing a presentation on the silver arawana and found your resources very helpful! Have you seen the segments on the video Amazon: Land of the Flooded Forest with the arawana brooding and feeding?

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