Iverson’s Fish Pond

IVERSON 01This neighboring backyard pond is fairly typical of commercially-installed ponds that have been left undisturbed for a number of years.  Approximately eight feet long, it has a rubber sheet bottom with little bottom  mud, and plants in pots.  However, local plants have populated the edge, bridging toward the center from a shallow margin of mosses and pond weed.  This provides a healthy habitat for a number of organisms; collections included marginal plants and duckweed, together with water and a very small amount of algae and mud scraped from the bottom.IVERSON 02This pond has also been invaded by bullfrogs (Lithobates catesbeiana) which are spreading throughout the Lower Mainland and Vancouver Island.  However, members of this invasive species in this pond have entirely succumbed to the accurate ministrations of Mr. Iverson’s air rifle.  One small frog, probably a Green Frog (Lithobates clamitans, also known as the Bronze Frog) was noted – this is a now-common introduced species also, but does not seem to have the same disastrous effect

Green Frog
Green Frog

on freshwater ecosystems as do the all-devouring bullfrogs.


Testate (shelled) amoebas are relatively common in Vancouver island ponds, and Iverson’s fish pond is no exception.  The individual particles of the testa can be highlighted by using partially polarized light, with the polarizer on the light source rotated to highlight the small stone particles without completely blacking out the background:

Modified by CombineZP
Testate Amoeba, CombineZP, stack of three images

The amoebae, themselves, however, are rarely seen out of the shell.  They can be persuaded to come out if the slide is left in a quiet, moist Petri dish for some time (Wim Von Egmond, personal communication)

(Sanguinis:  “So what do expect???  You get sucked up in a drain pipe, spat out onto an endless, featureless plain, then get 100 pounds of glass plate smacked on your head and see how frisky you’d be!  Hiding out and calling your attorney, that’s what you’d be!)

Nontestate amoebae are much less commonly seen locally, but one was found in this pond:AMOEBA 01This amoeba has ingested an unfortunate bright green algal cell in addition to other material.


Taxonomy of the phylum Rotifera is presently in flux, but is largely divided into two groups: the Bdelloid rotifers and Monogonont rotifers.  Iverson’s pond is home to members of both groups.  The Bdelloids, common in local waters, are present in moderate numbers in this pond; a video of a typical Bdelloid rotifer is best seen in the post from the Backyard Bird Bath.  The Monogonont rotifers are encountered less commonly in our area, even though there are more species worldwide.  This small Monogonont, probably one of the Keratella species, stayed in one place long enough for both a photograph and a video:ROTIFER, MONOGONATA, POSSIBLY KERATELLA

Interestingly, a rotifer of almost identical morphology was described as the new species Keratella trapezoida in the waters of the Yangtze River in 1998.

National Institute for Environmental Studies.Keratella Rotifers.  http://www.nies.go.jp/chiiki1/protoz/morpho/rotifera/r-kerat1.htm
Wikipedia.  “Rotifers.”  https://en.wikipedia.org/wiki/Rotifer
University of California Museum of Paleontology.  “Introduction to the Rotifera.”
Zhuge, Y. and Huang, X.  “On a New Species of Keratella.”  Hydrobiologia 387/388:35-35 (1998). http://link.springer.com/article/10.1023%2FA%3A1017000617930#page-1

Iverson’s Fish Pond

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