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Sow Bugs, Pill Bugs, Isopods, Lawn Shrimp and Amphipods

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Unidentified

an aquatic lawn shrimp?
Wed, May 6, 2009 at 3:11 PM
hi, i have found these swimmers in a stray cat’s drinking bowl that someone has set up in the woods, not far from a busy road. ill take it as the bowl is never dumped out if these lived in them. fortunately i had a big ziploc bag and collected the specimen, and was kind enough to wash their bowl and poured bottled water in it, and was greeted by two grateful beautiful longhaired cats. i was able to collect 11 of them but some died in transit, i placed the little guys in my fishtank and its been a few hours and theyre still okay. i took pictures and a couple videos with my fujifilm camera aided with a 10x triplet magnifier with the intent to send in the photos here, i am actually surprised that on the frontpage was a photo of dead lawn shrimps and they looked very similar to what i have found, except i found my little guys a live and swimming in a kitty bowl.
dogafin
pensacola, fl

Dear dogafin,
Your observation that your specimens resembled the Lawn Shrimp was quite astute. We are certain that your specimens are also Crustaceans, quite possibly Freshwater Shrimp in the genus Gammarus. Gammarus and Lawn Shrimp are both in the order Amphipoda. We located a fishing website that has information on Gammarus which are also known as Scuds. The The Backyard Arthropod Project A Field Guide to the North Side of Old Mill Hill, Atlantic Mine, MI also has some good information. We might be way off base here with the genus ID because the location was so odd. We can only guess that at one point the cat bowl was filled with water from a pond inhabited by the Crustaceans. We gladly welcome a professional identification on this somewhat odd sighting.

Fri, May 8, 2009 at 6:34 AM
Dear WTB,
I’ve worked on benthos of the Great Lakes and inland lakes in Michigan for close to ten years now and have seen a few amphipods in that time. From these pictures its difficult to say much more than an amphipod. If there’s a pond or lake near by its possible that these could, at the very least, be in the family gammaridae but the could also be Hyallela. The way to determine this is to see if there are accessory flagella (small segmented appendage) on the 4th segment of the first (top pair) of antennae. If there’s no flagellum its Hyallela; if there is a flagellum its more likely to be Gammarus or at least in the family gammaridae.
carterg,
Ann Arbor, MI

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