Crayfish

A crayfish was spotted in the shallows of Bull Run, under several inches of water. I estimate it was 3-4 in (~7.6-10.2 cm) in length.

Many crayfish can be particularly hard to identify from a photograph and many new species are still being discovered in Virginia’s waterways. This large crayfish is from the Family Cambaridae and is likely a native species. Other crayfish found in Northern Virginia, like the rusty crayfish (Orconectes rusticus) and red swamp crayfish (Procambarus clarkii), were likely introduced via the food industry and pose a serious threat to native crayfish populations. Source Credit: John Burke, Ecologist III, Stormwater Management Branch, Fairfax County Department of Public Works and Environmental Services.

10 MAY 2017 | Fairfax County, VA | crayfish (underwater)

Notice the first, second, and third pairs of walking legs feature chelae (plural).

A chela /kˈiːlə/, also named claw, nipper, or pincer, is a pincer-like organ terminating certain limbs of some arthropods. The name comes from Greek (χηλή) through New Latin (chela). The plural form is chelae. Legs bearing a chela are called chelipeds. Source Credit: Chela (organ), Wikipedia.

Also notice the slimy stuff on the rocks that makes them super slippery!

The slimy, slippery coating you find on rocks in aquatic systems is periphyton. In freshwater systems, periphyton is mostly comprised of algae but other microorganisms and detritus also collect on submerged rocks. Periphyton serves as an essential food source to many aquatic organisms and can also act as a bioindicator, signaling changes in water chemistry and nutrient levels in the system (Chetelat et al. 1997). Source Credit: John Burke.

Tech Tip:  My Canon 580EX Speedlite external flash unit was set for 1/16 power in order to penetrate the water and illuminate the subject on a bright, sunny day.

Copyright © 2017 Walter Sanford. All rights reserved.

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