Sunday, February 17, 2013

Sampling for Chytrid Fungus

Harbinger of Spring- Click to enlarge
Before we talk about chytrid fungus I have to show you Barb's Harbinger of Spring, found after searching the leaf littered forest floor.  After two days of scouring the ground like a beagle sniffing a rabbit, she tracked one down.  This set of tiny blossoms officially proclaimed the season change in mid-February.

We had received a call from Rhonda Rimer of the Missouri Department of Conservation who wanted to come to Bull Creek to check out our amphibians.  She was hoping to find wood frog eggs which look somewhat similar to spotted salamander eggs that also also appear February or March.  She also wanted to sample for chytrid fungus.  This was a good excuse to avoid work.

Newts look like bait!
Why the interest in chytrids?  There are over 1000 chytrid species in the world that occur in water and moist soil.   Most feed on dead or rotting organic matter but a few are parasites of plants or invertebrates.  They flew under the radar of the public until the discovery of a new species was found on the skin of frogs in 1999.  It was named called Batrachochytrium dendrobatidis that translates as "frog chytrid".  This is usually referred to as simply Bd.

This new finding quickly took on great importance as it appears able to infect virtually all amphibians.  It is now proven to cause severe population declines and extinctions and has been called “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and it’s propensity to drive them to extinction." (Gascon et al, 2007)

Rhonda is sampling amphibians around the Ozarks as part of a Missouri-wide screening.  She began by wading into the muck of our pond, sweeping the bottom debris into a large net.  We hit pay dirt, counting 27 central newts clustered along the sunny side with none in the shaded colder water.  One net full of debris yielded the 10 squirming males, apparently a fraternity party preparing for the arrival of the females.

Swabbing for Bd
One lucky newt got the swab massage for Bd.  After wiping both ends carefully with cotton and the other end of the stick, the swab was placed in transport media to keep any Bd alive until it reached the lab.  The newt didn't seem to mind the strokes and I thought he might have giggled a little as she tickled it under the chin, but it might have been my imagination after seeing too many Geico commercials.

Egg clusters on sticks underwater
We didn't have any luck finding wood frog eggs but did find globs of spotted salamander eggs in two ponds.  In one pond the water was shallow and clear enough that we could see them from the bank.  The difference between spotted salamander and wood frog eggs, both deposited in early spring, can only be appreciated by holding them.

Our spotted salamander eggs

Salamander (left) and frog eggs- NY DEC
The salamander egg mass is covered by a heavy coat of clear jelly, holding the mass firmly together.  Wood frog eggs have a separate layer of jelly around each egg without the outer coat holding them together.

It was a great day in nature, even if we did have to miss a day of working in the woods.

More on herp eggs?  (Frog and salamander)  Check out this site.

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