Friday, February 13, 2015

"I'ts not easy being green..."

Wherever have they been during all the hot dry days of summer and the cold of winter?!!  But here they are; back again, singing in the night. Night falls and first tentatively, then in earnest the frog chorus begins.  These are tiny Pacific Tree frogs – but they produce the sound of a brass band!  We do have other species in our locale – in deep cold ponds we have bullfrogs, and in ponds and streams there are spotted frogs and red legged frogs.  
Pacific Tree Frog
Most of us have a positive good feeling about frogs– whether we learned of them from Kermit on Sesame Street or what we remember from high school biology.  Maybe you were lucky enough to grow up with frogs living nearby in a pond. I associate frogs with the warm days of spring and summer – I think of them as fascinating but secretive little fellows.

Kermit the frog!  Hear his sing:

First lets get a couple of things straight:

1.  Frogs and Toads are entirely different species.  Frogs are adapted to spend their life in and close to water. Toads are adapted to live on land…but they need moist settings.  They both must lay eggs in a similar manner in water.

Pacific Toad

2.  Handling frogs or toads will not give you warts.  When you pick one up they are not coated with mucous like a fish; their skin is leathery and wet…They feel cold because they are ectothermic– meaning that they take on the temperature of their surroundings– heat is not generated within their body by metaboolism.  Being an endotherm like us takes a lot of work to eat enough more to generate all the heat that we need to stay warm.

3.  Kissing a frog does not produce a prince – (or princess) – interesting thought though.
"Yes he did turn into a prince - but there were complications"

When I taught Biology, it was traditional every year to receive big sealed buckets of dead frogs stored in formaldehyde, The smell was so strong that it burned the nostrils!  I stored my frogs in fresh water for a day to remove some of the smell.  The organ systems of the frog are similar to those in the human and after studying human biology; it was fascinating for students to dissect the frog and see the same organs arranged in a complete organism.
Frog organs

There are significant differences –mostly in scale and size.  The frog heart has only 3 chambers – not four like ours, which results in a less efficient transfer of oxygen throughout the body. (In addition the frog  gains most of his or her oxygen directly from the water through their skin). They have a big long stomach, 3 lobes to their liver, 2 lungs, underneath the small intestines a small long ribbon-like pancreas, gall balder, urinary bladder, and reproductive organs.  The unlucky students who received a female find them loaded with eggs (unlucky because it was a lot of work to remove them).

Frog eggs - after they are released in water -

  The mouth of the frog had an opening to the glottis that leads to the lungs; there are also openings to the vocal sacs, which permit air to vibrate the vocal apparatus to produce the famous “ ribbit” sound… Since frogs have no diaphragm to breath they have to inflate the mouth sac (bottom of jaw) and force air into the lungs through the glottis.  Its even possible to study  the regions of the brain if you are a good surgeon and can cut  carefully through the bone… (I know some of you are my ex-students – does this bring back memories?)

Spotted Frog
So now when I hear my little Pacific tree frog friends I can visualize all of these systems doing just what they are supposed to do to lead to a happy healthy frog singing through the night

Frogs are also the “Canary in the coal mine” so to speak – Large numbers of highly abnormal frogs are being recently found – especially in polluted water – particularly in water polluted with vast amounts of plastic pollution.  A scientist in his laboratory was studying the effects of sex hormones on organisms… He had the apparatus set up and returned to do the experiment. 

Mutant frog
He checked his pure solutions one more time before the test and discovered that one was polluted with a female sex hormone – Impossible he said – this was pure when I set it us… through tests he established that water in contact with his plastic tubing had gained a chemical that mimics the hormone effect.  Think of a swamp with plastic bags and bottles contaminating the water. Other chemicals also have mutagen (mutation causing) effects. These effects are most noted in frogs that live in the water with constant exposure – but what about us exposed to plastics and other contaminants – there is more research to be done.
Bull frog
It is also somewhat a mystery why whole population of frogs are dying due to a bacterial or fungal disease – worldwide. Is this due to a ‘new’ transplanted disease organism?  Is it due to something weakening the frogs and making them more susceptible?  Can we learn from populations that remain healthy?  Troubling mystery!
Spring P{eeper

Last summer I spoke to a frog researcher in Tuolumne meadows from UC Berkeley.  She had studies several species living in high mountain lakes that are frozen solid for several months each year.  Those high mountain frogs, she said, appeared healthy.  Possibly due to their isolation and to their long breeding cycle that could require more than one year.