Thursday, February 14, 2013

Apolitical Newt


Barb and Julian
We spent Sunday afternoon with Michelle Bowe collecting twigs and buds for the next Master Naturalist meeting.   It is always humbling to go out with a pro and have several of my identifications of small trees and shrubs gently shot down.  The one that hurt was what I thought was a yellowwood, a very uncommon plant, in southern Missouri.  Mine was so uncommon it turned out to be a big and very common Carolina buckthorn.

Michelle's accomplice was young Julian, a good natured and irrepressible young bundle of energy accompanied by his bodyguard, her husband Brian Edmonds.  There is no better way to spend an afternoon than wandering the woods with a young naturalist who views the world from a knee-high vantage point.

Julian and newt-found friend
Brian's specialty is amphibians and we patrolled our ponds looking for them.  We didn't try to explain to Julian that "Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia"*  as he didn't seem interested.  However he was on the alert to explore everything less than a foot from the ground, including testing the temperature of creek and pond water on his legs.

We struck out looking for spotted salamanders but Brian spotted a pair of newts swimming in the pond.  With patience he was able to catch one by hand and demonstrated its features to Julian who was more interested in petting it.


Adult Male Newt
Brian explained that there is only one newt species found east of the Rockies.  It goes by the undistinguished name of a eastern, or more formally as Notophthalmus viridescens.  There are four subspecies of the eastern newt and ours is the central newt, Notophthalmus viridescens. v. louisianensis .  Get past the dull names and everything about them becomes interesting.


Red Eft Phase- Patrick Coin
Newts hatch from eggs in the water and live as tadpoles initially.  In late summer they lose their gills and crawl out on land to live for several years as a form called an eft.  Although the color can vary, they are commonly called red efts.

Eventually they reach sexual maturity and head back to the pond to live the aquatic life while looking for love.  They no longer have gills but are able to absorb oxygen through their skin.  They eat a varied diet of insects, molluscs, worms and the eggs of other amphibians.

So how do you tell the boys and girls apart?  Like many species, they develop some distinguishing characteristics during mating season.  The rest of the year we can't separate them and they might not care during that time either.  Here are some clues which Rhonda Rimer taught me the next day. (see the next blog for more amphibians)
  • Males during breeding season develop a higher fin and a swollen cloaca, below on the left.
  • They develop cornified, hard bumps called tubercles on the inside of their thighs, which aid in their grasp of the female, below right.

Swollen orange cloaca
Cornified thigh nodules













A newt has a very interesting sex life.  I am referring to the aquatic newt, not the capitalized Newt in the Austin Lounge Lizard's song on Youtube.  The female is very much in charge of accepting the favors of the male, including whether to pick up the sperm packet or leave it alone to wither.  Tom Johnson describes the scene in Amphibians and Reptiles of Missouri.

The male climbs on the back of the female and holds on for several hours, an act of amplexus similar to frogs.  Next he hangs on while waving his tail in the water to push currents with a pheromone "scent" forward to excite her into taking his gift to her.  He also rubs his chin against her snout as seen in detail at wcsu.edu.

He then performs some dance moves in front of her, and if she expresses interest by nosing his tail, he releases his spermatophore into the shallow water.  He then tries to herd her to his sperm packet on the bottom.  If she continues to express interest, she will settle over it and pick it up in her cloaca, ready to fertilize her eggs.  However, even then, she may change her mind leaving his gift and his high hopes lay deserted on the bottom of the pond.  If he is successful, the female will spend the next several weeks depositing her fertilized eggs one at a time.

As if he didn't have enough troubles, rival males may try to displace him during amplexus or interfere with his herding the female while dropping his own spermatophore.  Rivals have even been seen allowing a male to mount them and discharge his spermatophore, therefore depleting the competition's fertilization chances.

Much more detailed information including toxic skin and neoteny where they skip the eft phase is at wcsu.edu and caudata.org.
*  Wikipedia

1 comment:

  1. Bob and Barb,

    We love your farm and look forward to visiting again! Thanks for inviting us out.

    Not to be too pedantic, but the genus _Notophthalmus_ has three species in the eastern US (one in FL and GA, another in TX). The species to which the Central Newt belongs has the largest range.

    The family to which newts belong have their greatest diversity in Europe, where they are the primary salamander family. In fact, their family name--Salamandridae--reflects the common name for the whole salamander group.

    We look forward to visiting again.

    B

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