Thursday, December 13, 2007

Ring cycle


Back in October, during a particularly rainy week, hundreds of ringed salamanders came out from under logs and small mammal burrows to breed in small ponds scattered throughout a deep wooded tract of land outside of Camdenton, Missouri. Explosive breeders, ringed salamanders laid over 500 eggs in one small pool of water that collected in a dolomitic shut-in. Since that night, the salamanders hatched. Despite the hard freeze that slammed into the Ozarks last week, hundreds of larval salamanders are swimming around in the shut-in pool, waiting out a six to eight month metamorphosis.

Ringed salamanders (Ambystoma annulatum) can only be found in the dolomite-based Ozark and Ouachita mountain ranges. Because of the rarity of their habitat, they are listed as a vulnerable species, garnering a state ranking of S3 in the Species of Special Concern listing. They breed in the fall and, if the pools don't dry up or freeze completely, they spend the winter underwater feeding primarily on zooplankton and invertebrates. While not too much is known about these fossorial animals, the breeding habits of the ringed salamander have been well-documented. The breeding cycle is such an orchestrated process that it has been likened to the liebesspiel, the loveplay, of spotted salamanders.

Males usually appear at the breeding pool first. They begin breeding after the females arrive. Each female is met with upwards of 2 to 25 courting males. The males nudge the female's cloaca and then swim away to deposit spermatophores at the bottom of the pool. According to the fantastic book, Salamanders of the United States and Canada (James W. Petranka), the more males that come into the breeding area, the less specific they get when depositing spermatophores; they'll actually begin nudging other males and females alike. After the spermatophore is deposited (or the following night), females will swim over the spermatophore, picking up the pocket of sperm with her cloaca. She stores the sperm in a chamber at the top of her cloaca. Later that night or the next evening, she will deposit fertilized eggs in clumps attached to vegetation or rocks. Breeding lasts only a couple of days.

While ringed salamanders traditionally feed on invertebrates during their larval stage, some of them become cannibalistic. In certain species of salamanders, the cannibalistic animals have morphological differences like recurved teeth and a slightly larger alimentary canal. Ringed salamander larvae are all the same morphologically, but the cannibals have an advantage: they metamorphose earlier and are traditionally larger animals.

During my first foray into the Ozarks several years ago, I had the great pleasure of rearing a handful of ringed salamanders. I had never seen one before that rainy night in late September when this large animal (pictured) cruised across my driveway in pursuit of my sewerage lagoon. Of the animals I reared, I had at least one cannibal in the group. Every week, the number of animals in the tank dropped. In the final days of captivity, I had two animals left. One bit a leg off the other one. Salamanders can regenerate limbs, and in a few weeks on a rainy night I released two little ringed salamanders around the dried up pond where I had found them. It is estimated that the desiccation of ponds during the winter can kill upwards of 90% of ringed salamander larvae. They have a long life span, so perhaps the two who spent the winter with me in the maintenance shed returned to the shut-in and continued the cycle this fall.

1 comment:

Anonymous said...

Wow, a friend at work's son is doing a report on salamanders. I pulled up this posting, then saw the link for my talented little sister, then it "clicked" Alyssa Vaughn, then I thought to myself, surely this has to be the younger sisters of Ashley. I even saw the link for Reese Fuller which has got to be related to my old camp hardtner friend Todd. I hope all three of yall are doing well. Merry Christmas, Bob Moseley bobmoseley@yahoo.com