Thursday, February 17, 2011

Punctum minutissimum : Small Spot

Right before I left Pennsylvania I decided to grab some photos of micro snails I found in the soil sample from before the snowfall. The soil sample came from the mountain bike path side of Frances Slocum State Park and yielded about 20 or so micro snail individuals. The above snail, is Punctum minutissimum, commonly called Small Spot.

This little fellow photographed measures a mere 1.09mm. If remember correctly, the umbilicus measures 0.28ish mm, but I am definitely sure that the umbilicus is contained about 3.8 times in the diameter (that math adds up). Everything pretty much jives with Pilsbry's opening paragraph about this creature:

The shell is very minute, depressed conoid, umbilicate, the umbilicus contained about 3.7 times in the diameter; thin, of corneous or very light brown tint, somewhat translucent, shining. Initial 1 1/2 whorls smooth, the rest sculptured with  close, somewhat unequal very delicate striae in the direction of the growth lines...

The only other known Punctidae known in the state of PA is Punctum vitreum. Size seems to overlap, but P. minutissimum is slightly smaller. A key difference seems to be that P. vitreum has the widest ribs of the Punctidae ( landsnail.pdf which I'm pissed because they took their snail pages offline, I should have crawled the site and saved it, but the pdf is still available if you can find it and it has pretty much all the info anyway). Another interesting tidbit from Pilsbry:

 Under the binocular, P. minutissimum looks as if it were molded out of bronze , but P. vitreum appears as if it was cut from yellowish crystal.
On a personal note, I'm still having a tough time with micro snails. My microscope is 40x and so I really can't get fine sculpture when looking through. But snapping a photo helps as I can zoom in a little more. Another problem is just handling them-- as evidenced by the photos in this post. I have to come up with systems to better handle my micro snails. I've already lost some interesting snails, for instance, crushing a shell which was either a Columella species or immature Ventricosa or Gastrocopta species. Very disappointed by that one. For someone who's very coordinated when it comes to things like sports and dancing, I turn into a proverbial bull in a china shop when micro snails are involved.

Range maps from Land Snails of Limestone Communities and Update of Land Snail Distributions in Pennsylvania (Pearce) with my Luzerne county added to range (in orange). Formerly unknown to Luzerne County.

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