Tuesday, June 06, 2017

The yellow-tipped little agate snail

kw: species summaries, natural history, natural science, museums, research, photographs

Earlier this year I completed two major projects to prepare about 17,000 data records at the Delaware Museum of Natural History for all the freshwater species of bivalves (clams and mussels) and gastropods, and load them to a new database system from which they can be served up via the internet. The principal portal is iDigBio. A secondary portal, from which it is easier to dig into the records on a museum-by-museum basis, is InvertEBase. Each project took about a year.

That done, I have begun working through the museum's data for terrestrial gastropods (land and tree snails), which total about 38,000 records. We decided to take these a cabinet or two at a time, for the most part. I am basically tackling between 1,500 and 2,000 records per mini-project. A first project took about a month, so I expect the sum of about 20 projects to take a couple more years, maybe three or more.

I am in the midst of inventory for three related families, and the first is Achatinellidae. These snails were so-named because they resemble the large tree snails of the family Achatinidae. The prefix "achat-" means "agate" in Greek, and refers to the striped appearance of the most familiar species, the giant African tree snail, Achatina achatina (Linné, 1758), also called the tiger snail.

The one shown in this image may have a shell as long as 8" (20cm). The suffix "-ell" means "small"; the snails of family Achatinellidae are much smaller than the Achatinidae, but many have a similar striped look.

The type genus (the one the family's description is based upon) is Achatinella, and the type species is Achatinella apexfulva (Dixon, 1789). As I was taking inventory of the specimen lots of this species, I noticed that some had been collected by a major donor to the museum, Munroe L. Walton, when he was quite young, not more than eleven years old. In the three photos below, you can see they were collected in Hawaii in 1901; Walton was born in 1890. First, the photos, which mostly speak for themselves. Commentary continues following.

Around the year 1900 it was common to distinguish the many color variations of variable species by assigning subspecies names. The original labels for the first two lots reflect this. The third lot was originally attributed to a different species because many of the shells in certain parts of Oahu are left-handed, such as the one on the right in the third picture. These are now recognized as part of the species apexfulva. The suffix "-fulva" means "yellow", and shells of this species have a yellow tip. Specimens of this species grow to 1.5-1.9 cm (0.6-0.75 inch).

The second lot shown has an added label, written by Edward W. Thwing, who may have been the actual collector of that lot or part of it. He was 22 years older than Walton. The designations "New." and "Newc." on some of the labels refer to Wesley Newcomb, a physician who became a curator of mollusks at Cornell in the 1870's and until 1888. He described the first specimens of many species in the family Achatinellidae.

Although Achatinella apexfulva does not have a common name, I call it the "yellow-tipped little agate snail" as a direct translation of its scientific name. The Achatinellidae in general are colorful and attractive. Sadly, most, including A. apexfulva, are now extinct.

No comments: