Mollusks such as snails and slugs may appear to be simple in composition at first glance—an issue that has caused an ongoing debate about just how many species this phylum can claim. Estimates of the total number of living mollusk species range from less than 100,000 to more than 200,000, and Rosenberg says there is little agreement in the malacology community as to how many species of mollusks have already been discovered.

Rosenberg is attempting to make some sense out of the confusion by studying mollusks both in the field and through various databases.

Using databases such as Macalog, a source created by Rosenberg for Western Atlantic marine gastropods, and the Biotic Database, for Indo-Pacific Marine mollusks, he is able to better document the known diversity of mollusks and estimate their total diversity.

Rosenberg’s curiosity for discovering species led him to Jamaica, which he says has one of the most diverse faunas of terrestrial mollusks in the world. Jamaica is home to 561 named species of terrestrial mollusks, with only 56 of those species occurring elsewhere.

Rosenberg and his colleagues traveled to Jamaica on seven three-to-four week expeditions, sampling at 607 sites throughout the island and collecting land snails, millipedes and other invertebrates with low dispersal ability.

More than 100 undescribed species—species that have either been previously unknown or have yet to be defined—were collected, including snails, millipedes, grasshoppers, earthworms, crabs, dipluran insects and isopods.

The collection of mollusk at the Academy, where Rosenberg sits as the chair of the malacology department, is the oldest in the country, and the second largest in the world. It currently has more than 430,000 catalogued lots containing approximately 10 million specimens, including 30,000-35,000 lots preserved in ethanol.

More About Gary Rosenberg

As curator of Malacology at the Academy of Natural Sciences of Drexel University, Gary Rosenberg researches the magnitude and origin of species-level diversity among the Mollusca—a phylum of invertebrate animals that includes snails, slugs clams and squid.

Difference between species of mollusks are often subtle and DNA studies are showing that there are many overlooked species, which has fueled an ongoing debate. Estimates of the total number of living mollusk species range from less than 100,000 to more than 200,000, and Rosenberg says there is little agreement as to how many species of mollusks have already been discovered.