Did you know that nearly every known species has one particular specimen, catalogued in some collection somewhere on Earth, to which its scientific name is officially attached? That specimen is known as the type specimen of the species. All subsequent findings of new specimens of the same species are identified based on that type. And when new species are discovered, publications detailing their descriptions not only describe the new species, but also describe how the organism is like and unlike other species, for taxonomic classification – all based on type specimens.
For this piece, Invertebrate Zoology (IZ) museum specialist Linda Ward gives us a behind the scenes look at the type specimens in the department’s wet collection.
A glance at IZ’s types
There are currently 68,523 catalogued type specimens in IZ’s collections, according to Linda. Of these, 34,619 are primary types, which include holotypes, syntypes, lectotypes, neotypes, and hapantotypes. The remainder are paratypes, allotypes, paralectotypes, and unconfirmed types. Sound complicated yet? Feel free to review type nomenclature here.
Linda estimates that 30% of IZ’s types were contributed by Smithsonian staff, while the rest are from researchers around the world. “The museum is known for its superb invertebrate collections and has become, over the years, one of the key institutions for researchers, especially those doing morphological studies,” says Linda.
In terms of IZ’s wet collection, there are 37,966 type specimens. The majority of these specimens are grouped together in a single location, as museums traditionally separate types from the larger collection. Most of these are then organized by phylum or sub-phylum, in alphabetical order. Some of the larger types are stored separately, on a shelf big enough to accommodate their oversized jars and buckets, while the smallest types are stored on slides in a cabinet. An example is the tiny ostracod Bathyconchoecia deeveyae Kornicker (USNM 123335), recovered from the South Pacific Ocean by trawl net (pictured).
One of IZ’s oldest holotypes is USNM 637 (Gorgonia trichostemma), from Mathuata Island in Fiji. This tiny coral was recovered on the U.S. Exploring Expedition, the Smithsonian’s first exploring and surveying voyage, which was underway from 1838-1842. The specimen is pictured in its current state (displayed in an ethanol bath) along with an image of the original ledger, the title page of volume published on the “zoophytes” recovered from the expedition, and an image of the hand-drawn, color plate, detailing what USNM 637 originally would have looked like.
Preservation and current research
Preservation creates a challenge for the museum community, where different types of specimens are best preserved by different means. Conditions such as temperature and humidity are very important aspects of long term specimen preservation; however, for wet specimens such as many of the specimens in IZ’s collections, the greater challenges are the storage solution, exposure to light, and the materials out of which storage containers are made.
The choice of storage solution can directly impact the tissue of the organism. Solutions are chosen based on the type of specimen, although ethanol is the common choice today. Certain soft-tissue organisms, such as polychaetes, are first fixed in formalin, which is then changed to a mixture of ethanol and sea water to retain the specimen’s morphology. Fixing in formalin can make it difficult to extract DNA from the tissues for molecular studies. The paratype of Riftia pachyptila (USNM 59952, pictured) is the first tube worm species ever recovered from a deep sea vent, collected during the 1979 Galapagos Rift Alvin Expedition conducted by Woods Hole Oceanographic Institution.
Exposure to light is damaging to the pigment compounds in the tissues of most invertebrates. Although the specimens in IZ’s storage facility are largely protected from UV radiation, which rapidly bleaches the color from organic tissues, nonetheless almost all specimens turn to ghostly shades of white within years of storage (a shelf of starfish types is pictured). Ethanol, unfortunately, facilitates this process, despite its usefulness as a general purpose storage solution. Hence, the wet specimens collected by the USEE were quickly mocked up in colorful hand-drawn artwork, and today, photographs are taken of new specimens from a variety of angles, to ensure that color variations and patterns are represented in the collection after they have been lost from the specimens themselves.
According to Linda, storage containers are the newest and most unknown challenge facing wet specimen storage. NMNH used to have an in-house glass blowing facility. Today, however, specimen storage containers are purchased from supply companies, which means the best option for many large specimens is often plastic buckets. Like the specimen tissues, plastics are light-sensitive, some more than others. Hence, plastics used in storage must be carefully selected for longevity. On the plus side, opaque plastics can help protect their sensitive contents from light exposure.
Linda, the museum specialist who watches over IZ’s wet types
Linda has been a member of the Smithsonian family since 1981, although her work with IZ’s types began only five and a half years ago. When asked what aspects of IZ’s type collection she finds particularly interesting, Linda remarked that “I like seeing the variety of taxa that come into the collection, but I am most fond of the polychaete worms, since that’s what I studied in college. I have personal experience as a master’s student coming to the museum to examine the types of the polychaete family Spionidae. The trip helped me with my thesis and my subsequent description of five new species of Spionidae.”
Part of Linda’s work with the type specimens includes interacting with the many researchers that visit IZ, in addition to helping with specimen loans. Unsurprisingly, she has very strong feelings about the importance of these aspects of her position, reflecting that IZ is “known for our willingness to loan types to those who can not come to the museum to study the collections. Specimens deposited here become readily accessible to the research community, and our stability as an institution, the breadth of our collections, our willingness to host researchers who want to study our collections, as well as the loaning of our specimens, has resulted in the continued addition of new types each month.”
In the future, duties related to the type specimens will be transferred to another member of the Collections Management staff in IZ. Until then, however, we can continue to thank Linda for her dedicated work with the types, and the significance of that work to furthering the research goals of the larger invertebrate zoology community.
by Liz Boatman
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