Collections by Preparation
|Whole specimens in ethanol||ca. 562,000 records (568,000 specimens)|
|Dry skeletal specimens||ca. 13,300 (13,700)|
|Cleared & stained skeletal specimens||ca. 4,400 (4475)|
|Whole specimens in formalin (mostly amphibian larvae)||ca. 8,300 (243,000)|
|Histological microscope slides||ca. 1,600 (96,000 slides)|
A single specimen may be a composite of various preparations. An extreme example would be a frog with an ethanol-preserved skin and viscera, cleared and stained head, dry postcranial skeleton, histological slides of its reproductive tract, and frozen blood, liver, etc. stored as tissue samples. This hypothetical specimen could also be a voucher for a publication, or other types of data such as photographs and vocalizations, all of which are searchable on the data base.
The largest component of our collection is stored in 70% ethanol (EtOH). Ethanol specimens were originally stored in ground glass jars and ceramic crocks, whereas small specimens are now stored in screw-top flint-glass jars with polypropylene lids or canning-style bailtop jars with synthetic gaskets, and large specimens are stored in stainless steel tanks. Prior to the 1890s, most ethanol specimens were simply preserved in "alcohol" (i.e. rum, distilled wine, spirits, etc.) and were then stored in EtOH. Currently, we 'fix' specimens in 10% formalin first, then transfer them to 70% EtOH for long-term storage.
Our largest ethanol specimen is a 3 m, ca.180 kg (ca. 400 lbs) American crocodile in a tank at the MSC. The smallest adult specimens are likely microhylid and leptodactylid frogs, smaller than a dime.
The majority of our other preparations have been incorporated into the collection during the last 50 years.
The majority of our dry collection is skeletal material, though there are a few skins (some old, stuffed skins and a few skins of very large specimens that were too big to preserve as ethanol specimens).
Cleared and Stained
The cleared and stained (C&S) collection consists mostly of small and/or fragile specimens that would be damaged or disarticulated in the process of making dry skeletal preparations. Most of our C&S specimens are prepared using a double staining technique that stains the bones red and some types of cartilage blue. The advantage of staining the cartilage blue is that a researcher can determine the relative positions of the adjoining bones, mineralization of growing bones (and therefore developmental stage of an individual), and see more detail in structures that contain substantial cartilaginous components, such as the hyoid apparatus and tadpole chondrocrania.
The formalin collection has been the fastest growing portion of our collection, having increased by nearly 500% in the last 25 years. This collection consists primarily of amphibian larvae, particularly tadpoles, stored in 10% formalin.
Much of our histological slide collection is made up of the think sections prepared for Ernest Wever's research on the structure of amphibian and reptile ears. There are also histological slides that were prepared for studies of skeletochronology, reproductive and emerging amphibian and reptile diseases.
The Division maintains a large collection of images (prints, negatives, slides, x-rays, digital). Digital images of cataloged specimens are linked directly to the records and are usually available on the publically accessible database. Some images that voucher important records (e.g., range extensions) are cataloged in the USNM Herp Image series. The Division is in the process of digitizing these physical images.
Audiotapes and Sound Files
The Division keeps both original working and archival copies of audio recordings, primarily of frog vocalizations, as vouchers for published works and future analyses. Recently, digital copies have been made of all USNM audiotapes that will be incorporated into the Macaulay Library archive of animal sounds. Typically these frog calls are themselves vouchered; that is, they were recorded from individuals that are now specimens in our collection. These recordings are an important taxonomic tool because frog calls are species-specific.
Division personnel and associated researchers routinely collect tissue samples when preparing specimens. The tissues and any associated DNA extracts are stored at the NMNH biorepository. The specimen from which the tissue derives is almost always preserved in the cataloged collection as a voucher for species verification.
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