|Type Specimen Article|
The United States Department of Agriculture Nematode Collection (USDANC) is one of the main research resources for nematological research in taxonomy, as it holds the largest type specimen collection of economically important plant- and insect-parasitic nematodes as well as an important collection of type material of free-living aquatic and terrestrial nematodes. These preserved specimens are the basis of taxonomic research. Such a collection helps in maintaining stability of zoological nomenclature and serves as a tool widely used by U. S. and international scientists to resolve various taxonomic and nomenclatorial problems.
The type specimen list is prepared in accordance with recommendations of the International Code of Zoological Nomenclature (Noffsinger, 1982; Ride et al., 1985), in which institutions serving as type specimen repositories are urged to "publish lists of type material in their collection". This collection is meeting the need for preservation of nematode type specimens, which stabilizes species nomenclature for research scientists throughout the world. Due to urban expansion, often it is impossible to collect additional specimens of a species from the original type locality. This collection serves as a valuable asset for knowledge or taxonomic revision of earlier described taxa.
Nematology research began in the United States in the late 1800's, and for many years collections of USDA nematologists remained as individual, personal collections (Golden, 1977; Handoo et al., 1996). The USDANC includes 100-year-old mounted specimens collected by pioneer workers, such as N. A. Cobb's original 1890 material of Mononchus longicaudatus (Golden and Huettel, 1990). From 1907 until his death in 1932, N. A. Cobb did extensive taxonomic research on plant, soil, freshwater, and marine nematodes. In 1918 Cobb was joined by G. Steiner from Switzerland. Until his retirement in 1956, Steiner made major contributions to nematode taxonomy, including insect parasites. Concurrently, Gerald Thorne joined USDA in Utah in 1918, and for the next 38 years published extensively on nematode taxonomy, almost exclusively in plant and soil forms. During the 1920's and 1930's other USDA scientists made significant contributions in taxonomy and other fields of nematology in the Washington, D.C. area, including B. G. Chitwood, J. R. Christie, and A. L. Taylor. Most of the specimens used by these early workers were retained in individual collections within the agency rather than in an organized, unified system. Unfortunately, over the years, many valuable specimens deteriorated and others were misplaced, or their habitat and collection records were lost (Golden, 1977; Handoo et al., 1997). Although many specimens isolated in the first half of the twentieth century were remarkably well-preserved, others were not. The process of salvaging the surviving specimens of previous USDA nematologists remains an ongoing effort. Fortunately, the Gerald Thorne Collection, developed by Thorne in Utah between 1918 and 1956, was well-organized and well-kept, and now forms an important segment of the present collection.
In 1960, with type specimens of 18 species, A. Morgan Golden officially established the USDA Nematode Collection at Beltsville, Maryland (Golden, 1962), creating an organized, unified repository of important specimens. Today, the type collection contains 1,430 species mounted and preserved on 5,177 metal and glass slides, and 404 vials from world-wide sources. It is one of the world's largest and most important sources of information for nematode taxonomic research and identifications, and it is widely used by U. S. and international scientists for their research purposes.
Including the type collection, the USDA Nematode Collection contains 34,000 permanent slides and vials, and 19,500 species entries. The USDA Nematode Collection is divided into the following constituent divisions: (i) Type Collection - for designated types; (ii) General Collection- for species from different hosts and regions, especially useful for variation studies and comparison and reference purposes; (iii) Mass Collection- a reservoir for difficult-to-identify species and undescribed taxa, most of which will be studied and described as taxonomic groups are revised; (iv) Demonstration Collection - exhibits showing symptoms and effects of various kinds of nematodes on a wide range of host plants; (v) Gerald Thorne Collection (including Thorne's South Dakota Collection) - for slides of important plant and soil species and higher taxa; (vi) Steiner Mermithid Collection - for slides of mermithid parasites of insects, with many types; (vii) Sample Records Division - for data on all samples and nematodes examined.
The collection is organized so that records of all specimens, which are on numbered slides or in vials, can be filed according to genus, species, host, and origin. This is an open-ended system that has permitted easy conversion to computerization and allows ready retrieval of specimens as well as data on nematode hosts, occurrence, and distribution. Growth of the collection has resulted from a number of factors, including restudy of material of earlier workers, the deposition of type and other specimens by colleagues throughout the world, the ongoing incorporation of material identified for researchers and other scientists, and the personal collecting efforts of A. M. Golden since 1956. Although most of the specimens are plant-parasitic nematodes, some are insect parasites or free-living soil, freshwater, or marine forms. Most specimens, including all types with pertinent records, are stored in fire-proof safes (Golden, 1962; Handoo et al., 1997).
Type specimens from scientists and other workers are always accepted and welcomed regardless of geographical origin. We strongly urge researchers and other workers at the different nematological centers and other institutions to continue to enrich this collection by depositing their valuable type and other specimens for the continuous growth of this indispensable collection. Upon deposit, the specimens become the property of the USDANC (United States Department of Agriculture Nematode Collection). The original names remain unchanged. One initial (T [type], G [general] or M [mass]) is added, followed by a USDANC accession number. The accession number receives a suffix (t [holotype and/or allotype] or p [paratype]), which differentiates the type slides from the general and mass slide collections. Also, if the depositor's slide or vial number is known, this number is added, as well.
In an ongoing preventive maintenance program of the collection, the slides are periodically checked for deterioration, and if necessary, the type specimens are remounted and the slides are resealed to prevent specimen degradation. Policies regarding the loan of type specimens are as follows: (i) Holotypes are unavailable for loan but like all specimens may be studied at the Nematology Laboratory at Beltsville, Maryland. (ii) Paratypes and other identified specimens (if more than one specimen is contained in the collection) are loaned for a limited period of two to three months to scientists in organizations of repute for research purposes; under special circumstances extensions are granted. (iii) Specimens may be loaned at the responsibility of a recognized scientist or laboratory for graduate students working on taxonomic revisions, variability studies, or for identification purposes. (iv) Any scientist who borrows the original type slides is not permitted to directly write on specimen slides; any suggested changes are to be indicated in correspondence.
This publication is a type specimen location reference and is not to be used for the status of the type species. No nomenclatorial changes are given. Also, it is not the purpose of this article to clarify the type status of the deposited specimens. Also, in the type specimens list, for any unpublished forms their names and their type numbers are presented for the sake of completeness, not as a statement of validity. The generic and specific names are arranged in alphabetical order and are given as indicated by the author(s) when the types were deposited in the type section of the USDANC. The complete title of the reference is not given for each species, only the author(s), date, source, and slide number(s). Also included are author(s) of designated types other than those of the original type series, e.g. paralectotype, allolectotype, neotype.
The purpose of this publication is to identify and make known to the scientific community the resources that exist in the type collection section of the USDA Nematode Collection, which exists to advance and stabilize nematode systematics. The curatorial staff of the collection is presently creating an electronically accessible database of the collection; relevant information is available on the Nematology Laboratory Website.