Species of Hymenolepis Weinland, 1858 (Platyhelminthes: Cestoda: Cyclophyllidea) have been used as tapeworm models in research and teaching since the 1950s when they were first domesticated in the laboratory of Clark P. Read . Adult parasites of rodents with beetle intermediate hosts, they benefit from easy culture in vivo using natural hosts that are themselves model organisms (e.g. Mus musculus L., Tribolium confusum Jacquelin du Val). Research on Hymenolepis, and especially H. diminuta (Rudolphi, 1819), H. nana (von Siebold, 1852) and H. microstoma, is underpinned by an extensive literature that includes much of our classical knowledge of tapeworm biology [e.g. ]. A recently initiated effort sponsored by The Wellcome Trust Sanger Institute to characterize the genome and adult and larval transcriptomes of H. microstoma http://www.sanger.ac.uk/sequencing/Hymenolepis/microstoma/ has brought this classical model into the genomic era, greatly advancing its utility for researchers interested in employing a practical tapeworm system that allows access to all life cycle stages. In light of this development, and the fact that laboratory isolates can vary in features of their biology , it is desirable to have a description of the exact strain on which the genome is based, and to thus anchor the data to a well-defined entity.
Hymenolepis microstoma was first described from the bile ducts of mice in 1845 by Dujardin  who placed it in the genus Taenia L., 1758, which housed all tapeworms known at that time. In 1891, Blanchard  transferred the species to the genus Hymenolepis and provided an expanded description of the species. Although Bear and Tenora  suggested synonymy between H. microstoma and H. straminea (Goeze, 1782), species status of H. microstoma historically has been widely accepted, and molecular data have shown both species to represent independent, albeit closely related, lineages [7, 8]. In contrast, the genus Hymenolepis has itself been overhauled on several occasions and its membership and internal structure remain controversial. For example, whereas Hughes [9, 10] accepted the generic assignment H. microstoma by Blanchard, Spasskii  subdivided the genus and transferred H. microstoma to the genus Rodentolepis Spasskii, 1954, which he erected to house the rodent-hosted species of Hymenolepis with armed rostella. At the same time Spasskii erected the genus Vampirolepis Spasskii, 1954, which Schmidt subsequently considered a senior synonym of Rodentolepis, thus resulting in the new combination Vampirolepis microstoma (Dujardin, 1854) Schmidt, 1986 . The genus Rodentolepis was retained by Czaplinski and Vaucher  in the most recent synoptic treatment of tapeworms , but this work did not consider species level taxa and therefore did not arbitrate on the generic assignment of H. microstoma. Thus although Vampirolepis microstoma  represents the most recent formal taxonomic assignment of the species, few investigators have adopted this name, and most reports refer to it as either a member of the genus Hymenolepis, or with less frequency, Rodentolepis. In our view, a natural circumscription of hymenolepid species will not be attained without the application of molecular data .
To this end, Haukisalmi et al.  recently used 28S rDNA to analyze phylogenetic relationships among 32 hymenolepidid species from rodents, shrews and bats, showing that both Hymenolepis and Rodentolepis represented paraphyletic assemblages. Although their work assigned H. microstoma to a 'Rodentolepis' clade, the lack of resolution and widespread paraphyly of the taxa in their analyses indicate that greater taxonomic representation and more robust data are needed before such nomenclatural circumscriptions can be made reliably. We therefore follow Blanchard  in recognizing the mouse bile duct tapeworm as a member of the genus Hymenolepis, employing the most common name in usage, whilst appreciating that a more comprehensive understanding of hymenlepidid interrelationships is likely to warrant generic reassignment.
Here we provide a description of a 'Nottingham' strain of H. microstoma based on light and scanning electron microscopy of laboratory-reared specimens from the same culture used to characterize the genome. History of the isolate, dating back to the laboratory of C. P. Read , suggests that it represents a model that has been widely employed and disseminated within the parasitological community for over 50 years, making the genome data directly relevant to a significant pre-existing literature on its biology.