Observations on the Fully Developed Cysticercoid of Hymenolepis Microstoma ( Cestoda: Cyclophyllidea )

JANUARY, 1963] HELMINTHOLOGICAL SOCIETY 67

Studies on Cysticercoid Histology. VII: Observations on the Fully Developed Cysticercoid of Hymenolepis microstoma ( Cestoda: Cyclophyllidea ). *

MARIETTA VOGE

Studies on the biology of Ht/menolepis microstoma by Dvorak et al (1961) demonstrated the close structural similarity of this species with Tlymenolepis nana. For this reason, the histology of the Cysticercoid of H. microstoma was investigated and compared with that described for H. nana by Voge and Heyneman (1960), to ascertain the extent of structural similarities or differences between the cysticercoids.

MATERIALS AND METHODS The strain of H. microstoma was obtained from Rice University, Houston, Texas, through the courtesy of Dr. Clarence Weinmann. Cysticercoids of H. microstoma were grown in the confused flour beetle, Tribolium confusum, maintained on enriched flour at 30°C. Infection of beetles was accomplished by feeding the beetles eggs obtained from gravid proglottids passed in the feces of infected white mice. Infected beetles were kept at 30°C and cysticercoids harvested eight days or one month after infection. Cysticercoids were fixed in Zenker's fixative, embedded in paraffin, and sectioned at 7 microns. Stains used were Mallory's aniline blue stain for the demonstration of fibrous tissue (Gridley, 1953), and Mayer's hemalum (Lillie, 1954) and Gomori's trichrome as used by Voge (1960), for nuclear and cellular morphology. DESCRIPTION A longitudinal section of the Cysticercoid of II. microstoma is presented in figure 1. The outermost layer is the delicate external membrane which surrounds the whole cysticercoid. The external membrane, which in some sections appears to consist of two layers, is separated by a narrow space from the next tissue layer. In old cysticercoids this space is filled with an acellular material which stains orange-red with Mallory's stain and red with Gomori's trichrome. It extends only over the body of the cysticercoid and is absent in the tail. Beneath this space is a layer of circular fibers which surrounds the body of the cysticercoid. The circular fibers are oriented transversely, cross- ing the longitudinal fibers beneath at an angle of approximately 90 degrees. The longitudinal fibrous layer is relatively thick and contains numerous nuclei. Fibers from this layer extend into the cysticercoid toil. Fibers of both fibrous layers stain an intense blue with Mallory's stain indicating the presence of connective tissue, while the nuclei in the longitudinal layer stain red. No nuclei Avere observed among the circular fibers in cysticercoids which Avere several Aveeks old. In eight day-old cysticercoids cells or nuclei are present adjacent and external to the layer of circular fibers. It seems likely that these cells are at least in part responsible for the formation of the circular fibrous layer. All fibers stain green with Gomori's trichrome. Beneath the longitudinal fibrous layer is a narrow, delicate tissue, the lining of the cysticercoid cavity (Fig. 1), which stains pink Avith Mallory's stain. *From the Department of Infectious Diseases, School of Medicine, University of Cali- fornia, Los Angeles. Aided by a grant (E-1583) from the National Institutes of Health, United States Public Health Service, Bethesda, Maryland. Thanks are due to Mr. Allen K. Berntzen for help with the drawings, and to Mrs. Nora Liang for technical assistance.

The nuclei in this layer are more elongate than those in the longitudinal fibrous layer. Within the cysticercoid cavity is the scolex with surrounding tissues. In living material the tissue surrounding the scolex is in contact with the lining of the cysticercoid cavity. In eight day-old individuals the scolex has a well developed cuticle, muscular suckers and a rostellum with fully-

Fig. 1. Free-hand diagram of longitudinal section of H. microstoma cysticercoid; cf, circular fibers; cs, cuticle of scolex; em, external membrane; Ifl, longitudinal fibrous layer; Ic, lining of cysticercoid cavity; t, tail; ts, tail space.

Copyright © 2011, The Helminthological Society of Washington JANUARY, 1963] HELMINTHOLOG1CAL SOCIETY 69 formed hooks. The tissue of the scolex is dense and compact when compared to the other tissues of the cysticercoid. The tail of II. microstoma may vary considerably in size and shape (Fig. 2). In some specimens the tail may be three or four times as long as the body part of the cysticercoid. Even in eight day-old individuals the tail eon- tains numerous fibers which have proliferated from the longitudinal fibrous layer. Posterior to the fibrous area there is in 8 or 10 day-old cysticercoids a fairly large space devoid of cells or nuclei, and filled with a very fine, granular material. This space gradually becomes smaller as the cysticercoids grow older and the tail assumes the shape characteristic for II. nana. The peripheral areas of the tail contain numerous spherical or elongate cells as well as nuclei. DISCUSSION Comparison of the histologic structure of Hymenolepis microstoma with that of II. nana shows that there exists a close similarity between the cysticercoids. They resemble each other in shape and size, in the organization of the fibrous layers and, to some extent, in the size and shape of cellular ele- ments. There are, however, certain differences between the two species. One of these concerns the space underlying the external membrane. This space is filled with an acellular substance of uniform appearance in H. microstoma and is apparently empty in II. nana cysticercoids of comparable age and manner of preparation. A more pronounced difference is observed in the tail which in H. microstoma may be very long and variable in shape. The frequently very large and well delimited acellular space in II. microstoma has not been observed in II. nana. Furthermore, the extensive proliferation of fibers from the longitudinal fibrous layer into the tail does not occur in H. nana- In view of these characteristics the two species can be differentiated on the basis of cysticercoid histology although the similarities between them are much more pronounced than are the differences.

Pig. 2. Variation in size and shape of the tail in cysticercoids of H. microstoma. All sketches made from eight day-old, living eysticercoids.

LITERATURE CITED DVORAK, J. A., JONES, A. W. and KUHLMAN, H. H. 1961. Studies on the biology of Hymenolepis microstoma (Dujardin, 1845). J. Parasit. 47: 833-838. GKIDLEY, M. F. 1953. Laboratory manual of special staining technics. Armed Forces Institute of Pathology, Washington, D. C. 205 pp. LILLIE, R. D. 1954. Histopathologic teclmic and practical histochemi.stry. The Blakiston Company, New York. 501 pp. VOGE, M. 1960. Studies on cysticercoid histology. I. Observations on the fully developed cysticercoid of Hymenolepis diminiita (Cestoda:Cyclophyllidea). Proc. Helm. Soe. Washington. 27: 32-36. — — and HEYNEMAN, D. 1960. Studies on cysticercoid histology. II. Observations on the fully developed cysticercoid of Hymenolepis nana (Cestoda: Cyclophyllidea). Helm. Soe. Washington. 27: 185-188.

Dentostomella grundrnanni n. sp. (Nematoda: Oxyuriclae) from Eutamias quadrivittatus (Say, 1823) M. B. CHITWOOD Beltsville Parasitological Laboratory, Animal Disease and Parasite Research Division, Agriculture Research Service, U. S. Department of Agriculture, Beltsville, Maryland In August 1955, Dr. Albert Grunclmann, University of Utah, forwarded to the Beltsville Parasitological Laboratory for identification some specimens of an unusual oxyurid from the western chipmunk, Eutamias quadrivittatus. The chipmunk was collected in the Dewey Bridge area of the Great Salt Lake Desert in Utah. These nematodes consist of three males and a tail frag- ment, and four females of a new species of the genus Dentostomella Shul'ts and Krepkogorskaia, 1932. The following is a report of a new geographical localitjr, as well as a new host record, for the genus. Dentostomella grundmanni n. sp. DIAGNOSIS : Dentostomella. Cuticle in both sexes thick, transparent, coarse- ly striated, appearing annular when contracted, cephalic inflation present. Head bearing four small submedian cuticular projections, each bearing one papilla; one papilla immediately internal to each projection. Six minute papillae of internal circle near small round mouth, (Fig. 4). Amphidial pore opening in cup-like depression, (Fig. 1). Lips absent, buccal capsule shallow with median tooth on anterior tip of each esophageal sector; esophagus very short, muscular, enlarged at both ends; esophago-intestinal valve in enlarged foregut. FEMALES : Length 13.4-17.8 mm, maximum width in vulvar region 0.6-0.8 mm, longer specimens narrower than short ones. Esophagus 0.33-0.35 mm long; nerve ring 0.2 mm, excretory pore 3.7-4.1 mm, and vulva 7.5-9.1 mm from anterior end. Anus 0.8 mm from tip of bluntly conical tail. Reproduc- tive system opisthodelpllic. Vagina vera muscular, directed cephalad, vagina uterina directed eephalad in part or entirely (Fig. 7), reflexing near junc- tion with common egg chamber which divides into two posteriorly directed uteri confined to posterior half of body. A large sperm reservoir (Fig. 2) lies between each ovary and oviduct, one pre, one post-vulvar. Both ovaries anterior to vulva, eggs 0.13-0.14 X 0.04-0.05 mm. MALES : Length 4-8 mm, width 0.18-0.33 mm; esophagus 0.23 mm long. Tail with cuticular inflation reaching almost to tip without supporting rays but with plaque-like markings on ventral surface. Single spicule 0.26 long, lightly sclerotized, distal tip bidentate. Four pairs caudal papillae; 1 pair