Robert E. Ogren

Predation behaviour of land planarians

Predatory behaviour of land planarians is seldom observed or reported. Aspects reported are (1) finding prey; (2) attack behaviour; (3) capture using adhesive mucus, pharyngeal action, poisonous secretions, physical embrace; (4) feeding by extension of pharynx, releasing copious digestive fluid. The species Bipalium kewense, B. adventitium and B. pennsylvanicum attack earthworms, immobilizing them by physical holding, digesting by pharyngeal secretions and then ingesting the treated tissue. Group attacks on giant African land snails involving chemotactic tracking, occur in Platydemus manokwari and Endeavouria septemlineata. Specialized capture methods are used by some species; Rhynchodemus sylvaticus uses an expanded cephalic hood to capture small insects and in Africa, termites are captured by the elongated anterior of Microplana termitophaga as planarians wait within the colony air shaft openings to ensnare the workers in sticky mucus. The result of extensive predation by land planarians may seriously reduce the prey, e.g., providing effective population control of giant land snails by introduced Platydemus manokwari, or causing serious depletion of desirable earthworm populations by the exotic Artioposthia triangulata in North Ireland.

Morphology and development of oncospheres of the cestode Oochoristica symmetrica Baylis, 1927.

In a recent paper (Ogren, 1957) the embryogeny of this tapeworm was described. The present paper deals exclusively with the structural and developmental changes of the oncosphere although both topics were summarized in an abstract (Ogren, 1956b). It has not been generally realized that the hexacanth embryo contains differentiated structures and undifferentiated embryonic cells. Moreover, the changes by which the sphere of blastomeres becomes an hexacanth embryo have not been described. In fact, this series of changes was not realized by the writer until after publication of the development of Mesocestoides (Ogren, 1956a). The oncosphere is a muscular embryo that manifests a series of cellular changes during its development before being eaten by the intermediate host. A knowledge of these changes helped in understanding how it is that oncospheres are prepared for infectivity and what original structures are present. Knowledge was also obtained of secretory activity by embryonic cells. The oncosphere of Oochoristica is a large spherical, muscular embryo (Fig. 19) characterized by the possession of 6 large hooks, a body of mesenchymal cells and irregular granular epidermal areas. Each oncosphere is enclosed by an outer shell and an inner non-cellular pseudoembryophore. The purpose of this paper is to describe the development of these structures. Answers to the following questions

The hexacanth embryo of a dilepidid tapeworm. I. The development of hooks and contractile parenchyma.

It has been of considerable interest for the writer to learn that oncospheres are not all produced in the same way. The kind of embryo and the manner of its production are related to taxonomic position of the genus. In the present series of papers the morphology and development of a typical dilepidid hexacanth embryo will be described as a probable pattern for certain genera of the family Dilepididae. The complete hexacanth embryo (Fig. 18) was an oncosphere which retained the embryonic epidermis that later developed prominent epidermal glands (Reid, 1948; Ogren, 1955, 1957).

Continuity of morphology from oncosphere to early cysticercoid in the development of Hymenolepis diminuta (Cestoda: Cyclophyllidea)☆

Abstract 1. 1. The structure of the early cysticercoid during the first forty-eight hours of development is a continuation of the infective oncosphere. The following basic structures were identified; the six hooks, binucleate medullary center, collar myoblasts, attached to the lateral hooks, a group of small anchor cells, two lacunas and extensive granular epidermal glands. 2. 2. The terms reorganizing oncosphere and posthexacanth condition are suggested as descriptive of the early cysticercoid. The duration of the posthexacanth condition is recognized as a period of transition and reorganization with the final result being the development of germinative cells. 3. 3. The first germinative cells arise in the epidermal glands. These early germinative cells are considered to be the same cells that formed the epidermal glands of the oncosphere. 4. 4. During the extended prophase of the germinative cells, growth occurs, nuclei and nucleoli enlarge and abundant cytoplasmic ribonucleic acid appears.

The mature oncosphere of Hymenolepis diminuta.

The hymenolepidid oncosphere consists of a muscular parenchyma, three pairs of distinctive hooks, a binucleate medullary center, and epidermal glands, and is invested by a thin cuticle. Something is already known of the development and morphology of other oncospheres (Ogren, 1957); however, few descriptions exist of the morphology of the hexacanth embryo of Hymenolepis diminuta. The morphology and development of Dilepis undula has recently been described (Ogren, 1958a, 1959a,b). Dilepid oncospheres are of the hymenolepidid type (Ogren. 1957) and thus are similar in structure and development to Hymenolepis diminuta. The present investigation was undertaken to study this similarity in detail and to elaborate on an earlier report (Ogren, 1958b). Description will be restricted to mature and post-mature oncospheres, both considered to be infective. The term post-maturation condition has been introduced by the writer to designate the state of the oncosphere and protective envelopes in the most gravid terminal proglottids of the strobila. These also are the oncospheres found in the stools. Their appearance has been described for Dilepis and may represent a more resistant condition (Ogren, 1959a).

The hexacanth embryo of a dilepidid tapeworm. III. The formation of shell and inner capsule around the oncosphere.

One of the interesting problems for the student of cestodes is to explain the origin and development of membranes about the mature oncosphere. These, many times, are diverse and modified by their differentiated condition. The only possible way to solve the problem is to follow the changes taking place during embryonic development. In the present paper the writer has employed the tapeworm Dilepis undula Schrank, and the methods previously used (Ogren, 1958, 1959). Studies of this and other similar tapeworm embryos indicated that there may be 4 envelopes enclosing and protecting cyclophyllidean oncospheres: (1) The outer shell, or shell capsule; (2) the rigid inner capsule, in some cases called the embryophore, formed between the oncosphere and the shell; (3) a colloidal or albuminous region beneath the shell; (4) in some cases, a thin membrane is found between the inner capsule and the oncosphere draped over the hooks.

The hexacanth embryo of a dilepidid tapeworm. II. The epidermal glands and post-maturation changes.

Interesting granular epidermal glands are characteristic of cyclophyllidean oncospheres of the hymenolepid-type (Ogren, 1957). These glands, first described by Reid (1948), are found in Choanotaenia, Hymenolepis, and Raillietina cesticillus. They are also present in Dictymetra, Diorchis, Protogynella, Oochoristica, and Dilepis (Ogren, 1953, 1958a). Probably all true genera in the families Hymenolepididae, Dilepididae and Linstowiidae will be found to have oncospheres with epidermal glands. Development of the gland area is similar in Hymenolepis nana, H. diminuta, and Oochoristica symmetrica. The gland differentiates from 2 bilateral primordia, that enlarge, spreading over the embryo to form a U-shaped area of several cells (Ogren, 1955, 1957, 1958b). The following study of Dilepis undula Schrank confirms this pattern. The hexacanth embryo has 4 overlapping periods of differentiation: (1) Morula formation; (2) hook and parenchyma development; (3) epidermal gland development; (4) post-maturation changes (Ogren, 1957). These periods are identifiable in Dilepis undula. The first 2 have been considered somewhat in Part I (Ogren, 1958a) along with methods. The present part combines description of epidermal glands and post-maturation changes.

CAPILLARIA BLARINAE, N. SP. (NEMATODA: TRICHURIDAE) FROM THE ESOPHAGUS OF THE SHORT-TAILED SHREW, BLARINA BREVICAUDA (SAY)*

Retracted cirrus (spicule sheath) lined by short stout spines; length of spinous part of cloaca, 0.116-0.128; width, 0.012-0.014. Distance from anus to spicule pouch, or point of entrance of spicule, 0.165-0.204; spicule length, base to tip, 0.179-0.363; width, 0.0043-0.0072; ejaculatory duct, length, 0.36-0.46; width, 0.026-0.033; total length of cloaca, 0.38-0.46; width, 0.023-0.027. Cirrus usually not everted. Body, blunt posteriorly, ending in two knob-like enlargements bearing a transparent bursal membrane (Fig. 1-3). The ratio of esophagus length to body length was approximately 1 :2.4-1 :3.6. The structural plan (Fig. 7) was similar to Trichuris. The seminal vesicle proceeded posteriorly beside the narrow intestine. Near the last fourth of the body the seminal vesicle enlarged to become the muscular ejaculatory duct which opened into the proximal end of the thick walled cloaca. The cloaca was lined by a thin cuticular membrane continuous with the external cuticle. These structures were best seen when the male was placed in glycerin and viewed from the side. The spicule pouch entered the mid region of the cloaca and its lining fused with the cloacal lining. The spicule, tightly enclosed by the spicule pouch, was difficult to distinguish. However, critical focusing at different levels under oil immersion revealed the spicule as a translucent rod whose proximal part arose as a continuation of the retractor fiber at the base of the spicule pouch (Fig. 8). Measurement of the spicule length was made from this point to the rounded tip. The retractor fiber passed anteriorly and was fused to the body wall. Along its anterior length it received large muscle fibers from the body musculature (Fig. 9).

Karyology of four land-planarian species of the genus Bipalium from Japan

We have empolyed a new scale for characterizing chromosomal forms in the karyotypes of four species of Bipalium from five localities in Japan. Specimens of Bipalium nobile Kawakatsu et Makino, 1982, from Yokohama had a diploid chromosome number of 2x = 10 (2m + 2sm + 2sm + st & sm + 2sm); specimens of the same species from Toyonaka had this number as well but with slightly different chromosomal form (2m + 2sm + sm & st + 2st + m & sm). An undescribed species from Sanjo, Bipalium sp. 2, with two dorsal stripes and a yellow head crescent, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m); and another undescribed species from Chichijima Island, Bipalium sp. 3, with five dorsal stripes, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m). A non-sexual bipaliid tentatively identified as Bipalium kewense Moseley, 1878, from Chichijima Island had 2x = 18 (2m + 2m + 2m + 2sm + 2st + 2sm + 2sm + 2sm + 2sm).

The cellular pattern in invasive oncospheres of Hymenolepis diminuta as revealed by an enzyme-acetic acid-orcein method.

Recently-hatched oncospheres in the invasive condition, obtained from washed centrifuged stools of infected rats, were prepared as fixed whole mounts on slides, treated with saliva or ribonuclease, then stained with acetic acid-orcein. The general morphology is described by means of a series of photomicrographs from dorsal to ventral levels through the body. The protoplasm of the penetration gland cells, following the dorsal body contour beneath the subcuticular musculature, had an extensive meshwork. The nucleus of each gland cell contained a small nucleolus and moderately evident chromosomes. The region behind the hooks contained the majority of cells, particularly five large embryonic pairs separable into two distinct classes. Class I cells included three pairs with very distinct, thickened chromosomes, arranged as a spireme, an irregular nucleolus, and dense, compact cytoplasm. The class II embryonic cells had the largest nuclei, indistinct chromosomes, but massive nucleoli rich in nucleoprotein. Although the oncosphere, a six-hooked embryo of tapeworms, has been examined for a number of years, knowledge of its cellular structure is still incomplete. The basic features of invasive oncospheres of Hymenolepis diminuta have been outlined briefly (Ogren, 1961, 1962; Voge, 1965). The purpose of 1 Contribution No. 25 to the Cytology and Differentiation of Oncospheres. 2 The research was supported by grants G12905, GB 1480, and GB 4328 from the National Science Foundation, Developmental Biology. The assistance of the following students is gratefully acknowledged: Kathleen Dennis, Maria R. Supko, and Sarah B. Leonard. TRANS. AMER. MICROSC. Soc. 86(3): 250-260. 1967. . . . i .