Daughter Sporocysts Research Articles

The treatment of molluscan schistosomiasis mansoni with chloramphenicol.

SummaryThe primary method for the control of schistosomiasis has been via an attack on the intermediate molluscan host either through environmental control or the use of molluscicides. The present study offers a new approach to the problem, through the suppression or destruction of the parasite within the snail. Chloramphenicol, an inhibitor of protein synthesis, provides complete suppression of the formation of cercariae from miracidia at concentrations as low as 20 ppm, as long as the snails are exposed to the drug. The drug has been shown to prevent the formation of mother sporocysts and to inhibit the development of cercariae from daughter sporocysts. The effect of chloramphenicol on protein synthesis-related processes appears to be selective as evidenced by ratios of complete parasite suppression to snail LD50, snail growth and snail egg-laying. Although chloramphenicol may not itself offer a practical field method for the control of schistosomiasis, it may lead to the finding of a more effective means of controlling the disease by the study and exploitation of this new approach to the problem.

The life cycle of Trichobilharzia brevis, n. sp., an avian schistosome from Malaya.

The life cycle of a dermatitis-producing schistosome from Malaya is described. Trichobilharzia breris n. sp. develops in the snail Lymnaea rubiginosa, and in domestic ducks (experimentally). Some development takes place in the lungs of white mice for about 5 days, when the schistosomulae disappear. In the snail, mother sporocysts develop in the heart and veins; daughter sporocysts appear as soon as 7 days after miracidial penetration: cercariae are released beginning 17 days after exposure. In ducklings, eggs of T. breris may be found as early as 11 days after exposure to cercariae. All stages of the life cycle except adult females are described and illustrated.

On the morphology and life cycle of the trematode Tanaisia zarudnyi (Skrjabin, 1924) Byrd and Denton, 1950, from the ruffed grouse, Bonasa umbellus L.

Tanaisia zarudnyi occurs in the ureters and kidney tubules of ruffed grouse from Ontario and Michigan. The dark brown, operculate eggs are fully developed when oviposited. They remain viable for long periods of time at 2 to −15 °C and can withstand a temperature of −49 °C for 1 to 2 days. They hatch only when ingested by some mollusc. Development occurs in the digestive gland of the terrestrial snails Anguispira alternata and Succinea ovalis. Daughter sporocysts complete development in 6 weeks, by which time they contain undeveloped cercarial bodies. Within the next 2 weeks, most of the distomate. brevicercous cercariae are fully developed. The cercariae encyst within the daughter sporocyst, utilizing the contents of subcuticular glands to form the cyst. Encysted metacercariae are killed in the gizzard when fed to chickens, but excyst when inoculated directly into the duodenum. Excystation apparently results from secretions of the anterior glands of the stimulated metacercaria rather than from digestion of the cyst wall by the host. A 6-week-old ruffed grouse became infected when fed metacercariae, but 9 older ruffed grouse, 17 chickens, 4 white-throated sparrows, and 6 pheasants, fed similarly, were not infected. Apparently there is both host and age resistance to infection with this parasite.

Studies on the host-parasite relationship between Schistosoma mansoni and the snail Australorbis glabratus.

Summary The host-parasite relationship between Schistosoma mansoni and the snail Australorbis glabratus has been studied in aquarium-reared (unsterile) and bacteriologically sterile snails. Detailed observations on the sites of development, routes of migration, and normal and abnormal histology of the parasite, and on the pathologic changes produced in the host, as seen in serial sections of snails fixed at various intervals after infection, showed these to be similar in snails of both types. By comparison with normal controls, it has been found that infection of aquarium-reared snails suppresses fecundity, that an acceleration of shell growth appears before the parasite matures, and that an eventual stunting of shell growth and a high mortality coincides with the period of heavy cercarial emergence and the appearance of intense host tissue reactions. From observations on the development of the parasite in relation to tissue changes and mortality among infected snails, it is concluded that the extensive migration of large numbers of cercariae, and the intense tissue reactions associated with trapped degenerating cercariae, are important factors in causing death of the snails. Regeneration of exhausted daughter sporocysts may contribute to the release of cercariae for periods of several months from surviving snails.

The anatomy, life history and size allometry of Mesocoelium monody Dollfus, 1929

Mesocoelium monodi Dollfus (1929) occurs in amphibia and lizards including Agama agama (L.) in Ghana. Its life cycle was studied because although over 30 species occur in this genus, the life cycle has been described imperfectly for only one other species. Tailless, stylet cercariae produced by daughter sporocysts in the digestive gland of the terrestrial gastropod Lamellaxis gracilis Hutton were shown to be the larvae of this parasite, when cercariae from this source which had encysted on the substratum and within the sporocyst developed into egg bearing adults after they had been fed to helminth free juvenile lizards reared from the egg in the laboratory. Metacercariae similar to those were also found in two species of ants. The anatomy of all the stages, including the adult, are described. Particular attention is paid to the considerable intraspecific variability in the adult and to changes in the size and position of the parts relative to total size. In the light of this information, it is shown that many of the characters used previously in specific diagnosis are unreliable. It is shown that the life cycle of M. monodi closely resembles that of Mesocoelium brevicaecum but not those described for other species in the Dicrocoeliidae. Support can therefore be given to the inclusion of the genus Mesocoelium in a separate subfamily Mesocoeliinae, as suggested by Dollfus (1929). However, it is considered that the resemblance of the adult to other members of the Dicrocoeliidae justifies its inclusion in this family until more knowledge of the life cycles is forthcoming.

The Life History of Haematoloechus breviplexus Stafford, 1902 (Trematoda: Haplometridae McMullen, 1937), with Emphasis on the Development of the Sporocysts

Embryonated eggs of Haematoloechus breviplexus Stafford, 1902 were fed to laboratoryreared specimens of Gyraulus similaris (F. C. Baker, 1919). Miracidia hatch in the snail intestine, then invade the intestinal epithelium, many penetrating only as far as the basement membrane, but some passing through to the hemocoel of the snail. In either location they metamorphose to the mother sporocyst which enlarges gradually as the germinal cells multiply. Those mother sporocysts that are enclosed by basement membrane soon become pedunculate and detach from the intestine when the basement membrane ruptures. By the 12th day, the limiting membrane of many mother sporocysts ruptures, freeing the germinal cells which continue multiplying in the hemocoel of the snail. Between the 12th and 22nd days, the germinal cells give rise to many daughter sporocyst embryos which also undergo their development in the hemocoel. There is no host cellular response to the parasite, and consequently, paletots do not develop around the sporocysts. Xiphidiocercariae of the Omatae group are produced within 31 days and encyst in the branchial basket of naiads of the dragonfly, Aeschna multicolor Hagen, 1861. Metacercariae were fed to newly metamorphosed specimens of Rana pretiosa (Baird and Girard, 1853), and young adults of H. breviplexus were recovered 22 and 23 days later. The development of sporocysts of H. breviplexus is compared to that of several other species of plagiorchioid trematodes formerly studied by the author. Sporocyst development of H. longiplexus Stafford, 1902 and H. parviplexus (Irwin, 1929) was also observed and found to be identical to that of H. breviplexus. New host and distribution records are given for H. longiplexus and H. breviplexus. The present report represents part of the results of a long-range investigation of sporocyst and paletot development of plagiorchioid trematodes. The work was done during the summers of 1963 and 1964. Knowledge of the life cycle of Haematoloechus variegatus (Rud., 1819) was contributed by van Thiel (1930), who fed metacercariae, from anopheline larvae, to frogs and recovered adults of H. variegatus. Krull (1930 and 1931) reported on the life histories of H. medioplexus Stafford, 1902 and H. parviplexus (Irwin, 1929). The host snail for the latter species is Gyraulus parvus (Say, 1817), whereas, Planorbula armigera (Say, 1818) serves as host for H. medioplexus. He observed all stages except the mother sporocyst, and found that dragonfly naiads of the genus Sympetrum Newman, 1833 serve as second intermediate hosts for both species. The definitive host for H. parviplexus is Rana clamitans Latreille, 1802, while R. pipiens Schreber, 1782 serves as host for H. medioplexus. Krull (1932) found metacercariae of H. longiplexus Stafford, 1902 in the damselfly, Lestes vigilax Hagen, 1862, fed some to bullfrogs, and recovered adults of this species. The host snail was unknown. Krull Received for publication 24 November 1964. (1933 and 1934) observed the daughter sporocysts and cercariae of H. complexus (Seely, 1906) in Pseudosuccinea columella (Say, 1817). Naiads of three species of dragonflies serve as second intermediate hosts, and Rana clamitans serves as definitive host. Ingles (1933) investigated the life cycle of H. oxyorchis Ingles, 1932 from Rana aurora (Baird and Girard, 1852) and found that Gyraulus parvus and G. vermicularis (Gould, 1847) serve as first intermediate hosts. Ingles observed a 50-dayold daughter sporocyst and found that the cercariae encyst in dragonfly naiads of the genus Sympetrum. None of the above authors observed the mother sporocyst of any species. MATERIALS AND METHODS Second and third generation laboratory-reared specimens of Gyraulus similaris (F. C. Baker, 1919) were used throughout the investigation. Snails were maintained in enameled pans of aquarium water to which was added powdered calcium carbonate and an abundance of aquatic plants. The thick basal parts of lettuce leaves were added as food. As the lettuce decayed, the snails fed on it readily. Only young snails, having a shell diameter of 1.5 to 2 mm, were used. Mature specimens of H. breviplexus were obtained from the lungs of Rana pretiosa (Baird and Girard, 1853). The trematodes were placed in dishes of aquarium water for release of eggs.

On the life cycle of Brachylecithum orfi Kingston and Freeman, 1959 (Trematoda: Dicrocoeliidae), from the liver of the ruffed grouse, Bonasa umbellus L. infections in the vertebrate and molluscan hosts.

The distribution and life cycle of a dicrocoeliid trematode, Brachylecithum orfi Kingston and Freeman, 1959, from the biliary ducts of the ruffed grouse, Bonasa umbellus, in Ontario and Michigan, have been studied in the definitive host and the intermediate molluscan hosts. Oval, dark brown, operculate eggs contain fully developed miracidia at oviposition. The eggs are coated with a lipid which prevents uptake of water and hatching until they are eaten by a mollusc; they will survive for more than 3 years at 2 °C and will tolerate exposure to −49 °C. The eggs hatch and larval stages develop in Zonitoides arboreus, Z. nitidus, Cionella lubrica, Deroceras laeve, and D. reticulatum, but not in 13 other species of terrestrial molluscs. Small, rounded, daughter sporocysts develop within the saclike mother sporocysts during the first 30 days after ingestion of eggs by suitable molluscs. Daughter sporocyst and cercarial development is completed 89–278 days after infection, depending on the species of mollusc and the temperature. The cercariae escape from the sporocyst endosac through a birth canal into the sinusoidal spaces of the mollusc. They migrate to the lung and out onto the dorsum of the mollusc via the respiratory pore, where they aggregate in numbers in slimeballs that are deposited on the substratum. Cercarial production continues for more than 100 days after onset. The longicercous, mesostomate xiphidiocercariae have a flame cell formula of 2((2 + 2 + 2) + (2 + 2 + 2)); they are provided with 6 preacetabular and 12 postacetabular glands, both groups of which open through pores lateral to the shank of the cercarial stylet. Cercariae in slime masses survive for 48 hours. When exposed to larval Colorado potato beetles, larval willow chrsyomelids, and mound-building ants, the cercariae penetrated the gut wall and encysted in the haemocoel, but died shortly afterwards.

The influence of host-parasite dispersion upon the capacity of Shistosoma mansoni miracidia to infect Australorbis glabratus.

Summary The capacity of the miracidium of Schistosoma mansoni to locate and infect Australorbis glabratus was investigated under several conditions of host-parasite dispersion. Experiments usually involved exposing isolated snails to one miracidium each in vessels of different dimensions. Infection of snails was assessed 13 to 15 days post-exposure by detecting daughter sporocysts in squash preparations of the hosts. Aspects of miracidial behavior were also explored. Most of the findings on the effects of host-parasite dispersion do not lend themselves to terse summarization. It is sufficient to note that miracidia were successful in locating and infecting hosts situated at distances of 86 cm on the horizontal, at distances of 33 cm downwards, and that there is reason to believe that these do not represent the limits of miracidial scanning capacity. Newly-emerged miracidia were found capable of a velocity of about 690 to 750 cm per hour. Study of known miracidial tropisms disclosed that negative geotropism is a stronger influence upon their behavior than is positive phototropism. However, the tropisms do not elicit an absolute response from all miracidia even when acting together. Other evidence indicated that neither miracidia nor snails become randomly dispersed in a vessel but that both organisms are found more frequently near the outer margins. This suggests that the perimeter of a vessel is an important parameter in assessing miracidium-snail interactions. Existing evidence that snails may “attract” miracidia has been reviewed and found wanting. The data developed in this study suggest several working hypotheses: (a) Under ordinary field conditions, water depth is probably not an important barrier to host-location by miracidia; (b) certain submerged “margins” may represent the sites where miracidium-snail interactions are likeliest to occur; (c) in view of the marked scanning capacity of the miracidium, the threshold below which snails may not become infected will vary according to the degree of miracidial pressure; and (d) in regions of high endemicity such density thresholds may be close to the extinction point of the snail populations.

Development of the Sporocyst Generations of Glypthelmins quieta (Stafford, 1900) (Trematoda:Plagiorchioidea), a Parasite of Frogs

The development of the mother and daughter sporocysts and the paletots of Glypthelmins quieta was studied in laboratory-reared specimens of Physa gyrina. Following the ingestion of embryonated eggs, the miracidia hatch in the snail digestive tract and soon penetrate the intestinal epithelium. Mother sporocysts develop between the epithelium and the underlying basement membrane. At first the mother sporocysts are spherical but later they develop an uneven or lumpy surface as basement membrane cells multiply and invade the mother sporocyst to form cellular membranes around individual daughter sporocysts. These membranes are the paletots. As daughter sporocysts develop they remain in a compact mass, all held together by their paletots. Fully developed paletots are composed of flattened epithelial cells and fine fibers. Cercariae are released between the paletot and the sporocyst body wall. Paletot formation is dependent upon a cellular response to the invading parasite by the host snail. This represents an attempt by the host to isolate or wall off the parasite. The method of development of the sporocyst generations and paletots of G. quieta was found to be similar to that of Haplometrana intestinalis, but quite different from that of Telorchis bonnerensis. On the basis of cercarial anatomy, method of development of the sporocysts, and origin of paletots, G. quieta is thought to be closely related to H. intestinalis. The author suggests that G. quieta be assigned to the family Macroderoididae. Information on the life cycle of Glypthelmins quieta has been published by Rankin (1944) and by Leigh (1937 and 1946). Rankin's observations were made on naturally infected snails. He illustrated only a welldeveloped daughter sporocyst. Leigh (1946) illustrated and described two developmental stages of the mother sporocyst, 18 and 36 days old respectively, and also a young and a welldeveloped daughter sporocyst. Leigh used field-collected snails for his egg-feeding experiments. Cheng (1961) published an account of the life history of G. pennsylvaniensis Cheng which utilizes Helisoma trivolvis (Say) as intermediate host. He illustrated and described four developmental stages of the mother sporocyst and two stages of the daughter sporocyst. He used specimens of H. trivolvis that had been collected from a supposedly helminth-free lake. The present paper is the third in a series published by the author on the comparative development of the paletots and the sporocyst generations of representative genera and species plagiorchioid trematodes. Received for publication 8 January 1962. *This investigation was supported by a research grant (No. E-950) from the National Institutes of Health, U. S. Public Health Service. MATERIALS AND METHODS Mature specimens of Glypthelmins quieta were obtained from the intestine of the bullfrog (Rana catesbeiana), purchased from the Lemberger Co., Oshkosh, Wisconsin. Laboratory-reared specimens of Physa gyrina were used throughout the investigation. The adult snails were collected and brought to the laboratory for oviposition. Egg masses were distributed to large fingerbowls containing aquarium water, stems of Elodea, soaked maple leaves, and powdered calcium carbonate. Young snails having a shell length of 2 to 3 mm were used for egg-feeding experiments. Groups of 25 to 30 snails were placed in 2-inch Stender dishes with embryonated eggs of G. quieta. The snails were permitted to ingest eggs for 15 to 20 minutes, after which they were transferred to clean culture dishes. Examination of snails was begun 1 hour after feeding eggs and continued daily. Most observations were made from living specimens. The snails were dissected in 0.2 per cent solution of sodium chloride and studied as wet preparations under the oil immersion objective. Dilute aqueous neutral red and acetocarmine were used to stain the germinal and somatic cells of the parasite. For more critical observation of histological details some infected snails were removed from their shells, placed in Heidenhain's Susa fixative, sectioned, and then stained with either Ehrlich's haematoxylin or Heidenhain's iron-haematoxylin. The age of the sporocysts is given in days in order to provide a more orderly sequence for the developmental stages. It is realized that the rate of development is affected by changes in the temperature of the environment.

Development of Mother and Daughter Sporocysts of Haplometrana intestinalis Lucker, a Plagiorchioid Trematode of Frogs

Development of Mother and Daughter Sporocysts of Haplometrana intestinalis Lucker, a Plagiorchioid Trematode of Frogs

Observations on the morphology and life cycle of Neodiplostomum intermedium (trematoda: Diplostomatidae).

1.Neodiplostomum intermediumPearson is recorded from four new hosts; as an adult from the water rat,Hydromys chrysogasterGeoffroy, and as a metacercaria (diplostomulum), from tadpole and adult of an undescribed tree frog,Hylasp., tadpole of (Hyla latopalmata(Günther)Mixophyes fasciolatusGünther and frog of an unidentified leptodactylid.2. The life cycle ofNeodiplostomum intermediumwas followed experimentally; the hosts were:Pettancylus assimilis(Petterd), a fresh-water limpet, as first intermediate host; tadpole ofHyla pearsoniCopland as second intermediate host;Hyla caerulea(Shaw) a tree frog, andHemisphaerodon gerrardiPeters, the pinktongued skink, as paratenic hosts; andRattus assimilis(Gould) and laboratory rats as definitive hosts.3. Descriptions are given of the morphology of the miracidium, mother sporocyst, daughter sporocyst, cercaria, and diplostomulum, with special reference to the structure of the miracidium and of the cercarial tail.4. Observations are given on the embryology of the miracidium, hatching of the egg, transformation of the miracidium into the mother sporocyst with special reference to the germinal cells, the route and manner of escape of cercariae from the snail host, the development of the diplostomulum with special reference to the reserve excretory system, and the movements of diplostomula during metamorphosis of the tadpole host.5. The haploid chromosome number is ten, as determined from squashes of testes. One paratype and a series of experimental adults have been compared with and found different fromNeodiplostomum(Fibricola)sarcophilusn.comb. The orthography and formal proposing of the names of the species ofFibricolatransferred toNeodiplostomumby Pearson (1959b) are corrected.The writer wishes to thank Dr M. J. Mackerras, Queensland Institute for Medical Research, for generously supplying water rats; Professor J. F. A. Sprent, University of Queensland Veterinary School, for his criticism of the manuscript; Mr K. Webber and his sons for their assistance in catching rats and for permission to collect snails, frogs and tadpoles from their streams; and Mr R. J. Ballantyne for technical assistance. This study was supported by a grant from the Rural Credits Fund of the Commonwealth Bank of Australia.

STUDIES ON THE STRUCTURE, LIFE HISTORY AND ECOLOGY OF THE TREMATODE PHYLLODISTOMUM SIMILE NYBELIN, 1926 (GORGODERIDAE: GORGODERINAE) FROM THE URINARY BLADDER OF BROWN TROUT, SALMO TRUTTA L.

SUMMARY Brown trout (Salmo trutta L.), salmon parr (Salmo salar, L.) and the eels (Anguilla anguilla (L.)) from certain rivers in West Wales were examined over a period of nearly two years for parasites. Large numbers of Phyllodistomum simile Nybelin were found in the urinary bladder of the trout from the River Teify. P. simile, was not found in any of the 274 salmon parr or 243 eels examined, probably due to an ecological immunity in the former and a physiological immunity in the latter. There was no evidence of a seasonal variation in the occurrence of P. simile in trout aged two years or more. Trout aged four or more years were more heavily infested than young trout and there was no indication of the development of a total immunity with increase in the age of fishes. The life history of P. simile was elucidated under experimental conditions by feeding the trout precocious metacercariae present in daughter sporocysts obtained from the gill lamellae and epibranchial cavity of the freshwater bi‐valve, Sphaerium corneum. The anatomy of the daughter sporocyst, the cercaria, metacercaria and the adult stages are described. The gorgoderid cercariae and the attempts to classify them into groups corresponding to those of the adults are discussed. It is suggested that attempts at discussing the evolution of the cercariae placed in the family Gorgoderidae may be premature in view of the fact that life histories have only been elucidated experimentally for cercariae of the macrocercous, cystocercous kind. The advantages in the life cycle of precocious encystment within the sporocyst are commented upon but it is also suggested that P. simile may have a second intermediate host, possibly the minnow, Pkoxinus phoxinus L. or a freshwater arthropod. The morphological changes that take place during the development of P. simile and their importance in specific diagnosis are discussed. It is suggested that in view of the more readily discernible differences between the larvae, certain larval features might well be used in distinguishing species of doubtful validity.

Life history ofGigantobilharzia huronensisNajim, 1950. A dermatitis-producing bird blood-fluke (Trematoda-Schistosomatidae)

1. The life cycle ofGigantobilharzia huronensisNajim, 1950, was determined experimentally. The snail,Physa gyrina(Say), served as the intermediate host. The natural definitive hosts were goldfinches (Spinus tristis tristis) and the cardinals (Richmondena cardinalis). Chicks and canaries served as susceptible hosts in the laboratory2. The shortest time recorded for the hatching of eggs in water is about 20 min. Cercariae were liberated from the snail as early as 24 days after exposure. Eggs were found in the faeces of the definitive host 31 days after the first exposure to the cercariae.3. Adult worms are elongate and filiform. Females are longer than males, and in both sexes the oral and ventral suckers are absent. The cuticle has no spines. A short gynaecophoric canal is present. Up to 300 testes are present in the male and the cirrus is spiny. Laurer's canal is present and vitelline follicles fill most of the body of the female. Eggs are spherical to very broadly ovoid in shape and averaged 93µ in length by 88µ in width. The uterus contains from one to several eggs at a time, and the genital pore is located shortly posterior to the mouth opening.4. The miracidium has a peculiar wide gap between the second and third rows of epidermal plates. The body covering consists of twenty-two epidermal plates arranged in four rows of 6:9:4:3. The mother sporocyst has an elongate, sac-like body. A birth pore is present in the mature mother sporocysts. The daughter sporocyst also has an elongate body, but the anterior end is covered with spines. A birth pore is present in the mature daughter sporocysts.5. The cercaria is an apharyngeal, furcocercous, brevifurcate, distome with pigmented eyespots; the body averaging 240µ in length by 72·5µ in width; the tail stem averaging 268·5µ in length by 30µ, in width; the furca averaging 146·8µ in length by 15µ in width. The furcae have fin folds. The body and tail are covered with spines. There are five pairs of penetration glands and an oral gland. The excretory system is usually 2[(2) + (2+1)]. The cercaria attaches to the surface film of the water with the body parallel to it and the tail hanging downward at different angles. The cercaria is a dermatitis producer in human skin.

Developmental Stages in the Digenea. III. Observations on the Number of Daughter Sporocysts and Cercariae Produced in Physa gyrina as a Result of Single and Multiple Ochetosomatid Egg-Exposures

Developmental Stages in the Digenea. III. Observations on the Number of Daughter Sporocysts and Cercariae Produced in Physa gyrina as a Result of Single and Multiple Ochetosomatid Egg-Exposures

A STUDY OF THE LIFE HISTORY OF TRICHOBILHARZIA CAMERONI SP. NOV. (FAMILY SCHISTOSOMATIDAE)

A cause of swimmer's itch in the lower Ottawa River is Trichobilharzia cameroni sp. nov. Its life cycle has been completed experimentally in laboratory-bred snails and in canaries and ducks, and the various stages are described. The eggs are spindle-shaped. The sporocysts are colorless and tubular. Mother sporocysts become mature in about a week. The younger daughter sporocyst is provided with spines on the anterior end and becomes mature in about three weeks. The development in the snail requires from 28 to 35 days. A few cercariae were found to live for up to 14 days at 50 °C., although their life at 16° to 18 °C. was about four days. Cercariae kept at room temperature for 60 to 72 hr. were found infective. The adults become mature in canaries and pass eggs in about 12 to 14 days. Physa gyrina is the species of snail naturally infected. It was found in one case giving off cercariae for five months after being kept in the laboratory. Domestic ducks were found to become infected until they were at least four months old, with the parasites developing to maturity in due course; no experiments were made with older ducks. Furthermore, miracidia were still recovered from the faeces four months after the duck had been experimentally infected, and it is suggested that migratory birds are the source of the local infection.

The Early Development of the Daughter Sporocysts of the Strigeoidea (Trematoda)

appear to be differences between species. However, there are rarely fewer than 12 or more than 30 in each sporocyst. The largest embryos of the germinal masses are at the ends and the production of free embryos in both mother and daughter sporocysts appears to be accomplished only by their breaking off. They are replaced by the growth of other embryos which in their turn separate from the masses; new embryos appear to be constantly formed from the germinal cells which persist in the germinal masses and multiply throughout the reproductive life of the germinal sacs. This mechanism for the multiplication of germinal cells in the strigeoid group produces in the mother sporocyst a sufficient number of daughters to fill completely the digestive gland of the snail host, and in the daughters the enormous numbers of cercariae which escape during the life of an infection. Up to the pres

The Germinal Development in the Daughter Rediae of an Ophthalmo-Xiphidiocercaria from Pomatiopsis lapidaria

ALLOCREADIIDAE. In fact, recent work indicates that this family should include only species with ophthalmo-xiphidiocercariae (Hopkins, 1934; Cable and Hunninen, 1942). The structure of cercariae of this type, especially the presence of a stylet and stylet glands, suggests that this family is related to the PLAGIORCHIOIDEA. We might go even further and suggest the hypothesis that this group on account of the presence of eye-spots in the cercariae and their development in rediae is more primitive than the PLAGIORCHIOIDEA, and may be close to the ancestral type from which the true plagiorchiids developed. This possibility made it of special interest to determine whether the germinal development in the daughter rediae of Cercaria pomatiopsidis showed any resemblance to that in the daughter sporocysts of the plagiorchiids. During the summer of 1948 we had the opportunity of examining 1282 specimens of Pomatiopsis lapidaria collected near Ann Arbor, Michigan, of which 37 or about 3.0 per cent were infected with C. pomatiopsidis. Most of the infections were mature or old but a few immature daughter rediae were available for study.

Further observations on Cercaria parvicaudata Stunkard and Shaw, 1931.

Previous article No AccessJournal ArticlesFURTHER OBSERVATIONS ON CERCARIA PARVICAUDATA STUNKARD AND SHAW, 1931HORACE W. STUNKARDHORACE W. STUNKARD Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Biological Bulletin Volume 99, Number 1August 1950 Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.2307/1538757 Views: 15Total views on this site © 1950 Marine Biological LaboratoryPDF download Crossref reports no articles citing this article.

The Early Larval Stages of Schistosoma mansoni Sambon, 1907 in the Snail Host, Australorbis glabratus (Say, 1818)

In a series of related studies Cort and his associates have presented information on the early larval stages of trematodes belonging to the groups Strigeata (Cort and Olivier, 1941), Schistosomatoidea (Cort and Olivier, 1943b; Cort, Ameel, and Olivier, 1944), Plagiorchioidea (Cort and Olivier, 1943a; Cort and Ameel, 1944), and the Fasciolatoidea (Cort, Ameel, and Van der Woude, 1948). In these investigations the morphology of the larval stages was studied in considerable detail and special emphasis was placed on determination of the method of reproduction. Prior to these studies, detailed information on the early developmental stages of trematodes in the groups mentioned was very meager. Two of the studies dealt with schistosomes. Cort and Olivier (1943b) reported on the early developmental stages of Trichobilharzia stagnicolae (Talbot, 1936). It was shown that the mother sporocysts are relatively large, elongate, sausageshaped sacs usually located in the head-foot region of the snail. They produce numerous daughter sporocysts by means of multiplication of the germinal cells (primary polyembryony) and by a special form of polyembryony involving germinal masses2 (secondary polyembryony). In the daughter sporocysts the cercarial embryos are also produced by multiplication of the germinal cells and by polyembryony involving germinal masses in the same manner as the daughters themselves were produced. In the second of the two studies dealing with schistosomes Cort, Ameel, and Olivier (1944), desribed the developmental stages of Schistosomatium douthitti (Cort, 1914). They found that division of the germinal cells in the miracidium results in production of about 200 germinal cells in the young mother sporocyst. Each of these germinal cells develops into one daughter sporocyst. These daughters leave the mother and migrate to the digestive gland. Germinal cells carried in the daughter sporocysts multiply until about 200 cells result. Most of these cells develop into cercariae, but a few give rise to germinal masses which in turn produce cercariae. No germinal masses were seen in the mother sporocysts and only a few were seen in the daughter sporocysts, suggesting that polyembryony by germinal masses in this species is relatively uncommon. It was felt desirable to compare the development of the schistosomes of man with that described for T. stagnicolae and S. douthitti. There is little available information on the early larval stages of Schistosoma haematobium and Schistosoma japonicum. Only Maldonado and Acosta-Matienzo (1947) have presented detailed in-

Studies on Germinal Development in Rediae of the Trematode Order Fasciolatoidea Szidat, 1936

In a program of investigations on the embryology of the digenetic trematodes which has been carried on for several years at the University of Michigan Biological Station, studies have been made of representatives of the strigeids (Cort and Olivier, 1941), the plagiorchiids (Cort and Olivier, 1943a; Cort and Ameel, 1944), and the schistostomes (Cort and Olivier, 1943b; Cort, Ameel, and Olivier, 1944). Multiplication of individuals in the mother and daughter sporocysts of these groups has been found to be both by direct division and separation of the germinal cells (primary polyembryony of the original zygote), and by a secondary polyembryony of germinal masses.2 These germinal masses are peculiar structures, composed both of unicellular and multicellular components. In the strigeid and plagiorchiid sporocysts the germinal masses are not attached to the body wall but float freely in the body cavities mixed with the developing embryos. From them break off the largest multicellular components to continue development into daughter sporocysts or cercariae. Since the germinal masses are constantly giving off embryos throughout the life of the sporocysts, it is evident that some of their unicellular components (germinal cells) must divide to form new germinal cells over a long period of time. These germinal masses in the strigeids and plagiorchiids can be interpreted, therefore, as floating centers of persistent multiplication of germinal cells, which bring about the production of the extraordinarily large numbers of individuals produced in the germinal sacs of these groups. The important thing, then, is not so much the presence in these germinal masses of small embryos (multicellular components), as the ability of some of their germinal cells (unicellular components) to continue dividing for such a long time. Since all the work reviewed above on the development in the germinal sacs of the digenetic trematodes was done on groups with daughter sporocysts in their life cycles, we decided in the summer of 1947 to devote most of our attention to the development of the germinal material in rediae. Descriptions and figures of rediae in the literature give a very confusing picture of the germinal material. In most cases, embryos in various stages of development are shown inside the rediae with the smallest ones usually near the posterior end of the body cavity. Also, in some cases, either small masses of germinal material or separate germinal cells are shown just at the posterior tip of the body cavity, sometimes attached to the wall. Brooks (1930) described and figured germ-masses in rediae belonging to several different trematode groups. His studies were all made on sections of fixed material, mostly of mature rediae. It is a little difficult to understand sQme of his figures and descriptions, and to follow his interpretations. On the other hand, in