Bilharziasis ranks with Tuberculosis and Malaria as the three most important endemic diseases of man in Rhodesia. The prominence given to bilharziasis in the endemic diseases pattern arises from its high prevalence, particularly in the African population. It is probable that bilharziasis was endemic in the country even prior to the arrival in the conntry of the European settlers in 1890, but it was not until Orpen (1915) described the results of a small survey that local infections were proven. He reported 182 (31 percent) urinary infections in 592 African prisoners examined in the Salisbury gaol. In the ensuing 15 years there was only scanty evidence of the prevalence of the disease. However, in the decade 1931 to 1940 the Annual Public Health Reports of Southern Rhodesia indicated increasing prevalence, and this stimulated interest in the problem and led to the establishment in 1939 of a specialised laboratory to study the parasites causing the disease. The unpublished records of this laboratory indicate that in more recent years the disease has increased not only in prevalence but also in its intensity in infected individuals. Surveys show that the urinary form of the disease is more widespread than the intestinal form. Both forms are becoming more prevalent but the rapid increase of the latter, considered by most authorities to be the more severe, indicates that a greater importance must be accorded to it in the future. Introduction, p. 1.

1. Culture methods for the maintenance of symbiotic adult and juvenile Convoluta roscoffensis have been developed. The growth of adults but not juveniles is dependent on nitrogen enrichment of the medium. 2. Electron microscopic studies suggest that the algal symbionts in adult Convoluta are intracellular. 3. Structural studies of the gametes and early development of Convoluta are described. 4. Relevant aspects of the biology of the natural Convoluta symbiont, Platymonas convolutae, and a range of related algae have been studied. The growth of all Platymonas and Tetraselmis species tested except P.convolutae is stimulated by 0.1 M glucose. Glucose supports the growth of T.tetrathele, T.suecica and P.subcordiformis in darkness. P.convolutae and T.tetrathele have two uptake systems for uric acid, which conform to Michaelis-Menten kinetics; a high affinity system, operating in the concentration range 0.2-4.5 pM, and a low affinity system, operating at higher concentrations of uric acid. Uric acid uptake by P.convolutae is abolished by uncouplers of phosphorylation. Exogenous uric acid is accumulated in cells of Platymonas and Tetraselmis species up to internal concentrations of 0.3 M. P. convolutae metabolises (2-14C) uric acid to (14 C) carbon dioxide in the dark. 5. Aposymbiotic juvenile and symbiotic adult Convoluta, under standard culture conditions, contain solid uric acid. The uric acid content of juveniles declines on infection with P.convolutae and related species. Uric acid is utilised in the adult symbiosis, particularly under conditions of nitrogen demand. 6. Motile cells of P.convolutae and related species and Chlamydomonas coccoides aggregate around Convoluta eggs. These algae 'settle' on the eggs, by an interaction initiated by contact between the algal flagella and egg capsule surface. Living and killed algae are trapped by the capsules. No evidence that P.convolutae cells exhibit chemotaxis towards Convoluta eggs has been obtained. 7. Juvenile Convoluta ingest species of Platymonas and Tetraselmis, Prasinocladus marinus and Chlamydomonas coccoides but no other algae tested. Ingestion of P.convolutae is not affected by pretreatment of the cells with lectins or proteolytic enzymes, but is reduced if the algae are killed. 8. Cells of C.coccoidea, but not P.convolutae and related species, are disrupted in juvenile Convoluta. 9. Juvenile Convoluta form a viable symbiosis with P.convolutae, Pr.marinus, T.tetrathele and T.verrucosa under laboratory conditions. The structural changes of P.convolutae and T.verrucosa during the development of the symbiosis are described. 10. It is proposed that Convoluta discriminate against species unrelated to P.convolutae on initial contact and in the digestive region of the host. Evidence for a recognition mechanism discriminating between P.convolutae and related species is discussed. The nature of the recognition mechanism(s) has not been established.

1. Convoluta roscoffensis is an intertidel flatworm symbiotic with the green alga, Platymonas convolutae. Field studies of a population of Convoluta on Shell Beach, Herm, Channel Islands, involved the measurement of seasonal changes in numbers of Convoluta and in environmental conditions. Features of the habitat were measured, including the nutrient levels in the beach run-off water flowing over Convoluta colonies and the light energy available. 2. The position of the colonies on the beach meant that they received about 60% of available PAR (photosynthetically active radiation) i.e. 4883 E m-2 in 1977. The spacing of worms in the colonies (mean density 9.3 x 10 to the power 5 worms m-2) was such that they did not haye to shade each other. 3. Nutrient analyses revealed that the beach run-off water is rich in nutrients, and dominated by nitrate (mean concentration 6-16υg atoms N03-N 1to the power -1). Uptake of nutrients from the run-off water by Convoluta was not apparent. 4. The Convoluta population was most abundant in September and numbers were lowest in May and June. This pattern of fluctuation in numbers showed some relation to seasonal changes in light intensity but not to changes in nutrient levels. 5. Primary productivity measurements (using the 14C technique) of symbiotic and free-living Platymonas showed that both types of algae achieved assimilation numbers (mg carbon fixed (mg chlorophyll 'a')-1 h-1) which were in the range 1-3. Photosynthetic rate was higher in worms incubated in Herm run-off water than in offshore seawater. Comparisons between symbiotic and free-living Platymonas were made with respect to photoinhibiting light levels and the amounts of dark carbon fixation. 6. Extrapolation of primary productivity values to Convoluta in the field gave an estimated annual production of 872.9 g carbon m to the power -2 of colony for 1977. This is comparable with values for rich ocean waters and coral reefs. 7. Primary production measurements were also made on a tropical algal-invertebrate system, Zoanthus sociatus, at Discovery Bay, Jamaica. The oxygen technique was used, so the values of assimilation number were not directly comparable with those obtained for Convoluta, but the symbionts of Zoanthus (Gymnodinium microadriaticum) achieved assimilation numbers similar to those published for other free-living species of Gymnodinium. The symbionts isolated from Zoanthus were of similar size to and contained similar amounts of chlorophyll 'a' to the Platymonas symbionts of Convoluta. 8. Structural studies of the development of symbiosis in Convoluta showed that the host and symbiont are in very intimate contact. There was evidence for the controlled and integrated growth of host and symbiont in the distribution and orientation of the 20,000-70,000 algae inside Convoluta. The ratios of algal to host protein and cell volume were measured and compared with values for other algal-invertebrate systems to discover whether any general statements may be made regarding the proportions of algal to host tissue in established symbioses.

This thesis describes my study of inhibition of brain regeneration in planaria. The flatworm (Dugesia tigrina) possesses a remarkable ability to regenerate lost parts, including the head. The primary objective of my study was to determine the extent to which an inhibiting substance, located in the head, would prevent regeneration of the brain. A secondary objective was to study whether DMSO (Dimethyl Sulfoxide) would facilitate the action of the inhibitor.

Asexual reproduction in the decapitated planaria, Dugesia dorotocephala, is inhibited by an extract of homogenized heads of the same or closely-related species. Decapitated planaria allowed to regenerate have reproduced asexually over 80% of the time, while those that have been cultured in a suspension of head homogenate have had asexual reproduction inhibited to less than 10%. The substance that inhibits asexual reproduction is heat labile. It requires a concentration of 2.0 heads/ml that contains .13 mg protein/ml to effectively inhibit asexual reproduction. A similar concentration of head homogenate from the related planaria, Dugesia tigrina, also contains the inhibitory substance. Head homogenate from the white planaria, Phagocata oregonensis, does not inhibit asexual reproduction. A preliminary study of other animal tissues indicates that brain homogenate from the chicken, fish, salamander, and gerbil inhibits, while a liver homogenate from these animals does not inhibit as much.

No description available.

Historical structuralism is presented as a research program in evolutionary biology. It uses patterns of common ancestry as initial hypotheses in explaining evolutionary history. Such patterns, represented by phylogenetic trees, or cladograms, are postulates of persistent ancestral traits. These traits are evidence of historical constraints on evolutionary change. Patterns and processes consistent with a cladogram are considered to be consistent with an initial hypothesis of historical constraint. As an application of historical structuralism, a phylogenetic analysis is presented for members of the digenean plagiorchioid genera Glypthelmins Stafford, 1905 and Haplometrana Lucker, 1931. The eight species studied are intestinal parasites of frogs and toads in North, Central, and South America. In a Wagner parsimony analysis of 21 morphological characters with both the PAUP and PHYSYS computer programs, a single phylogenetic tree with a consistency index of 84.8% can be inferred. This suggests strong historical constraint in the evolution of the characters examined. It is postulated that the eight species form a monophyletic group (clade), consisting of two less inclusive clades. Glypthelmins hyloreus and G. pennsylvaniensis comprise one of these clades; G. robustus, G. shastai, H. intestinalis, G. californiensis, G. quieta, and G. facioi comprise the other. G. robustus, found in Bufo marinus in Colombia, is both the southernmost and the most plesiomorphic member of its clade. Glypthelmins californiensis, G. quieta, and G. facioi form a clade, and parasitize frogs in the Rana pipiens complex in Mexico, eastern North America, and Central America, respectively. Glypthelmins shastai and H. intestinalis, the latter of which is the only member of its genus, form a western North American clade, and parasitize Bufo boreas and Rana pretiosa, respectively. The phylogenetic analysis includes a redescription of G. shastai, the synonymy of the genus Haplometrana with Glypthelmins, the redescription of H. intestinali s as G. intestinalis, an emended diagnosis of the genus Glypthelmins, and the first account of the life cycle of G. californiensis. Three aspects of phylogenetic analysis are examined in detail. These are the coding of multistate character trees, the use of parasite data to infer host relationships, and the properties of the Consistency Index and the F-Ratio. It is proposed that the Consistency Index be calculated without non-homoplasious autapomorphic characters. For the present study, this modification gives a value of 76.9%. Using the phylogenetic tree as a general reference system of patterns of common ancestry, it is inferred from developmental studies that (1) there is no conflict between the phylogenetic relationships indicated by only larval or only adult characters, and that (2) the evolution of some of the characters involved certain types of heterochrony. Paedomorphic heterochrony is inferred to have occurred in the evolution of the uterus in G. shastai, H. intestinalis, G. californiensis, G. quieta, and G. facioi. Peramorphic heterochrony is inferred to have occurred in the evolution of the penetration glands in G. facioi, and of the hindbody in H. intestinalis. The relatively longer hindbody of H. intestinalis was experimentally induced to show paedomorphic development by raising specimens of H. intestinalis in Bufo boreas, which is the host of G. shastai, its sister-species. By one year after infection, the relative length of the hindbody is shorter, and is equal to that of the primitive state found in G. shastai. The phylogenetic relationships among the anuran hosts are re-analyzed. There is 80% congruence between them and the postulated phylogenetic tree for their parasites, suggesting strong historical association between the parasite and host groups. This inference of coevolution is further supported by the concordance of the present geographical distributions of the parasites and their hosts with the historical geology of the areas in which they occur. This implies an historical association between the areas and the organisms. / Science, Faculty of / Zoology, Department of / Graduate

The taxonomy of the polyclad flatworms is fairly well-known and some attention has been given to study of their physiology. Investigations of an ecological nature, however, are scarce; in fact, no ecological studies have been made on the Pacific Coast of North America. Else- where, Pearse and Wharton (1938) investigated the general ecology of Stylochus frontalis, associated with oysters on the coasts of Florida, and occasional notes have appeared, reporting on polyclads as predators on oysters and barnacles (Book, 1925: Wolke, 1954; Loosanoff, 1956: Skerman,1960)

The Capsalidae is a diverse family of ectoparasites of marine fish (Platyhelminthes: Monogenea). It is a large family with approximately 180 described species and many more yet to be discovered. Capsalids have a global distribution and parasitise a diversity of hosts from the Chondrichthyes to bony fishes. A morphological classification exists for the family based on a few key characters such as testes number, their arrangement and morphology of the posterior attachment organ (haptor). Phylogenetic relationships within the family and its position within the Monogenea are largely unexplored. I have used various molecular phylogenetic techniques to resolve relationships and explore the evolution and radiation of this family. Specimens from the Capsalidae and other monogenean families (outgroups) were obtained through fresh collections and generous donations by other parasitologists. Specimens were stored in 95% undenatured ethanol. Three unlinked nuclear genes (28S ribosomal RNA, Histone 3 and Elongation Factor 1 α) and two mitochondrial genes (Cytochrome Oxidase 3 and Cytochrome B) were amplified for 78 capsalid taxa in 28 genera representing all nine subfamilies and 30 outgroup taxa (eight Polyopisthocotylea and 22 Monopisthocotylea). Analyses showed the Capsalidae is monophyletic, with the sister group remaining unresolved. Some analyses supported Gyrodactylidae and Udonellidae as the sister group but in other analyses, it was unresolved with the Monocotylidae and Microbothriidae also possible sister groups. The Capsalinae, Encotyllabinae and Nitzschiinae are monophyletic, but analyses did not support monophyly for the Benedeniinae, Entobdellinae and Trochopodinae. Monophyly was supported for Capsala, Capsaloides, Encotyllabe, Entobdella, Listrocephalos, Neobenedenia, Nitzschia and Tristoma, but Metabenedeniella is paraphyletic and Benedenia and Neoentobdella are polyphyletic. Comparisons of the distribution of character states for the small number of morphological characters on a molecular phylogeny show a high frequency of apparent homoplasy. Consequently the current morphological classification for the Capsalidae shows little correspondence with the phylogenetic hypotheses I present. I also sequenced the first complete mitochondrial (mt) genome for a capsalid species, Benedenia seriolae. The mt genome of B. seriolae shows some tRNA rearrangements in comparison to three Gyrodactylus spp. (Gyrodactylidae), the only other complete monopisthocotylean mt genomes sequenced. It also lacks the duplicated, conserved non-coding regions present in Gyrodactylus spp. making the genome smaller in size. I combined this genome with other available platyhelminth mt genomes to investigate the monophyly of Monogenea and the evolution of diet across the Neodermata. Results confirm paraphyly for the Monogenea and also suggest paraphyly for the epidermal feeding Monopisthocotylea. I hypothesise that the Monopisthocotylea represent the first shift to parasitism in the Neodermata from a free living ancestor and following this, there was a dietary shift to blood feeding (Polyopisthocotylea). The Digenea and Cestoda independently evolved dietary specialisations to suit their diverse microhabitats and broad range of vertebrate final hosts. Using Elongation Factor 1 α I have estimated molecular divergence dates for the Neodermata, Monogenea and Capsalidae. Molecular clock analyses estimate the Neodermata diverged from the free living platyhelminths 513 million years ago (mya) (95% HPD [highest posterior density]: 473–605) before the appearance of vertebrates in the fossil record. The Monogenea diverged from the other neodermatan classes 441 mya (95% HPD: 420–547) coinciding with the appearance of fish in the fossil record. The most recent common ancestor of the Capsalidae arose approximately 235 million years ago (95% HPD: 200–274) following the Permian/Triassic extinction event and coinciding with the diversification of bony fishes in the marine environment. I compared the capsalid phylogeny to a phylogeny of fishes that I generated using eight nuclear and three mt genes to explore the evolution and the radiation of the Capsalidae across fishes. There is no significant global signal of coevolution with only five parasite-host associations that may be a result of coevolution. Estimated molecular divergence dates are also compared and do not reveal temporal congruence. Radiation of the family may have been driven by host switching constrained by shared host ecology, biology, behaviour and plasticity in morphological adaptations by the parasites. This study advances our understanding of the evolution of this monogenean family and provides insights into the evolution of the Neodermata and the complicated realities of reconstructing the evolutionary history of parasitic groups. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1522353 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2010

Species interact and exploit one another for a number of reasons, including transportation, shelter or nutrition such as in parasitic relationships. Parasitism is an important aspect in life and is common in all taxonomic groups. Parasites are often host-specific and can be endoparasites or ectoparasites. The phylum Platyhelminthes includes the class Monogenea or monogenetic parasitic flukes. Monogeneans are mainly parasitic in fish but the family Polystomatidae, also commonly referred to as polystomes, are found on the skin and gills of the Australian lungfish, tadpole gills, kidneys and urinary bladders of frogs, gills and skin of salamanders, cloaca and phalodeum of caecileans, on the eye, in the nose, mouth or urinary bladder of freshwater turtles and on the eye of the hippopotamus. Polystomes have a cosmopolitan distribution, and are found on all hospitable continents. Polystome species were first discovered in the 1758. Between 1961 and 1980 French researchers focussed on Central and West Africa and described a large number of parasites. Polystome discovery has steadily decreased in the last 30 years, however despite this, new species are still being discovered annually. The list of currently known polystomes is most likely only a small portion of the species that exists. Wherever scientists searched for polystomes, new species were discovered. The current distribution of polystomes is not at all a true reflection of their global distribution but merely an indication of research effort. Monogenean flatworms exhibit many variations in the morphology of the intestinal tract. These parasites display two distinct diets, where one group mainly feeds on blood while the other mainly feeds on mucus and epithelial tissues. Thus the feeding habits and other factors such as the shape of the caeca, the presence/absence and number of medial and lateral diverticula as well as anastomosis may play a role in the morphology of the intestinal tract, which can be used as a classification tool to classify polystome species into specific genera. The three aims of the study were to:  Conduct a literature study to compile a species list and source of information on all valid polystome taxa.  Review the intestine shape of all polystomes and evaluate it as a taxonomic characteristic.  Conduct a species description of a new North American chelonian polystome belonging to the genus Polystomoides. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015