Ultrastructure of Gametocyst of Parasitic Protozoan, Nematopsis sp. in Black Tiger Shrimp Penaeus monodon from the Gulf of Thailand

Ultrastructure of gametocyst of Nematopsis sp., a protozoa parasite of black tiger shrimp Penaeus monodon from the Gulf of Thailand is described. Ball-shaped gametocysts of about 110–160 µm diameter were found in close contact with the intestinal wall of shrimps. Surface of the gametocyst cyst wall or capsule is wrinkled with a circular bare area at one pole that contains a central pore 4–5 µm in diameter. The interior of the gametocyst is composed of numerous gymnospores and membranous sacs. Gymnospores varied in size with an average diameter of 6–8 µm. Ball-shaped gymnospores were composed of numerous, radially arranged, cone shaped sporozoites. Average width and length of sporozoites were 0.8–1.2 µm and 3–5 µm, respectively, with their rostral part pointing outward and caudal part, inward connecting to the residual cytoplasm in the centre of a gymospore. The rostral part of the sporozoite contains an oval nucleus, rough endoplasmic reticulum, mitochondria and a group of secretory granules. Membranous sacs were composed of two types of globular granules; large electron lucid granules and small dense granules

The phylogeography of Indoplanorbis exustus (Gastropoda: Planorbidae) in Asia

<p>Abstract</p> <p>Background</p> <p>The freshwater snail <it>Indoplanorbis exustus </it>is found across India, Southeast Asia, central Asia (Afghanistan), Arabia and Africa. <it>Indoplanorbis </it>is of economic importance in that it is responsible for the transmission of several species of the genus <it>Schistosoma </it>which infect cattle and cause reduced livestock productivity. The snail is also of medical importance as a source of cercarial dermatitis among rural workers, particularly in India. In spite of its long history and wide geographical range, it is thought that <it>Indoplanorbis </it>includes only a single species. The aims of the present study were to date the radiation of <it>Indoplanorbis </it>across Asia so that the factors involved in its dispersal in the region could be tested, to reveal potential historical biogeographical events shaping the phylogeny of the snail, and to look for signs that <it>I. exustus </it>might be polyphyletic.</p> <p>Results</p> <p>The results indicated a radiation beginning in the late Miocene with a divergence of an ancestral bulinine lineage into Assam and peninsular India clades. A Southeast Asian clade diverged from the peninsular India clade late-Pliocene; this clade then radiated at a much more rapid pace to colonize all of the sampled range of <it>Indoplanorbis </it>in the mid-Pleistocene.</p> <p>Conclusions</p> <p>The phylogenetic depth of divergences between the Indian clades and Southeast Asian clades, together with habitat and parasitological differences suggest that <it>I. exustus </it>may comprise more than one species. The timescale estimated for the radiation suggests that the dispersal to Arabia and to Southeast Asia was facilitated by palaeogeographical events and climate change, and did not require human involvement. Further samples from Afghanistan, Africa and western India are required to refine the phylogeographical hypothesis and to include the African Recent dispersal.</p

DNA-Sequence Variation Among Schistosoma mekongi Populations and Related Taxa; Phylogeography and the Current Distribution of Asian Schistosomiasis

Schistosomiasis is a disease caused by parasitic worms of the genus Schistosoma. In the lower Mekong river, schistosomiasis in humans is called Mekong schistosomiasis and is caused by Schistosoma mekongi. In the past, Mekong schistosomiasis was known only from the lower Mekong river. Here DNA-sequence variation is used to study the relationships and history of populations of S. mekongi. Populations from other rivers are compared and shown to be S. mekongi, thus confirming that this species is not restricted to only a small section of one river. The dates of divergence among populations are also estimated. Prior to this study it was assumed that S. mekongi originated in Yunnan, China, migrated southwards across Laos and into Cambodia, later becoming extinct in Laos (due to conditions unsuitable for transmission). In contrast, the dates estimated here indicate that S. mekongi entered Cambodia from Vietnam, 2.5–1 Ma. The pattern of genetic variation fits better with a more recent, and ongoing, northwards migration from Cambodia into Laos. The implications are that Mekong schistosomiasis is more widespread than once thought and that the human population at risk is up to 10 times greater than originally estimated. There is also an increased possibility of the spread of Mekong schistosomiasis across Laos

Studies On The Ecology Of The Miracidium Of Schistosoma Mansoni (sambon) In Relation To Its Snail Intermediate Host, Biomphalaria Glabrata (say) In A Static Water Habitat.

PhDBiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/186319/2/7104755.pd

Summary statistics for the time series observations of <i>Neotricula aperta</i> population density in the Mun river at Ban Hin Laht.

<p>The sampling period was 1990–2011.</p

Confidence intervals (95%) for estimates of mu, with the “best-fit” GSS model, based on the original (empirical) data set, from bootstrapped data sets and from simulations (where mu = 0).

<p>Confidence intervals (95%) for estimates of mu, with the “best-fit” GSS model, based on the original (empirical) data set, from bootstrapped data sets and from simulations (where mu = 0).</p