Dynamics of parasite population and its histopathological and histophysiological effects in the stomach of a freshwater fish

The caryophyllaeid cestode Lytocestoides fossilis infects the freshwater catfish Heteropneustes fossilis. The study was conducted for two consecutive years (2004-06) to record the bio-statistical data of the parasite. The incidence, intensity, density and index of infection of the parasite have been recorded. The infection was more during June to September, moderate during February to May and low during October to January. The parasite brought about severe histopathological changes in the stomach of infected fish. The changes observed in the stomach of fish included structural damage of the villi, inflammation, and fibrosis associated with hyperplasia and metaplasia. The hypertrophy of mucous layer led to vacuolation and necrosis. Histochemical changes were noticed with enhanced carbohydrate, protein and lipid contents. The enhanced substrate content in the infected organ might be due to the disfunctioning of the digestive tract, which results in the accumulation of various metabolites. Mucus secretion was triggered as a protective interaction against parasitic invasion. The parasitic infection affects the general metabolic state of the host and as the result, the fish becomes sluggish and moribund

Plicate species of the diatom genus Thalassiosira (Bacillariophyta) from the Atlantic and Gulf coasts of southeastern United States, with the description of T.livingstoniorum sp.nov.

Long-term observations of a marine planktonic plicate Thalassiosira species, T. cedarkeyensis Prasad, from the Gulf coasts of Florida, Alabama, and Mississippi and the Atlantic coasts of Florida and Georgia demonstrate its wide occurrence in the southeastern United States and its ability to form extensive blooms. We also report for the first time its ability to form typical Thalassiosira chains, linking sibling cells by threads of chitin. A closely related and co-occurring diatom, T. livingstoniorum, is described on the basis of investigations conducted during 20002011 as a new species from many localities in Apalachee Bay on the Gulf coast and Indian River Lagoon on the Atlantic coast of Florida. It differs from T. cedarkeyensis in areola density, presence of continuous cribra on loculate areolae, arrangement and distribution of valve processes, and the number of satellite pores surrounding the valve-face fultoportulae. We have not yet found any evidence of chain formation in T. livingstoniorum. Thalassiosira cedarkeyensis and T. livingstoniorum can be easily distinguished in Naphrax-mounted preparations in light microscopy (LM), and they represent two different groups (lineages?) of plicate species with reference to internal cribrum structure of the loculate areolae. Their differences may justify placement in two different genera. Although T. cedarkeyensis (which has individual cribra on the proximal siliceous layer like T. hyperborea) is abundant and widespread on the Gulf and Atlantic coasts of the southeastern United States, T. livingstoniorum (which has continuous cribra like T. lacustris) has been found, thus far, only in Florida coastal waters. Comparisons are made between these two species and the other morphologically similar extant and extinct plicate species. Thalassiosira livingstoniorum and T. cedarkeyensis, although widespread and frequently encountered during warmer months, may be easily overlooked sources of primary production in the nutrient-rich northeastern Gulf of Mexico

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Not AvailableApproximately 70% of shrimp consumed globally is farmed. India is ranked among the top five shrimp farming countries globally, and occurs mainly in the eastern coastal state of Andhra Pradesh (AP). More than 90% of the farms are less than 2 ha and are farmer owned, operated and managed. The objective of this study was to increase our understanding of climatic and socio-economic factors influencing this sector, through a survey of 300 shrimp farmers in AP in 2009/10. The farming communities were divisible into two groups: members of a society/cooperative and those operating individually. The latter were large scale adopting more intensive practices. The average production cost was Indian Rupees (IRS) 80,186 ha-1 and net income in summer and winter was IRS 221,901 and IRS 141,715, respectively. The mean technical efficiency estimated using Stochastic frontier function was 7% and 54%. The present study attempts to explain the difference in efficiencies using socio-economic and climatic variables, the latter being a novel approach. Among socio-economic variables, farming experience and membership in society were found to have a significant influence to improve technical and economic efficiencies. Further improvements in identifiable facets of the practices and a consequent increase in technical efficiency will make the sector less vulnerable to climatic change impacts.Not Availabl