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Oxford, MD, United States

Kimmel D.G.,University of Cambridge | Boicourt W.C.,University of Cambridge | Pierson J.J.,University of Cambridge | Roman M.R.,University of Cambridge | Zhang X.,Cooperative Oxford Laboratory
Journal of Plankton Research | Year: 2010

The biological response of mesozooplankton (250-2000 m size range) to hypoxia in the northern Gulf of Mexico was investigated using an optical plankton counter (OPC) and a high-capacity pump. We sampled the water column in an area with the most persistent occurrence of hypoxia every 4 h for a 24-h period in both years. The amount of hypoxic bottom water differed between 2006 and 2007, with 2006 having more widespread bottom hypoxia than 2007. Large-sized mesozooplankton (>1000 m) were more abundant in 2006 and were found in greater abundance and biomass in hypoxic water. Small- (250-500 m) and mid-sized (500-1000 m) mesozooplankton showed diel variability, but did not appear to respond to hypoxia. The opposite pattern was observed in 2007, where smaller-sized mesozooplankton were dominant and diel variability in this size class was not detected, whereas large- and mid-sized mesozooplankton did show evidence of diel variability in 2007. Using a vital staining technique (neutral red), we found a significantly higher proportion of stained mesozooplankton in oxic, surface waters compared with deep, hypoxic waters. These findings show that mesozooplankton vertical and diel distributions differed between a year with widespread, bottom hypoxia and a year with a thin layer of hypoxic water. It remains unclear as to what is driving these size differences, the direct impact of hypoxia on mesozooplankton individual or egg mortality, differential predation in the water column or other factors such as more nutrient input related to increases in zooplankton production. © The Author 2010.

Dungan C.F.,Cooperative Oxford Laboratory | Bushek D.,Rutgers University
Journal of Invertebrate Pathology | Year: 2015

During the early 1950s, Sammy M. Ray discovered that his high-salt modification of fluid thioglycollate sterility test medium caused dramatic in vitro enlargement of Perkinsus marinus (=. Dermocystidium marinum) cells that coincidentally infected several experimentally cultured oyster gill tissue explants. Subsequent testing confirmed that the enlarged cells among some oyster tissues incubated in Ray's fluid thioglycollate medium (RFTM) were those of that newly described oyster pathogen. Non-proliferative in vitro enlargement, cell wall thickening, and subsequent blue-black iodine-staining of hypertrophied trophozoites (=hypnospores. =. prezoosporangia) following incubation in RFTM are unique characteristics of confirmed members of the protistan genus Perkinsus. A number of in vitro assays and manipulations with RFTM have been developed for selective detection and enumeration of Perkinsus sp. cells in tissues of infected molluscs, and in environmental samples. RFTM-enlarged Perkinsus sp. cells from tissues of infected molluscs also serve as useful inocula for initiating in vitro isolate cultures, and cells of several Perkinsus spp. from both in vitro cultures and infected mollusc tissues may be induced to zoosporulate by brief incubations in RFTM. DNAs from RFTM-enlarged Perkinsus sp. cells provide useful templates for PCR amplifications, and for sequencing and other assays to differentiate and identify the detected Perkinsus species. We review the history and components of fluid thioglycollate and RFTM media, and the characteristics of numerous RFTM-based diagnostic assays that have been developed and used worldwide since 1952 for detection and identification of Perkinsus spp. in host mollusc tissues and environmental samples. We also review applications of RFTM for in vitro manipulations and purifications of Perkinsus sp. pathogen cells. © 2015 Elsevier Inc.

Matsche M.A.,Cooperative Oxford Laboratory
Journal of Applied Ichthyology | Year: 2011

Dose-response experiments were conducted at 14 and 24°C to evaluate the efficacy and physiological effects of tricaine methanesulfonate (MS-222) to induce and maintain surgical anesthesia in juvenile Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). Anesthetic induction time, duration of hyperactivity, recovery time and total handling time of fish were inversely related to MS-222 concentration and water temperature. Minimum effective concentration of MS-222 to maintain anesthesia with fewest signs of stress was 85mgL-1. Sensitivity to stimuli and body movements progressively increased when fish were exposed to a lower maintenance concentration (70mgL-1) of MS-222, resulting in reduced biopsy success rates and traumatic injury to internal organs during laparoscopy as fish regained consciousness. Anesthesia with MS-222 resulted in bradychardia, near medullary collapse, elevated signs of stress (plasma cortisol and reddening of the skin) and a generalized hemo-concentration consisting of erythrocyte swelling and increased protein and monovalent ion concentrations. Magnitude of hematologic changes and stress indicators increased with decreasing MS-222 concentration and increased water temperature while plasma chemistry changes increased in magnitude with decreasing MS-222 concentration. This study demonstrates that rapid induction of surgical anesthesia with a relatively high concentration of MS-222 results in reduced signs of physiological stress, and that empirical evaluation of maintenance dosage is important to achieve the best balance between safety, efficacy and stressful side effects for invasive surgical procedures. © 2011 Blackwell Verlag, Berlin.

Two methods for colorimetric in situ DNA probe hybridization (CISH) assays on paraffin-embedded tissue sections were compared. The heated method used heat (90-100°C) to denature DNA in the sample prior to probe hybridization, while the unheated method used a standard hybridization temperature of 42°C. Both procedures were tested on tissue samples that harbored the mollusk protozoan pathogens Perkinsus marinus, P. chesapeaki, or Haplosporidium nelsoni, the protozoan and bacterial fish pathogens Myxobolus cerebralis (myxosporidean) or Renibacterium salmoninarum (bacterial), or the crab viral pathogen Callinectes sapidus reovirus. Samples were fixed in either formalin or Davidson's fixative and embedded in paraffin for histological examination. The heated method is labor intensive and highly prone to human error, while the unheated method is less labor intensive and can be completed in a shorter period of time. Both methods yielded similar hybridization results. The use of complex and expensive prehybridization buffers did not improve the performances of the tested CISH assays. Prehybridization heat denaturation of DNA in assayed samples increased both assay duration and loss of samples but did not improve hybridization signals.

A portable electro-immobilization and laparoscopy system is described that is suitable for sex determination, gonadal biopsy and immediate release of largemouth bass Micropterus salmoides. Continuous direct current at a power density of 52·2μWcm-1 for 2min was sufficient to immobilize fish for surgery, but induced a mild, transient hypokalaemia and hyperglycaemia. Insertion of a 4·8mm laparoscopic instrument set through the urogenital pore provided access to the gonads for examination and biopsy with mild tissue trauma. © 2013 The Fisheries Society of the British Isles.

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