Fossilized nuclei and germination structures identify Ediacaran "animal embryos" as encysting protists

Globular fossils showing palintomic cell cleavage in the Ediacaran Doushantuo Formation, China, are widely regarded as embryos of early metazoans, although metazoan synapomorphies, tissue differentiation, and associated juveniles or adults are lacking. We demonstrate using synchrotron-based x-ray tomographic microscopy that the fossils have features incompatible with multicellular metazoan embryos. The developmental pattern is comparable with nonmetazoan holozoans, including germination stages that preclude postcleavage embryology characteristic of metazoans. We conclude that these fossils are neither animals nor embryos. They belong outside crown-group Metazoa, within total-group Holozoa (the sister clade to Fungi that includes Metazoa, Choanoflagellata, and Mesomycetozoea) or perhaps on even more distant branches in the eukaryote tree. They represent an evolutionary grade in which palintomic cleavage served the function of producing propagules for dispersion.     

Effects of Rotifer and Artemia Fatty-Acid Enrichment on Survival, Growth and Pigmentation of Summer Flounder Paralichthys dentatus Larvae

Abstract— Enrichment of live food for marine fish larvae with highly unsaturated fatty acids (HUFA) has been shown to improve survival, growth and stress resistance in many species and to decrease pigmentation abnormalities in flatfish. In order to aid the developing summer flounder industry, we conducted an experiment in which summer flounder larvae were fed diets differing in HUFA composition to determine whether enrichment with a commercially available product would increase survival and growth and reduce the incidence of abnormal pigmentation. We also examined whether growing unenriched rotifers on different species of algae would affect the survival, growth and pigmentation of the flounder larvae to which they were fed. Growth of summer flounder larvae was significantly better when they were fed HUFA-enriched Mtifers and Artemia rather than unenriched and, among the unenriched treatments, was significantly better when the larvae were fed rotifers raised on Isochrysis galbana rather than on Tetraselmis suecica . The percentage of larvae that failed to complete metamorphosis during the experiment was significantly higher in the unenriched treatments than in the enriched treatments. Neither survival nor percentage of individuals with pigmentation abnormalities were significantly different among the treatments.     

Partial Replacement of Fish Meal with Plant Protein Sources Singly and in Combination in Diets for Summer Flounder,Paralichthys dentatus

Soybean meal (SBM), corn gluten meal (CGM), and canola protein concentrate (CPC) as alternative protein sources to fish meal (FM) were individually evaluated for growth performance at 0, 20, 30, 40, and 50% replacement with amino acid (AA) supplementation using juvenile summer flounder, Paralichthys dentatus, in an 8‐wk feeding. Two‐way ANOVA indicated no significant main effect for plant protein source, but a significant main effect for replacement level. Comparison of the individual treatments revealed significant differences in weight gain (WG) between the FM treatment and 50% replacement level for all protein sources, as well as between the FM treatment and 30% replacement with CPC. Replacement of FM with SBM at 40% resulted in the least cost/kg WG. In a follow‐up study, a combination of SBM–CGM–CPC at 40% replacement was evaluated with and without AA, phytase (0.2%), or taurine (1%), versus FM and SBM (40% replacement of FM) with AA. The SBM–CGM–CPC diet with either AA or taurine provided a significantly better food conversion ratio and less cost/kg WG than the SBM diet, and the SBM–CGM–CPC diet with taurine provided a significantly better protein efficiency ratio than the SBM diet. On the basis of these results, more study of taurine in plant protein diets for summer flounder appears warranted.     

Prevalence of sparganosis by county of origin in Florida feral swine

Sparganosis is a parasitic infection in amphibians, reptiles and mammals including feral swine and man. It is caused by migration of the metacestode (spargana) of Spirometra. The primary objective of this study was the determination of the prevalence of gross sparganosis in Florida county of origin in slaughtered feral swine. Tracebacks to county of origin were conducted for Florida feral swine with and without gross sparganosis. Feral swine trapped in Florida and presented for slaughter in a Texas slaughter establishment from May to December 1999 was the sample population.Overall prevalence of sparganosis in Florida feral swine was 6.9%. Because Highlands county had the same prevalence, other counties were compared to it. Sparganosis was detected in 17 Florida counties. Swine originating from Osceola or Hillsborough counties (4.3 and 1.8% prevalence, respectively) had lower prevalence of sparganosis than in Highlands, whereas those from Marion county (21.7% prevalence) had a higher prevalence.Transmission to humans may occur via consumption of infected feral swine, other species of secondary intermediate hosts or the primary intermediate hosts.     

Effect of triiodothyronine on the growth and survival of larval striped bass (Morone saxatilis)

This study was carried out to test the effect of triiodothyronine (T₃) on the growth and survival of larval striped bass (Morone saxatilis). Growth and survival of striped bass held in 5 ppt seawater and treated with various doses of T₃ were measured beginning at 5 and 16 days after hatching. Body content of T₃ was measured by radioimmunoassay. T₃ dissolved in the 5 ppt seawater was taken up by larval striped bass in a dose-dependent manner, and affected the growth and survival of the fish. At 5 days after hatching, T₃ at 100 ng ml^–1 and 50 ng ml^–1 retarded the growth of larval striped bass and caused a lower survival rate than T₃ at 25 ng ml^–1 or the control treatment. At 16 days after hatching, T₃ at 100 ng ml^–1 retarded the growth of larval fish and caused a higher mortality. T₃ at 10 ng ml^–1 and 1 ng ml^–1 did not show any effect on either survival or growth. Body content of T₃ returns to control levels within days following end of treatment. The results indicate that exogenous T₃ can be detrimental to the growth and survival of larval striped bass.     

Effects of Larval Stocking Density on Laboratory-Scale and Commercial-Scale Production of Summer Flounder Paraliehthys dentatus

Abstract.— Three experiments investigating larval stocking densities of summer flounder from hatch to metamorphosis, Paralichthvs dentalus, were conducted at laboratory‐scale (75‐L aquaria) and at commercial scale (1,000‐L tanks). Experiments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/L, and 10, 20, and 30/L, respectively. The laboratory scale experiment tested the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried out in two separate filtered, flow‐through seawater systems at URI Narragansett Bay Campus (laboratory‐scale), and at GreatBay Aquafarms, Inc. (commercial‐scale). At both locations, the larvae were raised in a “greenwater” culture environment, and fed rotifers and brine shrimp nauplii according to feeding regimes established for each location. Water temperature was maintained at 21C (± 2) and 19C (± 1) for the duration of laboratory and commercial experiments, respectively. Experiments 1 and 2 at the commercial location were terminated at 42 and 37 d post hatch (dph), respectively, and the laboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew to an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercial scale experiments I and 2, respectively. At laboratory scale, no significant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). Final survival percentage was not affected by stocking density in either commercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Experiment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively. Similarly, there was no significant difference in final survival percentage among treatments in the laboratory experiment, which averaged 59, 55, 56, and 37% for treatments of 10, 20, 30, and 40L. respectively. Since larval length was not different between the intermediate densities (20 and 30 Iarvae/L), and because high‐density rearing can produce a much greater numerical yield per tank, we recommend a density of 30 larvaen as an optimal stocking density for the hatchery production of summer flounder.     

Spatial dependency of soil nutrient availability and microbial properties in a mixed forest of Tsuga heterophylla and Pseudotsuga menziesii, in coastal British Columbia, Canada

Spatial variations in nutrient concentrations and turnover may contribute to variations in productivity within forest ecosystems and be responsible for creating and maintaining diversity of plant species. The aim of this study was to relate spatial patterns in soil nutrient availability and microbial properties in the forest floor and mineral soil in order to explore the controls on variations in nutrient availability in the two horizons. Microbial C, N and P, extractable N and P, and plant-available nutrients as estimated by plant root simulator probes were measured. We then used geostatistical techniques to determine the scale of spatial autocorrelation in the forest floor and mineral soil. Several of the measured variables were spatially autocorrelated at a scale of tens to hundreds of meters. Although more variables were autocorrelated in the mineral soil than in the forest floor, spatial patterns in gravimetric moisture content and nutrient concentrations in the two horizons generally overlapped. The spatial patterns were probably caused by differences in topography, except for ammonium whose shorter range of spatial autocorrelation may reflect variations in nitrogen content of the canopy.     

Partitioning of Fish and Diet Selection as Methods for the Reduction of Cannibalism in Paralichthys dentatus Larviculture

Partitioning of larvae and diet selection were examined as strategies to reduce cannibalism in summer flounder Paralichthys dentatus . Methods of partitioning included physical grading by size, baffle interference, and a control. The baffle consisted of a barrier with cells 14-mm square and walls 9-mm high. The barrier was positioned horizontally at a depth where it would divide the tank into two equal volumes of water. Factors which may characterize cannibalism were quantified, including: total length, developmental stage, pigmentation, wet weight, and biomass. Engineered to reduce cannibalism, the baffle instead contributed to a decrease in survival for at least one experiment ( P < 0.05). Grading by size did not significantly increase survival over that of the untreated control ( P > 0.05). Mean developmental stage of P. dentatus in the graded treatment was significantly less than fish in either the control or baffle treatments ( P < 0.05). A factorial design of partition strategy and weaning diet did not demonstrate any difference in survival or measured character ( P > 0.05). Finally, both inert feeds and live Artemia sp. nauplii were examined for their contribution to the Occurrence of cannibalism. Predicted differences between live and artificial diets were not significant ( P > 0.05). During experiments, cannibalism was principally observed in late larval and early juvenile stages and was not restricted to post-metamorphic juveniles feeding on premeta-morphic larvae. Methods normally employed to reduce cannibalism (partitioning of larvae and diet selection) do not appear to be effective for P. dentatus .