Broodstock management of Crassostrea gigas: II. Broodstock conditioning to maximize larval survival

The results of time-course conditioning trials indicate that there is an optimum conditioning interval during which the proportion of viable gametes is at a maximum. When matings are accomplished before or after this optimum interval, reduced gamete viability results. In this case, spawning and fertilization may appear to be normal, but setting success is substantially reduced.The degree of conditioning required to reach this optimum window is dependent on the stage of gonadal development in the broodstock when conditioning is started, and reflects substantial seasonal variation, which is repeated on an annual cyclic basis.Performance of the larval rearing system, reflected in the proportion of ova which survive to the spat stage, may be substantially improved by managing broodstock conditioning to maximize the proportion of viable gametes. This may be accomplished by empirical observation of the annual gonadal cycle in the area where the broodstock is maintained, and then determining the optimum conditioning interval for the various seasons.     

Effect of Lipid Source and Concentration on Somatic Growth of Juvenile Green Sea Urchins, Strongylocentrotus droebachiensis

Supplying juvenile sea urchins with an abundant supply of resources and essential nutrients for growth will facilitate somatic growth and, hence, improve the success of the sea urchin aquaculture industry. Lipids are essential in physical processes such as membrane production and are a concentrated source of energy. This study, using prepared diets, tested the effects of lipid sources containing different major fatty acids (i.e., n‐3 and/or n‐6) (Part 1) and lipid concentration (i.e., 1, 3, 7, and 10%) (Part 2) on the somatic (i.e., test or shell) growth of two size cohorts (7.0‐ and 15.3‐mm average initial test diameter [TD]) of juvenile green sea urchins, Strongylocentrotus droebachiensis. The growth of the sea urchins fed prepared diets was compared to the growth of sea urchins fed a kelp reference diet, Laminaria longicruris. After both feeding trials, the kelp‐fed sea urchins had superior test growth and were more similar in physical appearance to wild sea urchins (i.e., test color, spine length, and gonad color). The sea urchins fed the prepared diets had pale test color, short, stubby spines, and large, pale‐colored gonads compared to wild sea urchins. The smaller cohort of sea urchins grew at a faster rate, but growth patterns for both cohorts were similar. The juveniles fed the prepared diets (in both feeding trials) had high initial growth rates that decreased after approximately 100 d compared to the kelp‐fed juveniles. Differences in test growth were not shown to be affected by sea urchin size (i.e., similar results for both cohorts) or by differences in dietary lipid sources (i.e., the presence of n‐3 and/or n‐6 fatty acids). However, the sea urchins fed diets with lower lipid concentration (≤3%) had larger average TDs than those fed diets with higher lipid concentrations (≥7%). Differences in test growth and physical appearance among those fed the prepared diets and kelp may have been because of nutritional deficiencies in the prepared diets.     

Putting marine sanctuaries into context: a comparison of estuary fish assemblages over multiple levels of protection and modification

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Characterization of Physicochemical Attributes and Muscle Protein Quality of Blue Catfish (Ictalurus furcatus) in Chesapeake Bay

ABSTRACT

Physicochemical attributes of Chesapeake Bay’s blue catfish and quality of muscle protein isolates (PIs) as influenced by storage condition and extraction methods were investigated. All fish were within the maximum consumable size limit. Those obtained during the autumn/winter and in Year 2 were larger with firmer fillets than their counterparts during the spring/summer and in Year 1. Protein was the predominant nutrient component. Protein extraction yield ranged from 35.3 ± 1.4% to 47.0 ± 5.1%, and β-sheet was the predominant secondary structure for all fish PIs. Salt-extracted PIs were whiter and had higher water holding capacity at neutral and alkali environments. The results of this study support the use of Chesapeake Bay blue catfish and muscle protein for potential value-added application.     

Discontinuity in fish assemblages across an elevation gradient in a southern Appalachian watershed, USA

Abstract –  We examine patterns in fish species assemblages in the Toxaway and Horsepasture rivers, two high elevation streams in North Carolina, USA. This region is noted for extreme topographical relief, high cumulative annual rainfall and many rare and endemic plants and animals. The study area encompasses a portion of the Blue Ridge Escarpment and the associated Brevard Fault Zone. We hypothesise that major waterfalls and cascade complexes have acted to limit invasion and colonisation by fishes from downstream. This hypothesis is supported by longitudinal fish assemblage patterns in our study streams. Fish species richness in Toxaway River increased from 4 to 23 between Lake Toxaway and Lake Jocassee, a distance of 10 river km. We found similar discontinuities in neighbouring Horsepasture River and Bearwallow Creek. We found no instances of species replacement along this elevation gradient, and the trend in increased diversity downstream showed discontinuities coincident with sharp elevation breaks. With regard to theories posited to explain community formation in headwater stream fish communities (especially in those characterised by high topographical relief), we suggest coloniser 'access' may be more important than other factors including competitive interactions.     

From southern swamps to cosmopolitan model: Humanity’s unfinished history with mosquitofish

The most widespread and numerous inland fish in the world is likely the mosquitofish (Gambusia affinis and G. holbrooki, Poeciliidae). Much has been written about the basic biology, the current distribution and the negative impacts of non-native populations of mosquitofish. Here, we instead review the relationship of humanity with mosquitofish. First, we review the early literature on the species and aim to resolve its path towards becoming the globally dominant fish for biological control of mosquitoes. We identify the initial advocates of mosquitofish use, we examine the reasons behind their advocacy, and we document the spread of their viewpoints into and from the globally foundational mosquito control texts. Second, we identify the people and institutions that facilitated early international translocations of mosquitofish, including, among others, David Starr Jordan, the Rockefeller Foundation and the International Red Cross. Third, we discuss the reduction in mosquitofish translocation and use during and after WWII, initially stemming from the discovery and use of other methods, like DDT and later from a recognition of the negative ecological consequences of non-native mosquitofish populations. Fourth, we propose that the future utility of mosquitofish is largely in its value as a model study organism. We provide an overview of the contributions mosquitofish have made to some major fields in biology. Finally, we suggest that the value of mosquitofish as a model system should increase into the future, behind a momentum of research advances, and as human-mediated range expansion will permit access to mosquitofish by yet greater numbers of biologists worldwide.     

MAGNETIC RESONANCE IMAGING CHARACTERISTICS IN FOUR DOGS WITH CENTRAL NERVOUS SYSTEM NEOSPOROSIS

Neosporosis is a polysystemic disease that can affect dogs of any age and can cause inflammation of the central nervous system. Antemortem diagnosis can be challenging, as clinical and conventional laboratory test findings are often nonspecific. A previous report described cerebellar lesions in brain MRI studies of seven dogs and proposed that these may be characteristic for central nervous system Neosporosis. The purpose of this retrospective study was to describe MRI characteristics in another group of dogs with confirmed central nervous system neosporosis and compare them with the previous report. The hospital's database was searched for dogs with confirmed central nervous system neosporosis and four observers recorded findings from each dog's MRI studies. A total of four dogs met inclusion criteria. Neurologic examination was indicative of a forebrain and cerebellar lesion in dog 2 and multifocal central nervous system disease in dogs 1, 3, and 4. Magnetic resonance imaging showed mild bilateral and symmetrical cerebellar atrophy in three of four dogs (dogs 2, 3, 4), intramedullary spinal cord changes in two dogs (dogs 3, 4) and a mesencephalic and metencephalic lesion in one dog (dog 2). Multifocal brain lesions were recognized in two dogs (dogs 1, 4) and were present in the thalamus, lentiform nucleus, centrum semiovale, internal capsule, brainstem and cortical gray matter of the frontal, parietal or temporal lobe. Findings indicated that central nervous system neosporosis may be characterized by multifocal MRI lesions as well as cerebellar involvement in dogs.     

Epstein-Barr viral DNA: infectivity for human placental cells

Purified DNA of Epstein-Barr virus (EBV) is regularly infectious by means of the "calcium" method of transfection. Cultured human placental cells exposed to EBV DNA of two transforming strains, FF41 and B95, produce virus that is capable of converting normal B lymphocytes into established cell lines. After treatment with EBV (FF41) DNA and EBV (HR-1) DNA the placental cells display antigens associated with the productive viral cycle. The placental cells have not developed foci or other signs of morphologic transformation.     

Imaging of small-scale features on 433 Eros from NEAR: evidence for a complex regolith

On 25 October 2000, the Near Earth Asteroid Rendevous (NEAR)-Shoemaker spacecraft executed a low-altitude flyover of asteroid 433 Eros, making it possible to image the surface at a resolution of about 1 meter per pixel. The images reveal an evolved surface distinguished by an abundance of ejecta blocks, a dearth of small craters, and smooth material infilling some topographic lows. The subdued appearance of craters of different diameters and the variety of blocks and different degrees of their burial suggest that ejecta from several impact events blanketed the region imaged at closest approach and led to the building up of a substantial and complex regolith consisting of fine materials and abundant meter-sized blocks.     

Evaluation of increased fiber,decreased amino acids,or decreased electrolyte balance as dietary approaches to slow finishing pig growth rates

In swine production, pig movement restrictions or packing plant closures may create the need to slow growth rates of finishing pigs to ensure they remain at a marketable body weight when packing plant access is restored. Although dietary formulations can be successful at slowing pig growth, precision is needed regarding how to best formulate diets to achieve growth rate reductions. Thus, the objective was to evaluate three dietary experimental approaches aimed at slowing growth rates in finishing pigs. These approaches consisted of either increasing neutral detergent fiber (NDF), reducing essential amino acids, or reducing the dietary electrolyte balance through the addition of acidogenic salts. A total of 94 mixed-sex pigs (72.4 ± 11.2 kg BW) across two replicates were individually penned and assigned to 1 of 8 dietary treatments (n = 11–12 pigs/treatment): 1) Control diet representative of a typical corn–soybean meal-based finisher diet (CON); 2) diet containing 15% NDF from soybean hulls (15% NDF); 3) diet containing 20% NDF from soybean hulls (20% NDF); 4) diet containing 25% NDF from soybean hulls (25% NDF); 5) diet formulated as per CON but with 50% of the soybean meal replaced with corn (89% Corn); 6) diet containing 97% corn and no soybean meal or synthetic amino acids (97% Corn); 7) diet containing 2% anhydrous calcium chloride (2% CaCl₂); and 8) diet containing 4% anhydrous calcium chloride (4% CaCl₂). Over 28 d, pig body weights and performance were recorded weekly. At d 28, all pigs were ultrasound scanned and switched to the CON diet to evaluate compensatory gain from d 28 to 35. Overall, increased NDF did not impact any growth performance parameter (P > 0.05). Amino acid restriction reduced average daily gain (ADG), average daily feed intake (ADFI), and gain:feed (G:F) linearly (linear P < 0.001). Similarly, ADG, ADFI, and G:F were linearly reduced with increased CaCl₂ inclusion (linear P < 0.001). ADG differed during the compensatory gain period (P < 0.001), with 4% CaCl₂-fed pigs having a 47% increase in ADG compared with CON-fed pigs. Conversely, 15% and 25% NDF-fed pigs had reduced ADG compared with CON-fed pigs during the compensatory gain period. Gain efficiency differed from day 28 to 35 (P < 0.001), with 4% CaCl₂-fed pigs having a 36% increase in G:F compared with CON-fed pigs. Altogether, these data demonstrate that both amino acid restriction and CaCl₂ inclusion are effective at slowing pig growth, albeit at greater inclusion rates.