Changes to the histological gill structure and haemolymph composition of early blue swimmer crab Portunus pelagicus juveniles during elevated ammonia‐N exposure and the post‐exposure recovery     

Nicholas Romano  Chaoshu Zeng 《Aquaculture Research》2010,41(4):468-480

It is yet unclear whether sub‐lethal ammonia‐N levels cause irreparable damage to aquatic crustaceans, or if recovery is possible, the potential factors involved. The aim was to investigate the effect of 0.706 and 2.798 mmol L^?1 ammonia‐N exposure on the haemolymph osmolality, Na⁺, K⁺, Ca²⁺, pH, ammonia‐N, total haemocyte counts (THC) and gill histopathology of Portunus pelagicus juveniles at 0, 3, 6, 12, 24 and 48 h respectively. Following 48 h, crabs were transferred to pristine seawater allowing a recovery period up to 96 h and similarly measured. In addition moribund crabs, induced from lethal ammonia‐N levels of 7.036 and 10.518 mmol L^?1, were measured for haemolymph osmolality/ions and pH levels. The results demonstrate that despite severe gill damage within 6‐ and 1 h of 0.706 and 2.798 mmol L^?1 ammonia‐N exposure, respectively, no significant change (P>0.05) in the haemolymph osmolality, Na⁺, K⁺, Ca²⁺ or pH levels occurred or by ammonia‐N‐induced morbidity. Although the gills can completely recover within 24 and 48 h post exposure to 0.706 and 2.798 mmol L^?1 ammonia‐N, respectively, likely facilitated by significant haemocyte increases (P<0.05) within the haemolymph and gill lamellae, dependent factors were the previous ammonia‐N concentration and recovery duration while individual variability was also noticed.  相似文献   

Complex interactions among successional trajectories and climate govern spatial resilience after severe windstorms in central Wisconsin,USA     

Lucash  Melissa S.  Ruckert  Kelsey L.  Nicholas  Robert E.  Scheller  Robert M.  Smithwick  Erica A. H. 《Landscape Ecology》2019,34(12):2897-2915

Landscape Ecology - Resilience is a concept central to the field of ecology, but our understanding of resilience is not sufficient to predict when and where large changes in species composition...  相似文献   

Populations of two annual clover species evolved in response to 13 years of grazing management and phosphate fertilizer application     

Hayley C. Norman  Philip S. Cocks  Nicholas W. Galwey 《Grass and Forage Science》2020,75(1):64-75

A Syrian grassland was subject to 13 years of replicated management treatments, namely a factorial design of 0 or 60 kg/ha annually of phosphate fertilizer, combined with relatively low or high sheep stocking intensities. Previous work found that differences in grazing intensity and phosphate induced changes in the structure of the legume community, presumably due to changes in competitive relationships. The aim of this study was to investigate how the populations of the predominant clover species, Trifolium campestre and Trifolium tomentosum, changed as a consequence of management treatments. We hypothesized that the populations from the fertilized or low grazing intensity treatments would express phenotypic traits associated with increased competitive ability and/or with risk mitigation. Populations of both ruderal-type clover species provided evidence of evolution but were largely responsive to different management factors. Assuming that heavy grazing and no fertilizer are the natural state of the grassland, addition of phosphate led to T. tomentosum plants that were wider and had larger seeds, traits associated with improved competitive ability. The populations from the fertilized paddocks had increased fecundity and a trend towards greater dormancy, traits associated with risk mitigation. In contrast, T. campestre plants became wider and more erect when stocking intensities were reduced and had greater seed dormancy in fertilized paddocks. The implication of this work is that the collection of germplasm from grasslands with a history of heavy grazing and fertilizer application may assist agronomists to find genotypes that are better adapted to pastures within ley farming systems in Australia.  相似文献   

Review: classical biological control of invasive stink bugs with egg parasitoids – what does success look like?     

Paul K Abram  Nicholas J Mills  Elizabeth H Beers 《Pest management science》2020,76(6):1980-1992

Although the enemy release hypothesis forms the theoretical basis for classical (=importation) biological control of invasive pests, its core assumptions are not always examined. This could contribute to unrealistic expectations for some biological control programs. In this paper we examine the assumptions that: (i) enemy release has contributed to the invasive nature of four exotic pentatomids in North America; and (ii) classical biological control with egg parasitoids has been or will be successful in reducing populations of these pests below economically significant levels. First, we review the history of biological control programs against invasive stink bugs to highlight the variable and controversial levels of success of introducing egg parasitoids against stink bugs. Then, we use simple stage‐structured matrix models to demonstrate that it may be easy to overestimate the contribution of egg parasitism alone to a reduction in stink bug population growth. Finally, we discuss what realistic expectations might be for success of biological control against invasive stink bugs using egg parasitoids in the context of integrated pest management programs. © 2020 Her Majesty the Queen in Right of Canada Pest Management Science © 2020 Society of Chemical Industry  相似文献   

Ontologies for transparent integrated human-natural system modelling     

J. Gary Polhill  Nicholas M. Gotts 《Landscape Ecology》2009,24(9):1255-1267

We propose an approach to modular agent-based land use modelling, based on ontologies in their computer science sense: formal representations of conceptualisations. The approach is primarily aimed at addressing the issue of model transparency. Human-natural systems models involve large numbers of submodels, making them difficult to understand for those not involved in their construction. We show that using ontologies to represent the structure and state of a simulation model improves transparency in two ways: First, the information about the structure and state is decoupled from the simulation software and can be independently processed. Second, the logics on which ontologies are based reflect more commonsense understandings of the relationships among concepts than those of computer programming languages.  相似文献   

The timing of puberty in cultured female yellowtail flounder, Limanda ferruginea (Storer): Oogenesis and sex steroid production in vivo and in vitro     

Anthony J. Manning  Margaret P.M. Burton  Laurence W. Crim 《Aquaculture (Amsterdam, Netherlands)》2008,279(1-4):188-196

This study examines puberty in female yellowtail flounder, correlating macroscopic, histological and endocrine parameters at the gonadal level. Short-term ovarian tissue incubations were used to study estradiol-17β production in relation to oogenic stage. Examining 2 year classes of young flounder demonstrated that cultured females retain phenotypic plasticity in reproductive age with pubertal onset occurring in one-year, two-year and three-year-olds. Immature ovaries were steroidogenic and capable of responding to gonadotropic stimulation. Endocrine puberty in females was detected by a peak in estradiol-17β production during the cortical alveolar oocyte stage prior to any ovarian evidence of vitellogenesis. Puberty, once initiated, proceeded to ovulation within 8 to 12 months; vitellogenic oocyte development followed the group synchronous pattern. Estradiol-17β was clearly the dominant of the two measured plasma hormones during pubertal onset and throughout vitellogenesis. Plasma testosterone was consistently detectable at low levels by mid-to late-vitellogenesis. Ovaries showed the highest sensitivity to gonadotropic stimulation in vitro during late-vitellogenesis. Variable plasma levels in both estradiol-17β and testosterone occurred in preovulatory and ovulating females during the captive spawning period. Together the results show that yellowtail flounder can mature at a young age and small size when culture conditions permit. In addition, the early sensitivity to gonadotropin by the immature ovaries may be an important physiological determinant for the timing of puberty in this species.  相似文献   

Seed and seedling characteristics of hybrid chestnuts (Castanea spp.) derived from a backcross blight-resistance breeding program     

Cipollini  Martin  Wessel  Nicholas  Moss  John Patten  Bailey  Natalie 《New Forests》2020,51(3):523-541

New Forests - American chestnut (Castanea dentata) was a foundation species in the eastern United States until chestnut blight (Cryphonectria parasitica) infestation resulted in range-wide...  相似文献   

Effects of compaction on soil hydraulic properties,penetration resistance and water flow patterns at the soil profile scale     

Mona Mossadeghi‐Bjrklund  Nicholas Jarvis  Mats Larsbo  Johannes Forkman  Thomas Keller 《Soil Use and Management》2019,35(3):367-377

The aim of this study was to quantify the effects of compaction on water flow patterns at the soil profile scale. Control and trafficked plots were established in field trials at two sites. The trafficked treatment was created by four passes track‐by‐track with a three‐axle dumper with a maximum wheel load of 5.8 Mg. One year later, dye‐tracing experiments were performed and several soil mechanical, physical and hydraulic properties were measured to help explain the dye patterns. Penetration resistance was measured to 50 cm depth, with saturated hydraulic conductivity (K_s), bulk density, and macroporosity and mesoporosity being measured on undisturbed soil cores sampled from three depths (10, 30 and 50 cm). Significant effects of the traffic treatment on the structural pore space were found at 30 cm depth for large mesopores (0.3–0.06 mm diameter), but not small mesopores (0.06–0.03 mm) or macroporosity (pores > 0.3 mm). At one of the sites, ponding was observed during the dye‐tracing experiments, especially in the trafficked plots, because of the presence of a compacted layer at plough depth characterized by a larger bulk density and smaller structural porosity and K_s values. Ponding did not induce any preferential transport of the dye solution into the subsoil at this site. In contrast, despite the presence of a compacted layer at 25–30 cm depth, a better developed structural porosity in the subsoil was noted at the other site which allowed preferential flow to reach to at least 1 m depth in both treatments.  相似文献   

Carbon and trace element mobility in an urban soil amended with green waste compost     

Luke Beesley  Nicholas Dickinson 《Journal of Soils and Sediments》2010,10(2):215-222

Background, aim and scope  

The amendment of degraded urban soils using recycled organic wastes offers potential improvements to physicochemical status and functionality, but there is a paucity of knowledge on the potential impact on residual contaminants in soil. The aim of this study was to evaluate the mobility of trace metals and arsenic (As) through an urban soil following amendment with green waste compost over an annual cycle.  相似文献   

Cuckoos combat socially transmitted defenses of reed warbler hosts with a plumage polymorphism     

R Thorogood  NB Davies 《Science (New York, N.Y.)》2012,337(6094):578-580

In predator-prey and host-parasite interactions, an individual's ability to combat an opponent often improves with experience--for example, by learning to identify enemy signals. Although learning occurs through individual experience, individuals can also assess threats from social information. Such recognition could promote the evolution of polymorphisms if socially transmitted defenses depend on enemy morph frequency. This would allow rare variants to evade detection. Female brood parasitic common cuckoos, Cuculus canorus, are either gray or rufous. The gray morph is a Batesian mimic whose hawk-like appearance deters host attack. Hosts reject this disguise through social learning, increasing their own defenses when they witness neighbors mobbing a cuckoo. Our experiments reveal that social learning is specific to the cuckoo morph that neighbors mob. Therefore, while neighbors alert hosts to local cuckoo activity, frequency-dependent social information selects for a cuckoo plumage polymorphism to thwart host detection. Our results suggest that selection for mimicry and polymorphisms comes not only from personal experience but also from social learning.  相似文献