Critical Stage In Life Cycle Research Articles

Effects of black soldier fly (Hermetia illucens) enriched with Schizochytrium sp. on zebrafish (Danio rerio) reproductive performances

Nutrient quality, with emphasis on lipid and fatty acid composition of broodstock diet, is one of the major dietary factors influencing fish oocytes maturation, reproductive success and offspring quality/survival. The Black Soldier Fly (BFS) (Hermetia illucens) is a valuable insect species characterized by a balanced essential amino acid profile comparable to fishmeal and has been demonstrated to be an eco-friendly and low-cost protein source in fish diets. However, as regards lipids, BFS is usually characterized by a poor content in polyunsaturated fatty acids which are essential for fish during critical life-cycle stages including oocyte maturation and reproduction.In the present study, full-fat enriched BSF prepupae meal was obtained from BSF larvae reared on coffee by-product (coffee silverskin) enriched with 10% of Schizochytrium sp. Successively, five experimental diets containing different full-fat enriched BSF prepupae meal inclusion levels (corresponding to the 0, 25, 50, 75 and 100% fish meal replacement) were tested during a six-month feeding trial performed on zebrafish (Danio rerio) to investigate, for the first time, the physiological effects on female fish growth, stress response, lipid metabolism and reproductive performances. A multidisciplinary approach including biometric, gas-chromatographic, histological and molecular analyses was used during the present study to have a comprehensive overview of fish responses to the test diets. Results highlighted that up to 50% of fish meal replacement with enriched BSF meal did not impair zebrafish physiological responses while higher replacement levels (75 and 100%) negatively affected fish stress response, oocytes maturation stages, spawning and hatching success.

Fungi isolated from host protocorms accelerate symbiotic seed germination in an endangered orchid species (Dendrobium chrysotoxum) from southern China.

To ensure long-term survival of epiphytic orchids through active reintroduction, more research on critical life cycle stages such as seed germination and seedling establishment are needed. In this study, we used in vitro germination experiments to investigate the role of mycorrhizal fungi in determining seed germination and growth in the endangered epiphytic orchid species, Dendrobium chrysotoxum. Symbiotic seed germination experiments were conducted for 90days under different light conditions with fungal strains isolated from protocorms of D. chrysotoxum and three sister species. Molecular analyses showed that five strains belonged to the typical orchid mycorrhizal family Tulasnellaceae, whereas the other two strains belonged to the Sebacinaceae and the genus Coprinellus. Fungal inoculation, light conditions, and their interaction had a significant effect on protocorm formation and seedling development. Three fungal isolates, including two from D. chrysotoxum and one from D. catenatum, significantly stimulated protocorm formation and seedling development under light conditions. However, fungi isolated from host protocorms (GC-14 and GC-15) produced the highest number of seedlings after 50days (49.5 ± 8.5%, 51.3 ± 9.0%, respectively), while the fungus isolated from D. catenatum protocorms produced the maximum number of seedlings only after 90days (48.7 ± 16.1%). To conclude, this study has shown that light conditions and the identity of fungi had a strong effect on in vitro seed germination and seedling formation in anepiphytic orchid, with fungi isolated from host protocorms leading to accelerated germination and seedling formation. Therefore, fungal source should be taken into account when using seeds and compatible fungi for seedling propagation and in situ reintroduction.

Sustainability of Mussel (Mytilus Galloprovincialis) Farming in the Po River Delta, Northern Italy, Based on a Life Cycle Assessment Approach

Molluscan shellfish aquaculture is considered a “green” industry because of the limited presence of chemicals and risk of pathogens during farming in licensed areas, which provide a safe, nutritive and healthy food source. Moreover, the environmental impact of their production is lower than all other fish animal per unit of protein. In particular, mussels’ production was the first organized mollusk aquaculture in Europe and is now one of the most extended. Italy is the second main European producer of mussels. Taking into account the relevance of the sector, Italian Mediterranean mussel (Mytilus galloprovincialis) aquaculture has been considered for a life cycle assessment (LCA), from a cradle-to-gate perspective. The mussel farms were located in the northern Adriatic Sea, close to the Po River Delta, a region traditionally vocated to bivalve aquaculture. Results have shown that the growing and harvesting phases are the most critical life cycle stages (“hotspots”) due to the production and use of boats, and the great quantity of non-recyclable high-density polyethylene (HDPE) socks used during the yearly productive cycle. Several improvement potentials have been identified and estimated by means of a sensitivity analysis. Furthermore, regarding the principal exporting countries to Italy (Spain and Chile), the transport factors in an overall sustainability assessment have been considered, in order to compare the local and global mussels supply chain.

Short-Term Forecasts of Insect Phenology Inform Pest Management

AbstractInsect pests cost billions of dollars per year globally, negatively impacting food crops and infrastructure, and contributing to the spread of disease. Timely information regarding developmental stages of pests can facilitate early detection and control, increasing efficiency and effectiveness. In 2018, the U.S. National Phenology Network (USA-NPN) released a suite of ‘Pheno Forecast’ map products relevant to science and management. The Pheno Forecasts include real-time maps and short-term forecasts of insect pest activity at management-relevant spatial and temporal resolutions and are based on accumulated temperature thresholds associated with critical life-cycle stages of economically important pests. Pheno Forecasts indicate, for a specified day, the status of the insect’s target life-cycle stage in real time across the contiguous United States. The maps are available for 12 pest species including the invasive emerald ash borer (Agrilus planipennis Fairmaire [Coleoptera: Buprestidae]), hemlock woolly adelgid (Adelges tsugae Annand), and gypsy moth (Lymantria dispar Linnaeus [Lepidoptera: Erebidae]). Preliminary validation based on in-situ observations for hemlock woolly adelgid egg and nymph stages in 2018 indicated the maps to be ≥93% accurate depending on phenophase. Since their release in early 2018, these maps have been adopted by tree care specialists and foresters across the United States. Using a consultative mode of engagement, USA-NPN staff have continuously sought input and critique of the maps and delivery from end users. Based on feedback received, maps have been expanded and modified to include additional species, improved descriptions of the phenophase event of interest, and e-mail-based notifications to support management decisions.

Salt and osmotic stress response of tobacco plants overexpressing Lepidium latifolium L. Ran GTPase gene

Our earlier study has identified Lepidium latifolium Ran (LlaRan) as a cold stress downregulated gene from L. latifolium, a cold desert plant. Further, independent transgenic tobacco (Nicotiana tabacum L. var Xanthi) lines overexpressing LlaRan were developed for functional characterization of the gene. We analysed the tolerance of tobacco plants over expressing LlaRan gene to salt and PEG stresses at germination which represents a critical stage in life cycle of the plants. Germination performance of the four independent transgenic lines (T1 generation) were assessed for germination under distilled water, NaCl (150 mM) and osmotic (15% PEG 4000) stresses. The emergence of radical, plumule and cotyledonary leaf were recorded for 10 days on daily basis and its rate assessed in terms of Timson’s index. It was observed that the germination of wild type tobacco seeds was better than the assessed transgenic lines. It may be inferred that the transgenic lines seeds under study were more sensitive to salt and drought stress elucidating their hypersensitivity at germination level.

Changes In Spring Arrival Dates of Rufous Hummingbirds (Selasphorus rufus) In Western North America In the Past Century

ABSTRACT Warming temperatures have been linked to advancing spring migration dates of birds, although most studies have been conducted at individual sites. Problems may arise ecologically if birds arrive or depart before or after associated food resources such as plants or insects reach critical lifecycle stages. Here, I compare mean first arrival dates of the Rufous Hummingbird (Selasphorus rufus), a prolific pollinator and long-distance migrant with the northernmost breeding range of any North American hummingbird, between 1895–1969 and 2006–2015 at eight observation locations in Oregon, Washington, and British Columbia. Historical arrivals were reported through the North American Bird Phenology Program, and recent arrivals were estimated from temporal occupancy patterns using eBird checklists. Results indicated that hummingbirds arrived 8 and 11 days later in the recent time period in two coastal cities in Oregon and 7–17 days earlier in northern, more inland cities in Washington and British Columbia. ...

Provisioning Behavior of Male and Female Eastern Screech-Owls During the Post-Brooding Period

Although most owls exhibit biparental care, the relative contributions of males and females during critical life cycle stages are poorly understood. Further information could improve our understanding of the feeding ecology of owls and of mechanisms that govern natural and sexual selection, particularly as they relate to the evolution of reversed sexual dimorphism. The objective of our study was to assess possible intersexual differences in provisioning behavior (visit rate and prey size and type) of slightly dimorphic Eastern Screech-Owls (Megascops asio; females 17% greater mass than males) during the post-brooding period when both adults provision nestlings. Pairs of Eastern Screech-Owls provisioned young with 16 different types of prey in our study with insects and crayfish (Family Astacidae) being the most common. We found no differences between females and males in provisioning rate or in mean size of prey delivered. Our findings suggest Screech-Owls are opportunistic feeders in the post-brooding period and that food niche partitioning does not occur between the sexes. These findings are inconsistent with the Role Differentiation and Ecological Hypotheses made for the evolution of reversed sexual dimorphism but support the Rate Ingestion Hypothesis which predicts that both sexes may take smaller prey during the post-brooding period to increase ingestion rate and decrease handling time. In addition our results contribute to an understanding of the feeding ecology and life history of one of the most widespread and recognizable raptors in North America.

Human Disturbance during Early Life Impairs Nestling Growth in Birds Inhabiting a Nature Recreation Area

Nature recreation conflicts with conservation, but its impacts on wildlife are not fully understood. Where recreation is not regulated, visitors to natural areas may gather in large numbers on weekends and holidays. This may increase variance in fitness in wild populations, if individuals whose critical life cycle stages coincide with periods of high human disturbance are at a disadvantage. We studied nestling development of blue tits (Cyanistes caeruleus) in a natural area where recreation activities intensify during weekends and other public holidays at picnic and leisure facilities, but not in the surrounding woods. In nests located near recreation facilities, blue tit nestlings that hatched during holidays developed slowly, and fledged with low body mass and poor body condition. However, nestlings that hatched outside of holidays and weekends in these nest boxes developed normally, eventually attaining similar phenotypes as those hatching in the surrounding woods. Within-brood variance in body mass was also higher in broods that began growing during holidays in disturbed areas. Our results show that early disturbance events may have negative consequences for wild birds if they overlap with critical stages of development, unveiling otherwise cryptic impacts of human activities. These new findings may help managers better regulate nature recreation.

Taking a life cycle look at crianza wine production in Spain: where are the bottlenecks?

Background, aim, and scope This paper presents the results of the LCA of wine production in the region of La Rioja (Spain). The aim of this study was twofold: to identify the most critical life cycle stages of an aged Spanish wine from the point of view of the associated environmental impacts and to compare its environmental performance with that of other wines and beers for which comparable information could be found in the scientific literature. All the product’s life cycle stages were accounted for, namely: grapes cultivation (viticulture), wine making and bottling, distribution and sales, and disposal of empty bottles.

Evolution of environmental cue response mechanisms: Adaptive variation in photorefractoriness

Appropriate timing of transitions between annual cycle stages (reproduction, plumage molt, migration) is critical to fitness for birds living in temporally varying environments. Environmental cue response systems permit birds to orchestrate these transitions. This paper focuses on how photorefractoriness and one neuroendocrine correlate of it (GnRH system plasticity) have evolved to permit appropriate timing of the transition from breeding to plumage molt. Photorefractoriness is defined by two criteria. Criterion 1: photoinduced gonadal regression occurs without any decline in photoperiod. Criterion 2: photoinduced gonadal regression cannot be reversed by increased photoperiod, even continuous light. Through a comparative approach we show that: (1) Loss of Refractoriness Criterion 1 and of GnRH system down-regulation appear to represent adaptive specializations favoring highly temporally flexible or continuous breeding, (2) Refractoriness Criteria 1 and 2 are not always concordant, and Criterion 2 in particular is not well-correlated with degree of temporal reproductive flexibility, (3) occurrence of some cue response traits are better-explained by phylogenetic relationships among taxa than by current reproductive schedules (seasonal, flexible, opportunistic), (4) substantial temporal flexibility can be achieved in a variety of ways besides adaptive modifications of refractoriness, such as relaxation of long-day requirements for reproductive development, and enhancement of non-photic cue responsiveness. These comparisons also highlight fundamental similarities between some of the most opportunistic species and seasonal breeders, such as an autumn reproductive hiatus during molt. Even in the face of substantial environmental unpredictability, selection may often strongly favor regular scheduling of particularly critical life cycle stages such as plumage molt.

INVESTIGATION OF SEED GERMINATION CHARACTERISTICS AND RECOVERY OF GERRMINATION IN THE HALOXYLON APHYLLUM UNDER DIFFERENT TEMPERATURE AND SALINITY CONDITIONS

Haloxylon aphyllum is one of the most important species in sandy and saline areas in deserts, and some ecophysiology characters for viability in unfavorable condition have evaluated in this species. Seed germination is the critical stages in life cycle for species survival. In this study investigated salinity and temperature stresses on percentage and velocity of germination using six salinity treatments (0, 100, 200, 300, 400 and 500 mM/I NaCI) under four different temperature regimes (20:10, 30:10, 25:15 and 35:25 DC). The results showed that seeds could germinate at very high salt concentration (500mM). However, highest germination percentage was obtained in distilled water and thermoperiod 20:1cfc. Increased on salinity and temperature caused decreased of percentage and velocity of germination. Seed germinated rapidly and no significant change in germination was noticed after 10d. Recovery of seed germination investigated when seeds were transferred to distilled water. The results indicated that recovery percentage was high in seeds were transferred from very saline treatment with Lower temperature.

Plant resource conservation planning in protected natural areas: an example from the Canary Islands, Spain

An approach to an overall management planning for the conservation of endangered species within protected natural areas is presented, based mainly on the development of methods for the diagnosis of the conservation status and the identification of critical life cycle stages (phenophases) of target species. This model includes other aspects inherent in the overall planning of a protected area so as to match its technical, human and economic resources in terms of research and conservation. We provide examples of some island endemics that are included in the “Recovery Plans for the Endangered Plants in the Canary Islands National Parks”. The use of demography and genetics is particularly emphasised. We propose reintroductions as one of the most important tools for the management and conservation of endangered plants and the use of “system dynamics” tools as an alternative to traditional population matrix analysis. We provide examples of the application of system dynamics to population dynamics studies and to the design of management actions.

Direct Perturbation Analysis for Better Conservation

Only demographic studies can link in a quantitative way observed trends in population growth rate to parts of the life cycle. Population growth rate has been used for some time to assess the overall status of populations in conservation management. More recently there has been an increasing interest in elaborating methods that can assess the relative importance of different life-cycle phases for observed population growth trends (Silvertown et al. 1993, 1996; Caswell 1996a; Royama 1996). This kind of information is essential to identifying critical life-cycle stages and concentrating management efforts on them. One tool that has become widely used to extract information from demographic data is population projection matrices (Caswell 1978, 1989a; van Groenendael et al. 1988; Silvertown et al. 1993, 1996; Schemske et al. 1994). Silvertown et al. (1996) discuss elasticity matrices as a way to identify such critical life-cycle stages and as an aid to constructing rules of thumb useful in plant conservation. They warn against a naive interpretation of elasticities and argue that the state of the populationits rate of increase-must be taken into account. We want to focus attention on some additional problems with the use of elasticity values for identifying key phases of the life cycle and to propose an alternative method that reduces these problems. The rate of increase of a population (X) depends on ageor stage-specific vital rates such as survival, growth, and reproduction. Sensitivity analysis explores this dependence by calculating the effects on X of infinitely small absolute changes to matrix element aij, which represents particular transitions in the life cycle (Caswell 1978, 1989a). Hence, the sensitivity sii of a matrix element aii is

Biotechnology in marine aquaculture

Intensification of production, modernization of technique, and improvement of cultivars are needed to increase the economic efficiency of marine aquaculture industries. To help achieve such improvements, modern methods of biochemical and genetic engineering can be adapted to control biological processes which intrinsically limit the efficiency and yield of production. Such applications now have been developed for improved production of molluscs. Critical life-cycle stages of several species of abalones and other commercially valuable molluscs which thus far have proved amenable to improved control by these means include reproduction, larval settlement, metamorphosis, and acceleration of early growth. Analysis of the physiological and molecular mechanisms which control reproduction in molluscs reveals a prostaglandin-dependent regulation of spawning in abalones and certain other species. Spawning of gravid adults can be induced by the addition of prostaglandins to the surrounding seawater, or, more reliably and inexpensively, by activation of the endogenous enzymatic synthesis of prostaglandin-related spawning triggers in response to added hydrogen peroxide. Peroxide activation of the prostaglandin-dependent spawning reaction has been found widely useful for obtaining synchronous and copious release of fully competent gametes in a large number of species of abalones, oysters, scallops, mussels, clams, and other valuable molluscs; a number of these species had not been successfully spawned by other methods. Settlement and metamorphosis of many molluscan species can be brought under similar biochemical control. Most efficiently and inexpensively, the natural biochemical requirement for induction of these critical developmental processes can be met by providing competent larvae with unique amino acid constituents associated with the naturally required inducing molecules. Thus, γ-aminoburyric acid (GABA) can be used simply, safely and inexpensively to induce complete and rapid larval settlement and metamorphosis — with minimal mortality — in many commercially important abalone species. This and similar neurotransmitter-related, amino-acid-derived compounds are proving comparably effective for the reliable induction of settlement and metamorphosis in a number of other valuable molluscan species. Recent analyses of the requirements for rapid early juvenile growth in abalones reveals a mechanism of growth-control which is susceptible to exogenous hormonal acceleration. Genetic cloning and amplification of recombinant-DNA templates for the efficient production of essential growth-regulating hormones, and substances required for enhanced nutritional efficiency and resistance of cultivars, are now in progress. Genetic engineering for the direct improvement of cultivated species soon will be within reach.

Biochemical and genetic engineering for improved production of abalones and other valuable molluscs

Intensification of production, modernization of technique, and improvement of cultivars are needed to increase the economic efficiency of molluscan cultivation industries in the United States and certain other countries. To help achieve such improvements, modern methods of biochemical and genetic engineering can be adapted to control biological processes which intrinsically limit the efficiency and yield of molluscan production. Critical life-cycle stages of several species of abalones and other commercially valuable molluscs which thus far have proved amenable to improved control by these means include reproduction, larval settlement, metamorphosis, and acceleration of early growth. Analysis of the physiological and molecular mechanisms that control reproduction in molluscs reveals a prostaglandin-dependent regulation of spawning in abalones and certain other species. Spawning of gravid adults can be induced by the addition of prostaglandins to the surrounding seawater, or, more reliably and inexpensively, by activation of the endogenous enzymatic synthesis of prostaglandin-related spawning triggers in response to added hydrogen peroxide. Peroxide activation of the prostaglandin-dependent spawning reaction has been found widely useful for obtaining synchronous and copious release of fully competent gametes in a large number of species of abalones, oysters, scallops, mussels, clams, and other valuable molluses; a number of these species had not been successfully spawned by other methods. Settlement and metamorphosis of many species can be brought under similar biochemical control. The efficient induction of settlement and metamorphosis of the larvae of many Haliotis (abalone) species normally requires contact with any of several crustose red algae usually associated with natural recruiting substrates. This requirement can be met by providing competent larvae with the essential algae or with specific proteins purified from these algae, although production of these inducers is both time consuming and costly. Most conveniently and inexpensively, this natural requirement can be met by providing the larvae with certain unique amino acid constituents normally associated with the inducing proteins. Thus, γ-aminobutyric acid (GABA) can be used simply, safely, and inexpensively to induce complete and rapid larval settlement and metamorphosis — with minimal mortality — in many commercially important abalone species. This and similar neurotransmitter-related, amino acid-derived compounds are proving comparably effective for the reliable induction of settlement and metamorphosis in a number of other valuable molluscan species. Recent analyses of the requirements for rapid early juvenile growth in abalones reveals a mechanism of growth control which is susceptible to exogenous hormonal acceleration. Present experiments aimed at genetic cloning and amplification of recombinant-DNA templates for the essential growth-regulating hormones, progress in the establishment of useful molluscan gene banks, and potential uses of this technology for molluscan aquaculture are described.