Dispersal Of Eggs Research Articles

Population genetics of Macrognathus siamensis (Synbranchiformes: Mastacembelidae): Implications for non-migratory fishery resources in the Mekong River basin

The spotted spiny eel, Macrognathus siamensis is an economically important freshwater fish in the Mekong River basin, which is undergoing dramatic biodiversity changes due to anthropogenic impacts. The species is non-migratory, with a moderate larval duration that facilitates downstream genetic connectivity. Restriction site-associated DNA sequence datasets that includes 3736 and 1244 single nucleotide polymorphisms representing putatively neutral loci, from all geographic sites and without the Tachileik site, indicate strong population structure in this sedentary fish, with a significant isolation-by-distance signature. This structure reflects isolation of tributary populations and downstream dispersal of these distinct populations to mix in the Mekong mainstem and contributes to increased genetic diversity in the lower reaches of the Mekong basin. Genetic data indicates that the dispersal of eggs and larvae downstream is not impeded by Khone Falls and that the falls prevent upstream dispersal of eggs and larvae. Despite this downstream connectivity, there is a strong population structure among above- and below-Khone Falls groups. An analysis of outlier loci putatively under selection provides evidence that the difference between connected metapopulations above and below the falls is due to the fundamental differences in environmental regimes. We hypothesize that instead of a physical barrier, the falls simply represents a demarcation between previously recognized upstream limited-floodplain environments and downstream extensive-floodplain environments. These findings emphasize the need to monitor genetic diversity of key sedentary fishery species to assess whether proposed dams along the river could affect genetic diversity downstream. This genetic diversity is particularly important for the resilience of downstream populations because of the many environmental impacts caused by dams, land use, and climate change. Early detection of reduced downstream genetic diversity could trigger remediation programs to ensure resilience and continued fisheries productivity of important non-migratory fish resources.

Reproduction of grass carp (Ctenopharyngodon idella) in the Maumee River, Ohio: Part 2—Optimal river conditions for egg and larval drift

This study uses a one-dimensional steady-state hydraulic model and the Fluvial Egg Drift Simulator (FluEgg) to model the drift and dispersion of grass carp eggs and larvae in the Maumee River, Ohio, for 180 scenarios representing different combinations of 10 river flows, 6 water temperatures, and 3 spawning locations. The FluEgg simulations were used to quantify in-river suspended hatching rates (the percentage of eggs that hatch within the river and in suspension) and in-river larval retention rates (the percentage of larvae that reach the gas bladder inflation stage within the river after hatching in suspension), and identify which scenarios produce the highest likelihood of recruitment. The simulations indicate that at low flows, in-river suspended hatching and larval retention rates in the Maumee River are limited by the capacity of the flow to keep fertilized eggs in suspension, whereas at high flows, the limiting factor is the distance available for the eggs/larvae to drift in the river. A wide range of scenarios result in eggs hatching within the river, but all larvae drift into Maumee Bay prior to the gas bladder inflation stage when flows exceed the mean annual flow. The simulations were assessed in the context of the hydraulic conditions that trigger spawning and maximize egg fertilization and the nursery habitat requirements for larval grass carp. The results indicate that the Maumee River, although suitable for grass carp spawning, may not be an ideal setting for recruitment unless Maumee Bay provides adequate nursery habitat for larvae.

Turtle-mediated dispersal of anostracan dormant eggs: Evidence for dominance hierarchy effects.

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Protected fish spawning aggregations as self-replenishing reservoirs for regional recovery.

Dispersal of eggs and larvae from spawning sites is critical to the population dynamics and conservation of marine fishes. For overfished species like critically endangered Nassau grouper (Epinephelus striatus), recovery depends on the fate of eggs spawned at the few remaining aggregation sites. Biophysical models can predict larval dispersal, yet these rely on assumed values of key parameters, such as diffusion and mortality rates, which have historically been difficult or impossible to estimate. We used in situ imaging to record three-dimensional positions of individual eggs and larvae in proximity to oceanographic drifters released into egg plumes from the largest known Nassau grouper spawning aggregation. We then estimated a diffusion-mortality model and applied it to previous years' drifter tracks to evaluate the possibility of retention versus export to nearby sites within 5 days of spawning. Results indicate that larvae were retained locally in 2011 and 2017, with 2011 recruitment being a substantial driver of population recovery on Little Cayman. Export to a nearby island with a depleted population occurred in 2016. After two decades of protection, the population appears to be self-replenishing but also capable of seeding recruitment in the region, supporting calls to incorporate spawning aggregation protections into fisheries management.

Ant mediated dispersal of spiny stick insect (Extatosoma tiaratum) eggs and Acacia longifolia seeds is ant-species dependent

Myrmecochory is a widespread mutualism between angiosperm plants and ants, where seed dispersal is facilitated by a nutrient-rich appendage known as the elaiosome. Some species of phasmids (Phasmatodea) have convergently evolved an appendage, the egg capitulum, that is analogous to the elaiosome. Research into ant-mediated dispersal of phasmid eggs is limited. It is unknown whether there are species-specific interactions between ants and phasmid eggs, nor if this variation in ant species behaviour towards eggs parallels behaviour towards seeds. We observed the behaviour of five Australian ant species towards Extatosoma tiaratum eggs and Acacia longifolia seeds. We found that ant species show significant variation in the likelihood of dispersing phasmid eggs and plant seeds. Iridomyrmex purpureus removed the largest quantities of eggs and seeds. Rhytidoponera metallica also removed large amounts of seeds but less eggs. Three species did not remove any eggs but removed small amounts of seeds. We found a species-specific component to dispersal of phasmid eggs and seeds by ants, indicating that this mutualism may depend on partner identity and abundance. Although seeds and eggs have convergently evolved to exploit ant behaviours, they elicit different behaviours in certain ant species, highlighting the complex nature of this interaction.

Coupling Lagrangian simulation models and remote sensing to explore the environmental effect on larval growth rate: The Mediterranean case study of round sardinella (Sardinella aurita) early life stages

The relationship between environmental conditions and early life-history traits of Sardinella aurita are investigated using material collected in two sites of the Central Mediterranean Sea. Individual mean daily growth during the planktonic phase has been determined by using otolith microstructure analysis, while Lagrangian simulation models allowed to estimate the daily position in space and time of each specimen from the hatching to the catch. Generalized Additive Mixed Models (GAMMs) have been implemented to explore the impact of environmental conditions at time t, t-1 day and t-2 days on the mean daily growth rate occurring at time t. Spatial analysis evidenced a wide dispersion of eggs and larvae in the coastal area of both sampling sites in correspondence to relatively warmer and chlorophyll-a enriched waters. Lagrangian simulations detected a complementary larval dispersal pathway able to transport larvae to a known retention area. Temperature at time t was the most important driver affecting the mean daily larval growth, followed by the food availability. On the other hand, models performed on lagged environmental covariates (t-1 and t-2) did not show any significant effect on the growth rate at time t. In addition to the sub-linear positive correlation between temperature and mean daily larval growth, model highlighted a decrease in the otolith core width at higher temperature that can be linked to an earlier stage of ontogeny at hatching. This study provided a useful methodological approach that takes advantage of available remote sensing data to perform ecological studies in support to fisheries management.

Detection of Echinococcus granulosus sensu lato in Environmental Samples from Ibadan, Oyo State, South West Nigeria.

Environmental contamination with parasite eggs poses a serious risk to public health. This study aimed to assess the presence of taeniid eggs and, in particular, E. granulosus s.l., in environmental samples in the city of Ibadan, South West Nigeria. To this purpose, soil (n = 200), fecal (n = 200) and water samples (n = 50) were examined by microscopic observation and the multiplex PCR method. The influence of specific environmental factors on E. granulosus s.l. egg dispersion was also evaluated. Taeniid eggs were microscopically found in 11.5%, 25.5% and 8.0% of soil, fecal and water samples, respectively. PCR analyses evidenced the presence of E. granulosus s.l. in 8.0%, 24.0% and 2.0% of soil, fecal and water samples, respectively. The proximity to slaughterhouses, the level of urbanisation and the local government area of belonging did not seem to affect E. granulosus s.l. egg dissemination patterns. Our results have clearly demonstrated that both urban and semi-urban areas of the city of Ibadan in Nigeria are highly contaminated by taeniid eggs and we recommend the adoption of appropriate measures to control E. granulosus s.l.

Evaluations of Lagrangian egg drift models: From a laboratory flume to large channelized rivers

To help better interpret computational models in predicting drift of carp eggs in rivers, we present a series of model assessments for the longitudinal egg dispersion. Two three-dimensional Lagrangian particle tracking models, SDrift and FluEgg, are evaluated in a series of channels with increasing complexity. The model evaluation demonstrates that both models are able to accommodate channel complexity and provide a wide range of dispersion coefficients: Kl=O(1−100)Hu∗ with H being water depth and u∗ being shear velocity. In a straight channel with Kl=O(1)Hu∗, SDrift predicts weaker longitudinal dispersion than FluEgg in the early stage as a result of weak vertical mixing associated with smooth wall turbulence. With sufficient time, SDrift and FluEgg predict similar egg dispersion, accounting for the differential advection due to the vertical velocity profile. In an idealized curved channel with Kl=O(10)Hu∗, dispersion is driven by both vertical and transverse velocity profiles. SDrift yields slightly larger dispersion coefficients than FluEgg. In a real river with channel-training structures and having Kl=O(100)Hu∗, SDrift predicts a stronger longitudinal dispersion than FluEgg due to substantial local turbulent eddies and velocity gradients. To summarize, FluEgg shows good performance in capturing dispersion due to vertical velocity profiles and cross-channel velocity gradients. SDrift shows excellent model capabilities of revealing various dispersion mechanisms in addition to the vertical and cross-channel velocity variations. They include the initial turbulent diffusion stage with growing dispersion coefficients and strong dispersion due to in-stream hydraulic structures and localized turbulence.

Monitoring the impact of introduced emerald ash borer parasitoids: factors affecting Oobius agrili dispersal and parasitization of sentinel host eggs

Monitoring the impact of introduced emerald ash borer parasitoids: factors affecting Oobius agrili dispersal and parasitization of sentinel host eggs

Dispersal of taeniid eggs: Experimental faecal contamination of forest environment followed by DNA detection in wild berries

To understand Taeniidae epidemiology, the principles of egg-dispersion dynamics under natural conditions must be known. In this study, non-zoonotic Taenia laticollis was used as a model parasite for the family Taeniidae (including Echinococcus spp.). An experiment to investigate dispersion from contaminated faeces to the surroundings was performed both with bilberries (Vaccinium myrtillus) and lingonberries (Vaccinium vitis-idaea), both of which are commercially harvested wild berries in Finland. For this experiment, 30 g of fox faeces was inoculated with 30,000 T. laticollis eggs for the bilberry experiment and 100,000 eggs for the lingonberry experiment. The faecal material was placed in the middle of good berry growth areas in four locations for bilberries and eight locations for lingonberries. After 41–42 days, berries at different distances (0–15 m) from the original contamination spot were collected and delivered to our laboratory. DNA was extracted from washed and sieved material and analysed using T. laticollis-specific semi-quantitative SYBR Green real-time polymerase chain reaction (qPCR). Taenia laticollis-specific DNA was recovered from 67% (8/12) of bilberry samples but not reliably from any of the lingonberry samples 0% (0/24), although the exposure dose was higher for those. The qPCR results suggest that under natural conditions, taeniid egg dispersion from the contamination spot is demonstrated but attachment is berry specific. The surface of bilberries may be more adhesive for taeniid eggs than the waxier and harder pericarp of the lingonberries or there might be a difference in the dispersal mechanism caused by different biotopes.

Connectivity Analysis Applied to Mesoscale Eddies in the Western Mediterranean Basin

The Western Mediterranean basin (WMED) is characterized by the presence of energetic and dynamic mesoscale cyclonic and anticyclonic eddies. They mainly originate along the Algerian and the Northern currents and have a large influence on the basin circulation. Eddies can last for months, with longer lifetimes associated with the anticyclones, which can move far from their areas of origin. As they partially isolate and transfer water masses, they also have an impact on water properties (physical, chemical and biological), pollutant’s dispersion and transport of eggs, larvae and planktonic organisms. In this study, a connectivity analysis method is applied to the anticyclonic eddies (AEs) identified by an automated hybrid detection and tracking algorithm south of 42°N in the WMED. The same methodology is also applied to the trajectories of Lagrangian surface drifters available in the study area. The purpose is to highlight the connections between different areas of the basin linked to eddy activities in addition to the connectivity due to the mean surface circulation. Drifter data analysis showed that all the WMED sub-basins are strongly interconnected, with the mean surface circulation allowing a shortcut connection among many areas of the basin. The connectivity analysis of the AEs tracks shows that although AEs are ubiquitous in the WMED, their connectivity is limited to well-defined regions, depending on their origin location. Three main regions: the south-western, the south-eastern and the northern parts of the basin are characterized by AEs recirculation, with sporadic export of eddies to the other WMED zones.

The Impact of Sea‐Ice Drift and Ocean Circulation on Dispersal of Toothfish Eggs and Juveniles in the Ross Gyre and Amundsen Sea

AbstractKnowledge about the early life history of Antarctic toothfish (Dissostichus mawsoni) is still incomplete, particularly on the spatial and temporal extent of spawning and the subsequent transport of eggs, larvae, and juveniles from the offshore spawning areas to the continental shelf. This study used a high‐resolution hydrodynamic model to investigate the impact of ocean circulation and sea‐ice drift on the dispersal of eggs, larvae, and juvenile Antarctic toothfish. The virtual eggs were released on seamounts of the Pacific‐Antarctic ridge in the Ross Gyre and advected using hydrodynamical model data. Particles were seeded annually over the years 2002–2016 and tracked for 3 years after their release. Recruitment success was evaluated based on the number of juveniles that reached known coastal recruitment areas, between the eastern Ross and Amundsen Seas, within 3 years. Sensitivities to certain juvenile behaviors were explored and showed that recruitment success was reduced by around 70% if juveniles drifted with sea‐ice during the second winter season as this carried them into the open ocean away from the shelf region. Recruitment success increased during the second winter season if juveniles were entrained in the Ross Gyre circulation or if they actively swam toward the shelf. These modeling results suggest that the ecological advantage of sea‐ice association in the early life cycle of toothfish diminishes as they grow, promoting a behavior change during their second winter.

Aerodynamics of the ejection-injection method of separation of entomophages

This article reveals the peculiarities of the transition to a cluster management system in the agro-industrial complex (AIC) of the Republic of Uzbekistan based on the use of innovative techniques and technology. It is shown that, despite the widespread use of agrotechnical, chemical methods of combating pests, diseases and sulfur plants, the issues of mechanization of biological control agents still remain unresolved, and improvised means of controlling them do not give the expected results. As the top priority tasks of the study, the author poses the issues of mechanization of the technological process of dispersal of eggs or pupae of entomophages using an unmanned drone equipped with an ejector-injection dispenser.The work also contains questions of the theory of dispersal of eggs of entomophages through an ejector-injection dispenser under the action of the lifting force of a local air jet or a suction pneumodynamic (injection) force created in the area of the dispenser windows, which allowed not only to significantly improve the design of the dispenser, but also to expand the technological capabilities of the proposed unmanned unit. apparatus.

Brown banded bamboo shark (Chiloscyllium punctatum) shows high genetic diversity and differentiation in Malaysian waters

The demersal brown banded bamboo shark Chiloscyllium punctatum is a major component of sharks landed in Malaysia. However, little is known about their population structure and the effect of high fishing pressure on these weak swimming sharks. Both mitochondrial DNA control region (1072 bp) and NADH dehydrogenase subunit 2 (1044 bp) were used to elucidate the genetic structure and connectivity of C. punctatum among five major areas within the Sundaland region. Our findings revealed (i) strong genetic structure with little present day mixing between the major areas, (ii) high intra-population genetic diversity with unique haplotypes, (iii) significant correlation between genetic differentiation and geographical distance coupled with detectable presence of fine scale geographical barriers (i.e. the South China Sea), (iv) historical directional gene flow from the east coast of Peninsular Malaysia towards the west coast and Borneo, and (v) no detectable genetic differentiation along the coastline of east Peninsular Malaysia. Genetic patterns inferred from the mitochondrial DNA loci were consistent with the strong coastal shelf association in this species, the presence of contemporary barriers shaped by benthic features, and limited current-driven egg dispersal. Fine scale population structure of C. punctatum highlights the need to improve genetic understanding for fishery management and conservation of other small-sized sharks.

The Suspected Contradictory Role of Parental Care in the Adaption of Planktonic Calanoida to Temporary Freshwater

Calanoida have the highest number of species among Copepoda in marine plankton, but not in fresh water, where the greatest number are Cyclopoida. Freshwater Cyclopoida also live in more freshwater sites than Calanoida. This could be a consequence of an invasion of freshwater by marine Cyclopoida before Calanoida. Similar to Cyclopoida, but different from marine Calanoida, freshwater Calanoida females produce egg sacs and care for eggs. This strategy is common among all freshwater plankton, suggesting that the evolution of parental care is an obliged adaption to conquer fresh water. Calanoida, different from Cyclopoida, survive adverse conditions as resting eggs. This life-cycle constraint obliges eggs to survive their mother’s death and wait in the benthos for a certain period. The necessity of completing embryonic development and the hatching of eggs far from the mother’s protection may be responsible for the relatively lower evolutionary success of Calanoida in fresh water compared to Cyclopoida (which rest as juveniles, thus protecting eggs in any moment of their development). Therefore, the brooding of eggs appears to be the obliged solution for Calanoida’s final establishment in fresh water, but the dispersion of eggs on the bottom after the mother’s death and during the rest period is probably the weak point in Calanoida’s competition with Cyclopoida.

Is the spread of the alien water boatman Trichocorixa verticalis verticalis (Hemiptera, Corixidae) aided by zoochory and drought resistant eggs?

Abstract Desiccation resistance is a key trait determining the distribution of aquatic insects, their potential for overland dispersal, and survival during drought periods in temporary waterbodies, as well as the spread of invasive species. Passive dispersal by waterbirds is considered to be a key process favouring the spread of invasive species and is more likely to occur for insects with eggs that are resistant to desiccation or gut passage. We investigated the hypothesis that the eggs of the alien boatman Trichocorixa verticalis verticalis are resistant to desiccation and digestion and thus able to disperse via waterbirds. We conducted experiments to test for egg resistance to desiccation in still air and under moving air conditions, to simulate bird flight. Oviposition on greater flamingo (Phoenicopterus roseus) legs and wetland plants was tested in the laboratory and in the field. Resistance of eggs to simulated gut passage was studied, as was the viability of eggs recovered from Eurasian coot (Fulica atra) droppings in the field. Only a fraction of eggs hatched after 8 hr of exposure to still air at 15°C (4% of exposed eggs), and after 2 hr exposure to air flow conditions at 20°C (8%). Oviposition on flamingo legs was confirmed in the laboratory but not in the field. However, oviposition rates were higher on plant stems than on flamingo legs. Digestion simulations showed very low resistance to chemical treatment and no resistance to scarification, and eggs recovered from coot droppings did not hatch. Our experiments demonstrated that T. v. verticalis cannot be considered to have eggs resistant to desiccation or gut passage. However, the dispersal of eggs on legs of flamingos or other waterbirds may occur as rare events. This epizoochory of eggs could potentially contribute to the expansion and gene flow of T. v. verticalis around the Mediterranean region.

Dispersal of fish eggs and larvae in a cascade of small hydropower plants with fish ladders

This study was conducted to investigate fish eggs and larvae dispersal in a river stretch influenced by small hydropower plants in Southeast Brazil. The main hypothesis is that the downstream dispersal of free-flowing eggs and larvae is likely to occur given the small size of the studied reservoirs and that passage through the dam may occur, with the fish ladder contributing to it. Eggs and larvae were collected fortnightly, between November 2016 and February 2017, from locations upstream of two dams, including lotic, transition and lentic zones. Additional samples were collected inside the fish ladders at each dam. Downstream dispersal of eggs and larvae was influenced by a combination of rainfall/flow variation and stage of the reproductive cycle, with the peak of rainfall during the summer coinciding with higher abundances. Under these conditions, eggs and larvae drifted downstream through the reservoirs and reached the dams. Once in the dam, they could pass through the fish ladder. This passage was correlated with larval density in the reservoir immediately upstream, although at very low densities compared with the other sampling sites located upstream of the fish ladders.

Pattern of egg distribution by Adzuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Chysomelidae) in stored chickpea under natural infestation

Under laboratory experimental condition female Adzuki bean beetles, Callosobruchus chinensis (L.) are known to evenly distribute their eggs over grains available for egg laying. However, currently there are no data on pattern of egg distribution by Adzuki bean beetle in large quantity of chickpea grain stored for extended period of time. The objective of this study was to determine the number and distribution of eggs among grains of chickpea stored in large quantity for 8 months and subjected to natural infestations. The experiment was conducted under room temperature and relative humidity at Debre Zeit Agricultural Research Center. The chickpea cultivars used were Natoli (desi type, 22 g per 100 seeds with Tuberculated seed coat texture) and Arerti (kabuli type, 26 g per 100 seeds with smooth seed coat texture) and for each cultivar there were 21 replicas of bags (40 cm wide and 70 cm high). From each bag, which contains 10 kg each, 25 chickpea grain samples were randomly selected at monthly intervals and examined for the presence or absence of Adzuki bean beetle eggs. Grains with eggs were categorized into frequency classes (i.e. 0, 1, 2, …, n) based on the number of eggs present on them. The variance to mean ratio was used to decide the type of egg dispersion pattern. In all the sampling dates and on both cultivars, the variance to mean ratios were highly significantly greater than one indicating that egg distribution by female Adzuki bean beetles on grains of chickpea was aggregated type. Moreover, further analysis of data had shown that the egg distribution pattern perfectly fits the negative binomial distribution, which confirms that the pattern of egg distribution on chickpea grains was aggregated/clumped type.

Application of high‐throughput single nucleotide polymorphism genotyping for assessing the origin of Engraulis encrasicolus eggs

Abstract Single nucleotide polymorphism (SNP) markers in anchovy (Engraulis encrasicolus) egg samples were analysed to detect their origin on a small spatial scale (200 km) by assigning genotypes to adult anchovy stocks. The novelty of this work is the application of a rapid high‐throughput method for genotyping each single anchovy egg, in a single execution, using a set of 96 genome‐wide SNPs in a dynamic array system with microfluidic technology (Fluidigm 96.96). The existence of two ecotypes in E. encrasicolus had already been identified based on SNP polymorphism in the Atlantic Ocean and in the Mediterranean Sea, showing that habitat type (offshore versus coastal/estuarine) is the most important component of genetic differentiation among populations of anchovy. In this work, anchovy egg genotypes from areas of the Western Mediterranean were assigned to adult populations. Only two localities in which adult anchovies were sampled represented donor populations for the coastal/estuarine egg genotypes. Although some degree of mixing among the hauls could exist, the assignment of egg groups to adult populations led to distinguishing the contributions of distinct ecotypes to new wild generations. We can conclude that the high rate of egg dispersion caused by marine currents and the different degrees of local retention could explain the genetic heterogeneity observed in the adult populations, where eggs from neighbouring spawning sites tend to mix. The results highlight that this technique represents a new and useful tool for addressing evolutionary questions, breed recognition, assignment, and connectivity assessment of individual eggs, and anchovy population dynamics, for the management of stocks.

Research on the transport and dispersion of Asian carp eggs in the “man-made flood pulse” in the middle Yangtze River by Reynolds-averaged numerical simulation

Eggs and early larvae of fishes is important to the early life stages of fish, it is closely related to the fish hatching and resource supplementation, the fish egg movement is essential to studied for re-operation ecological-flow determination, re-operation effect evaluation and fish spawning ground repair. In this paper, fish eggs of Four major Chinese carps were used as the object of study, and the fish eggs were generalized to sediment-like particles. Assuming that their diameter was constant and other mechanical properties were given, the analytic solution considering the change of lateral velocity along the curve were proposed, and the improved three- dimensional hydrodynamic model was used to simulate the distribution characteristics of the fish eggs of the sediment - like particles in the curved channel. (1) cross-section: In straight river section, cross-section of eggs distribution is more uniform in vertical direction, the middle concentration is slightly larger than the two sides in horizontal direction; in the bent river, from the convex bank to the depression concentration gradually reduced. (2) Longitudinal section: the overall concentration of eggs showed a decreasing trend along the trend, the bank near the shore, the egg concentration is increase in a certain time and region, affected by the flow field conditions. The research results can provide the basis for the egg movement simulation by the sink channel and the law of its movement.