Egg Abundance Research Articles

Oviposition dynamics of Aedes aegypti in Central Argentina.

Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) is the vector of multiple arboviruses. To evaluate the association between environmental factors and the oviposition activity of Ae. aegypti in Argentina, data on the presence and abundance of eggs were collected using ovitraps, between September of 2018 and May of 2019, in the cities of Villa María, Río Cuarto and Salsipuedes (Córdoba province, Argentina). We analysed the relationships between oviposition and five environmental factors: Temperature, precipitation, vegetation cover, human population density and distance to sites with a potential high density of larval habitats, like cemeteries and trash dumps. Environmental factors' data were collected using satellite image products. The oviposition activity was randomly distributed in three cities. Using generalized linear mixed models, we show that the house where each ovitrap was placed was a source of variability in oviposition, suggesting the relevance of microsite factors and the importance of domestic control actions. Ae. aegypti oviposition was positively correlated with night-time temperature of the previous 3 weeks, and in a context-dependent manner, it was positively correlated with human population density, vegetation cover and precipitation. The consistency and magnitude of these relationships varied between cities, indicating that oviposition is related to a complex system of environmental variables.

Importance of a turbulent river section below a giant waterfall for fish spawning: Indications from drift and dispersion patterns of early life stages

AbstractSeasonal drift patterns of fish eggs and larvae were analysed along the river section downstream the Iguaçu River Falls to the confluence with Paraná River, over three spawning seasons. This river section is situated in a narrow rocky canyon characterized by a steep slope, which leads to highly turbulent and fast flowing conditions in a series of rapids. Water transit time in this river stretch of 20 km was short (5–11 h), the flow‐velocity in rapids can reach values of more than 6 m s−1. Densities of drifting eggs and larvae varied between three spawning seasons, and differences of eggs were more pronounced compared to larvae. Eggs and larvae were observed all along the river section. A spatial, longitudinal distribution pattern of larvae was found, with higher numbers in the upper section. A distinct spatial sequence of different embryonic stages was observed, with the highest abundance of early stages. Larval densities were low in comparison to egg densities, and preflexion and flexion stages predominated. High abundance of buoyant eggs in drift indicates fish spawning in rapid and turbulent waters of the Iguaçu River, particularly downstream from the Iguaçu Falls. Rainfall and turbidity may be the main trigger for spawning. Spawned eggs drifted quickly towards the confluence, most are likely to hatch in the Paraná River, while larvae disperse to nursery habitats even in the river section below the falls. Thus, inshore zones along the whole stretch provide nursery habitats for larval development of fish species exhibiting different reproductive strategies.

Spatial Heterogeneity and Seasonal Distribution of Aedes (Stegomyia) aegypti (L) in Abidjan, Côte d'Ivoire

Although the urban areas of Abidjan, Côte d'Ivoire have faced recurrent outbreaks of Aedes-borne arboviruses, the seasonal dynamics of local populations of the key vector Aedes aegypti remained still underexplored for an effective vector control. The current study thus assessed the seasonal dynamics and the spatial distribution of Ae. aegypti in three neighborhoods of Abidjan city. Aedes eggs were collected using ovitraps in three different neighborhoods (Anoumambo, Bromakoté, and Petit-Bassam) during the four climatic seasons of Abidjan. Aedes egg samples were immersed into distilled water, and emerged larvae were reared until the adult stage for species morphological identification. Spatial autocorrelation was measured with the Moran's Index, and areas with high egg abundance were identified. In total, 3837 eggs were collected providing 1882 adult mosquitoes in the 3 neighborhoods. All the specimens belonged to only one Aedes species, Ae. aegypti. The average of 15.89 eggs per ovitrap, 13.67 eggs per ovitrap, and 19.87 eggs per ovitrap were obtained in Anoumambo, Bromakoté, and Petit-Bassam, respectively, with no statistical difference between the three sites. A higher abundance of Ae. aegypti was observed during the long rainy season and the short dry season. The Moran analysis showed a clustered distribution of Ae. aegypti eggs during the long rainy season in the three sites and a random spatial distribution during the short dry season. Ovitraps with high number of eggs were aggregated in the peripheral part (near to the lagoon) of Anoumambo and Petit-Bassam in central Bromakoté and extending along the railway during the long rainy season. This study revealed a heterogeneous potential risk of transmission of arbovirus according to neighborhood. It provided data to better understand Ae. aegypti ecology to select appropriate periods and places for Aedes vector control actions and surveillance of arboviruses in Abidjan.

The long-term ichthyoplankton abundance summer trends in the coastal waters of the Black Sea under conditions of hydrometeorological changes

In this study a long-term literature and field-monitoring dataset collected from the Sevastopol coast in the Black Sea during summer seasons from 1960 to 2017 were examined. Principal component analysis (PCA) and ANOVA analysis clearly demonstrate changes in the dynamics of ichthyoplankton abundance due to wind conditions, temperature, and salinity. The results specifically showed significant relationship between the abundance of eggs (r = 0.82) and repeatability northeasterly winds and between larvae abundance and speed northeasterly wind (r = 0.64). As the wind speed increases, the surface water temperature decreases and salinity rises. According to the data on the temperature and wind speed, the period of occurrence of local upwellings in summer near the coast of Sevastopol was determined ~8 and 20–25 years. Based on analysis of linear trends for the summer periods from 1960 to 2017 in this area a decrease in the number of fish eggs and occurrences of larvae and a general reduction in temperatures, salinity, speed and repeatability northeasterly winds was observed. Long-term ichthyoplankton data monitoring can be used to validate model results and provide further predictions of changes in ecosystem components.

Spatiotemporal spawning patterns and early growth of Japanese sardine in the western North Pacific during the recent stock increase

AbstractSpatiotemporal patterns in spawning of fish influence growth and survival by affecting the environment experienced by offspring during their early life stages. Therefore, identifying changes in spawning patterns can help researchers understand population dynamics and recruitment fluctuations. The Japanese sardine Sardinops melanostictus is a small pelagic fish that undergoes large stock fluctuations. Although spawning patterns are known to change spatially and temporally with stock abundance, little information is available on the processes underlying stock increases. This study aimed to describe changes in spawning pattern and early growth of Japanese sardine during the recent period of stock increase and to clarify the effects of different spawning periods on offspring growth. We examined trends in egg abundance in the western North Pacific in 2004–2018 and analyzed hatch dates and growth trajectories by otolith microstructure analysis of juveniles from the Kuroshio–Oyashio transition region (the species’ main nursery area). During the study period, the main spawning area shifted from the western to the eastern part of this region off Japan, and spawning in the eastern part roughly coincided with juvenile hatch dates. Hatch dates also shifted from mid‐March at the earliest to February and early March from 2013 onward. Although early‐hatched cohorts (which originate offshore of eastern Japan) experienced slower initial growth, they likely played an important role in the recent stock increase. Successful recruitment of these cohorts may have been facilitated by factors such as early hatching and transport to the nursery, which reduces the frequency of predator encounters.

Oceanographic influences on the early life stages of a mesopelagic fish across the Chilean Patagonia

Environmental conditions, such as sea surface temperatures and salinities, may exert important influences on the life history traits of marine organisms, particularly on the early stages of fishes. We studied the interaction between spring environmental conditions, egg and larval abundances, and growth rates, of pearlside Maurolicus australis along a 10° latitudinal range in western Patagonia. Using onboard field experiments, otolith-based back-calculated daily growth rates, CTD data, together with sea surface temperature (SST, 2002–2019) and chlorophyll-a (Chl-a, 2017–2018) satellite images, we studied the effect of short-term mesoscale variability on larval growth as well as their interactions with environmental conditions. SST of 2017 and 2018 were similar, with colder than average (2003–2018) springs for both years. Onboard experiments indicated that egg size directly influenced the size-at-hatch, though this was independent of lipid reserves. Larvae were categorized into Oceanic (Oc), Inner Seas (IS) and off the Southern Ice Fields (SIF). On the shelf (Oc), larvae were more abundant with faster growth rates; a second maximum density was observed off the SIF. The latter individuals had the smallest otolith-at-size and showed the slowest recent growth rates, despite spatially coinciding with relatively large Chl-a concentrations (>8 mg m−2). Latitudinally, the decrease in sea surface temperatures and the rise in vertical salinity gradients, reduced the recent larval growth of the pearlside. However, daily fluctuations in SST did not trigger significant variations in the back-calculated detrend growth rates. Although low temperatures in the SIF lead to slow growth rates of M. australis, compared to the northern population, the area presents some benefits regarding food availability, retention and protection from predators. Moreover, it is possible that the low temperatures might affect the energy balance of fish larval stages by intervening in the allocation of energy for tissue formation and metabolism, resulting in slow growth rates in the southern population.

Effective low-cost preservation of human stools in field-based studies for helminth and microbiota analysis

Molecular studies of gastrointestinal infections or microbiotas require either rapid sample processing or effective interim preservation. This is difficult in remote settings in low-income countries, where the majority of the global infectious disease burden exists. Processing or freezing of samples immediately upon collection is often not feasible and the cost of commercial preservatives is prohibitive. We compared fresh freezing (the ‘gold standard’ method), with low-cost chemical preservation in (i) a salt-based buffer consisting of DMSO, EDTA and NaCl (DESS) or (ii) 2.5% potassium dichromate (PD), for soil-transmitted helminth detection and microbiota characterisation in pre-school and school-aged children from north-western Thailand. Fresh frozen samples were frozen at −20°C on collection and maintained at −80°C within ~3 days of collection until molecular analysis, with international shipping on dry ice. In contrast, chemically preserved samples were collected and stored at ~4°C, transported on wet ice and only stored at −20°C on arrival in Australia ~8 weeks after collection, with international shipping on wet ice. DESS and PD provided better sensitivity for STH diagnosis, estimating higher infection rates (>80% for Ascaris lumbricoides and >60% for Trichuris trichiura; versus 56% and 15% for these parasites in fresh frozen samples) and egg abundance (inferred as gene copy number estimates). All methods performed similarly for microbiota preservation, showing no significant differences in alpha-diversity based on overall richness or inverted Simpson’s Index. All three methods performed similarly for RNA and protein preservation in a small subset of samples. Overall, DESS provided the best performance, with the added benefit of being non-toxic, compared with PD, hence making it particularly applicable for studies in remote and resource-poor settings.

Oviposition behavior of wild yellow fever vector mosquitoes (Diptera: Culicidae) in an Atlantic Forest fragment, Rio de Janeiro state, Brazil

Although there are many studies on the control of mosquito vectors of the yellow fever virus (YFV) in tropical forests, there are still few ecological studies regarding abiotic factors effect on these mosquitoes. Here we characterize these effects on oviposition behavior, abundance, and diversity of mosquito vectors of YFV. The study was conducted in Córrego da Luz Municipal Park, in Casimiro de Abreu, Rio de Janeiro state, Brazil, from July 2018 to December 2019. Ovitraps were placed at ground level and 3 m high. The data were tested for normality using the Shapiro–Wilk test, followed by an independent sample analysis, the Mann–Whitney test. The Shannon Diversity Index was used to evaluate the abundance of mosquitos' eggs collected at both ground level and 3 m high. We highlight the presence of Haemagogus janthinomys and Hg. leucocelaenus, primary YFV vectors in forest areas. The abundance of Hg. leucocelaenus (63%), Hg. janthinomys (75%), and Aedes terrens (58%) was higher at the height of 3 m, while Ae. albopictus (52%) was higher at ground level. Aedes albopictus was positively correlated with temperature. Culicidae monitoring is essential for assessing the YFV transmission cycle in Atlantic forest fragments.

Early Life Stages of Fishes in Lake Taal, Philippines: Assessment and Implications for Biodiversity Management and Conservation

Lake Taal is the third largest lake in the Philippines and its fisheries provide livelihood to thousands of locals in its coastal areas. This study was conducted to recommend possible strategies and measures to conserve and protect the population of fishes, especially of the early life stages (ELS). The composition, abundance, and distribution of ELS and the environmental factors affecting these were investigated through monthly ichthyoplankton surveys and monitoring of water parameters, phytoplankton, and zooplankton abundances in 12 equidistant stations from January 2015 to December 2018. A total of 26,345 fish eggs and 9,140 fish larvae were collected, of which 88.9% of the fish larvae were morphologically identified into eight families, while the rest were unidentified. Families Terapontidae (44.5%) and Gobiidae (37.0%) numerically dominated the identified larvae catch. Distribution of the egg, yolk sac, and pre-flexion stages (ELS) significantly varied across stations. Three stations on the northern basin of the lake showed the highest fish egg abundance (731.82, 246.47, and 381.28 ind 100 m–3) while stations on the west, northwest, and eastern bay of the lake showed the highest abundance of fish larvae (153.76, 121.28, and 94.64 ind 100 m–3). The temporal distribution of ELS was highly associated with zooplankton, green algae, and salinity while spatial distribution was highly associated with the majority of the water parameters and chlorophyll a. Seasonal and annual distribution of ELS showed significant variation, which reveals possible spawning patterns of the identified fish larvae and the influence of varying environmental conditions to the distribution of ELS. Based on these, the identified possible spawning and larval foraging grounds are recommended as protected zones. Reduction of nutrient inputs to minimize changes in the lake trophic condition is also recommended.

Shedding light on the link between the spatial distribution of eggs and survival in Northeast Arctic cod

AbstractSpreading the offspring in space and time may offer bet‐hedging benefits by buffering environmental influences on parts of the offspring distribution. It has previously been shown that high mean age and size of spawners in the Northeast Arctic stock of Atlantic cod (Gadus morhua) is positively associated with high abundance and wide spatiotemporal distribution of eggs. However, little support has been found for a wide egg distribution acting as a buffer against environmental influences by leading to higher mean or less variable recruitment. The lacking relation between egg distribution and recruitment can be due to data limitation or alternatively that wide egg distributions may be of limited relevance for survival in later stages. To investigate these two alternatives, we analysed the output from a mechanistic coupled physical–biological drift model that projected the abundance of juvenile cod on the nursing grounds in the Barents Sea from empirically estimated egg distributions. The projections were performed with initial egg distributions reflecting the expected distributions at high and low mean weight of the spawners. We found that the extended distribution at the fringes only marginally contributed to recruitment, as a large proportion of the extra eggs at high mean age and size of spawners did not reach suitable nursing areas or failed to grow to a suitable size by the end of the season. In conclusion, our results suggest that the buffering effect of a geographically wide distribution of spawning products is insignificant compared to other effects on recruitment.

A preliminary assessment of larval fish assemblages on artificial reefs in the nearshore Southern Brazil

Artificial reefs (ARs) have been deployed on the inner shelf of Paraná, Southeast Brazil, as protection against destructive trawling activities, and to offer habitat for local fauna for recovery of biodiversity. The purpose of this study was to develop a preliminary characterization of the ichthyoplankton community associated with both artificial and natural reefs in the Currais Archipelago, and perform a comparison of fish larvae composition between ARs and nearby unconsolidated substrate. Two sampling methods were used, light traps and a plankton net. A total of 12 families and 14 species were identified, expanding the total species list in the area by eight species and three families. Differences among assemblages on ARs and unconsolidated substrate indicate that ARs seem to be effective attractors to fish larvae. Particular attention is drawn in regard to the "attractor effect" for exotic species that do not naturally reside in the area, such as Omobranchus punctatus. The large abundance of fish eggs on ARs suggests that these artificial structures can improve local production. These results are the first step needed to better define guidelines for sustainable use and management of ARs and Currais Archipelago, a Marine National Park.

Spawning strategy of Japanese anchovy Engraulis japonicus in the coastal Yellow Sea: Choice and dynamics

AbstractUnderstanding the relationships between hydrodynamics and the spawning activities of small pelagic fishes is crucial for understanding their recruitment dynamics and for fisheries management. Here, we clarify the effects of marine environmental factors and the associated hydrodynamic processes on the spawning activities of the Japanese anchovy Engraulis japonicus in the coastal Yellow Sea using data from in situ ichthyoplankton surveys (7 recent years), a hydrodynamic model and satellite remote sensing. We confirmed the peak spawning period (May and June) and primary spawning location (Haizhou Bay). We defined the ‘spawning temperature optima’ hypothesis to identify the optimal spawning temperature (13.0–18.0°C) for the Japanese anchovy based on egg occurrence and abundance. We detected fortnightly variation in spawning behaviour, which peaked after the spring tide. Anchovy eggs showed evident aggregation in the nearshore upwelling area during May and June, while strong upwelling in July may cause a negative spawning‐site choice in upwelling zone. These findings clarify the effects of hydrodynamics on the spawning behaviour of the Japanese anchovy in the coastal Yellow Sea.

The importance of making testable predictions: A cautionary tale.

We found a startling correlation (Pearson ρ > 0.97) between a single event in daily sea surface temperatures each spring, and peak fish egg abundance measurements the following summer, in 7 years of approximately weekly fish egg abundance data collected at Scripps Pier in La Jolla California. Even more surprising was that this event-based result persisted despite the large and variable number of fish species involved (up to 46), and the large and variable time interval between trigger and response (up to ~3 months). To mitigate potential over-fitting, we made an out-of-sample prediction beyond the publication process for the peak summer egg abundance observed at Scripps Pier in 2020 (available on bioRxiv). During peer-review, the prediction failed, and while it would be tempting to explain this away as a result of the record-breaking toxic algal bloom that occurred during the spring (9x higher concentration of dinoflagellates than ever previously recorded), a re-examination of our methodology revealed a potential source of over-fitting that had not been evaluated for robustness. This cautionary tale highlights the importance of testable true out-of-sample predictions of future values that cannot (even accidentally) be used in model fitting, and that can therefore catch model assumptions that may otherwise escape notice. We believe that this example can benefit the current push towards ecology as a predictive science and support the notion that predictions should live and die in the public domain, along with the models that made them.

Relationship between environmental variables and egg abundance of the four major Chinese carps, downstream of the Three Gorges Reservoir

AbstractReservoir “eco‐operation” is an ecological flow regulation measure, such as mimicking a flood process to stimulate fish spawning. Since 2011, the Three Gorges Reservoir (TGR) eco‐operation trials have been carried out to facilitate the spawning of the four major Chinese carps (FMCC) below the Gezhouba Dam. Until now, the response of FMCC spawning to new hydrologic conditions is seldom documented. Using ecological monitoring data from 2012 to 2017, this study analyses annual variations in environmental factors and FMCC spawning, and the correlations between them. During the date of FMCC egg occurrence, there was no significant difference both in annual mean water temperature (TEM) and water transparency (TRA) among years, while there was significant difference in annual mean river flow. The annual egg abundance of FMCC ranged from 135 to 610 million, with an average of 286 million. The peak spawning of FMCC occurred 3 to 5 times annually, while the scattered spawning occurred about 2 to 3 times. Classification and Regression Trees and Random Forests were used to model the daily egg abundance of FMCC. Daily flow (FLO) and flow increase multiple (FIM) were determined as the most important factors for FMCC spawning. The models predicted daily egg abundance of FMCC in the Shashi section could reach to 3.16 × 107 ind. for FLO exceeding 10,000 m3/s and FIM below 49.12. The results might be helpful to deeply understand the role of flood peak process on fish spawning and the optimization of TGR eco‐operation on FMCC spawning.

Seasonal and spatial variation in abundance of the copepod Calanus sinicus: Effects of decreasing dissolved oxygen and small jellyfish bloom in northern Yellow Sea, China, nearshore waters

A hypoxia event occurred in the nearshore of the northern Yellow Sea in summer 2016, and a bloom of small jellyfish occurred in June of this year. As a key copepod species in the Yellow Sea, Calanus sinicus exhibits early recruitment mainly in this nearshore area. Therefore, this study assessed the effects of these two phenomena on C. sinicus especially on their early recruitment. Sampling in nearshore waters was performed every month from May to December, except for October 2016. The numerical abundance of eggs and nauplii (E + N), copepodites and adults (C + A) of C. sinicus was determined in relation to environmental factors. Results showed that dissolved oxygen (DO) concentrations decreased from June on, attaining a minimum in August, and showed a significant positive relationship with C. sinicus E + N abundance. This suggested that decreasing DO had potential negative effects on early recruitment of C. sinicus. The abundance of small jellyfish, dominated by Sugiura chengshanense (Hydromedusa), also showed a significant positive relationship with C. sinicus E + N abundance, indicating a potential predator-prey relationship between them. Spatial relationships were also examined between E + N abundance and DO concentration in July and with small jellyfish abundance in June. Both bottom DO (B-DO) and E + N abundance in inshore waters were significantly lower than those in offshore water in July, indicating a potential negative effect of low B-DO (<6 mg L−1) in nearshore water. Spatial variation of small jellyfish abundance showed no correlation with C. sinicus abundance in June, but the non-overlapping patchy distribution also suggested their potential predator-prey relationship. Together, both the seasonal and spatial results indicated that low DO and a small jellyfish bloom in nearshore waters had detrimental effects on early recruitment of C. sinicus. These negative effects thus have the potential to indirectly impact the trophodynamics of fishery resources in the northern Yellow Sea.

Cladocera resting egg banks in temporary and permanent wetlands

Cladocerans are important filter-feeders transferring energy up the food web to different invertebrate and vertebrate predators. Along the flood period, cladocerans are one of the primary food sources for juvenile fish in floodplain. Resting egg banks allow cladoceran populations to overcome the environmental stress, related to several limnological changes, including complete drying of temporary wetlands. After drought, resting egg banks influence cladoceran community attributes during the cyclic and successional processes driven by episodic flood events. In this study we compared the taxonomic richness of active (from the water column) and dormant (from the sediment) Cladocera assemblages and analyzed the structure of resting egg banks, comparing the diversity, abundance and apparent viability/unviability of the eggs, between six temporary and six permanent wetlands, located along the Ovens River Floodplain, Victoria, Australia. The qualitative analysis shows higher taxonomic richness in active assemblages from temporary (24 taxa) than permanent (13 taxa) wetlands compared to dormant assemblages present in resting egg banks (9 taxa) from temporary and permanent wetlands. However, richness was influenced by taxonomic level of identification, with the majority of resting eggs only being identified to the taxonomic level of family (i.e. Chydoridae). Total taxa richness within egg banks was similar between wetland types, however, on average higher Shannon’s diversity of resting eggs was found within permanent (1.53) than temporary (0.82) wetlands. This is likely to be due to more stable wetlands not providing appropriate cues to trigger dormancy induction or breakage for specific populations, leading to higher values of evenness in permanent than temporary wetlands. Comparing permanent and temporary wetlands, higher abundance of resting eggs (more than four times) consisting of higher abundance of unviable eggs and similar viable egg abundance to permanent wetlands, was found within temporary wetlands, suggesting that the increased resting egg abundance in temporary wetlands is balanced by the losses due to factors such as predation, parasitism or other physical damage, during the terrestrial phase. Despite resistant outer shell structure, this study highlights that the damage to egg integrity is intensified in wetlands that undergo dry phases. Cladoceran resting egg banks represent the potential assemblage to recover after disturbance events such as drying, and information about these is important to ensure appropriate management and conservation of floodplain biodiversity.

Effects of Water Filtration and Temperature on Microbial Colonization and Survival of Lake Sturgeon Eggs

AbstractPhysical and biotic factors that affect development and survival during the embryonic period of fish are major concerns in aquaculture, particularly when individuals are produced using natural surface water sources. We quantified the effects of bacterial community taxonomic composition and abundance, water filtration treatment, and incubation temperature on the development and survival of embryos from Lake Sturgeon Acipenser fulvescens, a threatened Great Lakes fish species. Eggs were fertilized and incubated using a two‐by‐two treatment design by manipulating water treatments (treated [filtered and UV treated] and untreated stream water) and temperature (12°C and 18°C) during incubation. Egg samples from five full‐sibling families were exposed to each rearing treatment. At different stages during development, eggs were analyzed for egg surface microbial community composition and abundance using terminal restriction fragment length polymorphism methods based on the 16S rRNA gene and quantitative PCR, respectively. Sanger sequencing identified egg‐associated microbial taxa. Microbial community composition derived from terminal restriction fragment length polymorphism was visualized using principal component analysis. Permutational multivariate analysis of variance revealed that the composition of microbial communities that developed on egg surfaces varied as a function of water filtration and temperature. Quantitative PCR analysis revealed that significantly higher microbial abundance was present on surfaces of eggs reared in untreated stream water than on those reared in treated stream water. Temperature did not affect egg surface microbial abundance. Significantly higher egg mortality was documented for eggs reared in unfiltered stream water (mean ± SD = 77.4 ± 17.6%) than for eggs reared in treated stream water (50.3 ± 14.7%). Temperature during incubation did not affect levels of egg mortality. Sequence analysis revealed that certain microbial taxa were associated with eggs characterized by higher survival, including Acidovorax spp. and Massilia spp., suggesting that they may be candidates for natural probiotics. Filtration and UV treatment of surface water was an effective method for modification of egg microbial community composition and quantity and significantly reduced egg mortality.

Aedes albopictus (Diptera: Culicidae) Monitoring in the Lazio Region (Central Italy).

The Asian tiger mosquito Aedes albopictus (Skuse 1894) is assuming an ever-increasing importance as invasive species in Europe and consequently as human health and nuisance concern. In Central Italy, the species has been recently involved in a chikungunya outbreak. A 3 yr Ae. albopictus monitoring was carried out in 21 municipalities of the Lazio region (Central Italy), belonging to three provinces. Samplings were performed on a weekly basis using ovitraps, in order to investigate climatic and spatial variables driving egg abundance and Ae. albopictus period of activity. A temperature of 10.4°C was indicated as lower threshold for the onset of egg-laying activity, together with a photoperiod of 13:11 (L:D) h. The whole oviposition activity lasted 8 mo (May–December), with 95% of eggs laid between early June and mid-November and a peak at the end of August. Egg abundance was positively influenced by accumulated temperature (AT) of the 4 wk preceding sampling and negatively by precipitation during the week before. Egg-laying activity dropped with decreasing AT, increasing rainfall, and with a photoperiod below 10:14 (L:D) h. Our results pinpointed the importance of fine-scaled spatial features on egg abundance. Some of these fine-scaled characteristics have been highlighted, such as the presence of vegetation and human footprint index. Our model estimated an almost doubled maximum number of laid eggs for the maximum value of human footprint. Compelling evidence of the relevance of fine-scaled characteristics was reported, describing cases where human-made breeding sites driven the abundance of Ae. albopictus.

Seasonal, interannual and spatial variability in the reproductive dynamics of Penaeus merguiensis

Penaeid prawns (shrimp) are short-lived and fecund, with a complicated life cycle that includes offshore spawning followed by a coastal or estuarine postlarval and juvenile phase. Factors affecting survival during the early life-history stages, and during movement between these stages, will affect variability in recruitment to the nursery ground, the offshore subadult and adult population, and, ultimately, catch. The inability to predict recruitment, and ultimately commercial offshore catch, has been complicated by an incomplete understanding of these factors. The reproductive dynamics of Penaeus (Fenneropenaeus) merguiensis were investigated by simultaneous adult and larval sampling on 66 lunar-monthly surveys from March 1986 to March 1992 in Albatross Bay, northeastern Gulf of Carpentaria, Australia. Egg production was seasonal, with the highest production from 6-mo-old newly recruited spawners, and another peak from 12mo-old spawners. Larval abundance (no. m-2) followed the same seasonal pattern as the abundance of eggs. However, interannual variation in egg and larval abundance was large, and there was a weak correlation between monthly egg and larval abundance. Larval abundance appeared to be further influenced by fluctuations in chlorophyll a concentration, a measure of food availability. There was evidence of a match/mismatch relationship between larval abundance and episodic chlorophyll increases. While there was no direct spawner (egg production)-fishery recruit relationship in P. merguiensis over the 6-yr study, there was a strong relationship between total larval abundance in spring and the size of the commercial catch 3 to 6 mo later. Therefore, factors affecting larval survival, including food availability, have significant implications for fishery production.

In-furrow fluopyram nematicide efficacy for Rotylenchulus reniformis management in cotton production

In-furrow nematicide application is a primary method for managing Rotylenchulus reniformis (Linford and Oliveira, 1940) in cotton (Gossypium hirsutum L.). Fluopyram is a relatively new non-fumigant nematicide and field data is needed to determine its efficacy at managing R. reniformis (reniform nematode, RN) in cotton production. To investigate, two experiments, consisting of multiple small plot field trials per experiment, were conducted in Quincy, FL. The first experiment evaluated optimal fluopyram application rate by comparing 0, 105, 131, 158, 184, and 236 g a.i./ha. The second experiment compared aldicarb, a common non-fumigant nematicide in cotton, with two fluopyram formulations, one at 184 g a.i./ha and another at 199 g a.i./ha. In the first experiment, fluopyram reduced RN abundances in 2 of 3 trials, and 236 g fluopyram/ha provided the most consistent management of RN soil populations, while 158 and 184 g fluopyram/ha were effective in one trial each. At 131 g a.i./ha or above, any fluopyram rate tested improved cotton yield compared with untreated in one trial, but did not affect yield in any other trial. In the second experiment, aldicarb reduced RN egg abundances in roots compared with untreated or fluopyram treatments. None of the nematicides affected yield in the second experiment. In summary, fluopyram was inconsistent for managing RN on cotton.