Egg Density Research Articles

Risk factors for Ascaris lumbricoides infection and its association with nutritional status and IQ in 14-Year old adolescents in Chitwan, Nepal

Inconsistent results have been obtained from studies investigating the association between soil-transmitted helminths (STHs) and nutritional status and cognitive outcomes. This study aimed to investigate the influence of STHs and nutritional status on the intelligence quotient (IQ) of adolescents in the Chitwan Valley, Nepal. In this birth cohort study from the Chitwan district of Nepal, 74 cohort participants were followed up after 14 years. The presence and egg density of the STHs were investigated following the Kato–Katz method. Full-scale IQ was evaluated using the Wechsler Abbreviated Scale of Intelligence-II (WASI-II). Multivariate regression analysis was also conducted to examine the associations of STHs and nutritional status with IQ scores, adjusting for adverse childhood experiences (ACE) and demographic and socioeconomic factors. The only STHs detected was for Ascaris lumbricoides, which was detected in 16% (12/74) of the study participants. Similarly, 16% (12/73) of participants reported undernutrition (body mass index (BMI) Z score<-2SD), and 33% (25/74) of participants had a developmental deficit (WASI II FSIQ < 69). There were no significant associations between the presence of A. lumbricoides or egg density and IQ scores. However, undernutrition (BMIZ<-2SD) increased the odds of a developmental deficit according to both univariate and adjusted multivariate models [i.e., adjusted odds ratio (aOR) 9.41; 95% CI (2.23 to 39.80)]. While the study primarily examines the association of STHs and nutritional status with IQ, it is important to note that adolescents with educated mothers or higher incomes also showed better cognitive development. The prevalence of undernutrition and associated developmental deficits characterized by an IQ < 69 was alarmingly high in this cohort of adolescents from Chitwan, Nepal. Despite the high prevalence of A. lumbricoides, its infection was not identified as significantly associated with cognition. However, it is noteworthy that a consistent favorable impact of an enriching postnatal environment, approximated by maternal education and family income, may improve neurodevelopmental indicators.

Assessing potential for biological control of Japanese giant silkworm Caligula japonica using Anastatus gansuensis, a thelytokous parasitoid firstly reported in Eupelmidae.

Caligula japonica, commonly known as Japanese giant silkworm (JGS), is a serious defoliating pest of fruit and forest trees in East Asia. To develop eco-friendly and cost-effective control methods for this pest, we evaluated the potential for biological control of JGS using its egg parasitoid Anastatus gansuensis reared on the Chinese oak silkworm (COS) Antheraea pernyi. We compared the reproductive traits and population increase potential of the parasitoid on JGS and COS eggs, as well as its functional response to host egg densities and mutual interference at different parasitoid densities. Anastatus gansuensis was confirmed to be strictly synovigenic, with most eggs maturing post-emergence, and produced <1% male offspring on both host eggs. Although A. gansuensis females reared from COS eggs had longer longevity and oviposition period, and higher fecundity and net reproductive rate compared to those reared from JGS eggs, the parasitoid had a higher intrinsic rate of increase on JGS than COS eggs. The parasitoid exhibited a type II functional response to increasing host densities, with mutual interference among foraging female wasps occurred at higher parasitoid densities. Our results indicate a high potential for biological control of JGS using A. gansuensis. The parasitoid can be efficiently reared on COS eggs and used against JGS. It may be essential to provide food for emerging adult parasitoids allowing time for egg maturation prior to the rearing or augmentative release of the parasitoid. Some mutual interference at high parasitoid rearing densities likely reduces per capita parasitization efficiency of A. gansuensis. © 2024 Society of Chemical Industry.

Insight into the Gut-Brain Axis and the Productive Performance and Egg Quality Response to Kudzu Leaf Flavonoid Supplementation in Late-Laying Hens.

(1) Background: Improving feed efficiency and the vitality of the reproductive system in the late stage of the egg-laying period is of great significance for prolonging the egg-laying cycle and improving egg quality. In the present study, a new flavonoid, which was extracted from kudzu leaf, was chosen to investigate its effects on the productive performance and egg quality of late-laying hens. (2) Methods: A total of 360 500-day-old Hy-Line Brown layer hens were randomly divided into a control treatment group (no KLF supplementation), and groups that received 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% KLF supplement treatments. Each treatment contained 6 replicates, with 10 hens in each replicate. Productive performance metrics, including the daily egg production, egg weight, the number of deformed eggs, egg quality, egg density, egg shape index, eggshell strength, yolk color, and the Haugh unit, were meticulously recorded for each replicate. Furthermore, microbial communities and hypothalamus gene expressions were investigated based on the results of the productive performance and egg quality. (3) Results: KLF supplementation significantly decreased the deformity rate while significantly increasing the eggshell strength in the finishing phase afterward (p < 0.05). Specifically, hens supplemented with 0.6% KLF possessed the lowest deformed egg rate. KLF supplementation significantly increased the relative abundances of Bifidobacterium sp., Blautia sp., Lactococcus sp., and Lactobacillus sp., while significantly decreasing Parasutterella sp. and Escherichia-Shigella sp. (p < 0.05). Furthermore, the interactive analysis showed the hypothalamus gene expression mainly interacted with probiotics, such as Bifidobacterium sp. and Lactobacillus sp., through ribosome biogenesis, nucleocytoplasmic transport, and cAMP signaling pathways. (4) Conclusions: The findings of the present study indicate that KLF supplementation significantly proliferated probiotics, such as Bifidobacterium and Lactobacillus, which may have further interacted with hypothalamus genes, thus decreasing the deformity rate while increasing eggshell strength in the finishing phase.

Buoyancy and vertical distribution of haddock (Melanogrammus aeglefinus) eggs during embryonic development: A comparison with cod (Gadus morhua)

AbstractVertical egg distributions are needed knowledge for understanding exposure to physical forcing, predation pressure, and modelling initial transport from the spawning areas. Egg density and size are the biotic factors determining vertical distributions while the ambient salinity and turbulent mixing are the physical factors contributing to their vertical distributions. Egg buoyancies and densities of Atlantic cod (Gadus morhua) have been extensively studied, while limited information on haddock (Melanogrammus aeglefinus) egg density is available. This is the first comprehensive study on haddock egg densities in Norwegian waters. Eggs were collected from pairs of spawning fish caught at the coast of western Norway and inserted into a density gradient column where density was measured. The haddock eggs were neutrally buoyant at salinities ranging from 28.5 to 31. The density changed during egg development, and the results from the measurements were used to model the vertical distribution of the eggs. The simulations showed that the changes in buoyancy substantially affected vertical distributions. A comparison to previously published data on cod eggs showed that haddock eggs are considerably more buoyant than the cod eggs and are—particularly during calm wind conditions—confined to the surface layer to a larger extent than the cod eggs. The more buoyant attribute of the haddock eggs, together with the lipophilic surface of the egg membrane, is suggested to make haddock eggs more vulnerable to buoyant pollutants, like hydrocarbons.

Black soldier fly (Diptera: Stratiomyidae) larvae reduce cyathostomin (Nematoda: Strongylidae) eggs but develop poorly on horse manure.

Cyathostomins are common digestive tract parasites of grazing horses that spread through contact with horse feces. Horse feces are colonized by a variety of organisms, some of which could serve to reduce parasite loads in horse pastures. Black soldier fly (Hermetia illucens L.; Diptera: Stratiomyidae) larvae (BSFL) could be an ideal candidate for biological control of cyathostomins, due to their near-global distribution, low risk of pathogen transmission, ability to develop on a variety of nutrient-poor substrates (including horse manure), and dramatic effect on microbial communities that cyathostomins depend on. Here, using controlled feeding bioassays, we evaluated the effect of BSFL on cyathostomin egg densities in horse manure while also tracking BSFL performance on manure relative to standard grain-based diets. We found that BSFL consumed less substrate, were slower to reach the prepupal stage, and ultimately yielded less biomass when reared on horse manure compared to grain-based diets. However, BSFL reduced average cyathostomin egg densities in horse manure by over 3-fold. Overall, our results suggest that despite horse manure being a poor substrate for BSFL growth, BSFL effectively reduce cyathostomin egg loads in infected horse manure, though the mechanisms by which they do this are uncertain. While BSFL are known to transform the microbial communities within a diversity of rearing substrates, their effect on larger, parasitic organisms in animal manures may be underappreciated. Promoting the decomposition of infected horse manure with BSFL might be a promising approach to managing parasite populations among grazing horses.

Optimizing and synchronizing Aedes aegypti colony for Sterile Insect Technique application: Egg hatching, larval development, and adult emergence rate

Mosquito Sterile Insect Technique (SIT) programs can be developed in smaller agencies through synchronization of the colony development to take advantage of the natural male early emergence. This paper examined key aspects of Ae. aegypti colony synchronization work, including egg hatching, larval development, and adult emergence to produce sufficient numbers of adult male mosquitoes within a specific timeframe for irradiation and release. Our data indicated that a relatively low percentage of males are required for colony propagation. Additional results highlighted that fresher Ae. aegypti eggs could yield as high as a 93 % hatching success than older eggs when placed under vacuum pressure in yeast infused water for 1.5 h. Eggs that were one-month old hatched (93 %) better than older eggs (0–32 %). A higher egg density in the hatching flask was correlated to a lower hatch rate, and higher larval density was related to unsynchronized pupae and delayed adult emergence. By keeping Ae. aegypti larvae at reasonable density, over 95 % of adults emerged on the first two days of emergence – indicating a high synchronicity. A standardized colony maintenance protocol therefore renders a synchronized larval development and adult male emergence which are critical in SIT programs.

Role of Non-Residential Larval Habitats in Aedes Spatiotemporal Egg Production.

Aedes mosquitoes play a pivotal role as vectors of several arboviral diseases, presenting significant public health challenges worldwide. Their invasive success in tropical regions has raised substantial medical concerns. In Guatemala, Aedes mosquitoes are widely distributed and are the primary vectors of the dengue virus. Efforts to control and monitor Aedes populations have evolved over time, incorporating strategies such as spatial repellents, larvicides, genetic modifications, and targeted interventions. Previous research has shown the heterogeneous spatial-temporal distribution of these mosquitoes within each season, influenced by temperature variations and favorable environmental conditions for breeding. This study analyzed hot-spot patterns of spatiotemporal egg density in Santa Elena de la Cruz, Petén, Guatemala, from March to September 2022. The aim was to determine whether these patterns were influenced by non-residential larval habitats with plant cover that are not treated by healthcare entities, as well as the proximity between such habitats. Our findings include the collection and registration of over 16,000 Aedes eggs during the study period. Local analyses revealed hot-spot patterns in egg densities associated with non-residential larval habitats and their proximity. These insights highlight critical focal points where targeted interventions could be implemented more effectively, resulting in cost-efficient mosquito vector control.

Ichthyoplankton dynamics in the Brazilian Pantanal: Contribution of an important tributary and maintenance of connectivity

AbstractIn order to investigate the reproductive dynamics of the ichthyofauna in the Brazilian Pantanal, this study examines the spatial and temporal distribution of ichthyoplankton, taxonomic composition, and its correlation with environmental factors within one of the most important sub‐basins, the Taquari River. Egg and larvae collections were conducted at 11 sampling points between October and March of 2017/2018 and 2018/2019. Significant differences were observed between collection points, months, and years, with higher ichthyoplankton densities in the Coxim and Taquari rivers, particularly between November and January. Twenty‐eight genera and/or species of fish were identified, including 10 long‐distance migratory species. Egg density showed a negative correlation with water temperature and rainfall. For larvae, water transparency and rainfall were both significant, negatively influencing larval abundance. However, different species tend to occur in environments with distinct abiotic qualities. Yolk‐sac, preflexion, and flexion larval development stages were distributed throughout the sub‐basin, especially near the Pantanal. Considering the data and analyses presented in this study, the importance of connectivity between these environments, specifically between the plateau and Pantanal, is evident, highlighting the significance of the entire sub‐basin for fish reproductive processes. Therefore, research focusing on the ecological processes influencing the distribution of ichthyoplankton offers valuable insights for ecosystem conservation and aids in effective environmental management.

Redundancy in microbiota-mediated suppression of the soybean cyst nematode

BackgroundSoybean cyst nematodes (SCN) as animal parasites of plants are not usually interested in killing the host but are rather focused on completing their life cycle to increase population, resulting in substantial yield losses. Remarkably, some agricultural soils after long-term crop monoculture show a significant decline in SCN densities and suppress disease in a sustainable and viable manner. However, relatively little is known about the microbes and mechanisms operating against SCN in such disease-suppressive soils.ResultsGreenhouse experiments showed that suppressive soils (S) collected from two provinces of China and transplantation soils (CS, created by mixing 10% S with 90% conducive soils) suppressed SCN. However, SCN suppressiveness was partially lost or completely abolished when S soils were treated with heat (80 °C) and formalin. Bacterial community analysis revealed that the specific suppression in S and CS was mainly associated with the bacterial phylum Bacteroidetes, specifically due to the enrichment of Chitinophaga spp. and Dyadobacter sp., in the cysts. SCN cysts colonized by Chitinophaga spp. showed dramatically reduced egg hatching, with unrecognizable internal body organization of juveniles inside the eggshell due to chitinase activity. Whereas, Dyadobacter sp. cells attached to the surface coat of J2s increased soybean resistance against SCN by triggering the expression of defence-associated genes. The disease-suppressive potential of these bacteria was validated by inoculating them into conducive soil. The Dyadobacter strain alone or in combination with Chitinophaga strains significantly decreased egg densities after one growing cycle of soybeans. In contrast, Chitinophaga strains alone required more than one growing cycle to significantly reduce SCN egg hatching and population density.ConclusionThis study revealed how soybean monoculture for decades induced microbiota homeostasis, leading to the formation of SCN-suppressive soil. The high relative abundance of antagonistic bacteria in the cyst suppressed the SCN population both directly and indirectly. Because uncontrolled proliferation will likely lead to quick demise due to host population collapse, obligate parasites like SCN may have evolved to modulate virulence/proliferation to balance these conflicting needs.BVs6NXuQzznnTv7j41Q5n6Video

New perspective on the role of Doru luteipes as a predator of the fall armyworm: Non‐consumptive effects, predatory preference and functional response

AbstractIn Brazil, the common earwig Doru luteipes (Scudder) (Dermaptera: Forficulidae) is considered an important biocontrol agent for the maize crop, consuming the fall armyworm Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae) eggs and caterpillars from 1st to the 3rd instar. Despite this, several aspects of the interaction between these species have not yet been studied. We aim to evaluate the non‐consumptive effects of earwigs on the oviposition of moths, the earwig's predatory preference between eggs and neonates and its functional response to S. frugiperda eggs. In no‐choice tests between plants with or without the presence of the predator, S. frugiperda moths deposited a smaller number of eggs on plants with risk of predation. In choice‐based tests, earwigs initially attacked newborn caterpillars, but preferred to feed on eggs. Males and females fed more on eggs with increasing supply density and consumption was adjusted to the type II functional response curve. D. luteipes males were more efficient predators than females when exposed to higher egg densities. These findings clarify aspects of the predatory role of D. luteipes on S. frugiperda that had not yet been addressed and suggest that the earwig has potential for impacting the colonization and population growth of S. frugiperda in maize crops, if conditions are favourable to its early arrival.

A comparative approach for life history and functional response demonstrates similar survival strategies for Trichogramma evanescens and T. pintoi.

Egg parasitoids are important biological control agents of lepidopteran pests of agricultural crops. Trichogramma evanescens Westwood and T. pintoi Voegele (Hymenoptera: Trichogrammatidae) are egg parasitoids with worldwide importance. The parasitoid selection necessitates comparative assessment of the life table traits and functional response analysis to provide insights into their effectiveness in pest control. In this study, we examined theirlife table traits including survivorship and reproductivity, and functional response and associated parameters i.e., attack coefficient and handling time. Life table parameters, using age-stage, two-sex theory, revealed similar survival and reproductive strategies for both species. For example, the female longevity, oviposition days and fecundity did not differ between both species. Exceptionally, the male longevity of T. evanescens was shorter than that of T. pintoi. The population growth parameters such as gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) did not differ between species. The polynomial logistic regression yielded a type III functional response and a non-linear least square analysis revealed different attack coefficient and similar handling time. However, their parasitism rate differed between the lowest (five eggs) and highest (80 eggs) initial host egg densities such that T. evanescens had a lower parasitism rate at the lowest density and higher parasitism rate at the highest density. The similarity in survival strategies and minor differences in host handling of both parasitoids are discussed in terms of relevance to applied biological control applications and evolutionary traits. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Host plants and landscape predict use of roadside habitat by breeding monarchs

Abstract Vegetation along roadside edges, while posing some risks, can also provide breeding habitat for monarch butterflies. We investigated how landscape and site‐specific factors affect the quality of roadsides as monarch breeding habitat. We surveyed more than 250 sites along roadsides throughout Minnesota for milkweeds, floral resources and monarch eggs and larvae. We found that milkweed distribution was affected by adjacent land use and geography, with milkweeds more likely to be present in roadsides adjacent to crop and grassland and the south and west of the state. The presence and density of monarch eggs and larvae were primarily driven by milkweed density, with the likelihood of monarch presence at each site increasing with milkweed density. The density of monarchs per plant increased in sites with lower densities of milkweed, suggesting that monarch eggs are concentrated more densely on fewer plants where milkweed is scarce and spread more thinly across plants where milkweed is common. Monarch density per milkweed increased as sites were farther from core grasslands, to the south, and on narrower roadsides, also suggesting use may be higher in areas with a scarcity of habitat. The density of monarch eggs and larvae was higher in mowed than unmowed milkweed. Our study suggests that roadside habitats effectively provide breeding locations for monarchs, regardless of adjacent land use type and even when distant to high‐quality natural areas. Our findings assist conservation practitioners in planning and managing roadside habitats for monarchs and other pollinators.

Presence of Arboviral Vector in Tourist Attractions and Public Places: Abundance, Associated Factors and Susceptibility to Temephos.

&lt;b&gt;Background and Objective:&lt;/b&gt; &lt;i&gt;Aedes&lt;/i&gt; mosquito is a competent vector of arboviruses, mainly dengue, chikungunya, Zika and yellow fever. The high incidence of arboviral infections among travelers indicated the vulnerability of tourist attractions and public places visitors to arboviral infections. This study aimed to determine the presence and population density of &lt;i&gt;Aedes&lt;/i&gt; mosquitoes at the places, as well as the susceptibility to temephos larvicide. &lt;b&gt;Materials and Methods:&lt;/b&gt; A total of 17 tourist attractions and public places in four districts/cities of Central Java Province were selected as study sites and 25-40 ovitraps were installed in each location for three days. The coordinates, altitude, vegetation density, shade, wind speed, air temperature and humidity were recorded. Ovistrips and water of each ovitrap were observed in the laboratory to determine the ovitrap index (OI) and egg density index (EDI), mosquito species and their susceptibility to temephos. &lt;b&gt;Results:&lt;/b&gt; A total of 12,231 eggs were obtained with a range, OI and EDI of 0-1,024, 42% and 31.93 eggs/trap, respectively. Vegetation density, shade and wind speed were significantly associated with the presence of &lt;i&gt;Aedes &lt;/i&gt;eggs in the ovitraps (p<0.05), while altitude, temperature and air humidity were correlated with the average of &lt;i&gt;Aedes&lt;/i&gt; eggs per ovitrap. &lt;b&gt;Conclusion:&lt;/b&gt; Although &lt;i&gt;Aedes&lt;/i&gt; larvae in all study sites were susceptible to temephos 0.02 mg/L the results indicated the vulnerability of visitors to &lt;i&gt;Aedes&lt;/i&gt;-borne diseases. Further investigation of arbovirus infections in &lt;i&gt;Aedes&lt;/i&gt; mosquitoes at tourist attractions and public places is necessary conducted to evaluate the potential and risk of pathogen transmission to visitors.

Influence of egg density on larval development and adult body size of cat fleas (Ctenocephalides felis).

Fleas (Siphonaptera) are holometabolous insects with larval and adult stages that exhibit vastly different ecologies from each other. Adult fleas are parasitic and feed exclusively on the blood of a vertebrate host, whereas flea larvae do not live on hosts and consume dried faecal blood from adult fleas. Because flea larvae rely on adult flea faeces for food, excrement and eggs must fall in the same location; thus, larval density is likely high in these restricted habitats. However, the influence of larval density on the subsequent adult stage has not been examined. In the present study, we utilized egg density to investigate density-dependent effects on larval development and adult body size in the cat flea (Ctenocephalides felis Bouché) (Siphonaptera: Pulicidae). Specifically, eggs were collected to create three different larval densities (n = 50, 100 and 150 per 56.7 cm2), and hatched larvae from all groups were fed an excess amount of adult faecal pellets. Larval development was measured by recording the proportion of eggs that developed to the pupal stage and the proportion of eggs that reached adulthood (eclosion). The body size of eclosed adults was quantified for both sexes using head length and length of the total body. We found that the number of eggs had no effect on the proportion of larvae that pupated or the proportion of larvae that eclosed; however, higher egg densities resulted in larger body sizes for both sexes. Overall, these data yield significant insight into how the ecology of larval fleas impacts the biology of the resultant adults.

Assessment of spawning habitat suitability for Amphidromous Ayu (Plecoglossus altivelis) in tidal Asahi River sections in Japan: Implications for conservation and restoration

AbstractThe Amphidromous Ayu (Plecoglossus altivelis), vital for Japan's riverine commercial fisheries, is experiencing population decline due to habitat degradation. In response, Japan is implementing restoration efforts by releasing juvenile fish and cultivating spawning habitats. This study, focusing on the Asahi River's Heidan area, evaluates Ayu spawning habitat suitability, especially in tidal zones, and its conservation implications. Through field surveys and numerical analysis, the research identifies optimal conditions for spawning amid dwindling numbers. Observations from the 2020 peak spawning season showed that water temperatures below 20°C are conducive to spawning, with the best sites producing up to 48,817 eggs/m2. Gravel sizes between 0.85 and 53.0 mm were identified as crucial for effective spawning. Notably, artificial spawning grounds established in 2019 showed no spawning activity, likely due to saline intrusion from tides. Using the three‐dimensional hydrodynamic‐aquatic ecosystem numerical model, the study assesses flow, substrate, and water quality's impact on spawning, corroborated by sensor data. A key finding is the negative correlation between salinity and egg density in tidal sections of the Asahi River. Furthermore, an artificial intelligence (AI)‐based YOLOv5 model, trained on underwater images, effectively detected Ayu aggregations, demonstrating an F1‐score of 0.757 in differentiating Ayu from other coexisting fish species in the same aquatic environment. This AI approach provides a nonintrusive method for monitoring Ayu populations and habitat preferences. The research underlines that successful spawning habitats require minimal saline intrusion, with optimal salinity and flow conditions. These insights are critical for spawning ground development, emphasizing the management of tidal effects and riverbed conditions to bolster Ayu populations and preserve aquatic ecosystems.

Larval density-dependent mortality of western corn rootworm (Coleoptera: Chrysomelidae) in Bt and non-Bt maize and implications on dose calculations†.

Transgenic crops producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) have been used to manage insect pests for nearly 30 years. Dose of a Bt crop is key to assessing the risk of resistance evolution because it affects the heritability of resistance traits. Western corn rootworm (Diabrotica virgifera virgifera, LeConte), a major pest of maize, has evolved resistance to all commercially available Bt traits targeting it, and threatens resistance to future transgenic traits. Past research shows the dose of Bt maize targeting western corn rootworm can be confounded by larval density-dependent mortality. We conducted a 2-year field study at two locations to quantify larval density-dependent mortality in Bt and non-Bt maize. We used these results to calculate dose for our method and compared it to three previously published methods. Additionally, adult emergence and root injury were analyzed for predicting initial egg density. Increased pest density caused greater proportions of larvae to die in Bt maize than in non-Bt maize. All methods for calculating dose produced values less than high-dose, and stochastic variation had the greatest impact on dose at high and low pest densities. Our method for calculating dose did not produce values positively correlated with pest density while the three other methods did. To achieve the most accurate calculation of dose for transgenic maize targeting western corn rootworm, density-dependent mortality should be taken into account for both transgenic and non-transgenic maize and assessed at moderate pest densities. © 2024 Society of Chemical Industry.

The American horseshoe crab (Limulus polyphemus) spawns regularly in salt marshes

While considered ecological generalists in most aspects of their life history, horseshoe crabs (Limulus polyphemus) have traditionally been regarded as reproductive habitat specialists, given that spawning is thought to occur primarily on beaches where conditions for embryonic development are considered optimal. Observations of horseshoe crabs spawning in other habitats were deemed isolated and the behavior non‐adaptive. Here, we used spawning and egg surveys to compare the use of beach and salt marsh habitats for spawning by the horseshoe crab in three US states along the Atlantic coast. We found similar spawning and egg densities in both habitats but were more likely to find eggs in marsh habitats, indicating that spawning in marsh habitats is common and geographically widespread. These results suggest that the conservation of salt marshes may be critical for the protection of this species and that management strategies should be revised to incorporate this generalist behavior.

Supplemental phosphorus can be completely replaced with microbial phytase in White Leghorn layer diets

ABSTRACT 1. A study was conducted to assess the possibility of totally replacing supplemental phosphorus sources in White Leghorn (WL) layer diets (aged 28 to 45 weeks of age) with microbial phytase supplementation. One thousand commercial layers (HyLine White) of 28 weeks of age were housed in California cages fitted in open-sided poultry shed at the rate of 20 layers in each replicate. Ten replicates were randomly allotted to each treatment, and the respective diet was fed from 28 to 45 weeks of age. 2. A control diet (CD) containing the recommended levels of non-phytate phosphorus (3.6 g/kg NPP) and four other test diets (2–5) having sub-optimal levels of NPP (2.4, 2.0, 1.6 and 1.2 g/kg), but with supplemental microbial phytase (600 FTU/kg) were prepared and fed for the trial duration. 3. The layers fed with lower levels of NPP with phytase had the same laying performance as the group fed the CD. Egg production, feed efficiency, egg mass, shell defects, egg density, shell weight, shell thickness, ash content and breaking strength of the tibia and sternum were not affected by feeding the lowest concentration of NPP (1.2 g/kg) plus microbial phytase. 4. Phytase supplementation in diets with sub-optimal levels of NPP (2.4, 2 and 1.6 g/kg) significantly improved the Haugh unit score compared to those fed the CD. 5. It was concluded that supplemental phosphorus can be completely replaced with microbial phytase (600 FTU/kg) in a diet without affecting egg production, shell quality or bone mineral variables in WL layers (28 to 45 weeks).

Predation of Raoiella indica (Acari: Tenuipalpidae) by Stethorus tridens Gordon (Coleoptera: Coccinellidae)

The red palm mite (RPM), Raoiella indica Hirst (Acari: Tenuipalpidae), is an invasive species in several American countries and has a wide range of hosts, causing significant damage, mainly to coconut and banana crops. Previous studies conducted in America have focused on the biological control of RPM through predatory mites and insects. Stethorus tridens Gordon (Coleoptera: Coccinellidae) is considered a promising biocontrol agent of phytophagous mites it has been observed on several cultures, and has a high predatory capacity. The aim of this study was to investigate S. tridens preferences among different developmental stages of RPM and estimating the functional and numerical responses of S. tridens over its most preferred prey-stage. Furthermore, the prey preference of S. tridents was examined between eggs of Tetranychus evansi Baker and Pritchard (its natural prey) and eggs of RPM through two-choice and non-choice experiments. The results showed that S. tridens prey on all developmental stages of RPM, with a marked preference for eggs over other stages of RPM. The functional response of this predator was type III, as consumption increased rapidly at intermediate egg densities. Predation on RPM eggs was unable to stimulate S. tridens reproduction, even at the highest densities. When we compared the food preference of S. tridens to eggs of T. evansi and RPM, we found that the predator preferred tetranychids. The results of this study suggested that RPM can be used as alternative prey to S. tridents, serving as a source of energy and allows for maintenance but not its reproduction.

Seasonal differences in amounts of oviposition habitat and egg‐laying by caddisflies in rivers with regulated versus unregulated flows

Abstract Few studies consider spatio‐temporal variation in egg‐laying for benthic insects in streams. However, such variation can have lasting effects on the numbers and distribution of offspring and subsquent life‐cycle stages. For species that require specific egg‐laying habitats, such as rocks that protrude from the water surface (emergent rocks, ER), densities of egg‐laying habitat can affect densities of benthic eggs and even larvae for some species. For such species, changes in water levels alter the spatio‐temporal distribution of ER and can affect densities of eggs and, potentially, larvae. Below dams, modified flow regimes may alter the temporal availability of ER. In this study we tested whether river regulation altered the availability of oviposition habitat and changed the phenology of oviposition compared to unregulated rivers. At multiple sites in two regulated (Murrumbidgee, Tumut) and three unregulated (Goobarragandra, Goodradigbee, Micalong) rivers (south‐east Australia), we surveyed densities of ER and egg masses of five species of caddisflies (family Hydrobiosidae) seasonally over 3 years (2019–2021). Samples of adults also were collected during two seasons using light traps. High flows in both regulated rivers submerged all rocks during spring and summer and low‐flow releases stranded rocks above the waterline at all (Murrumbidgee River) or most (Tumut River) sites during autumn and winter. No ER or egg masses were observed on any date in the Murrumbidgee River, despite relatively large catches of adults. On the Tumut River, low densities of ER and egg masses were twice observed at one site, during seasons (winter, autumn) when oviposition was low in the unregulated rivers. In unregulated rivers, ER and egg masses (five species, four genera) were present at all sites but with lower densities in winter than in other seasons. During peak oviposition periods, densities of egg masses per site were not strongly related to densities of ER. In summer 2019, ER in two unregulated rivers were blanketed by sheets of algae and sediment that appeared to prevent oviposition because no egg masses were observed at this time. In regulated rivers, aseasonal flows precluded egg‐laying by submerging (summer, autumn) or stranding (winter, spring) all or most ER. In contrast, ER were available all year in the unregulated rivers and egg‐laying occurred all year, except when ER were blanketed by algae and sediment. Within seasons, local densities of egg masses may be limited by numbers of gravid females, rather than numbers of ER, which differs from previous research. Identifying impediments to reproduction is critical to understanding variability in population numbers in natural and altered systems. Our observations of oviposition failure downstream of dams present a new hypothesis for why some insect species are absent from channels where flows are regulated for irrigation. Blankets of algae may similarly preclude reproduction in rivers with low‐flow conditions, but this remains untested.