Large Larvae Research Articles

Effects of dietary succinic acid supplementation on growth performance, digestive ability, intestinal development and immunity of large yellow croaker (Larimichthys crocea) larvae

The application of artificial micro-diet is an effective way to improve and standardize the quality of aquatic animal larvae. However, the widespread adoption of micro-diet faces a bottleneck due to the limited utilization capacity of the larvae. A 30-day feeding experiment was carried out to investigate the effect of dietary succinic acid (SA) on the growth performance, digestive ability, intestinal development, and immunity of large yellow croaker larvae (initial body weight 11.33 ± 0.57 mg). Four isonitrogenous and isolipidic diets were formulated, incorporating 0.00%, 0.01%, 0.02% and 0.03% SA separately. The results showed that a diet with 0.02% SA significantly increased both the final body weight and the specific growth rate of the larvae. Regarding digestive ability, 0.01% SA supplementation significantly enhanced trypsin activity in both intestinal and pancreatic segments. In addition, 0.01% SA supplementation notably improved amylase activity in the intestinal segment, while diets with 0.01%-0.02% SA significantly improved lipase activity in the pancreatic segment. In terms of intestinal development, 0.01% SA supplementation remarkably boosted the activities of alkaline-phosphatase and leucine-aminopeptidase on brush border membrane in intestine. Furthermore, 0.03% SA supplementation significantly increased the expression of occludin. In terms of immunity, larvae fed diets with 0.01%-0.02% SA exhibited significantly higher lysozyme activity compared to the control group. Supplementation with 0.01% SA also significantly increased both iNOS activity and NO content. In summary, the findings of this study suggested that adding 0.02% SA can improve the growth performance of large yellow croaker larvae by improving digestive enzymes activities, promoting intestinal development, and enhancing nonspecific immunity.

Age and calorific restriction impact immature black soldier fly (Diptera: Stratiomyidae) thermal tolerance and preference

Abstract Thermal tolerance and preference are traits commonly considered when mass-producing farmed animals as temperature impacts production. In this study, the impact of age and calorific restriction of immature black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae) on associated thermal tolerance and preference was examined. Both age (7-d-old for young larvae and 14-d-old for old larvae) and calorific restriction (led to size differentiation, small for calorific restriction and large for non-restriction) within a given stage influenced thermal tolerance (i.e. KR50) and thermal preference. Results indicate the interaction between age and calorific restriction was significant on both larval and prepupal thermal tolerance but not thermal preference. Median heat tolerance KR50 ranged from 46.4 °C (large, old prepupae) to 48.4 °C (large, young larvae). Median cold tolerance KR50 ranged from 21.6 °C (small, young larvae) to 32.1 °C (small, old larvae). Young larvae preferred median temperatures ∼3.0 °C greater than old larvae. Large larvae preferred median temperatures ∼2.0 °C lower than small larvae. Results from this study indicate ontogeny (i.e. stage of development) and calorific restriction have significant impacts on black soldier fly thermal tolerance and preference. Precise regulation of temperature in an industrial setting is necessary for optimal batch production of the black soldier fly (e.g. survival) and for colony maintenance (e.g. prepupae producing adults and potentially eggs). The same can be said with regards to maintaining consistent age and calorific restriction of immatures produced within each batch as variation in such traits impacts thermal tolerance and preference (e.g. survival to harvest for producing protein or adults for colony) as well. The methods and temperatures used in this study could serve as a foundation for developing standard operating procedures for regulating temperatures experienced by black soldier fly larvae industrially produced.

Life-stage specificity and temporal variations in transcriptomes and DNA methylomes of the reef coral Pocillopora damicornis in response to thermal acclimation

Understanding the acclimation capacity of reef corals across generations to thermal stress and its underlying molecular underpinnings could provide insights into their resilience and adaptive responses to future climate change. Here, we acclimated adult brooding coral Pocillopora damicornis to high temperature (32 °C vs. 29 °C) for three weeks and analyzed the changes in phenotypes, transcriptomes and DNA methylomes of adult corals and their brooded larvae. Results showed that although adult corals did not show noticeable bleaching after thermal exposure, they released fewer but larger larvae. Interestingly, larval cohorts from two consecutive lunar days exhibited contrasting physiological resistance to thermal stress, as evidenced by the divergent responses of area-normalized symbiont densities and photochemical efficiency to thermal stress. RNA-seq and whole-genome bisulfite sequencing revealed that adult and larval corals mounted distinct transcriptional and DNA methylation changes in response to thermal stress. Remarkably, larval transcriptomes and DNA methylomes also varied greatly among lunar days and thermal treatments, aligning well with their physiological metrics. Overall, our study shows that changes in transcriptomes and DNA methylomes in response to thermal acclimation can be highly life stage-specific. More importantly, thermally-acclimated adult corals could produce larval offspring with temporally contrasting photochemical performance and thermal resilience, and such variations in larval phenotypes are associated with differential transcriptomes and DNA methylomes, and are likely to increase the likelihood of reproductive success and plasticity of larval propagules under thermal stress.

Does Size Matter? Small and Large Larvae of Pikeperch (Sander lucioperca) in a Comparative Gene Expression Analysis

Size differences are common in the aquaculture of fishes. In the larviculture of cannibalistic species such as pikeperch, they majorly influence mortality rates and consequently provoke losses in the aquaculture industry. With this study, we aim to reveal molecular differences between small and large pikeperch of the same age using a set of 20 genes associated with essential developmental processes. Hereby, we applied a general study design to early and late larval pikeperch before the onset of piscivory to explore the causes of growth differences in these developmental groups. The analysis of the expression levels showed developmental but not size-related differences in PGC1A, TGFB1, MYOD1, MRF4, and the collagens COL1A1 and COL1A2. Furthermore, increased head lengths were found in larger late larvae compared to their smaller conspecifics. While no uniquely size-related expression differences were found, the expression patterns of PGC1A in combination with TGFB1 as regulators of the citric acid cycle indicate a possible influence of mitochondrial energy metabolism. Furthermore, expression differences of MYOD1 and MRF4 point out possible temporal advantages of myogenetic processes in the larger late larval group and hypothesise growth advantages of the larger late larvae resulting from various influences, which provide a promising target for future research.

Novel hatching cue in the neotropical damselfly Megaloprepus caerulatus: larval adaptation and maternal constraint

The evolution of sibling cannibalism as a maternal strategy is particularly challenging to explain when nurseries are shared among multiple females. Such is the case for the damselfly, Megaloprepus caerulatus, whose females lay eggs in bark above the water line in large, water-filled tree holes. Asynchronous egg hatching appears to be a maternal bet-hedging strategy to increase the chances that cannibalistic offspring hatch during windows of opportunity, which occur after the remaining large larvae emerge, having eaten all others. We investigated the proximate causes of asynchronous hatching. By monitoring the pattern of egg hatching under ambient temperature in an insectary, we found that egg hatching co-occurred with lower ambient temperatures, which decreased with increasing rainfall. Treating fully developed eggs to a lower temperature for two hours triggered increased hatching relative to controls at ambient temperature. Dissection of control clutches indicated that embryonic development of siblings was asynchronous. Results suggested that the hatching trigger is adaptive. Rainfall assures a recharge of the larval habitat with water and provides wet conditions essential for neonate mobility on bark. Only 40% of neonates in a 4-day drying treatment survived; none survived the 8- and 14-day treatments. This novel hatching trigger should increase the number of neonates entering the nursery after rains, constraining a mother’s control over the timing of egg hatch, while increasing the competition among related and unrelated offspring for limited windows of opportunity in the shared nursery.

Development and Seasonal Variations of the Larvae of Three Mesopelagic Fishes near Coral Reefs in the Red Sea

This work aims to describe the larval stages and the seasonal variation in the abundance of three mesopelagic species whose larvae are surprisingly abundant near coral reef areas in the Red Sea. The larvae were collected monthly using a plankton net (500 µ) from three coastal coral reef areas surrounding Sharm El-Sheikh on the Egyptian Red Sea coast between January and December 2015. The identification of larvae was based on the morphological and meristic characteristics according to the available literature. The larvae of this species were divided into preflexion, flexion, and postflexion stages and they were also categorized according to their size into relevant size classes. Mesopelagic fishes were represented in the collection by four species belonging to four families: Vinciguerria mabahiss (Family: Phosichthyidae), Benthosema pterotum (Family: Myctophidae), Astronesthes martensii (Family: Stomiidae; subfamily: Astronesthinae), and Trichiurus sp. (Family: Trichiuridae). In general, a total of 3678 larvae were collected, of which 1191, constituting about 32% of the total fish larvae, belonged to mesopelagic species. The most abundant species was V. mabahiss, with 677 larvae that constituted 18% and 57% of the total larvae and mesopelagic fish larvae, respectively. The second most abundant species was B. pterotum, which was represented by 485 larvae (13% of the total larvae and 40% of the mesopelagic fish larvae). A. martensii was represented by the lowest number of larvae (29 larvae, 2%). Most larvae of the three species were small and in the preflexion stage, whereas larger larvae are absent. They are highly abundant in the cooler months of the year between November and April. The high number of preflexion larvae may indicate that the three mesopelagic species spawn in the colder times of the year.

The effect of ocean acidification on otolith morphology in larvae of a tropical, epipelagic fish species, yellowfin tuna (Thunnus albacares)

Increasing ocean acidification is a concern due to its potential effects on the growth, development, and survival of early life stages of tuna in oceanic habitats and on the spatial extent of their suitable nursery habitat. To investigate the potential effects of increasing CO2 on otolith calcification of 9-day old pre-flexion stage yellowfin tuna (Thunnus albacares), an experiment was conducted at the Inter-American Tropical Tuna Commission's Achotines Laboratory in Panama during 2011. Fertilized eggs and larvae were exposed to mean pCO2 levels that ranged from present day (355 μatm) to two levels predicted to occur in some areas of the Pacific in the near future (2013 and 3321 μatm), and to an extreme value equivalent to long-term projections for 300 years in the future (9624 μatm). The results indicated significantly larger otoliths (in area and perimeter) with significant, and increasing, fluctuating asymmetry at acidification levels similar to those projected for the near future and long-term. Otoliths increased significantly in size despite a significant decrease in somatic length with increasing pCO2. A consistent correlation between otolith and somatic growth of yellowfin tuna larvae among treatments was evident (i.e., larger otoliths were still associated with larger larvae within a treatment). The observed changes in otolith morphology with increasing ocean acidification have the potential to indirectly affect larval survival through dysfunction of the mechanosensory organs, but this remains to be verified in yellowfin tuna larvae.

Body-weight gains in Blaberus craniifer cockroaches and the intensity of their infection with gregarines and nematodes

Intestinal parasites are considered to be able to hinder growth of the host animals, reducing the extent of food metabolism, damaging the intestines’ integrity by filling it with products of their metabolism. However, a long co-evolution can mitigate the negative impact of a parasite on the host organism. To study how parasites – nematodes Cranifera cranifera (Chitwood, 1932) Kloss, 1960 (Oxyurida, Thelastomatidae) and gregarines Protomagalhaensia granulosae Peregrine, 1970 and Blabericola cubensis (Peregrine, 1970) Clopton, 2009 (Eugregarinorida, Blabericolidae) – afffect the growth rates of cockroaches, we performed an experiment on 200 larvae of Blaberus craniifer Burmeister, 1838 (Blattodea, Blaberidae), varying in weight and age. We monitored changes in their body weight, intensity of food consumption, and after the experiment we counted gregarines in the midgut and nematodes in the hindgut. As a result, we found that 100% of the cockroaches were infected with two species of gregarines and one species of nematodes. The intestines of small cockroach larvae (weighing 300–400 mg) contained 16–18 specimens of gregarines on average. Large larvae had a weak tendency towards increase in the intensity of gregarine infestation. Similarly, there occurred changes in the intensity of nematode invasion: young larvae were infected on average by 8–10 specimens of nematodes and large larvae had an average of 12–14 nematodes. At the level of tendency, nematodes were observed to enhance the cockroaches’ growth rates following increase in intensity of the parasitic infection. We found that the two groups of parasites had no effect on one another: the number of gregarines had no effect on the number of specimens of nematodes and vice-versa, the number of nematodes had no effect on the number of gregarine specimens. Perhaps, this is related to different localizations of the parasites: gregarines for most of their life feed in the small intestine, while nematodes feed in the large intestine. Therefore, growth rates of the cockroaches in our experiment have not changed due to the parasites. This indicates minimization of negative effects of gregarines in the midgut and nematodes in the hindgut on the host’s life cycle, developed over long co-evolution.

Vacuum extraction: an effective larval sampling method for spotted-wing drosophila in small fruit crops.

Detecting and sampling the pest for pest management, either through enumerating their life stages or by quantifying the crop damage, is the cornerstone in deploying integrated pest management. Currently, for spotted-wing drosophila, Drosophila suzukii Matsumura, larval extraction from the fruit samples involves immersing the fruits in hot water, salt, or sugar solution. We are introducing a novel, fast, and effective larval sampling technique where D. suzukii larvae can be extracted from infested fruits by subjecting the fruit samples to vacuum pressure. We optimized the vacuum pressure and vacuum duration for larval extraction from blueberries by testing a range of vacuum pressures and durations. A vacuum pressure of -98 kPa for 60 min resulted in the maximum larval recovery of the small, medium, and large larvae from blueberries. A 30-min incubation at -98 kPa also yielded similar results. Larval extraction at -98 kPa for 60 min on average recovered 61, 70, and 83% of larvae from 2, 4, and 6-day incubated fruit samples, respectively. The fruit sample size (37, 149, and 298 g) did not affect the larval extraction efficacy. Additionally, comparing larval extraction efficacy at -98 kPa with the salt and sugar extraction, incubated for 10, 30, and 60 min, suggests that vacuum extraction is comparable to or more efficient than the salt and sugar methods in extracting larvae from the infested blueberries. Overall, our results indicate that vacuum sampling is a promising method for detecting D. suzukii larval infestation in small fruit crops.

Invasive parasites and global change: Evidence for the recent and rapid spillover of a potential pathogen of tilapias with a complex, three-host life cycle

Biological invasions pose a serious threat to local flora and fauna and have negative impacts on ecosystems. Invasive parasites can also cause severe losses in aquaculture. In this article, we provide evidence of the recent spillover of an African parasite with a complex, three-host life cycle that has rapidly and successfully established itself in the Middle East, most likely due to the recent migration of its final hosts (great cormorant) from Africa. This case of parasite introduction into a country with intensive aquaculture is also important from an economic point of view, since large (up to 2 cm long) larvae of this parasite, the cyclophyllidean tapeworm Amirthalingamia macracantha (Cestoda) localised in the liver, can be pathogenic to their fish hosts, including farmed and wild fish, as shown by our histopathological examination of heavily infected fish. Since its first detection in Israel in November 2020, the parasite has spread rapidly and is currently found in both migratory (great cormorant, Phalacrocorax carbo) and non-migratory birds (pygmy cormorant, Microcarbo pygmaeus), as well as in fish intermediate hosts, including farmed tilapia in several farms in Israel and wild cichlids. There are numerous examples of the spillover of introduced parasites, including those that parasitise fish of commercial importance, but have a direct life cycle or use only a single intermediate host. Tilapines are the second most important group of farmed fish in the world after carps and are produced mainly in Southeast Asia, Central and South America. The global spread of great cormorants and the early evidence that pygmy cormorant may also harbour A. macracantha pose the risk of further spread of this invasive parasite to other countries and areas. In addition, global warming and reductions in foraging and resting areas near these waters may allow the parasite to complete its life cycle in new hosts.

Profitability of cotton, Gossypium hirsutum (L.), when controlling bollworm, Helicoverpa zea (Boddie), with variable treatment thresholds

Crops expressing Bacillus thuringiensis proteins have offered valuable crop protection benefits including reduced foliar insecticide use and crop yield protection. Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) has developed resistance to one or more Bt proteins, which consequently threatens these benefits. This has resulted in a renewed emphasis on the implementation of action thresholds for H. zea management decisions in cotton. Field experiments were conducted in College Station, TX; Stoneville, MS; and Blackville, SC, during 2020–2021 to evaluate current H. zea threshold recommendations for Texas, Mississippi, and South Carolina. Three Bt cotton technologies and five thresholds were evaluated. The Bt cotton technologies evaluated included non-Bt (NBT), Bollgard® 2 (BG2; Cry1Ac + Cry2Ab), and Bollgard® 3 (BG3; Cry1Ac + Cry2Ab + Vip3Aa). Across years and locations, within NBT cotton, all thresholds, including 20% oviposition, 6% fruiting forms injury, ≥3% large larvae, and preventive sprays, resulted in greater control of H. zea and higher yield and profitability relative to non-treated NBT cotton. The threshold using 6% injury to squares and bolls was the most effective in terms of yield relative to the preventive spray. Across years and locations, the BG2 cotton sprayed based on 20% oviposition or preventively resulted in greater control of H. zea, and all treatments resulted in a yield or profitability equivalent to that of the non-treated BG2 cotton. For BG3 cotton, spraying based on any of the thresholds was not beneficial. For NBT and BG2 cotton, thresholds of 20% oviposition, 6% injury to fruiting forms, or ≥3% large larvae provided a reduction in insecticide applications relative to the preventive spray treatment, suggesting that these thresholds were effective triggers for controlling H. zea.

An Optimized Small-Scale Rearing System to Support Embryonic Microinjection Protocols for Western Corn Rootworm, Diabrotica virgifera virgifera.

Western corn rootworm (WCR), a major pest of corn, has been reared in laboratories since the 1960s. While established rearing methods are appropriate for maintaining WCR colonies, they are not optimal for performing germline transformation or CRISPR/Cas9-based genome editing. Here we report the development of an optimized rearing system for use in WCR functional genomics research, specifically the development of a system that facilitates the collection of preblastoderm embryos for microinjection as well as gathering large larvae and pupae for downstream phenotypic screening. Further, transgenic-based experiments require stable and well-defined survival rates and the ability to manipulate insects at every life stage. In our system, the WCR life cycle (egg to adult) takes approximately 42 days, with most individuals eclosing between 41 and 45 days post oviposition. Over the course of one year, our overall survival rate was 67%. We used this data to establish a quality control system for more accurately monitoring colony health. Herein, we also offer detailed descriptions for setting up single-pair crosses and conducting phenotypic screens to identify transgenic progeny. This study provides a model for the development of new rearing systems and the establishment of highly controlled processes for specialized purposes.

Quantification of lipid droplets in hatchery reared veliger larvae of the green-lipped mussel, Perna canaliculus

Domestication efforts and selective breeding in bivalve aquaculture would greatly benefit from reliable screening biomarkers in the early life stages of development (e.g., larvae). In this study the lipids remaining at the completion of embryo development in selectively-bred/hatchery reared green-lipped mussel, Perna canaliculus, were targeted and quantified using two approaches: confocal laser scanning microscopy and image analysis (CLSM/IA) on Oil Red-O stained larva (i.e., lipid droplet number and volume distribution), and Iatroscan thin layer chromatography/flame ionization detection (TLC/FID) (i.e., energetic and structural lipid classes content). Four groups of newly formed pre-feeding veliger larvae, produced from two genetically distinct families (FA, FB) that completed embryo development at either low (L, 17 °C) or high (H, 21 °C) temperatures, were evaluated. The FB produced offspring better equipped to deal with higher temperatures during embryonic development, with greater survival, higher normal development, and larger larvae than FA when developing at 21 °C. In terms of lipids content, CLSM/IA showed that each individual larva had overall between 83 and 157 lipid droplets (ranging in volume from 2.5 to 294 μm3). The TLC/FID estimation of mean total lipid content ranged from 4.1 to 6.9 ƞg larva−1 (29–39% structural lipid and 62–69% energetic lipid). Both lipid quantification methods were successful in detecting differences among larval groups with different genetic backgrounds, as well as providing insight into the ability to cope with changes in the growing environment when relying on maternal energy sources (triacylglycerol-TAG identified as the main source of energy for early development). Stronger differences between the two families were identified using CLSM/IA than with TLC/FID (i.e., with FA having overall more and larger lipid droplets). However, TLC/FID was able to distinguish FA larvae reared at high temperatures from the other groups (due to lower levels of TAG, 46% of total lipids, versus 52–56% in the other groups), therefore being more sensitive to the pooled population response compared to the individual lipid droplet quantification in CLSM/IA. The application of these tools, when fully developed, could be extended to controlled commercial operations to diagnose and predict larval performance, enabling more directed early screening and informing production and breeding decisions.

DEVELOPMENT OF METHODS OF BREEDING WORK WITH INSECTS OF THE SPECIES HERMETIA ILLUCENS

Background. The insect Hermetia illucens (black soldier fly), is widely used for the disposal of food and agricultural waste. This is due to the omnivorous nature of the fly in relation to protein and carbohydrate foods and a fast reproductive cycle. The big problem of industrial cultivation of this insect is the degeneration of populations of the black soldier fly. When bred in captivity, due to the relatively small number of population, the degradation of key parameters, such as viability, fertility, productivity, etc. of H. illucens culture occurs. It is noted that during the first five generations, despite polygamy during crossing, the effect of harmful recessive alleles in a homozygous state manifests itself. Currently, the problem of degeneration of flies associated with inbred depression is solved by mass cultivation of large outbred populations in cages, with periodic reintroduction of producers from natural populations.
 Purpose. Development of a method for crossing lines of Hermetia illucens flies for breeding, determining patterns of population development, as well as increasing their productivity and adaptive potential.
 Materials and Methods. In selection work with the lines of the insect species H. illucens, individual crossing was used. Individual selections were made by selecting larvae and pupae by size and body weight. The crosses were carried out according to the scheme: one male and one female were placed in plastic containers while maintaining the required temperature and humidity. Eggs obtained from this pair of flies were placed on a nutrient substrate in a separate container, hatched larvae were cultured in isolation in the same container. During the growth process, the largest larvae and pupae from this population were selected. After the formation of adult individuals (images) of flies, they were examined, their sex was determined and again one male and one female were placed in a separate container. Thus, inbred lines of isofemale (descendants of one female) flies were obtained.
 Results. We developed the method of individual crossing made it possible to trace the development of populations of flies obtained from one female and one male, to consider the patterns and changes in the population. The tendency of the degeneration of the fly population in inbred crosses was determined, in each subsequent generation there were fewer fertilized eggs and larvae. This is due to the fact that recessive lethal genes become homozygous and manifest their effect. Subsequent selections in each generation of the largest and most active larvae will create a population devoid of most lethal and harmful genes.
 Conclusions. As a result of the research work carried out, it was possible to develop a method of individual crossing of males and females of the insect Hermetia illucens. It was determined that the time from oviposition onset to the maximum number of larvae occurs on 3-4th day after egg laying. With the crossing of close relatives, the tendency of the degeneration of the fly population was determined, in each subsequent generation there were fewer fertilized eggs and larvae. This is due to the manifestation of recessive lethals. Subsequent selections in each generation of the largest and most active larvae will create a population devoid of most lethal and harmful genes. Populations of inbred flies have stable characteristics for this species and, despite a decrease in the number of fertilized eggs in clutches, as well as a smaller number of larvae obtained from them, they have normal distribution of size and body weight, which allows selection for economically valuable traits.

Host Specificity in Canopy Nesting Forms of Ochrogaster lunifer: The Larger Children Do Not Care

The 'mother knows best' hypothesis is tested in a species of processionary moth feeding on acacias and eucalypts in Australia. The processionary moth Ochrogaster lunifer (Lepidoptera: Notodontidae; Thaumetopoeinae) is a social caterpillar living in large colonies on a number of tree and shrub species. Five nesting types-canopy, trunk, tree-hugger, hanging, and ground-have been described, and this study deals with canopy nesters on various species of acacias (Acacia spp.) and eucalypts (Eucalyptus spp. and Corymbia spp.). Reciprocal transplant experiments conducted over three years confirm the 'mother knows best' hypothesis, as colonies performed better on the natal host plant than on the recipient ones. Young first instar larvae were less likely to establish on a non-natal host than the mature larvae, and all acacia-sourced canopy egg masses failed to establish on eucalypts. Large larvae were able to establish on transplant hosts. This suggests a strong preference-performance link at what is likely a species level, confirming preliminary results recently published on genetic divergence. Canopy nesting forms also have a lower realised fecundity than the ground nesting form on acacias from the same geographic area, but higher than another canopy nesting form from western Australia. Further observations on ecological and genetic traits are required to draw conclusions about the separation of lineages in the canopy nesting form of O. lunifer, by including populations from other parts of the range for both the herbivore and the host plants.

Efficacy and sorption of sulfur dioxide as a fumigant for control of navel orangeworm (Amyelois transitella) on stored pistachios

Sulfur dioxide (SO2) fumigation was evaluated for postharvest control of navel orangeworm (NOW), Amyelois transitella, on stored pistachios in a laboratory study. Sorption of SO2 on pistachios were measured at 5, 15, and 25 °C. Because of rapid sorption of SO2 on pistachios after SO2 injection, 3 h short fumigations were used to determine effective treatments against NOW eggs, larvae, and pupae. SO2 fumigation was effective against all of the life stages tested. However, large larvae in infested pistachios were most tolerant and eggs were most susceptible to SO2 fumigation. Smaller larvae were more susceptible to SO2 fumigation than larger larvae. Complete controls of eggs, larvae, and pupae were achieved in 3 h fumigations with 0.2, 2.0, and 1.0% SO2, respectively. Large SO2 fumigation trials each with 4.5 kg pistachios were conducted in a 19.8L chamber and complete control of 6th instar larvae were achieved in 3 h fumigation with about 1.6–1.8% SO2 at ambient temperatures of 18–21 °C. The results showed that SO2 fumigation has potential to control NOW on stored pistachios as well as to control other postharvest pests on stored products.

Effects of supplemental fulvic acid on survival, growth performance, digestive ability and immunity of large yellow croaker (Larimichthys crocea) larvae.

A 30-day feeding trial was designed to evaluate the effect of supplemental fulvic acid (FA) on survival, growth performance, digestive ability and immunity of large yellow croaker (Larimichthys crocea) larvae (initial body weight 11.33 ± 0.57mg). Four isonitrogenous and isolipids diets containing 0.00%, 0.01%, 0.02% and 0.04% FA were formulated, respectively. Results showed that the supplementation of 0.04% FA significantly improved survival rate of large yellow croaker larvae. Meanwhile, supplemental FA significantly increased final body weight and specific growth rate. Based on the specific growth rate, the optimal supplementation was 0.0135% FA. Larvae fed the diet with 0.01% FA had significantly higher villus height than the control. The supplementation of 0.01%-0.02% FA significantly increased the muscular thickness of intestine. Moreover, supplementation of FA significantly increased mRNA expression of intestinal epithelial proliferation and barrier genes (pcna, zo-1 and zo-2). Diets supplemented with 0.02%-0.04% FA significantly increased the activity of trypsin in the intestinal segment, while 0.01%-0.02% FA significantly increased the activity of trypsin in the pancreatic segment. Compared with the control, supplementation of FA remarkably increased activities of alkaline phosphatase and leucine aminopeptidase in the brush border membrane of intestine. Larvae fed the diet with 0.01% FA significantly increased activities of lysozyme and total nitric oxide synthase. Furthermore, the supplementation of 0.01% to 0.02% FA significantly decreased the mRNA expression of pro-inflammatory cytokines (tnf-α and il-6). Concurrently, supplemental FA significantly increased anti-inflammatory cytokine (il-10) mRNA expression level. In conclusion, this study indicated that the supplementation of FA could improve the survival rate and growth performance of larvae by promoting intestinal development, digestive enzymes activities and innate immunity.

Effects of Intraspecific Competition and Larval Size on Bioconversion of Apple Pomace Inoculated with Black Soldier Fly

Waste from apple juice and cider industries (pomace) compares poorly against spent grains and other relatively high-nutrient wastes as a substrate for bioconversion by the black soldier fly (BSF: Hermetia illucens). However, global pomace production exceeds 24 million tonnes annually and novel management approaches are required to reduce waste to landfill. We examined the effects of BSF inoculation densities (intraspecific competition) and larval size categories on cohort weight gains and apple pomace waste reduction. We found that, by increasing larval densities, cohort biomass and bioconversion rates (BRs) increased; however, at very high densities (overcrowding), BRs declined and cohorts lost weight. Furthermore, larger larval size classes accelerated substrate desiccation, possibly because of greater demands for water by older larvae. Larger larvae have slower relative growth rates and BRs compared to smaller size categories and require comparatively less dry weight substrate. Our results suggest that overcrowding on low-nutrient substrates reduces BRs and could exaggerate differences between BSF relative performances in comparative studies, particularly if intraspecific interference competition for space and exploitation competition for water diminish BSF weight returns at the end of the bioconversion cycle. We make a series of recommendations for the use of BSF in pomace waste reduction.

Comparative demography, population projection, functional response and host age preference behavior of the parasitoid Goniozus legneri on two lepidopterous insect hosts

BackgroundThis study was conducted to investigate life table characteristics of the parasitoid species, Goniozus legneri Gordh (Hymenoptera: Bethylidae), a major gregarious larval ecto-parasitoids of the carob moth, Ectomyelois ceratoniae Zeller (Lep.: Pyralidae). Demographic parameters of G. legneri reared on two hosts, the carob moth and the flour moth, Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae), were studied under laboratory conditions using age-stage, two-sex life table. Host stage preference and the functional response of this parasitoid were also determined.ResultsThe duration of the immature period, adult pre-ovipositional period and total pre-ovipositional period of G. legneri reared on E. kuehniella was significantly longer than that of those reared on E. ceratoniae, while fecundity and ovipositional days of the wasp were greater/longer in females reared on E. ceratoniae. There were also significant differences in intrinsic and finite rates of increase and mean generation time between wasp parasitoid reared on two hosts. Moreover, population projection indicated that the G. legneri population can grow swifter when reared on E. ceratoniae than on E. kuehniella. Based on the experiments conducted to determine the larval stage preferences of G. legneri, for both hosts, larger larvae were more preferred stages compared to smaller ones, thereby fulfilling the optimal oviposition theory. The functional responses of G. legneri to different population densities of E. kuehniella two last instar larvae were determined as type III at 25 °C and 60% RH.ConclusionThe results offer valuable information on some life history attributes of G. legneri. Although G. legneri performed better on E. ceratoniae larvae than on E. kuehniella, as the use of E. ceratoniae larvae as the main host in rearing of G. legneri might be a laborious process and can increase the production costs, E. kuehniella can be used as an alternative host. Further studies are required under greenhouse and field conditions for effective use of this biocontrol agent against the carob moth.

Testing Barley Samples for Potential Insect Infestations with a Conductance Mill

Highlights The conductance mill successfully detected seeds infested with large larvae, over 80% in barley and wheat. Barley seeds, infested with medium larvae, were detected at a lower rate than wheat; ~40% for barley vs. ~65% for wheat. The feed-rate of barley samples was slower than the wheat and the resulting ground barley material contained higher fractions of large particles, over #20 mesh sieve. Abstract. A laboratory mill was developed by Pearson and Brabec (2007) which typically detects 50% to 80% of infested kernels of wheat, brown rice, or popcorn. Barley is another cereal grain of similar size as wheat. Barley is normally sold with its hull attached to the seed, which makes detection of insect infestations more difficult. The objective of this study was to determine the potential of using the conductance mill to detect barley kernels infested by the lesser grain borer, Rhyzopertha dominica (F.), in comparison to detection in wheat. As in previous studies, these experiments found that the conductance mill could detect infested kernels of wheat containing large and medium larvae at a rate of ~90% and ~65%, respectively. For barley, the detection of infested kernels was over ~80% for large larvae and ~40% for medium larvae. Also, we showed that adults that were freely moving throughout the grain mass could also be detected. Approximately ~65% of the adults were detected in wheat while that percentage was reduced to ~35% in barley. The hull on the barley seems to function as an insulator during the conductance measurement and thus reduces detections. Also, the hull seems to affect the feed rate of material through the mill. The feed-rate for wheat was 500 g in 50 s, while the feed-rate for barley was 500 g in ~80 s. Despite these pitfalls, the conductance mill could still be considered as a useful tool with inspecting barley sample, because there was significant detection of insects in the samples and 1000 g sample of barley could be processed in ~4 min. Keywords: Barley, Detection, Rhyzopertha dominica, Sampling, Wheat, X-ray.