Larval Production Research Articles

Identification of High‐Occupancy Areas and Movement Dynamics of Age‐0 Lake Sturgeon in the Lower Fox River, Wisconsin

AbstractThe lower Fox River (LFR) is a highly urbanized and fragmented system with a legacy of pollution. Benthic dredging and sediment cleanup combined with capping have been implemented with the goal of remediating the polychlorinated biphenyl contamination and improving the health of resident fish and wildlife populations. The LFR hosts a small population of adult Lake Sturgeon Acipenser fulvescens that spawns at the base of the first barrier, De Pere Dam. Recent research suggests that larval production is limited and no juveniles have been documented residing within the system, although limited sampling has been conducted. The objectives of this study were to describe age‐0 Lake Sturgeon movement patterns, quantify the duration of river residency, and identify areas of congregation in the LFR. To track fish, a total of 38 age‐0 and 1 age‐1 Lake Sturgeon were obtained from nearby wild populations and hatchery settings, implanted with acoustic transmitters, released below De Pere Dam, and actively tracked, daily, for ~40 d (August–October in 2018 and 2019). Sixty‐nine percent of the acoustically tracked age‐0 Lake Sturgeon remained in the LFR for >50% of the study period, and emigration events appear to be related to increases in river discharge. Individuals residing within the LFR tend to congregate within six areas of the LFR encompassing 6% of total river area. The results suggest that suitable habitat exists in the LFR for age‐0 and age‐1 Lake Sturgeon, that discharge may cue downstream movement, and that high‐occupancy areas (likely areas of preferred habitat) are present in the LFR. Long‐term monitoring of larval production, survival, and age‐0/juvenile dynamics will continue to help identify recruitment bottlenecks, improve knowledge of juvenile ecology, and guide future restoration goals.

Distribution and seasonal spread of zooplankton in Iraqi waters

A summary of zooplankton research done in Peruvian marine waters is presented. We first provide a brief overview of the evolution of zooplankton studies off Peru before reviewing zooplankton biodiversity, regional distribution, seasonal and interannual fluctuation, trophodynamics, secondary production, and modeling are some of these topics. We evaluate research on various meroplankton, macroplankton, mesoplankton, and microplankton groups and provide a list of species from both published and unpublished sources. Three regional zooplankton groups have been identified: · A shelf group on the continental shelf dominated by Acartia tonsa and Centropages brachiatus; · A slope group on the continental shelf with siphonophores, bivalves, foraminifera, and radiolaria · An oceanic group with adiversity of species. Where the continental shelves are thin, between 4-6°S and 14-16°S, the largest zooplankton abundances and biomasses were frequently seen. The diversity of species varies according to distance from the shore. As a result of advection, peaks in larval production, trophic interactions, and community succession, species composition and biomass also change significantly over short time intervals. Based on the detrimental consequences of weak summer upwelling intensity or exceptionally high and persistent winter upwelling on zooplankton abundance off Peru, an intermediate upwelling hypothesis is put forth. This concept states that a window of optimal environmental conditions for zooplankton groups is produced by intermediate upwelling. Finally, we identify significant knowledge gaps that demand future attention.

LARVOTHERAPY IN THE TREATMENT OF DIFFICULT-TO-HEAL LESIONS: INTEGRATIVE REVIEW

Objective: To analyze the evidence available in the literature about the use of larvotherapy in the treatment of difficult-to-heal wounds. Method: This is an integrative review, having as a guiding question: what evidence is available in the literature about the use of larvotherapy in the treatment of wounds that are difficult to heal? The inclusion criteria were: original articles, literature review and experience reports, from 2016 to 2021, available online in full, in Portuguese, English and Spanish and that answered the research question. Exclusion criteria were: duplicate articles, letters to the editor, dissertations, theses, monographies and research with animals. Searches took place at Virtual Health Library and United Station National Library of Medicine between August and September 2021. Results: Ten articles were selected. The main advantages were: selective debridement, bactericidal or bacteriostatic action, and promotion of granulation tissue and healing factors. The main disadvantages were: pain, discomfort, prejudice, and weaknesses with the larval production market. Conclusion: The advantages found outweigh the disadvantages evidenced. Therefore, larvotherapy is favorable to treat wounds that are difficult to heal.

Seasonal Occurrence and Relative Abundance of Marine Fish Larval Families over Healthy and Degraded Seagrass Beds in Coastal Kenya

Seagrass beds provide critical nursery habitats and spawning grounds for new generations of fish. The habitats are under threat from human activities and climate change, and with that, an important ocean service is lost that limits fish production. The present study investigates patterns in the larval occurrence and abundance in seagrass meadows at two locations with varying degrees of seagrass fragmentation. Monthly ichthyoplankton sampling was conducted during the northeast monsoon (NEM) and southeast monsoon (SEM) seasons in 2019 and 2020. A total of 42 larval fish families belonging to 37 genera and 21 species were identified. Dominant families were Labridae (29.5%), Blenniidae (28.7%), Gobiidae (26.0%), Engraulidae (23.3%) and Scaridae (22.3%). Canonical Correspondence Analysis and regression analysis revealed water temperature, dissolved oxygen and pH as the most important abiotic variables driving taxonomic composition of larval assemblages, while zooplankton and chlorophyll-a were the most important biotic factors. Fish larvae were more abundant in healthy seagrass habitats as compared to degraded ones. However, despite some loss in functionality, the degraded sites equally played a role in supporting some species, including Gobiidae and Blenniidae. Seasonality influenced larval abundance at the two sites, with a peak in mean abundance coinciding with the NEM season. Interannual variability in fish larval abundance was observed at both sites, indicating that factors controlling larval production varied between the years. This study demonstrates the important role of seagrass meadows in the replenishment of fish stocks and supportive evidence for their management and conservation.

L-carnitine solution used on Rhamdia quelen thawed sperm activation boosts sperm movement, maintains larval quality, and permits to optimize the sperm use

The activation of cryopreserved sperm with solutions containing L-carnitine can improve sperm quality after thawing, owing to its involvement in several metabolic pathways. Sperm movement and viability for fertilization, hatching, and larval normality were assessed in Rhamdia quelen thawed sperm activated with L-carnitine solutions. Sperm from 24 males were cryopreserved in 0.25 mL straws. After thawing, the sperm movement was assessed by CASA (Computer-Assisted Sperm Analysis) in samples activated with distilled water containing 0.0 (control), 47.8, 96.2, 144.5, 192.3, and 240.7 mM L-carnitine, and another one with 79.9 mM D-fructose (control). Sperms from another 24 males were cryopreserved in an identical manner and used in the fertilization assays. Considering the sperm movement, fertilization assays were carried out using 0.0, 96.2, and 144.5 mM L-carnitine, and 79.9 mM D-fructose solutions. Greater motility and velocity were achieved with 144.5 mM L-carnitine at 28 and 18 s after activation, respectively. Linearity was not affected by time. The greater mean motility was provided by 144.5 mM as well as the greater mean velocity and linearity by 192.3 mM L-carnitine. Fertilization and hatching were not influenced; however, 144.5 mM L-carnitine and 79.9 mM D-fructose solutions produced more normal larvae. In summary, the L-carnitine solution increased sperm movement and maintained larval quality and production, similar to a conventional fructose activation solution.

Detoxication and bioconversion of aflatoxin B1 by yellow mealworms (Tenebrio molitor): A sustainable approach for valuable larval protein production from contaminated grain

Yellow mealworm (Tenebrio molitor) is a supplementary protein source for food and feed and represents a promising solution to manage grain contaminated with Aflatoxin B1 (AFB1). In this study, AFB1 present in different concentrations in wheat bran was treated and removed via bioconversion by yellow mealworm of different instars, with emphasis on the bioconversion performance and metabolism of AFB1. Upon application of wheat bran spiked with 100 μg/kg AFB1 to 5th–6th instar yellow mealworms, the conversion rate of AFB1 was up to 87.85 %. Low level of AFB1 (< 2 μg/kg) was accumulated in the larval bodies, and the survival rate, development and nutrition contents of yellow mealworm were not significantly affected. It was revealed that 1 kg of wheat bran contaminated with AFB1 increased the weight of yellow mealworms from 138 g to 469 g, containing approximately 103 g of protein. The bioconversion of AFB1 by yellow mealworms led to generation of 13 metabolites in the frass and 3 metabolites in the larvae. AFB1 was detoxicated and removed via phase I metabolism comprising reduction, dehydrogenation, hydration, demethylation, hydroxylation, decarbonylation and ketoreduction, followed by phase II metabolism involving conjugation of amino acid, glucoside and glutathione (GSH). The toxicity of AFB1 metabolites was deemed lower than that of AFB1 according to their structures. This study provides a sustainable approach and theoretical foundation on using yellow mealworms for cleaner grain contamination management and valuable larval protein production via bioconversion of food and feed contaminated by AFB1.

Survival and Fecundity of Anopheles stephensi and Anopheles albimanus Mosquitoes (Diptera: Culicidae) After Ingesting Bovine Blood Containing Various Veterinary Systemic Parasiticides.

Systemic parasiticides in livestock can control zoophilic malaria vectors that contribute to residual malaria transmission. Membrane feeding techniques were used to screen seven systemic parasiticidic drugs currently in veterinary use for livestock and dogs. Drugs were tested in two laboratory strains of zoophilic Anopheles - A. stephensi (South Asian vector) and A. albimanus (Central American vector). To assess the relative potentials of these drugs, the resultant LC-50 for each drug was compared with what is known about the pharmacokinetic of the drug. Drugs with LC-50 values below the reported maximum plasma concentration of treated animals were considered as showing the most promise for use in the field. Ivermectin and fipronil showed the greatest promise for use in cattle against A. stephensi. Fipronil showed the greatest promise for use in cattle against A. albimanus. Both fluralaner and afoxolaner were highly effective against both mosquito species but pharmacokinetic data for these drugs in cattle are lacking. Eprinomectin, moxidectin and abamectin showed marginal to no promise for either mosquito species. At sublethal doses, ivermectin, fipronil, and afoxolaner (but not fluralaner) significantly reduced the larval production of surviving A. stephensi and A. albimanus. Further testing of candidate systemic parasiticides, including their product formulations, in livestock against field-collected populations of Anopheles is the next logical step toward full implementation of this strategy to manage zoophilic vectors.

Improvement of breeding methods of predatory mites Neoseiulus cucumeris and Transeius montdorensis for biological plant protection

The possibility of breeding of phytoseiid predatory mites Neoseiulus cucumeris and Transeius montdorensis using hardwood sawdust as a substrate and frozen dried fruit mite (Carpoglyphus lactis) as feed was studied. The number of larvae produced by N. cucumeris was 31.5 % lower on frozen feed in sawdust than in the control, while in T. montdorensis it was lower by 47.7 %. The number of individuals surviving to adulthood compared to the control was lower by 28.6 % and 42.9 %, respectively. The maximum daily growth rate of the population was reduced relatively to the control by 3.7 individuals in N. cucumeris, and by 4.5 in T. montdorensis –. On frozen feed in bran, N. cucumeris produced 20.5 % fewer larvae than in the control, T. montdorensis – 35.1 % fewer larvae. The number of individuals surviving to adulthood was reduced by 18.3 % and 35.3 %, respectively, compared to the control. The maximum daily population growth rate was 1.7 individuals lower than in the control in N. cucumeris, and – 3.9 individuals lower in T. montdorensis. On live feed in sawdust, larval production was similar to the control (lower by 1.1 % in N. cucumeris and 14.2 % in T. montdorensis). The number of individuals was reduced relatively to the control by 1.7 % and 14.8 %, respectively. The maximum daily population growth rate in N. cucumeris is slightly lower (by 0.7 individuals) than in the control, and in T. montdorensis it even exceeded the control by 0.6 individuals per day. Our results showed the possibility of using sawdust as a cheaper substrate for breeding of both species of predatory mites and poor performance of the frozen feed compared to the live one.

Feasibility of housefly larvae-mediated vermicomposting for recycling food waste added digestate as additive

The development of methods for the efficient treatment and application of food waste digestate is an important research goal. Vermicomposting via housefly larvae is an efficient way to reduce food waste and achieve its valorization, however, studies on the application and performance of digestate in vermicomposting are rarely. The present study aimed to investigate the feasibility of the co-treatment of food waste and digestate as an additive via larvae. Restaurant food waste (RFW) and household food waste (HFW) were selected to assess the effects of waste type on vermicomposting performance and larval quality. Waste reduction rates of 50.9%–57.8% were observed in the vermicomposting of food waste mixed with digestate at a ratio of 25%, which were slightly lower than those for treatments without the addition of digestate (62.8%–65.9%). The addition of digestate increased the germination index, with a maximum value of 82% in the RFW treatments with 25% digestate, and decreased the respiration activity, with a minimum value of 30 mg-O2/g-TS. The larval productivity of 13.9% in the RFW treatment system with a digestate rate of 25% was lower that without digestate (19.5%). Materials balance shows that larval biomass and metabolic equivalent had decreasing trends as the amount of digestate increased and HFW vermicomposting exhibited lower bioconversion efficiency than that of RFW treatment system regardless of the addition of digestate. These results suggest that mixing digestate at a low ratio (25%) during vermicomposting of food waste especially RFW could lead to considerable larval biomass and generate relatively stable residues.

Sustainable palm weevil farming as nutrition supplementation at maternity waiting homes in Liberia

BackgroundFood insecurity is a global health challenge exacerbated by COVID-19. In Liberia, two-thirds of pregnant women are anemic, one-third of children are stunted, and 70% of households experienced food insecurity due to COVID-19. Edible insects are a nutritious, environmentally responsible, and cost-effective dietary supplement used throughout sub-Saharan Africa. Rearing palm weevil insects at maternity waiting homes (MWHs)—residential dwellings near hospitals where pregnant women await childbirth and receive postpartum services—could serve as a nutritious supplement for expectant mothers in Liberia and provide an income generating activity for MWHs.MethodsFollowing a one-day training, sixteen participants established palm weevil rearing sites at four MWHs in Liberia. Pre- and post-knowledge scores were assessed immediately prior to and following training. Pre-and post-knowledge scores were analyzed using paired t-test. Participants tracked two palm weevil rearing cycles (four months), using harvest amounts, turnover, barriers to implementation, and income generated as metrics. The number of women attending MWHs was recorded throughout the study period (July-December 2020).ResultsSixteen participants from four MWHs completed the training and two rearing cycles (four months) successfully. All participants showed statistically significant increases in knowledge scores following the one-day workshop with a pre-test score of 2.31 and post-test score of 7.75 out of 10 (p < 0.001). Over the 6-month study, 217 women stayed in four MWHs. Larval production from the various rearing centers ranged from 120 to 721 larvae, with all four sites producing enough palm weevil to sustain MWH residents who desired to consume the insects. One site successfully commercialized its harvest to sell approximately 50% for a total of 2,000 LD (13 USD) in income. Three of the four sites continued edible insect production beyond the four-month study period.ConclusionsAn edible insect project using palm weevil larva is one promising intervention as a nutrition supplement for expectant mothers at pre-established MWHs in rural Liberia. Edible insect rearing also has potential as an income generating activity for MWHs. Future studies should focus on addressing common barriers of remote implementation and metric tracking during the COVID-19 pandemic and reinforcing infrastructure to protect larvae rearing supplies.

Poultry red mite (Dermanyssus gallinae) poses a risk in the rearing of black soldier fly (Hermetia illucens)

The larvae ofHermetia illucens L. (Insecta: Diptera: Stratiomyidae), also known as black soldier fly (BSF), has the unique ability to recycle nutrients from organic wastes. The BSF larvae biomass is a cheap and sustainable protein source that can be used in the feeding of fish, chickens, pigs, and pets. The BSF is a non-pest species, but its mass rearing conditions can attract pathogens and parasites due to the high temperature and moisture requirements. The published literature on the BSF cover aspects such as larval production, conversion efficiency during the rearing stage, adult longevity and mating. However, no published data are available on any parasitic or disease outbreaks in BSF colonies. The present paper reports the first case of an ectoparasite in a BSF colony. The poultry red mite (Dermanyssus gallinae) is an invasive predator of the larvae and pre-pupae of BSF, quickly deteriorating the production and health of BSF colony.

Does tank background colour influence the growth, survival, and carotenoid content in fishes? An illustration in filament barb, Dawkinsia filamentosa (Valenciennes, 1844)

The various environmental factors have a significant impact on cultured species. One such factor influencing larval production in finfish hatcheries is the tank colour. The current study appraised at how different background tank colours such as white, red, blue, green, and black influenced the growth, survival, and body pigmentation of filament barb, Dawkinsia filamentosa. The experiment was conducted for 30 days and the fish were fed with powdered diet thrice a day containing 30% crude protein and 4% crude lipid at satiation level. At the end of study, it was found that the final body length in the black colour tank (15.33 ± 0.17 mm) was significantly (p < 0.05) higher compared to other tank colour groups. In comparison to other treatments, the final body weight (65.17 ± 1.48 mg) and average daily weight gain (1.56 ± 0.05 mg day−1) in the black colour tank was found to be significantly (p < 0.05) higher, while the white colour tank (35.83 ± 1.64 mg; 0.59 ± 0.06 mg day−1) were significantly (p < 0.05) lower. The fish reared in the black colour tank had significantly (p < 0.05) higher specific growth rate (4.22 ± 0.07% day−1) and thermal growth coefficient (19.4 ± 0.6), whereas the white colour tank had the lowest (SGR = 2.24 ± 0.17% day−1; TGC = 7.27 ± 0.71). The survival rate was significantly (p < 0.05) higher in black colour tank (78.33 ± 1.67%) and lowest survival was observed in white tank colour (56.67 ± 3.33%), which represented an improvement of almost 20% for the fishes reared in black colour tank. Fish reared in black tank had the significantly higher level of carotenoid content (2.33 ± 0.08 μg g−1) and fish reared in white tank had lower body carotenoid level (1.02 ± 0.05 μg g−1). It was observed that the different tank colour did not (p > 0.05) cause any change in the stress and non-specific immune parameters of filament barb. Based on the findings, it can be stated that black background colour is the best tank colour for rearing and production of filament barb.

Methodologies for Patellid Limpets’ Aquaculture: From Broodstock Management to Juveniles

The production of cultured limpets is a recent research field contributing to aquaculture diversification, focusing on low trophic species while reducing the carbon footprint. Limpets are gastropods that colonize rocky substrates and are mostly present on tidal and subtidal shores. This animal group is in high commercial demand and is endangered in several regions. The aquaculture production of limpets has been traditionally challenging. The most successful reproduction method has been gonadal dissection, as artificial spawning induction has shown limited success to date. Moreover, methods for larval culture, settlement, and juvenile growth have been poorly developed and remain largely unknown. In recent years, advances in this field have led to the optimization of methods to enhance larval production, larval culture, settlement induction of competent larvae, and management of post-larvae and juveniles. The present manuscript reviews these advances, obtained within the framework of AQUAINVERT project, focusing on broodstock management, gametes release, larval production, larviculture, settlement, and grow-out of post-larvae, and providing an update on the actual state of the art in limpets’ aquaculture.

Diversity of larval habitats of Anopheles mosquitoes in urban areas of Benin and influence of their physicochemical and bacteriological characteristics on larval density

BackgroundThe implementation of anti-larval strategies in the fight against malaria vectors requires fundamental knowledge of their oviposition sites. The aim of this study was to assess the spatial and temporal distribution of Anopheles breeding sites as well as the influence of abiotic and biotic factors on the proliferation of larvae in urban and non-urban areas of Benin.MethodsSampling of Anopheles larvae was carried out during the rainy and dry seasons in urbanized and non-urbanized areas of the cities of Cotonou, Bohicon, Parakou, and Natitingou in Benin. The Anopheles larval breeding sites were georeferenced and characterized by their nature, type, physicochemical (pH, temperature, dissolved oxygen, conductivity, turbidity, salinity) and biological attributes (larval density and coliform density).ResultsA total of 198 positive breeding sites for Anopheles larvae were identified, comprising 163 (82.3%) in the rainy season and 35 (17.7%) in the dry season. Out of these larval habitats, 61.9% were located in urbanized areas, and were predominantly puddles. Principal component analysis revealed a high positive correlation of larval density with temperature and dissolved oxygen, and with salinity in the coastal zone. In addition, cross-sectional analysis of the microbiological results with larval density showed a significant negative correlation between larval productivity and faecal coliform load.ConclusionsThis study indicated the presence of multiple larval habitats of Anopheles in the urban areas which were created through human activities, and associations between larval density and intrinsic factors of the habitats such as temperature, dissolved oxygen and faecal coliform load. This type of information may be useful for the implementation of appropriate control strategies in urban areas, including regulation of the human activities that lead to the creation of breeding sites, proper environmental management and targeted larvicidal use.Graphical abstract

Fecundity of First-Generation Captively Reared Heterelmis comalensis (Coleoptera: Elmidae).

The Comal Springs riffle beetle Heterelmis comalensis Bosse, Tuff, and Brown is listed as endangered by the U.S. Fish and Wildlife Service. Rearing this species in captivity is important to maintaining a refuge which is a goal of the Edwards Aquifer Habitat Conservation Plan. Although captive larval production has been observed for years, the production of larvae per female has been relatively unknown. Production chambers were constructed from PVC to house one female and male and the production of larvae was monitored ca. monthly until the female died. Females were found to be iteroparous and produced 29.3 ± 37.1 larvae. The number of larvae produced was found to be a function of female longevity rather than size. Other aspects of captive production and observations from the study are discussed.

The Dark Septate Endophyte, Phialocephala fortinii J2PC4, Mitigates Southern Rice Black-Streaked Dwarf Disease and Impacts the Mortality of White Back Planthopper

Southern rice black-streaked dwarf disease (SRBSDD), caused by the southern rice black-streaked dwarf virus (SRBSDV) and transmitted by the white-backed planthopper (WBPH), is a severe disease responsible for significant yield losses in Southeast Asia, including China. The present study investigated utilization of dark septate endophyte (DSE) fungi against SRBSDD and WBPHas a new, effective approach for managing this disease. An isolate of the DSE fungus, Phialocephala fortinii J2PC4, was selected based on its effective symbiosis with rice. Phialocephala fortinii J2PC4 significantly promoted the growth of the rice, increasing plant height (14.8%), fresh weight (59.5%), and dry weight (60.5%) relative to the untreated control in growth-promotion experiments. In experiments assessing disease and pest suppression, growth of rice plants P. fortinii J2PC4 also promoted growth, increasing plant height(22.4%), fresh weight (74.0%), and dry mass (32.4%). Plants infested with WBPH for 48 hours exhibited a WBPH mortality rate of 8.2% in P. fortinii J2PC4 treated plants compared to 1.5% in the control plants. Disease incidence of SRBSDD in the plants treated with P. fortinii J2PC4 exhibited a 28.5% reduction in SRBSDD disease incidence compared to control plants. P. fortinii J2PC4 colonization of rice seedlings decreased the malondialdehyde (MDA) content, increased the superoxide dismutase (SOD) and peroxidase (POD) activity in rice leaves and induced the expression of the resistance-related genes, AOS, PR1a, and PR1b. In contrast POX1 and OsSAUR2 were down-regulated, relative to control plants. Larval production by WBPH in P. fortinii J2PC4 treated plants was also 24.7% lower than control plants in the pest resistance experiment. Our results provide new insights on use of the DSE fungus, P. fortinii J2PC4, as a biofertilizer and a biocontrol agent, which can potentially be applied as a new, safe and effective treatments for growth stimulation and disease and pest control in rice plants.

Hatching phenology of the brown shrimp Crangon crangon in the southern North Sea: inter-annual temperature variations and climate change effects

Abstract Crangon crangon is a key species in the southern North Sea and the most valuable target of coastal fisheries. Recruitment and stock development are highly variable. As recruitment is based on larval production, we determined the timing of larval release in relation to the annual temperature course and the winter water temperature. The annual temperature courses over 50 years (1961–2010) showed a strong inter-annual variation but also a continuous increase in winter water temperatures. The share of ovigerous C. crangon females starts to increase in October/November, reaches a maximum in May, and decreases continuously towards September/October. During cold winters (0°C), egg development is strongly retarded and hatching of larvae culminates in a sharp peak in early June. Warm winters (6°C) facilitate embryogenesis and the earliest larvae hatch in January and February. The temperature sums from November to April correlated significantly with the lowest winter water temperatures. Consequently, the lowest winter water temperatures provide a good indication for the appearance of C. crangon larvae and an estimate for the match or mismatch with the spring bloom and the production of microzooplankton, the preferred food of C. crangon larvae.

Effects of elevated temperature on reproduction and larval settlement in Leptastrea purpurea.

As global ocean temperatures continue to rise, severe declines in coral reef health and diversity are reported on a global scale. Recovery of coral reefs relies on reproduction and increased rates of successful recruitment, which can vary tremendously across coral species. We investigated the effects of increased temperatures in the environment of parental colonies on larval production, size, settlement and survival, in the heat-resistant coral Leptastrea purpurea in Guam. Thanks to two tank experiments (eleven and four weeks, respectively) conducted over two consecutive years we found that larvae released by heat-treated parents (30 °C) were significantly smaller in size but greater in number, had normal settlement behavior and increased post-settlement survival rates compared to those released by control parent colonies (28 °C). We conclude that changes in the environment of parental L. purpurea colonies trigger an anticipatory maternal effect which leads to the release of preconditioned larvae with an increased chance of survival.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00338-022-02241-y.

A hungry need for knowledge on the black soldier fly digestive system

The interest towards the black soldier fly (BSF), Hermetia illucens, has grown impressively in the last few years, fostered by the legislative changes in the European landscape that have lifted the ban regarding the use of BSF larvae as feedstuff. In addition, bioconversion mediated by the larvae of the BSF is viewed as one of the most promising technologies for organic waste processing and valorisation. Finally, new, alternative applications to exploit various larval products such as lipids, chitin, antimicrobial peptides, and frass are being explored. However, this positive trend, confirmed by the increasing number of companies that deal with BSF mass rearing and processing, is in sharp contrast with the limited information on the biology of this insect, in particular on aspects related to its digestive features. This lack of knowledge needs to be carefully considered and filled in coming years, as a deep characterisation of the morphology, physiology, transcriptomics, and proteomics of the digestive system of the insect, as well a fine dissection of related aspects as gut microbiota and pathogens, is a prerequisite to improve the amazing bioconversion capabilities of this dipteron. So far, the larval stages received the most attention in research, but there might still be a lot to win by focusing more on the adult stage. Further expanding the basic knowledge on both the larval and the adult gut could lead to unexpected findings and open new perspectives to produce value-added bioproducts.

Transformation of food waste to source of antimicrobial proteins by black soldier fly larvae for defense against marine Vibrio parahaemolyticus

Insect biorefinery by black soldier fly larvae (BSFL), Hermetia illucens, has emerged as an innovative technique for the valorization of food waste. However, despite BSFL being an attractive natural source of antimicrobial proteins (AMPs), there is a scarcity of research on the antimicrobial activity and transcriptome expression of AMPs derived from BSFL following waste treatment. In the present study, food waste treatment was performed by BSFL with a substrate C/N ratio ranging from 21:1 to 10:1, marine Vibrio parahaemolyticus (VP) was selected as the model aquaculture pathogen, the antimicrobial activities of AMPs in vitro and zebrafish in vivo were examined, and the molecular mechanism of the C/N-dependent AMP difference was expounded. Findings were made that the AMP extract of C/N16:1 resulted in relatively higher antimicrobial activity in vitro than that of other C/Ns. Further, the AMPs of C/N16:1 exhibited a promising in vivo defense effect for elevating the 96-h survival rate of zebrafish from 0% to 39% after VP infection, comparable to the animal antibiotic sulfamethoxidine. The results of transcriptome analysis reveal that lysozymes were the highest expressed components in the AMP gene family. The C/N16:1 BSFL significantly up-regulated 12 out of 51 lysozyme genes compared with C/N21:1, which likely contributed to the improvement of AMP antimicrobial activity. Further, C/N16:1 significantly up-regulated the expression of lysozyme, glycosyl hydrolase and muscle protein genes compared with C/N21:1, which likely enhanced the defense ability of the immune system, the utilization of the starch-like substrate, and the mobility of the larvae, thereby facilitating the larval transformation and AMP production. Overall, such results indicate that waste C/N ratio interacted with the activity and expression of BSFL AMPs through transcriptome regulation, and the BSFL AMPs derived from food waste could be used for the defense against marine pathogens to support the sustainable development of aquaculture.