Some Insect Species Are Good-Quality Protein Sources for Children and Adults: Digestible Indispensable Amino Acid Score (DIAAS) Determined in Growing Pigs.

BACKGROUND: Insect species are suitable for farming as "mini livestock" for human and animal consumption. It is important to assess the protein quality of relevant species to understand the potential of these novel protein sources in future sustainable food systems. OBJECTIVES: We aimed to determine the protein quality of 5 insect species-lesser mealworm (LMW), yellow mealworm, house cricket (HC), banded cricket (BC), and black soldier fly-using the digestible indispensable amino acid score (DIAAS) in a pig model. METHODS: Five diets were formulated to contain 10% insect crude protein (CP). A nitrogen (N)-free diet was included to estimate endogenous losses. In a 6 × 6 Latin square design, 6 ileal cannulated crossbred [Duroc × (Danish Landrace × Yorkshire)] male pigs with an initial body weight of 35 ± 2 kg were fed the 6 diets. Each diet was fed for 1 wk over 6 wk. Ileal digesta were collected for 8 h on days 5 and 7 each week. Analyzed CP, amino acid (AA) contents, and calculated values of standardized ileal digestibility for CP and AAs were used to assess the DIAAS of each insect. RESULTS: The DIAAS for young children aged 6 mo-3 y and for older children, adolescents, and adults identified sulfur AAs (cysteine + methionine) as the first limiting AA in all 4 species of cricket and mealworm. For young children, both cricket species had DIAASs > 75 and for older children, adolescents, and adults both cricket species and LMW had DIAASs > 75. CONCLUSIONS: Both cricket species (HC and BC) are classified as good-quality protein sources for young children aged 6 mo-3 y and for older children, adolescents, and adults. One mealworm species, LMW, is a good-quality protein source for older children, adolescents, and adults.

Some Insect Species Are Good-Quality Protein Sources for Children and Adults: Digestible Indispensable Amino Acid Score (DIAAS) Determined in Growing Pigs.

BACKGROUND: Insect species are suitable for farming as "mini livestock" for human and animal consumption. It is important to assess the protein quality of relevant species to understand the potential of these novel protein sources in future sustainable food systems. OBJECTIVES: We aimed to determine the protein quality of 5 insect species-lesser mealworm (LMW), yellow mealworm, house cricket (HC), banded cricket (BC), and black soldier fly-using the digestible indispensable amino acid score (DIAAS) in a pig model. METHODS: Five diets were formulated to contain 10% insect crude protein (CP). A nitrogen (N)-free diet was included to estimate endogenous losses. In a 6 × 6 Latin square design, 6 ileal cannulated crossbred [Duroc × (Danish Landrace × Yorkshire)] male pigs with an initial body weight of 35 ± 2 kg were fed the 6 diets. Each diet was fed for 1 wk over 6 wk. Ileal digesta were collected for 8 h on days 5 and 7 each week. Analyzed CP, amino acid (AA) contents, and calculated values of standardized ileal digestibility for CP and AAs were used to assess the DIAAS of each insect. RESULTS: The DIAAS for young children aged 6 mo-3 y and for older children, adolescents, and adults identified sulfur AAs (cysteine + methionine) as the first limiting AA in all 4 species of cricket and mealworm. For young children, both cricket species had DIAASs > 75 and for older children, adolescents, and adults both cricket species and LMW had DIAASs > 75. CONCLUSIONS: Both cricket species (HC and BC) are classified as good-quality protein sources for young children aged 6 mo-3 y and for older children, adolescents, and adults. One mealworm species, LMW, is a good-quality protein source for older children, adolescents, and adults.

Rethinking organic wastes bioconversion: Evaluating the potential of the black soldier fly (Hermetia illucens (L.)) (Diptera: Stratiomyidae) (BSF).

Population growth and unprecedented economic growth and urbanization, especially in low- and middle-income countries, coupled with extreme weather patterns, the high-environmental footprint of agricultural practices, and disposal-oriented waste management practices, require significant changes in the ways we produce food, feed and fuel, and manage enormous amounts of organic wastes. Farming insects such as the black soldier fly (BSF) (Hermetia illucens) on diverse organic wastes provides an opportunity for producing nutrient-rich animal feed, fuel, organic fertilizer, and biobased products with concurrent valorization of wastes. Inclusion of BSF larvae/pupae in the diets of poultry, fish, and swine has shown promise as a potential substitute of conventional feed ingredients such as soybean meal and fish meal. Moreover, the bioactive compounds such as antimicrobial peptides, medium chain fatty acids, and chitin and its derivatives present in BSF larvae/pupae, could also add values to the animal diets. However, to realize the full potential of BSF-based biorefining, more research and development efforts are necessary for scaling up the production and processing of BSF biomass using more mechanized and automated systems. More studies are also needed to ensure the safety of the BSF biomass grown on various organic wastes for animal feed (also food) and legalizing the feed application of BSF biomass to wider categories of animals. This critical review presents the current status of the BSF technology, identifies the research gaps, highlights the challenges towards industrial scale production, and provides future perspectives.

Ingestion of Insect Protein Isolate Enhances Blood Amino Acid Concentrations Similar to Soy Protein in A Human Trial.

BACKGROUND: Increased amino acid availability stimulates muscle protein synthesis (MPS), which is critical for maintaining or increasing muscle mass when combined with training. Previous research suggests that whey protein is superior to soy protein in regard to stimulating MPS and muscle mass. Nevertheless, with respect to a future lack of dietary protein and an increasing need for using eco-friendly protein sources it is of great interest to investigate the quality of alternative protein sources, like insect protein. OBJECTIVE: Our aim was to compare the postprandial amino acid (AA) availability and AA profile in the blood after ingestion of protein isolate from the lesser mealworm, whey isolate, and soy isolate. DESIGN: Six healthy young men participated in a randomized cross-over study and received three different protein supplementations (25 g of crude protein from whey, soy, insect or placebo (water)) on four separate days. Blood samples were collected at pre, 0 min, 20 min, 40 min, 60 min, 90 min, and 120 min. Physical activity and dietary intake were standardized before each trial, and participants were instructed to be fasting from the night before. AA concentrations in blood samples were determined using ¹H NMR spectroscopy. RESULTS: A significant rise in blood concentration of essential amino acids (EAA), branched-chain amino acids (BCAA) and leucine was detected over the 120 min period for all protein supplements. Nevertheless, the change in AA profile was significantly greater after ingestion of whey than soy and insect protein (p < 0.05). Area under the curve (AUC) analysis and AA profile revealed comparable AA concentrations for soy and insect protein, whereas whey promoted a ~97% and ~140% greater AUC value than soy and insect protein, respectively. A tendency towards higher AA concentrations beyond the 120 min period was observed for insect protein. CONCLUSION: We report that ingestion of whey, soy, and insect protein isolate increases blood concentrations of EAA, BCAA, and leucine over a 120 min period (whey > insect = soy). Insect protein induced blood AA concentrations similar to soy protein. However, a tendency towards higher blood AA concentrations at the end of the 120 min period post ingestion was observed for insect protein, which indicates that it can be considered a "slow" digestible protein source.

Effects of Insect Protein Supplementation during Resistance Training on Changes in Muscle Mass and Strength in Young Men.

During prolonged resistance training, protein supplementation is known to promote morphological changes; however, no previous training studies have tested the effect of insect protein isolate in a human trial. The aim of this study was to investigate the potential effect of insect protein as a dietary supplement to increase muscle hypertrophy and strength gains during prolonged resistance training in young men. Eighteen healthy young men performed resistance training four day/week for eight weeks. Subjects were block randomized into two groups consuming either an insect protein isolate or isocaloric carbohydrate supplementation within 1 h after training and pre-sleep on training days. Strength and body composition were measured before and after intervention to detect adaptions to the resistance training. Three-day weighed dietary records were completed before and during intervention. Fat- and bone- free mass (FBFM) improved significantly in both groups (Mean (95% confidence interval (CI))), control group (Con): (2.5 kg (1.5, 3.5) p < 0.01), protein group (Pro): (2.7 kg (1.6, 3.8) p < 0.01) from pre- to post-. Leg and bench press one repetition maximum (1 RM) improved by Con: (42.0 kg (32.0, 52.0) p < 0.01) and (13.8 kg (10.3, 17.2) p < 0.01), Pro: (36.6 kg (27.3, 45.8) p < 0.01) and (8.1 kg (4.5, 11.8) p < 0.01), respectively. No significant differences in body composition and muscle strength improvements were found between groups. In young healthy men, insect protein supplementation did not improve adaptations to eight weeks of resistance training in comparison to carbohydrate supplementation. A high habitual protein intake in both Con and Pro may partly explain our observation of no superior effect of insect protein supplementation.

Role of temperature on growth and metabolic rate in the tenebrionid beetles Alphitobius diaperinus and Tenebrio molitor.

Insects are increasingly used as a dietary source for food and feed and it is therefore important to understand how rearing conditions affect growth and development of these agricultural animals. Temperature is arguably the most important factor affecting metabolism and growth rate in insects. Here, we investigated how rearing temperature affected growth rate, growth efficiency and macronutrient composition in two species of edible beetle larvae: Alphitobius diaperinus and Tenebrio molitor. Growth rates of both species were quantified at temperatures ranging from 15.2 to 38.0 °C after which we measured protein and lipid content of the different treatment groups. Metabolic rate was measured in a similar temperature range by measuring the rate of O2 consumption (V·O2) and CO2 production (V·CO2) using repeated measures closed respirometry. Using these measurements, we calculated the growth efficiency of mealworms by relating the energy assimilation rate to the metabolic rate. Maximum daily growth rates were 18.3% and 16.6% at 31 °C, for A. diaperinus and T. molitor respectively, and we found that A. diaperinus was better at maintaining growth at high temperatures while T. molitor had superior growth at lower temperatures. Both species had highest efficiencies of energy assimilation in the temperature range of 23.3-31.0 °C, with values close to 2 J assimilated/J metabolised in A. diaperinus and around 4 J assimilated/J metabolised in T. molitor. Compared to "conventional" terrestrial livestock, both species of insects were characterised by high growth rates and very high energy conversion efficiency at most experimental temperatures. For A. diaperinus, lipid content was approximately 30% of dry mass and protein content approximately 50% of dry mass across most temperatures. Temperature had a greater influence on the body composition of T. molitor. At 31.0 °C the lipid and protein content was measured to 47.4% and 37.9%, respectively but lipid contents decreased, and protein contents increased when temperatures were higher or lower than 31.0 °C. In summary, rearing temperature had large and independent effects on growth rate, energy assimilation efficiency and protein/lipid content. Accordingly, temperature is a critical parameter to control in commercial insect rearing regardless if the producer wants to optimise production speed, production efficiency or product quality.

Time-course profiling of molecular stress responses to silver nanoparticles in the earthworm Eisenia fetida.

The molecular mechanism of silver nanoparticle (AgNP) toxicity, particularly its temporal aspect, is currently limited in the literature. This study seeks to identify and profile changes in molecular response patterns over time during soil exposure of the earthworm Eisenia fetida to AgNPs (82±27 nm) with reference to dissolved silver salt (AgNO3). Principal component analysis of selected gene and enzyme response profiles revealed dissimilar patterns between AgNO3 and AgNP treatments and also over time. Despite the observed difference in molecular profiles, the body burdens of total Ag were within the same range (10-40 mg/kg dry weight worm) for both treatments with apparent correlation to the induction pattern of metallothionein. AgNO3 induced the genes and enzymes related to oxidative stress at day 1, after which markers of energy metabolism were all suppressed at day 2. Exposure to AgNPs likewise led to induction of oxidative stress genes at day 2, but with a temporal pattern shift to immune genes at day 14 following metabolic upregulation at day 7. The involvement of oxidative stress and subsequent alterations in immune gene regulation were as predicted by our in vitro study reported previously, highlighting the importance of immunological endpoints in nanosilver toxicity.

C60 exposure induced tissue damage and gene expression alterations in the earthworm Lumbricus rubellus.

Effects of C60 exposure (0, 15 or 154 mg/kg soil) on the earthworm Lumbricus rubellus were assessed at the tissue and molecular level, in two experiments. In the first experiment, earthworms were exposed for four weeks, and in the second lifelong. In both experiments, gene expression of heat shock protein 70 (HSP70) decreased. For catalase and glutathione-S-transferase (GST), no significant trends in gene expression or enzyme activity were observed. Gene expression of coelomic cytolytic factor-1 (CCF-1) did not alter in earthworms exposed for four weeks, but was significantly down-regulated in the lifelong exposure. Histology of earthworms exposed to C60 in both experiments showed a damaged cuticle, with underlying pathologies of epidermis and muscles, as well as effects on the gut barrier. However, tissue repair was also observed in these earthworms. Overall, these data show that sub-lethal C60 exposure to earthworms via the soil affects gene expression and causes tissue pathologies.

Earthworms and humans in vitro: characterizing evolutionarily conserved stress and immune responses to silver nanoparticles.

Little is known about the potential threats of silver nanoparticles (AgNPs) to ecosystem health, with no detailed report existing on the stress and immune responses of soil invertebrates. Here we use earthworm primary cells, cross-referencing to human cell cultures with a particular emphasis on the conserved biological processes, and provide the first in vitro analysis of molecular and cellular toxicity mechanisms in the earthworm Eisenia fetida exposed to AgNPs (83 ± 22 nm). While we observed a clear difference in cytotoxicity of dissolved silver salt on earthworm coelomocytes and human cells (THP-1 cells, differentiated THP-1 cells and peripheral blood mononuclear cells), the coelomocytes and differentiated (macrophage-like) THP-1 cells showed a similar response to AgNPs. Intracellular accumulation of AgNPs in the coelomocytes, predominantly in a phagocytic population, was evident by several methods including transmission electron microscopy. Molecular signatures of oxidative stress and selected biomarker genes probed in a time-resolved manner suggest early regulation of oxidative stress genes and subsequent alteration of immune signaling processes following the onset of AgNP exposure in the coelomocytes and THP-1 cells. Our findings provide mechanistic clues on cellular innate immunity toward AgNPs that is likely to be evolutionarily conserved across the animal kingdom.

NORMA-Gene: a simple and robust method for qPCR normalization based on target gene data.

BACKGROUND: Normalization of target gene expression, measured by real-time quantitative PCR (qPCR), is a requirement for reducing experimental bias and thereby improving data quality. The currently used normalization approach is based on using one or more reference genes. Yet, this approach extends the experimental work load and suffers from assumptions that may be difficult to meet and to validate. RESULTS: We developed a data driven normalization algorithm (NORMA-Gene). An analysis of the performance of NORMA-Gene compared to reference gene normalization on artificially generated data-sets showed that the NORMA-Gene normalization yielded more precise results under a large range of parameters tested. Furthermore, when tested on three very different real qPCR data-sets NORMA-Gene was shown to be best at reducing variance due to experimental bias in all three data-sets compared to normalization based on the use of reference gene(s). CONCLUSIONS: Here we present the NORMA-Gene algorithm that is applicable to all biological and biomedical qPCR studies, especially those that are based on a limited number of assayed genes. The method is based on a data-driven normalization and is useful for as little as five target genes comprising the data-set. NORMA-Gene does not require the identification and validation of reference genes allowing researchers to focus their efforts on studying target genes of biological relevance.

Limit-test toxicity screening of selected inorganic nanoparticles to the earthworm Eisenia fetida.

The toxicity of a range of inorganic (Ag, Cu, Ni, Al(2)O(3), SiO(2), TiO(2) and ZrO(2)) nanoparticles (NP) and their corresponding metal salt or bulk metal oxide were screened for toxicity toward the earthworm Eisenia fetida using the limit-test design (1000 mg/kg). This study provides the first ecotoxicological life history trait data on earthworms for each these NPs, as well as for AgNO(3), Al(2)O(3), SiO(2), TiO(2) and ZrO(2). Significant effects were observed on survival for AgNO(3) (2.5% of controls), CuCl(2) (17.5% of controls) and NiCl(2) (32.5% of controls) and on reproduction (AgNO(3), CuCl(2), NiCl(2), Ag-NP, Cu-NP, TiO(2)-NP); with total reproductive failure in both silver treatments. Ag-NP, Cu-NP and TiO(2)-NP were the only NPs that caused toxic effects to E. fetida. The toxicity could not be singularly related to particle size or zeta potential or to the inherent element constituting the NPs (e.g. Ag).

Time is of the essence.

An organism is a dynamic system, and its life history results from underlying processes in time. The effects of biological and chemical stressors on this system therefore also change temporally. In the present short communication, we emphasize the importance of including time as a factor in stress ecology and ecotoxicology and argue that current standard test protocols may benefit considerably from this, improving data interpretation and thus also risk assessment and risk management.

Hsp70 expression and metabolite composition in response to short-term thermal changes in Folsomia candida (Collembola).

In the present study the joint transcriptomic and metabolomic responses in Folsomia candida (Collembola) to temperature changes on a short-term scale were studied. Change in heat tolerance was examined as survival after a 35 degrees C heat shock (2h) in the course of either a fluctuating temperature regime (8 to 32 degrees C; pre-treated) or a constant temperature (20 degrees C; control) over a period of 24h. Exposure to a temperature increase from 20 to 32 degrees C (2.4 degrees C min(-)(1)) induced a significantly increased heat tolerance which continued throughout the experiment. Expression of the gene encoding heat shock protein Hsp70 was assessed at the mRNA level using real time quantitative polymerase chain reaction (QPCR). Hsp70 was rapidly induced and significantly increased by the temperature increase. The relative concentrations of low molecular weight metabolites were analysed in F. candida using nuclear magnetic resonance spectroscopy ((1)H NMR). A significant metabolomic divergence between pre-treated and control collembolans was evident; partly due to a significantly reduced relative concentration of five free amino acids (arginine, leucine, lysine, phenylalanine and tyrosine) in pre-treated collembolans. These results, obtained from ecological transcriptomics and metabolomics jointly generated insight on various levels into the combined responses to a changing environment.

Gene transcription in Daphnia magna: effects of acute exposure to a carbamate insecticide and an acetanilide herbicide.

Daphnia magna is a key invertebrate in the freshwater environment and is used widely as a model in ecotoxicological measurements and risk assessment. Understanding the genomic responses of D. magna to chemical challenges will be of value to regulatory authorities worldwide. Here we exposed D. magna to the insecticide methomyl and the herbicide propanil to compare phenotypic effects with changes in mRNA expression levels. Both pesticides are found in drainage ditches and surface water bodies standing adjacent to crops. Methomyl, a carbamate insecticide widely used in agriculture, inhibits acetylcholinesterase, a key enzyme in nerve transmission. Propanil, an acetanilide herbicide, is used to control grass and broad-leaf weeds. The phenotypic effects of single doses of each chemical were evaluated using a standard immobilisation assay. Immobilisation was linked to global mRNA expression levels using the previously estimated 48h-EC(1)s, followed by hybridization to a cDNA microarray with more than 13,000 redundant cDNA clones representing >5000 unique genes. Following exposure to methomyl and propanil, differential expression was found for 624 and 551 cDNAs, respectively (one-way ANOVA with Bonferroni correction, P

Exposure to mercury reduces heat tolerance and heat hardening ability of the springtail Folsomia candida.

We investigated the combined effects of mercury (HgCl(2)) and acute heat on survival of the springtail Folsomia candida. The springtails were exposed to a range of aqueous concentrations (0-48 mg Hg(2+)/L) of HgCl(2) for 24 h. Subsequently, the same individuals were exposed to a range of high temperatures, from 20 to 35.5 degrees C. We found a highly significant synergistic interaction between effects of mercury and heat, with a reduced tolerance to heat after exposure to sublethal concentrations of mercury. Further, the heat hardening ability of F. candida was studied at sublethal concentrations of mercury. F. candida was able to heat harden (exposure to a mild heat treatment increasing survival of subsequent severe heat); however, when the springtails experienced a previous exposure to as little as 1 mg Hg(2+)/L, heat hardening failed to improve survival of heat shock at 34.5 degrees C, even though this was much lower than concentrations affecting survival without heat stress. Mild heat stress is known to induce the heat shock protein, HSP70, and real-time quantitative PCR confirmed that pre-acclimation to 32 degrees C did indeed cause >5-fold up-regulation of HSP70 expression. This up-regulation was not affected by previous exposure to 1 mg Hg(2+)/L.

Outlining eicosanoid biosynthesis in the crustacean Daphnia.

BACKGROUND: Eicosanoids are biologically active, oxygenated metabolites of three C20 polyunsaturated fatty acids. They act as signalling molecules within the autocrine or paracrine system in both vertebrates and invertebrates mainly functioning as important mediators in reproduction, the immune system and ion transport. The biosynthesis of eicosanoids has been intensively studied in mammals and it is known that they are synthesised from the fatty acid, arachidonic acid, through either the cyclooxygenase (COX) pathway; the lipoxygenase (LOX) pathway; or the cytochrome P450 epoxygenase pathway. However, little is still known about the synthesis and structure of the pathway in invertebrates. RESULTS: Here, we show transcriptomic evidence from Daphnia magna (Crustacea: Branchiopoda) together with a bioinformatic analysis of the D. pulex genome providing insight on the role of eicosanoids in these crustaceans as well as outlining a putative pathway of eicosanoid biosynthesis. Daphnia appear only to have one copy of the gene encoding the key enzyme COX, and phylogenetic analysis reveals that the predicted protein sequence of Daphnia COX clusters with other invertebrates. There is no current evidence of an epoxygenase pathway in Daphnia; however, LOX products are most certainly synthesised in daphnids. CONCLUSION: We have outlined the structure of eicosanoid biosynthesis in Daphnia, a key genus in freshwater ecosystems. Improved knowledge of the function and synthesis of eicosanoids in Daphnia and other invertebrates could have important implications for several areas within ecology. This provisional overview of daphnid eicosanoid biosynthesis provides a guide on where to focus future research activities in this area.

Linking molecular and population stress responses in Daphnia magna exposed to cadmium.

DNA microarrays can be used to measure environmental stress responses. If they are to be predictive of environmental impact, we need to determine if altered gene expression translates into negative impacts on individuals and populations. A large cDNA microarray (14000 spots) was created to measure molecular stress responses to cadmium in Daphnia magna,the mostwidely used aquatic indicator species, and relate responses to population growth rate (pgr). We used the array to detect differences in the transcription of genes in juvenile D. magna (24 h old) after 24 h exposure to a control and three cadmium concentrations (6, 20, and 37 microg Cd2+ L(-1)). Stress responses at the population level were estimated following a further 8 days exposure. Pgr was approximately linear negative with increasing cadmium concentration over this range. The microarray profile of gene expression in response to acute cadmium exposure begins to provide an overview of the molecular responses of D. magna, especially in relation to growth and development. Of the responding genes, 29% were involved with metabolism including carbohydrate, fat and peptide metabolism, and energy production, 31% were involved with transcription/translation, while 40% of responding genes were associated with cellular processes like growth and moulting, ion transport, and general stress responses (which included oxidative stress). Our production and application of a large Daphnia magna microarray has shown that measured gene responses can be logically linked to the impact of a toxicant such as cadmium on somatic growth and development, and consequently pgr.

Systems biology meets stress ecology: linking molecular and organismal stress responses in Daphnia magna.

BACKGROUND: Ibuprofen and other nonsteroidal anti-inflammatory drugs have been designed to interrupt eicosanoid metabolism in mammals, but little is known of how they affect nontarget organisms. Here we report a systems biology study that simultaneously describes the transcriptomic and phenotypic stress responses of the model crustacean Daphnia magna after exposure to ibuprofen. RESULTS: Our findings reveal intriguing similarities in the mode of action of ibuprofen between vertebrates and invertebrates, and they suggest that ibuprofen has a targeted impact on reproduction at the molecular, organismal, and population level in daphnids. Microarray expression and temporal real-time quantitative PCR profiles of key genes suggest early ibuprofen interruption of crustacean eicosanoid metabolism, which appears to disrupt signal transduction affecting juvenile hormone metabolism and oogenesis. CONCLUSION: Combining molecular and organismal stress responses provides a guide to possible chronic consequences of environmental stress for population health. This could improve current environmental risk assessment by providing an early indication of the need for higher tier testing. Our study demonstrates the advantages of a systems approach to stress ecology, in which Daphnia will probably play a major role.

Reproduction recovery of the crustacean Daphnia magna after chronic exposure to ibuprofen.

In mammals, the pharmaceutical ibuprofen (IB), a non-steroidal anti-inflammatory drug, primarily functions by reversibly inhibiting the cyclooxygenase (COX) pathway in the synthesis of eicosanoids (e.g. prostaglandins). Previous studies suggest that IB may act in a similar manner to interrupt production of eicosanoids reducing reproduction in the model crustacean Daphnia magna. On this basis withdrawal of IB should lead to the recovery of D. magna reproduction. Here we test whether the effect of IB is reversible in D. magna, as it is in mammals, by observing reproduction recovery following chronic exposure. D. magna (5-days old) were exposed to a range of IB concentrations (0, 20, 40 and 80 mg l(-1)) for 10 days followed by a 10 day recovery period in uncontaminated water. During the exposure period, individuals exposed to higher concentrations produced significantly fewer offspring. Thereafter, IB-stressed individuals produced offspring faster during recovery, having similar average population growth rates (PGR) (1.15-1.28) to controls by the end of the test. It appears that maternal daphnids are susceptible to IB during egg maturation. This is the first recorded recovery of reproduction in aquatic invertebrates that suffered reproductive inhibition during chronic exposure to a chemical stressor. Our results suggest a possible theory behind the compensatory fecundity that we referred to as 'catch-up reproduction'.

Chronic toxicity of ibuprofen to Daphnia magna: Effects on life history traits and population dynamics.

The non-steroidal anti-inflammatory drug (NSAID) ibuprofen (IB) is a widely used pharmaceutical that can be found in several freshwater ecosystems. Acute toxicity studies with Daphnia magna suggest that the 48h EC(50) (immobilisation) is 10-100 mgIBl(-1). However, there are currently no chronic IB toxicity data on arthropod populations, and the aquatic life impacts of such analgesic drugs are still undefined. We performed a 14-day exposure of D. magna to IB as a model compound (concentration range: 0, 20, 40 and 80 mgIBl(-1)) measuring chronic effects on life history traits and population performance. Population growth rate was significantly reduced at all IB concentrations, although survival was only affected at 80 mgIBl(-1). Reproduction, however, was affected at lower concentrations of IB (14-day EC(50) of 13.4 mgIBl(-1)), and was completely inhibited at the highest test concentration. The results from this study indicate that the long-term crustacean population consequences of a chronic IB exposure at environmentally realistic concentrations (ngl(-1) to microgl(-1)) would most likely be of minor importance. We discuss our results in relation to recent genomic studies, which suggest that the potential mechanism of toxicity in Daphnia is similar to the mode of action in mammals, where IB inhibits eicosanoid biosynthesis.