High cadmium and mercury concentrations in the tissues of the orange-back flying squid, Sthenoteuthis pteropus, from the tropical Eastern Atlantic.

The orange-back flying squid, Sthenoteuthis pteropus, plays an important role in the eastern tropical Atlantic Ocean (ETA) pelagic food web, as both predator and prey. Specimens of S. pteropus were caught off the Cape Verde Islands and concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn were measured in the digestive gland. Among the analysed elements, Cd showed the highest average concentration with values among the highest ever recorded in cephalopods. In addition to the digestive gland, Hg concentrations were also analysed in the buccal mass and mantle tissue. Among the three tissues, buccal mass showed the highest Hg concentrations. In females, Hg concentrations in the buccal mass were positively correlated with stable isotope ratios (δ13C and δ15N) and mantle length, showing both bioaccumulation with age and bioamplification along the trophic levels. High Cd and Hg concentrations in the digestive gland and muscle respectively would lead to elevated exposure of squid-eating top predators such as yellowfin tuna, swordfish or dolphinfish, which are commercially harvested for human consumption. This study provides a deeper understanding of the trace element contamination in an abundant and ecologically important, but poorly studied pelagic squid in the ETA.

Demographic responses to mercury exposure in two closely related Antarctic top predators.

Although toxic chemicals constitute a major threat for wildlife, their effects have been mainly assessed at the individual level and under laboratory conditions. Predicting population-level responses to pollutants in natural conditions is a major and ultimate task in ecological and ecotoxicological research. The present study aims to estimate the effect of mercury (Hg) levels on future apparent survival rates and breeding performances. We used a long-term data set (-10 years) and recently developed methodological tools on two closely related Antarctic top predators, the South Polar Skua Catharacta maccormicki from Adélie Land and the Brown Skua C. lonnbergi from the Kerguelen Archipelago. Adult survival rates and breeding probabilities were not affected by Hg levels, but breeding success in the following year decreased with increasing Hg levels. Although South Polar Skuas exhibited much lower Hg levels than Brown Skuas, they suffered from higher Hg-induced breeding failure. This species difference could be attributed to an interaction between Hg and other environmental perturbations, including climate change and a complex cocktail of pollutants. By including Hg-dependent demographic parameters in population models, we showed a weak population decline in response to increasing Hg levels. This demographic decline was more pronounced in South Polar Skuas than in Brown Skuas. Hence, Hg exposure differently affects closely related species. The wide range of environmental perturbations in Antarctic regions could exacerbate the demographic responses to Hg levels. In that respect, we urge future population modeling to take into account the coupled effects of climate change and anthropogenic pollution to estimate population projections.

Mother-embryo isotope (δ¹5N, δ¹³C) fractionation and mercury (Hg) transfer in aplacental deep-sea sharks.

Stable carbon (δ¹³C) and nitrogen (δ¹5N) isotopic values and total mercury (Hg) concentrations were analysed in muscle and liver of mothers and embryos of two aplacental shark species, Squalus megalops and Centrophorus moluccensis. Embryos of the two species had similar or lower isotopic values than their respective mothers, the only exception being for δ¹³C, which was higher in the liver of C. moluccensis embryos than in their mothers. Hg concentrations were systematically lower in embryos compared with their mothers suggesting a low transfer of this element in muscle and liver.

Simple and rapid formic acid sample treatment for the isolation of HgSe nanoparticles from animal tissues.

The present work explores for the first time the potential of formic acid on the extraction of tiemannite (HgSe) nanoparticles from seabird tissues, in particular giant petrels. Mercury (Hg) is considered one of the top ten chemicals of major public health concern. However, the fate and metabolic pathways of Hg in living organisms remain unknown. Methylmercury (MeHg), largely produced by microbial activity in the aquatic ecosystems is biomagnified in the trophic web. HgSe is considered the end-product of MeHg demethylation in biota and an increasing number of studies focuses on the characterization of this solid compound to understand its biomineralization. In this study, a conventional enzymatic treatment is compared with a simpler and environmentally friendly extraction by using formic acid (5 mL of = 50 % formic acid) as exclusive reagent. The analyses by spICP-MS of the resulting extracts from a variety of seabird biological tissues (liver, kidneys, brain, muscle) reveal comparable results by both extraction approaches in terms of nanoparticles stability and extraction efficiency. Therefore, the results included in this work demonstrate the good performance of employing organic acid as simple, cost effective and green procedure to extract HgSe nanoparticles from animal tissues. Moreover, an alternative consisting of a classical enzymatic procedure but with ultrasonic assistance reducing the extraction time from 12 h to 2 min is also described for the first time. The sample processing methodologies developed, combined with spICP-MS, have emerged as powerful tools for the rapid screening and quantification of HgSe nanoparticles in animal tissues. Finally, this combination allowed us to identify the possible occurrence of Cd particles and As particles associated with HgSe NPs in seabirds.

Variation in blood mercury concentrations in brown skuas (Stercorarius antarcticus) is related to trophic ecology but not breeding success or adult body condition.

Mercury is a pervasive environmental contaminant that can negatively impact seabirds. Here, we measure total mercury (THg) concentrations in red blood cells (RBCs) from breeding brown skuas (Stercorarius antarcticus) (n = 49) at Esperanza/Hope Bay, Antarctic Peninsula. The aims of this study were to: (i) analyse RBCs THg concentrations in relation to sex, year and stable isotope values of carbon (δ13C) and nitrogen (δ15N); and (ii) examine correlations between THg, body condition and breeding success. RBC THg concentrations were positively correlated with δ15N, which is a proxy of trophic position, and hence likely reflects the biomagnification process. Levels of Hg contamination differed between our study years, which is likely related to changes in diet and distribution. RBC THg concentrations were not related to body condition or breeding success, suggesting that Hg contamination is currently not a major conservation concern for this population.

Trophic ecology drives trace element concentrations in the Antarctic octopod community.

Despite the Antarctic Ocean being considered a pristine environment, elevated trace element concentrations have been reported in many marine organisms. The Antarctic Ocean is particularly vulnerable to climate change, which can also affect the bioaccumulation of trace element concentrations in biota. While Antarctic octopods are key components of the regional food webs as prey for a variety of predators (e.g., seals, fish, and seabirds), their contamination state by trace elements remains largely unknown. This study investigated the trace element concentrations in relation to the trophic ecology in Antarctic octopods. Stable isotope values (δ13C and δ15N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were measured in eight different species (Adelieledone polymorpha, Pareledone aequipapillae, P. albimaculata, P. aurata, P. charcoti, P. cornuta, P. felix, and P. turqueti) sampled near Elephant Island, close to the Antarctic Peninsula. Stable isotopes of δ15N varied among species, with significant differences between A. polymorpha and P. aurata suggesting potential niche segregation. Trace element concentrations also differed among species and with sampling depth, which likely reflects their trophic ecology. The data presented in this study provides the first insight into the trace element concentrations for these endemic octopods in this vulnerable habitat and their stable isotope values.

Large-scale survey of lithium concentrations in marine organisms.

Trace metals such as Cu, Hg, and Zn have been widely investigated in marine ecotoxicological studies considering their bioaccumulation, transfer along trophic webs, and the risks they pose to ecosystems and human health. Comparatively, Li has received little attention, although this element is increasingly used in the high-tech, ceramics/glass, and medication industries. Here, we report Li concentrations in more than 400 samples, including whole organisms and different organs of bivalves, cephalopods, crustaceans, and fish. We investigated species from three contrasting biogeographic areas, i.e. temperate (Bay of Biscay, northeast Atlantic Ocean), tropical (New Caledonia, Pacific Ocean), and subpolar climates (Kerguelen Islands, southern Indian Ocean), among diverse trophic groups (filter-feeders to meso-predators) and habitats (benthic, demersal, and pelagic). Although Li is homogeneously distributed in the ocean (at 0.18 µg/mL), Li concentrations in soft tissues vary greatly, from 0.01 to 1.20 µg/g dry weight. Multiple correspondence analyses reveal two clusters of high and low Li concentrations. Li distributions in marine organisms appear to be mostly geographically independent, though our results highlight a temperature dependency in fish muscles. Li is consistently bio-reduced through the trophic webs, with filter-feeders showing the highest concentrations and predatory fish the lowest. Strong variations are observed among organs, consistent with the biochemical similarity between Na and Li during transport in the brain and in osmoregulatory organs. Fish gills and kidneys show relatively high Li concentrations (0.26 and 0.15 µg/g, respectively) and fish brains show a large range of Li contents (up to 0.34 µg/g), whereas fish liver and muscles are Li depleted (0.07 ± 0.03 and 0.06 ± 0.08 µg/g, respectively). Altogether, these results provide the first exhaustive baseline for future Li ecotoxicology studies in marine coastal environments.

Influence of sexual dimorphism on stable isotopes and trace element concentrations in the greater hooked squid Moroteuthopsis ingens from New Zealand waters.

The Chatham Rise, one of the highest offshore-primary production regions in New Zealand waters, hosts a great abundance and diversity of deep-sea cephalopods including the greater hooked squid, Moroteuthopsis ingens. Stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Se, V, and Zn) were assessed in female and male specimens of different size classes (89-563 mm mantle length). Values of δ13C and δ15N were overall higher in females and δ13C was further influenced by size and sex. Both muscular mantle (the largest fraction of the total body mass) and digestive gland (the known main storage organ for Ag, Cd, Cu and Zn in many cephalopods) tissues were analysed. Higher levels of Cd were observed in males than in females. A positive effect was found between size and Hg concentrations, which could be related to the ontogenetic descent of larger specimens into deeper waters, where they are exposed to higher Hg concentrations, and/or dietary shifts toward Hg-enriched prey with increasing size. This study provides trace element data for this abundant and ecologically important species, and further reveals higher trace element concentrations (especially Hg) in M. ingens from the Chatham Rise, compared to specimens from the sub-Antarctic zone.

Trace element analysis reveals bioaccumulation in the squid Gonatus fabricii from polar regions of the Atlantic Ocean.

The boreoatlantic gonate squid (Gonatus fabricii) represents important prey for top predators-such as marine mammals, seabirds and fish-and is also an efficient predator of crustaceans and fish. Gonatus fabricii is the most abundant cephalopod in the northern Atlantic and Arctic Ocean but the trace element accumulation of this ecologically important species is unknown. In this study, trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn) were analysed from the mantle muscle and the digestive gland tissue of juveniles, adult females, and adult males that were captured south of Disko Island off West-Greenland. To assess the feeding habitat and trophic position of this species, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were measured in their muscle tissue. Mercury concentrations were positively correlated with size (mantle length) and trophic position. The Hg/Se ratio was assessed because Se has been suggested to play a protective role against Hg toxicity and showed a molar surplus of Se relative to Hg. Cadmium concentrations in the digestive gland were negatively correlated with size and trophic position (δ15N), which suggested a dietary shift from Cd-rich crustaceans towards Cd-poor fish during ontogeny. This study provides trace element concentration data for G. fabricii from Greenlandic waters, which represents baseline data for a northern cephalopod species. Within West-Greenland waters, G. fabricii appears to be an important vector for the transfer of Cd in the Arctic pelagic food web.

Phenoloxidase activation in the embryo of the common cuttlefish Sepia officinalis and responses to the Ag and Cu exposure.

The prophenoloxidase (proPO) system catalyzing the melanin production is considered as implicated in the innate immune system in invertebrates. The phenoloxidase (PO)-like activity was detected in the cuttlefish embryo sampled at the end of the organogenesis and few hours before hatching. Various modulators of the PO activity were used to assess the triggering of the proPO activating system. The results demonstrated the evidence of a true PO activity in the cuttlefish embryo. However, SDS and LPS granted contrasting effects on the PO-like activity between the developmental stages suggesting a progressive maturation of the proPO system from the embryonic to the juvenile stages. In eggs exposed to dissolved trace metals all along the embryonic development, Ag (1.2 microg L(-1)) inhibited the PO-like activity in the cuttlefish embryo except at hatching time, suggesting the synthesis of a new "juvenile" form of the PO enzyme. In similar conditions as for Ag, Cu (230 microg L(-1)) stimulated and then inhibited the PO-like activity according to a progressive metal accumulation within the egg and suggesting the occurrence of a threshold, above which the toxicity of the essential metal reduced the PO activity.

Trends in concentrations of selected metalloid and metals in two bivalves from the coral reefs in the SW lagoon of New Caledonia.

The concentrations of nine elements (Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn) were measured in the oyster Isognomon isognomon and the edible clam Gafrarium tumidum from different sites along the SW New Caledonian coast which is subjected to important chemical inputs due to intense land-based mining activities (New Caledonia is the third world producer of nickel). Results indicate that concentrations in the two organisms mirrored the geographical differences in contamination levels as established through element analyses in sediment. On the basis of organism analyses, two out of the seven investigated stations can be considered as relative "reference" sites, except for As, for which very high levels were detected in clam and oyster tissues (up to 441 microg g(-1) dry wt for clams). Overall, our results indicate that both tropical organisms investigated could be used as valuable bioindicator species for surveying metal contamination in the coastal waters of New Caledonia with reasonable perspectives of wider application to other coral reef environments.

Does trophic level drive organic and metallic contamination in coral reef organisms?

Metallic and organic pollutants constitute a serious threat for coral reef ecosystems, potentially affecting a great number of species interacting within complex trophodynamic processes. Pesticides, PCBs and trace elements were measured on coral reef communities of three Pacific islands (Moorea, Wallis and New Caledonia) in relation with δ15N values, a proxy of trophic level. Several potential sources of organic matter, benthic invertebrates and fish belonging to various trophic strategies were sampled at each island. Wallis and New Caledonia displayed, respectively, the highest concentrations of pesticides and trace elements. In the three islands, most trace element concentrations (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and V) decreased when δ15N was rising (i.e. bioreduction), whereas Hg and Se biomagnified with increasing δ15N values. Only few trace elements in some islands did not show any significant trend in relation with δ15N (i.e., Ag in New Caledonia, Zn in Wallis and As plus Zn in Moorea). PCBs concentrations showed a significant bioreduction in New Caledonia and in Moorea, but a significant biomagnification in Wallis. Aldrin and heptachlor were the only pesticides to show a similar significant bioreduction in the three islands. Other pesticides, such as chlordecone, diazinon, endosulfan I and II, heptachlor-epoxide A and B, lindane and pp'-DDE displayed contrasted patterns (e.g. chlordecone significantly biomagnified in New Caledonia, significantly bioreduced in Wallis and did not displayed any significant trend in Moorea). Finally, for unclear reasons, Moorea displayed only negative significant correlations between δ15N and all pesticides (except pp'-DDT). Our results highlight that trophic level, here assessed through δ15N values, is a good predictor of metallic trace elements biomagnification or bioreduction in coral reef organisms. However, at large spatial scale, trophic level relevance to predict pesticides and PCBs biomagnification or bioreduction should be considered with caution and studied in close relation with local characteristics.

Seabird colonies as relevant sources of pollutants in Antarctic ecosystems: Part 2 - Persistent Organic Pollutants.

Despite typically not being taken into account (usually in favour of the 'global distillation' process), the input of persistent organic pollutants (POPs) through biological activities can be indeed relevant at the local scale in terrestrial polar environments when seabird colonies are considered. Seabirds can bioaccumulate and biomagnify POPs, gather in large numbers and excrete on land during their reproductive season, thus making them locally as relevant secondary sources of POPs. The first part of this study indicated that these colonies act as so for several essential and non-essential trace elements, and this second part tests the same hypothesis concerning POPs using the very same samples. Lichens (n = 55), mosses (n = 58) and soil (n = 37) were collected from 13 locations in the South Shetlands Archipelago during the austral summers of 2013-14 and 2014-15. They were divided in colony (within the colony itself for soil and within and surrounding the colony for vegetation) and control (at least 150 m away from any colony interference) and analysed for POPs such as organochlorine pesticides, polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers and stable isotopes (C and N). Results showed that colonies act clearly as a secondary source for PCBs and likely for hexachlorobenzene. As in the first part, probable local sources other than the colonies themselves are hypothesised because of high concentrations found in control sites. Again, soil seemed the most adequate matrix for the intended purposes especially because of some particularities in the absorption of animal-derived organic matter by vegetation, pointed out by stable isotope analyses.

Differential bioaccumulation behaviour of Ag and Cd during the early development of the cuttlefish Sepia officinalis.

Cuttlefish eggs were exposed to background concentrations of dissolved Ag and Cd, using the radiotracers (110m)Ag and (109)Cd. At different time of the embryonic development (50 days), some eggs were placed in non-contaminating conditions. During the experiment, the uptake and depuration kinetics, and distribution of these metals among the egg compartments (i.e. eggshell, vitellus, peri-vitelline fluid and embryo) were assessed. In parallel, experiments were conducted with sub-lethal concentrations of stable Ag and Cd (2 and 1 microgl(-1), respectively) to compare the metal behaviour at higher concentrations. From the spawning date up to 1 month of development, both metals were taken up efficiently by the eggs, reaching load/concentration ratio (LCR) of 1059+/-75 and 239+/-22 for (110m)Ag and (109)Cd, respectively. From this time onwards, (110m)Ag activity continued to increase in eggs, whereas (109)Cd kinetics displayed a significant decrease. Whatever the developmental stage, Cd was mainly associated with the eggshell all along the exposure experiment. In addition, both stable Cd concentrations and (109)Cd LCR remained low in the embryo all along the embryonic development, indicating that the eggshell acted as an efficient shield against the penetration of this metal. In contrast, (110m)Ag passed through the eggshell from day 30 onwards and was then accumulated in the embryo, which contained more than 40% of the whole egg metal burden at the end of the exposure period. In depuration conditions, it is noteworthy that Ag continued to accumulate in the embryo indicating translocation processes from the eggshell and a high affinity of the metal for the embryo tissues. Overall our results showed that at day 30 of the embryonic development the cuttlefish eggshell becomes permeable to Ag but not to Cd. Exposure to stable metals confirmed the saturation capacities of the eggshell for Cd and the Ag penetration properties.

Accumulation of nine metals and one metalloid in the tropical scallop Comptopallium radula from coral reefs in New Caledonia.

Uptake of waterborne Cd, Co, Mn and Zn was determined in laboratory experiments using radiotracer techniques (109Cd, 57Co, 54Mn and 65Zn). Labelled Zn was mainly accumulated in the digestive gland (65%) and Co in kidneys (81%); Cd and Mn were similarly distributed in digestive gland and gills. In a complementary field study, Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn were analysed in scallops collected at two stations showing different contamination levels. Digestive gland and kidneys displayed the highest concentrations. Ag, As, Cd, and Fe differed in soft tissues from the two stations, suggesting that Comptopallium radula could be a valuable local biomonitor species for these elements. Low Mn and Zn concentrations found in kidneys suggest that their content in calcium-phosphate concretions differs from the other pectinids. Preliminary risk considerations suggest that As would be the only element potentially leading to exposure of concern for seafood consumers.

Bioaccumulation of persistent organic pollutants in female common dolphins (Delphinus delphis) and harbour porpoises (Phocoena phocoena) from western European seas: geographical trends, causal factors and effects on reproduction and mortality.

Concentrations of polychlorinated biphenyls (PCBs) in blubber of female common dolphins and harbour porpoises from the Atlantic coast of Europe were frequently above the threshold at which effects on reproduction could be expected, in 40% and 47% of cases respectively. This rose to 74% for porpoises from the southern North Sea. PCB concentrations were also high in southern North Sea fish. The average pregnancy rate recorded in porpoises (42%) in the study area was lower than in the western Atlantic but that in common dolphins (25%) was similar to that of the western Atlantic population. Porpoises that died from disease or parasitic infection had higher concentrations of persistent organic pollutants (POPs) than animals dying from other causes. Few of the common dolphins sampled had died from disease or parasitic infection. POP profiles in common dolphin blubber were related to individual feeding history while those in porpoises were more strongly related to condition.

Geographic, seasonal and ontogenetic variation in cadmium and mercury concentrations in squid (Cephalopoda: Teuthoidea) from UK waters.

Cadmium (Cd) and mercury (Hg) levels were measured in the tissue samples of two loliginid (Alloteuthis sp. and Loligo forbesi) and two ommastrephid (Todarodes sagittatus and Todaropsis eblanae) squid species collected from research cruise and fishery (market) samples in UK waters during 2004-05. Concentrations of Cd were generally higher in the ommastrephids, in all tissues except muscle. Hg concentrations were higher in T. sagittatus than in the loliginids. In L. forbesi, metal concentrations differed between tissues and also varied in relation to body size, geographic origin, and season. Cd levels decreased with increasing body size. This may be related to a shift in the diet with growth, since small L. forbesi feed on benthic invertebrates that have relatively high Cd concentrations, whereas larger individuals prey mainly on fish that have low Cd concentrations. Hg levels increased with body size, indicating its retention, and they were highest at the end of the spawning season and in squid from the English Channel and the Scottish West Coast. It is likely that the ambient concentration of Hg in seawater plays an important part in its accumulation in squid tissues. As it is a short-lived species, L. forbesi may therefore function as a bioindicator species for Hg contamination of the marine environment. Our results indicate that there is no significant danger to humans from consuming squid from UK waters.

Metal and metalloid concentrations in the giant squid Architeuthis dux from Iberian waters.

This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in the tissues of the giant squid Architeuthis dux from the Mediterranean and Atlantic Spanish waters. As for other families of cephalopods, the digestive gland and the branchial hearts of Architeuthis showed the highest concentrations of Ag, Cd, Co, Cu, Fe, Ni, Se, V and Zn, highlighting their major role in the bioaccumulation and detoxification processes. With the exception of Hg, the muscles showed relatively low trace element concentrations. Nevertheless, this tissue contained the main proportion of the total As, Cr, Hg, Mn, Ni, and Zn body burden because muscles represent the main proportion of the squid mass. These findings suggest that the metal metabolism is overall the same as other cephalopod families from neritic waters. In females, Zn concentrations increased in the digestive gland with the squid's weight likely reflecting physiological changes during sexual maturation. Comparing the trace element concentrations in the tissues of Architeuthis, higher Ag, Cu, Hg and Zn concentrations in the squid from the Mediterranean reflected different exposure conditions. In comparison to other meso-pelagic squids from the Bay of Biscay, Cd concentrations recorded in the digestive gland suggest that Architeuthis might feed on more contaminated prey or that it displays a longer life span that other cephalopods.

Seabird colonies as relevant sources of pollutants in Antarctic ecosystems: Part 1 - Trace elements.

Global distillation is classically pointed as the biggest responsible for contaminant inputs in Polar ecosystems. Mercury (Hg) and other trace elements (TEs) also present natural sources, whereas the biologically mediated input is typically ignored. However, bioaccumulation and biomagnification combined with the fact that seabirds gather in large numbers into large colonies and excrete on land might represent an important local TEs input. A previous work suggested these colonies as sources of not only nutrients, but also organic contaminants. To evaluate a similar hypothesis for TEs, samples of lichen (n = 55), mosses (n = 58) and soil (n = 37) were collected in 13 locations within the South Shetlands Archipelago during the austral summers of 2013-14 and 2014-15. They were divided in: "colony" (within the colony itself for soil and bordering it for vegetation) and "control" (at least 50 m away from colony interference), analysed for TEs (As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) and stable isotopes (C and N). In most cases, soil seems the best matrix to assess colonies as TEs sources, as it presented more differences between control/colony sites than vegetation. Colonies are clearly local sources of organic matter, Cd, Hg and likely of As, Se and Zn. Conversely, Co, Cr, Ni and Pb come presumably from other sources, natural or anthropogenic. In general, isotopes were more useful for interpreting vegetation data due to fractionation of absorbed animal-derived organic matter. Other local Hg sources could be inferred from high levels in control sites, location and wind patterns.

Non-competitive resource exploitation within mosquito shapes within-host malaria infectivity and virulence.

Malaria is a fatal human parasitic disease transmitted by a mosquito vector. Although the evolution of within-host malaria virulence has been the focus of many theoretical and empirical studies, the vector's contribution to this process is not well understood. Here, we explore how within-vector resource exploitation would impact the evolution of within-host Plasmodium virulence. By combining within-vector dynamics and malaria epidemiology, we develop a mathematical model, which predicts that non-competitive parasitic resource exploitation within-vector restricts within-host parasite virulence. To validate our model, we experimentally manipulate mosquito lipid trafficking and gauge within-vector parasite development and within-host infectivity and virulence. We find that mosquito-derived lipids determine within-host parasite virulence by shaping development (quantity) and metabolic activity (quality) of transmissible sporozoites. Our findings uncover the potential impact of within-vector environment and vector control strategies on the evolution of malaria virulence.