Parasite Abundance Research Articles

How do noncompetent hosts cause dilution of parasitism? Testing hypotheses for native and invasive mosquitoes.

Parasite dilution occurs in varied systems, via multiple potential mechanisms. We used laboratory manipulation and field surveys to test for invader-induced parasite dilution via two specific mechanisms: host-host competition and encounter reduction. In the laboratory, single Aedes triseriatus larvae were exposed to one of eight combinations of: parasitic Ascogregarina barretti, +/-1 cohabiting Aedes albopictus larva during parasite exposure, and +/-1 cohabiting A. albopictus larva after infectious parasite removal. Larval infection intensity (predicted to decrease via dilution by encounter reduction) was not significantly affected by A. albopictus. Adult infection prevalence and intensity (predicted to decrease via dilution by host-host competition) were significantly greater with A. albopictus, suggesting parasite amplification by interspecific competition, an effect potentially mediated by competition increasing A. triseriatus development time. In the field, we tested for effects of potential dilution host abundances on prevalence and abundance of A. barretti in A. triseriatus larvae. Piecewise path analysis yielded no evidence of host-host competition impacting parasitism in the field, but instead indicated a significant direct negative effect of Aedes spp. abundance on parasite abundance in A. triseriatus, which is consistent with dilution via encounter reduction in the field, but only in tree holes, not in man-made containers. Our results are consistent with the hypothesis that a noncompetent invader can alter the native host-parasite relationship, but our laboratory and field data yield differing results. This difference is likely due to laboratory experiment testing for per capita effects of dilution hosts on parasitism, but field analysis testing for effects of dilution host abundance on parasitism. Individually, host-host competition with the invader amplifies, rather than dilutes, parasite success. In contrast, our path analysis is consistent with the hypothesis that dilution of parasitism results from increased abundance of noncompetent hosts in the field.

Equal contributions of feline immunodeficiency virus and coinfections to morbidity in African lions.

Feline immunodeficiency virus (FIV) is a pathogenic lentivirus related to human and simian immunodeficiency viruses that has been associated with AIDS-like pathologies in domestic and wild cats, as well as in hyenas. Despite known pathologies, progressive immunosuppression and ill health effects driven by these lentiviruses in association with other secondary infections remain understudied in free-ranging species. Here, the role of coinfections by gastrointestinal parasites and tick-borne hemoparasites for FIV disease progression was explored in 195 free-ranging African lions (Panthera leo) living in Kruger National Park (KNP), South Africa. Using statistical methodology, we evaluated the effects of FIV on a range of health indicators to explore how direct and indirect effects of FIV and associated coinfections align to determine lion health outcomes. Findings show direct negative effects of FIV on host immunity and nutritional status, and exacerbation of aggressive behaviors, conditions which may increase exposure/susceptibility to other secondary infections. When taken together, the contribution of coinfecting parasites to morbidity in lions is of similar magnitude as direct effects of FIV infection alone, suggesting that the particular coinfection assemblage may play a role in mediating disease progression within natural lion populations.

Biotic and abiotic drivers affect parasite richness, prevalence and abundance in Mytilus galloprovincialis along the Northern Adriatic Sea.

Although it is generally known that a combination of abiotic and biotic drivers shapes the distribution and abundance of parasites, our understanding of the interplay of these factors remains to be assessed for most marine host species. The present field survey investigated spatial patterns of richness, prevalence and abundance of parasites in Mytilus galloprovincialis along the coast of the northern Adriatic Sea. Herein, the relationships between biotic (host size, density and local parasite richness of mussel population) and abiotic (eutrophication and salinity) drivers and parasite richness of mussel individuals, prevalence and abundance were analysed. Local parasite richness was the most relevant factor driving parasite species richness in mussel individuals. Prevalence was mainly driven by eutrophication levels in three out of four parasite species analysed. Similarly, abundance was driven mainly by eutrophication in two parasite species. Mussel size, density and salinity had only minor contributions to the best fitting models. This study highlights that the influence of abiotic and biotic drivers on parasite infections in mussels can be differentially conveyed, depending on the infection measure applied, i.e. parasite richness, prevalence or abundance. Furthermore, it stresses the importance of eutrophication as a major factor influencing parasite prevalence and abundance in mussels in the Adriatic Sea.

Plant Parasitic Nematode Abundance and Diversity in Potato (Solanum tuberosum) Cultivation at Various Altitudes in Wonosobo and Banjarnegara

Plant-parasitic nematodes are one of the causes of yield loss in potato cultivation. Currently, information on the diversity, abundance, and dominance of potato parasitic nematode genera is not available. This research aimed to determine the pattern of distribution, abundance, and dominance of parasitic nematode genera on potato plant (Solanum tuberosum) in Wonosobo and Banjarnegara Districts at various altitudes i.e.: 1,250--1,500; 1,500--1,750; 1,750--2,000; and 2,000--2,250 meters above sea level (m.a.s.l.). Soil rhizosphere and root samples were collected, and nematodes were extracted using the Whitehead tray modification technique. The nematodes were adjusted with Formalin Acetic acid Alchohol (FAA), mounted, and identified based on morphological characters. The diversity index was determined to distinguish plant-parasitic nematode diversity. Six genera of potato plant-parasitic nematodes were found, namely Meloidogyne, Hirschmanniella, Globodera, Criconemoides, Helicotylenchus, and Xiphinema. The highest population of plant-parasitic nematodes was found at 1,250–1,500 m.a.s.l. from both root and soil samples. The nematode populations were 56.67 nematodes/5 g root and 103.33 nematodes/100 g of soil. The abundance of parasitic nematodes did not differ significantly among different altitudes in both districts. The dominant parasitic nematodes in soil samples were Meloidogyne with 16.78%, while Globodera was 13.98%. The Shannon-Wiener index implied that the diversity of parasitic nematodes of potato plants and stability of community in Wonosobo and Banjarnegara Districts were categorized as low.

Weighing the predictors: host traits and coinfecting species both explain variation in parasitism of Rock Ptarmigan

AbstractTesting hypotheses in ecological and evolutionary parasitology can require testing whether host traits or coinfecting parasites explain variation in parasitism by focal species. However, when host traits and coinfecting parasites are considered separately, relations between either and parasitism by focal species can be spurious—a problem that is addressed when both are considered together. We assessed whether abundances of focal parasites related to host age/sex and coinfecting parasites for three endoparasites and nine ectoparasites of Icelandic Rock Ptarmigan (Lagopus muta) collected over 12 yr (2006–2017), and quantified the variation in focal parasitism explained by these predictors. Host traits and coinfecting parasites explained significant variation in abundance of all nine focal parasite species for which models converged, when those models were based on groups of parasites sharing tissue tropism and/or transmission pathways and included year as a random effect. We found a single spurious relation: a host age–sex interaction effect that was removed once concurrent parasitism was considered. When considering focal parasites within groups of coinfecting parasites, we found cases of positive, negative, and lacks of correlations. The amount of variation in focal parasite abundance explained by host traits versus coinfecting parasites depended on the focal parasite and its group. Overall variation explained was both related to the prevalence of the focal parasite, possibly due to underlying parasite aggregation, and similar to variation explained in other models in ecology and evolution. We conclude that host traits and coinfecting parasites often combine to determine infection by focal species. Future studies should also explore the mechanisms underlying parasite–parasite relations and their potential impacts on host demography for this and other study associations, and assess relative effects of host traits and coinfecting parasites on focal parasitism.

Digital Droplet PCR-Based Environmental DNA Tool for Monitoring Cryptocaryon irritans in a Marine Fish Farm from Hong Kong

The adoption of new investigative strategies based on environmental DNA (eDNA) can be used to monitor parasites, associated bacterial microbiomes, and physical-chemical parameters in fish farms. In this study, we used the economically important and globally distributed fish ciliate parasite Cryptocaryon irritans as a model to understand the parasite abundance and potential drivers of its presence in marine fish farms. Environmental (rainfall) and physical-chemical (temperature, oxygen, salinity, pH) data collected from a marine fish farm in Hong Kong were analyzed together with the eDNA approach targeting C. irritans abundance based on digital droplet PCR and 16S metagenomics to determine associations and triggers between parasites and specific bacterial groups. Rainfall and temperature demonstrated positive associations with high abundance of C. irritans (eDNA) at the studied marine fish cage farm. However, rainfall was the only parameter tested that demonstrated a significant association with parasite eDNA, indicating that the raining season is a risky period for fish farmers in Hong Kong. Coraliomargarita was the bacterial genus with the most significant relationship with low abundance of C. irritans in water. Understanding the environmental triggers of ciliate parasites propagation and associated bacterial microbiome could elucidate new insights into environmental control, microbial management, and promote the reduction of chemical use in marine fish farms.

Parasites of the past: 90 years of change in parasitism for English sole

Historical data are extremely rare but essential for ascertaining whether contemporary infectious disease burdens are unusual. Natural history collections are a valuable source of such data, especially for reconstructing long timelines of parasite abundance. We quantified the parasites of 109 museum specimens of English sole (Parophrys vetulus), an economically important flatfish, collected from Puget Sound, Washington, over a 90‐year period (1930–2019). We counted nearly 2,500 individual parasites representing 23 distinct species/morphotypes and four broad taxonomic groupings. Of the 12 taxa that were prevalent enough to include in the analysis, nine did not change in abundance over time, two (an acanthocephalan and a trematode) decreased, and one (another trematode) increased. By broad taxonomic grouping, nematodes, trematodes, and leeches exhibited no change over time, whereas acanthocephalans declined significantly. The diverging patterns among parasite taxa suggest a double‐edged sword of responses to long‐term ocean change: some parasites might be on the rise, while others are declining.

Why do parasites exhibit reverse latitudinal diversity gradients? Testing the roles of host diversity, habitat and climate.

The latitudinal diversity gradient (LDG) - in which species richness decreases from the equator toward the poles - is among the most fundamental distributional patterns in ecology. Despite the expectation that the diversity of parasites tracks that of their hosts, available evidence suggests that many parasites exhibit reverse latitudinal gradients or no pattern, yet the rarity of large-scale datasets on host-parasite interactions calls into question the robustness of such trends. Here, we collected parasitological data from a host group of conservation importance - lentic-breeding amphibians - to characterize the form and direction of relationships among latitude, parasite richness, and parasite load. The contiguous USA. 2000 to 2014. Lentic-breeding frogs and toads and their helminth parasites. We collected information on parasite richness and infection load for 846 amphibian populations representing 31 species. We combined these data with environmental and biological data to test for LDGs and potential mechanisms. Both parasite richness and abundance increased across 20 degrees of latitude - a reverse LDG. For parasite richness, this pattern was partially explained by latitudinal increases in wetland area, landcover diversity, and the richness of waterbirds - which function as definitive hosts for many amphibian parasites. Host body size also correlated positively with latitude and helminth richness, potentially reflecting increased habitat availability, greater host longevity, or a persistent phylogenetic signal. Parasite abundance associated positively with wetland area and landcover diversity, but negatively with amphibian taxonomic richness. Longitude exhibited non-linear relationships with parasite abundance and richness, which we suggest stem from large-scale variation in host availability (e.g., migratory bird flyways). With growing interest in the distribution of parasites and pathogens, these results highlight the importance of inverse latitudinal gradients while emphasizing the explanatory influence of host body size, habitat availability, and host diversity.

Diversity of endohelminths parasitizing bred Muscovy ducks Cairina moschata domestica (Anseriformes: Anatidae) from the eastern Brazilian Amazon.

Raising of Muscovy ducks Cairina moschata domestica for subsistence of human populations is common in northern Brazil, although their helminth infections have been poorly investigated, despite the possible presence of helminths with zoonotic potential. The aim of this study was to investigate the diversity of parasite endohelminths in C. moschata domestica raised in the Marajó Island region, state of Pará, Brazilian Amazon region. Of 33 specimens examined, 90.9% were parasitized by one or more parasite species, for a total of 926 parasites recorded. The species mean richness of endohelminths varied from 0 to 6, and there was a predominance of hosts with 1 to 2 species of parasite endohelminths and low prevalence and low abundance of parasites. This was the first report of larvae of Anisakis sp., Contracaecum sp., Hysterotylacium sp., Raphidascaris sp., Eustrongylides sp., Syngamus sp., Ascocotyle sp. and Athesmia heterolecithodes for C. moschata domestica. The parasitic community of C. moschata domestica was composed of 11 species, with a high species richness for nematode species and a small number of digeneans.

Lutzomyia longipalpis Antimicrobial Peptides: Differential Expression during Development and Potential Involvement in Vector Interaction with Microbiota and Leishmania.

Antimicrobial peptides (AMPs) are produced to control bacteria, fungi, protozoa, and other infectious agents. Sand fly larvae develop and feed on a microbe-rich substrate, and the hematophagous females are exposed to additional pathogens. We focused on understanding the role of the AMPs attacin (Att), cecropin (Cec), and four defensins (Def1, Def2, Def3, and Def4) in Lutzomyia longipalpis, the main vector of visceral leishmaniasis in the Americas. Larvae and adults were collected under different feeding regimens, in addition to females artificially infected by Leishmania infantum. AMPs’ gene expression was assessed by qPCR, and gene function of Att and Def2 was investigated by gene silencing. The gene knockdown effect on bacteria and parasite abundance was evaluated by qPCR, and parasite development was verified by light microscopy. We demonstrate that L. longipalpis larvae and adults trigger AMPs expression during feeding, which corresponds to an abundant presence of bacteria. Att and Def2 expression were significantly increased in Leishmania-infected females, while Att suppression favored bacteria growth. In conclusion, L. longipalpis AMPs’ expression is tuned in response to bacteria and parasites but does not seem to interfere with the Leishmania cycle.

Impacts of Seagrass on Benthic Microalgae and Phytoplankton Communities in an Experimentally Warmed Coral Reef Mesocosm

The effects of seagrass on microalgal assemblages under experimentally elevated temperatures (28°C) and CO2 partial pressures (pCO2; 800 μatm) were examined using coral reef mesocosms. Concentrations of nitrate, ammonium, and benthic microalgal chlorophyll a (chl-a) were significantly higher in seagrass mesocosms, whereas phytoplankton chl-a concentrations were similar between seagrass and seagrass-free control mesocosms. In the seagrass group, fewer parasitic dinoflagellate OTUs (e.g., Syndiniales) were found in the benthic microalgal community though more symbiotic dinoflagellates (e.g., Cladocopium spp.) were quantified in the phytoplankton community. Our results suggest that, under ocean acidification conditions, the presence of seagrass nearby coral reefs may (1) enhance benthic primary productivity, (2) decrease parasitic dinoflagellate abundance, and (3) possibly increase the presence of symbiotic dinoflagellates.

Host-parasite associations in a population of the nectarivorous bat Anoura geoffroyi (Phyllostomidae) in a cave in a Brazilian ferruginous geosystem

Parasitic relationships between Neotropical bats and their ectoparasites are not well known, even though parasitism is one of the factors that can affect the fitness of a host population. This study characterized parasite-host relationships in relation to sex, age, body size and reproductive status in a population of Anoura geoffroyi using the indices of Prevalence, Mean Intensity and Mean Abundance. Total prevalence for 93 sampled bats was 94.6%. Two species of streblid flies that are considered primary parasites of A. geoffroyi, Exastinion clovisi (n = 203) and Anastrebla modestini (n = 152), were the most abundant ectoparasites, followed by Trichobius sp. (n = 7). Two mite species, Periglischrus vargasi (Spinturnicidae) (n = 98) and Spelaeorhynchus praecursor (Spelaeorhynchidae) (n = 11), were also found. We recorded higher mean abundance and intensity of parasitism in pregnant females compared to reproductive males and reproductively inactive females, for different specific associations of ectoparasites. Host age and body condition had no effect on the parasitological indices. Even with high rates of parasitism, parasitic load did not influence host body condition, but infestation rates by mites were higher in reproductive males and higher by flies in reproductive females, showing that ectoparasites can have variable influences between the different stages of the life history of these host bats. Thus, the reproductive activity of the hosts could be an adverse factor for resistance to parasite infestations.

Phenological and intrinsic predictors of mite and haemacoccidian infection dynamics in a Mediterranean community of lizards.

Ectotherms are vulnerable to environmental changes and their parasites are biological health indicators. Thus, parasite load in ectotherms is expected to show a marked phenology. This study investigates temporal host–parasite dynamics in a lizard community in Eastern Spain during an entire annual activity period. The hosts investigated were Acanthodactylus erythrurus, Psammodromus algirus and Psammodromus edwardsianus, three lizard species coexisting in a mixed habitat of forests and dunes, providing a range of body sizes, ecological requirements and life history traits. Habitat and climate were considered as potential environmental predictors of parasite abundance, while size, body condition and sex as intrinsic predictors. Linear models based on robust estimates were fitted to analyse parasite abundance and prevalence. Ectoparasitic mites and blood parasites from two haemococcidian genera were found: Lankesterella spp. and Schellackia spp. Habitat type was the only predictor explaining the abundance of all parasites, being mostly higher in the forest than in the dunes. The results suggest that particularities in each host–parasite relationship should be accounted even when parasites infect close-related hosts under the same environmental pressures. They also support that lizard parasites can be biomarkers of environmental perturbation, but the relationships need to be carefully interpreted for each host–parasite assemblage.

Diversity of ectoparasites and endoparasites infecting Brachyplatystoma vaillantii (Siluriformes: Pimelodidae), a large migratory catfish from the Amazon

ABSTRACT Brachyplatystoma vaillantii is a large migratory catfish widely distributed in the Amazon basin, but its parasitic fauna is still poorly known. As it is an important fishery resource in the region of the Amazonas River estuary, the aim of this study was to investigate the parasite community in B. vaillantii from a tributary of the Amazonas River estuary system, in Brazil. We examined 31 juvenile fish, of which 80.6% were parasitized, and a total of 586 parasites were collected. We identified Dermidospermus brachyplastystimae and Dermidospermus araguiensis (Monogenea), Genarchella genarchella (Digenea), Harriscolex piramutab (Cestoda), Pseudoterranova sp. (Nematoda), Ergasilus xinguensis (Crustacea) and mites (Acarina). The dominance was of Pseudoterranova sp. larvae. The parasite community of B. vaillantii was composed of low values of species richness (2.0 ± 1.4), evenness (0.18 ± 0.21) and diversity (0.32 ± 0.37), with predominance of ectoparasite species with low prevalence, low abundance and overdispersion. Host body weight was the main correlate of parasite diversity and abundance, and a diet rich in crustaceans and other invertebrates may be important in structuring the parasite community of B. vaillantii. This is the first report of Dermidospermus brachyplastystimae and D. araguiensis, Pseudoterranova sp. and G. genarchella for B. vaillantii.

Abundance of anuran parasites and pesticide pollution from lowland and highland golf courses

Aim: This study aimed to determine the pesticide pollution and prevalence of protozoa in anurans from lowland and highland golf courses in Malaysia and to observe the relationship between environmental factors (water quality index and pollutants) and the presence of protozoa in anurans. Methodology: Water quality index and pesticide levels (metsulfuron methyl) were measured at three locations, i.e. Jeriau river, Fraser's hill golf course in Pahang, and UKM Danau golf club in Selangor. Microscopy techniques were used to identify and examine the prevalence of protozoa and haemoparasites in anuran organs (stomach, kidney, liver, intestine, rectum, and blood). Results: A total of 140 anurans were collected from the study areas. Jeriau river had the highest water quality compared to Fraser's hill golf course and UKM Danau golf club. Metsulfuron methyl concentrations at all three locations were under permissible level (0.001–0.01 mg l-1). Approximately, 30% of the anurans were infected with ≥ 1 protozoa, of which 22.14% were from phylum Opalinata and 10.71% were from phylum Ciliophora (Nyctotherus cordiformis). Approximately 44.44% of the anurans were infected with ≥ 1 groups of haemoparasites, which included Trypanosoma, Haemogregarina, Lankesterella, Aegyptianella and Microfilaria. Interpretation: No significant relationship was found between the environmental parameters and the abundance of protozoa and haemoparasites in anurans from three locations, indicating that the prevalence of protozoa and haemoparasites in anurans is not influenced by environmental factors.

Ectoparasites infecting Mugil curema (Mugiliformes: Mugilidae) in Amapá state estuary, in the northern Brazilian coast region.

In fish, one of the most important interactions is that occur between parasite species and environment. Wild fish interactions with parasites of different taxa can result in diseases for fish and consequently damages to the fishing industry. This study investigated the ectoparasite fauna in Mugil curema (Valenciennes, 1836), in Amapá state estuary, in Brazilian coast region. The parasite prevalence was 51.4%, and a total of 282 parasites were collected among Ligophorus brasiliensis (Abdallah, Azevedo & Luque 2009), Excorallana longicornis (Lemos de Castro, 1960), larvae of Gnathia sp. and Ergasilus atafonensis (Amado & Rocha, 1995), but L. brasiliensis was the dominant parasite. The parasites presented highly aggregated dispersion, except for Gnathia sp. that had a random dispersion. There was a predominance of hosts non-parasitized and parasitized by one species. The relative condition factor did not differ between parasitized and non-parasitized fish. The body size of hosts did not influence the parasite abundance. The community of ectoparasites consisted of low species richness with low infection levels. This is the first study on parasites of fish from the coast of the State of Amapá and is the first report of Gnathia sp. for M. curema.

Effects of nano- or microplastic exposure combined with arsenic on soil bacterial, fungal, and protistan communities

The soil protistan community makes important contributions to the ecological functions of soil. However, our knowledge of the effects of pollutants, especially plastic particles, on the soil protistan community is still very limited compared to our knowledge on other soil microbes, such as bacterial and fungi. In this study, we revealed the effects of combined and single pollution caused by arsenic (As) and microplastics/nanoplastics (MPs/NPs) on bacterial, fungal and protistan communities. Our results revealed that combined pollution through As and MPs/NPs distinctly affected the composition and structure of the soil protistan communities (P < 0.05), but in the case of bacteria, only some families were altered, and there was no impact on fungi. Changes of soil protistan communities might be mainly due to As pollution, and MPs/NPs exposure increased this detrimental effect. Further, As + MPs exposure greatly increased the abundance of soil protistan parasites, and As + NPs exposure caused an evident decrease in the abundance of soil protistan consumers (P < 0.05). These findings indicate that combined pollution by As and MPs/NPs can affect the ecological functions of soil by altering soil protistan communities. These results will help enhance our understanding of the impact of plastic particles on soil ecosystems.

Diversity and Ecology of Endohelminth Parasites in a Fish Assemblage of an Amazon River Tributary in Brazil.

This study investigated the diversity and ecology of endohelminth parasites in an assemblage of 15 omnivorous and four piscivorous fish species in a tributary of the Amazon River (Brazil). Fish were collected bimonthly to evaluate the diversity and ecology of endohelminth parasites in omnivorous and piscivorous fish species in a tributary of the Amazon River using traditional methods and other methods. A total of 4,234 parasites of 19 species (8 Nematoda, 5 Acanthocephala, 4 Digenea and 2 Cestoda) were sampled from 531 fish specimens. Procamallanus (Spirocamallanus) inopinatus and Contracaecum sp. were the predominant parasite species, and the parasites showed an aggregated dispersion pattern. Positive correlation was shown between the abundance of Contracaecum sp., Hysterothylacium patagonense and P. (S.) inopinatus, and the body size of 15.8% of the host fish examined. No difference was shown for Shannon diversity index and evenness between omnivorous and piscivorous hosts, but the richness, abundance and intensity of parasites were greater in piscivorous host fish. In the fish assemblage, the presence of parasites in the larval and adult stages suggests that these are intermediate, paratenic and definitive hosts, reflecting the feeding habits of the omnivorous and piscivorous host species. 74.1% of the parasite species were new records for the different host species examined. The size of the hosts, trophic level and diet had an influence on the structuring of endohelminth communities and infracommunities.

Multivariate Abundance Analysis of Multi-Host/Multi-Parasite Lungworms in a Sympatric Wild Ruminant Population

In the analysis of a multi-host/multi-parasite system and its associated risk factors, it is particularly interesting to understand the natural dynamics among pathogens, their hosts, and the environment in wildlife populations. This analysis is particularly feasible in a scenario where multiple overlapping host populations are present in high densities, along with a complex community of parasites. We aimed to describe and analyze the naturally occurring lungworm polyparasitism in a wild ruminant community in Southeast Spain. The respiratory tracts of 250 specimens belonging to four different species (red deer, mouflon, Iberian ibex, and fallow deer) were studied. Almost half (48.0%) of the animals were infected with bronchopulmonary nematodes. Seven different nematodes were identified of which two genera (Protostrongylus spp. and Dictyocaulus spp.) and three additional species (Cystocaulus ocreatus, Muellerius capillaris, and Neostrongylus linearis) were recorded in at least two ruminants, with the mouflon as the commonest host. Our study shows a significant effect of host species and sampling area, plus a marginal effect of age, on parasite multivariate abundance at the host population level. Mouflon and adults of all hosts appear to carry the highest parasite load on average. From a spatial perspective, the highest parasite abundance was detected at the central part of the park.

Life history evolution of sea lamprey is predicted to reduce the effectiveness of pesticide control

Pesticide resistance can evolve in pest populations as a strategy to increase reproduction and survival in the face of strong selective pressures imposed by chemical control. Invasive sea lamprey (Petromyzon marinus) in the Great Lakes have not evolved physiological resistance after 62 years of control with a chemical pesticide, 3-trifluoromethyl-4-nitrophenol (TFM), which is applied to tributaries to target the larval stage of the life cycle. However, it is unknown whether sea lamprey life histories could evolve in response to TFM. Sea lamprey larvae undergo metamorphosis within tributaries, transforming from filter feeders into parasites that emigrate to the lake where they prey on other fishes. We developed an eco-genetic model to evaluate if TFM treatment, which has an estimated mortality rate on larvae >90%, can cause evolution of the ages and lengths at metamorphosis and maturation. Our model predicts a rapid decrease in the size threshold at metamorphosis, resulting in an earlier age at outmigration from tributaries, and reducing the probability of larvae dying from pesticide treatment. The evolutionary response in metamorphosis increased with the number of tributaries treated each year. Conversely, there was little evolution of the size threshold at maturation. Importantly, we identify a cost of evolution to sea lamprey control whereby TFM-induced evolution of metamorphosis causes an increase in parasite abundance, which is the life stage destructive to fish populations. Mitigation measures are prudent to recognize and address the potential for reduced efficacy of TFM control and the resultant threat posed to fisheries resources in the Great Lakes.