Identification of California Condor Estrogen Receptors 1 and 2 and Their Activation by Endocrine Disrupting Chemicals

Microplastic in northern anchovies (Engraulis mordax) and common murres (Uria aalge) from the Monterey Bay, California USA - Insights into prevalence, composition, and estrogenic activity

Microplastic (particle size <5 mm) is considered an emerging threat to the marine environment, yet data are limited for coastal ecosystems. To provide information related to microplastic in a coastal system, we used alkaline tissue digestion and Raman spectroscopy to quantify the prevalence and composition (e.g. fiber, fragment, foam, etc.) of anthropogenic microparticles in the digestive tracts of northern anchovies (Engraulis mordax, anchovy, n = 24), and common murres (Uria aalge, murre, n = 19) from the Monterey Bay, California USA. We also determined microplastic prevalence and composition in seawater (n = 12 17-h sampling periods representing ∼46,000 L sampled) from two Monterey Bay intake systems (Moss Landing, CA and Santa Cruz, CA USA). Microparticles recovered from murre digestive tracts were assessed for estrogenic activity using an in-vitro estrogen receptor activation assay. Suspected anthropogenic microparticles based on visual characteristics were recovered from all sample types with ∼2 particles per 1000 L from the seawater sampling periods, 58% prevalence in anchovies, and 100% prevalence in murres. Across samples of seawater, anchovies, and murres, the most abundant microparticle type found were fibers (78%), followed by fragments (13%), foam (6%), film (2%), and beads (1%). Raman spectroscopy identified 57% of microparticles (excluding dye-prominent and unknown) as plastic (synthetic, semi-synthetic, or blends). Almost one quarter (23%) of the murre digestive tracts contained microparticles that exhibited estrogenic activity. Our study describes the widespread occurrence, composition, and potential estrogenic activity of microplastic in the Monterey Bay and provides important information to aid in the understanding of microplastic contamination in coastal systems.

Assessing Marine Endocrine-Disrupting Chemicals in the Critically Endangered California Condor: Implications for Reintroduction to Coastal Environments

Coastal reintroduction sites for California condors (Gymnogyps californianus) can lead to elevated halogenated organic compound (HOC) exposure and potential health impacts due to the consumption of scavenged marine mammals. Using nontargeted analysis based on comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS), we compared HOC profiles of plasma from inland and coastal scavenging California condors from the state of California (CA), and marine mammal blubber from CA and the Gulf of California off Baja California (BC), Mexico. We detected more HOCs in coastal condors (32 ± 5, mean number of HOCs ± SD, n = 7) than in inland condors (8 ± 1, n = 10) and in CA marine mammals (136 ± 87, n = 25) than in BC marine mammals (55 ± 46, n = 8). ∑DDT-related compounds, ∑PCBs, and total tris(chlorophenyl)methane (∑TCPM) were, respectively, ∼7, ∼3.5, and ∼148 times more abundant in CA than in BC marine mammals. The endocrine-disrupting potential of selected polychlorinated biphenyls (PCB) congeners, TCPM, and TCPMOH was determined by in vitro California condor estrogen receptor (ER) activation. The higher levels of HOCs in coastal condors compared to those in inland condors and lower levels of HOC contamination in Baja California marine mammals compared to those from the state of California are factors to consider in condor reintroduction efforts.

Identification of California condor (Gymnogyps californianus) estrogen receptor variants and their activation by xenoestrogens

California condors released in costal sites are exposed to high levels of xenoestrogens, particularly p,p'-DDE, through scavenging of marine mammal carcasses. As a result, coastal condors carry a higher contaminant loads and experience eggshell thinning when compared to their inland counterparts. Given that condor estrogen receptors (Esrs) are activated by physiologically relevant levels of xenoestrogens, differences in vulnerability to endocrine disruption may exist depending on which Esr variant(s) an individual condor possesses. This work aims to characterize genetic polymorphisms in estrogen receptor genes (ESRs) in California condors; one identified for condor estrogen receptor 1 (ESR1) (N161S, E162D) and one in the ESR2 (T114M) gene. Each variant was confirmed in individual founder birds by direct PCR sequencing as well as in first generation offspring to understand the introduction of the alleles into the pedigree (6 birds for ESR1 and 5 birds for ESR2). Site-directed mutagenesis was performed on wild type receptors to produce each of the full-length ESR variants and activation of Esr1 and Esr2 variant and wild type receptors by xenoestrogens was compared. Maximal activation of the variant form of Esr1 was significantly higher (p < 0.05) in response to ethinyl estradiol (EE₂), o,p'-DDE, p,p'-DDE, p,p'-DDT and p,p'-DDD compared to wild type Esr1. For Esr2 the wild type maximal activation was higher in response to o,p'-DDE, p,p'-DDE, o,p'-DDT, and p,p'-DDT. Although significant differences in activation of condor Esr variants by xenoestrogens occurred at high (micromolar) concentrations, they correspond to circulating concentrations previously reported in coastal birds. Release and relocation of California condors to the coast is a promising avenue for recovery, however, reproductive problems associated with xenoestrogen exposure pose a sub-lethal threat to long-term success. Based on above findings, future release decisions could be informed by ESR form(s) individual birds possess to reduce deleterious effects of xenoestrogen exposure and ultimately improve reproductive success in wild populations.

Reproductive Impacts of Endocrine-Disrupting Chemicals on Wildlife Species: Implications for Conservation of Endangered Species

Wildlife have proven valuable to our understanding of the potential effects of endocrine-disrupting chemicals (EDCs) on human health by contributing considerably to our understanding of the mechanisms and consequences of EDC exposure. But the threats EDCs present to populations of wildlife species themselves are significant, particularly for endangered species whose existence is vulnerable to any reproductive perturbation. However, few studies address the threats EDCs pose to endangered species owing to challenges associated with their study. Here, we highlight those barriers and review the available literature concerning EDC effects on endangered species. Drawing from other investigations into nonthreatened wildlife species, we highlight opportunities for new approaches to advance our understanding and potentially mitigate the effects of EDCs on endangered species to enhance their fertility.

Integrating Genomic Data Sets for Knowledge Discovery: An Informed Approach to Management of Captive Endangered Species

Many endangered captive populations exhibit reduced genetic diversity resulting in health issues that impact reproductive fitness and quality of life. Numerous cost effective genomic sequencing and genotyping technologies provide unparalleled opportunity for incorporating genomics knowledge in management of endangered species. Genomic data, such as sequence data, transcriptome data, and genotyping data, provide critical information about a captive population that, when leveraged correctly, can be utilized to maximize population genetic variation while simultaneously reducing unintended introduction or propagation of undesirable phenotypes. Current approaches aimed at managing endangered captive populations utilize species survival plans (SSPs) that rely upon mean kinship estimates to maximize genetic diversity while simultaneously avoiding artificial selection in the breeding program. However, as genomic resources increase for each endangered species, the potential knowledge available for management also increases. Unlike model organisms in which considerable scientific resources are used to experimentally validate genotype-phenotype relationships, endangered species typically lack the necessary sample sizes and economic resources required for such studies. Even so, in the absence of experimentally verified genetic discoveries, genomics data still provides value. In fact, bioinformatics and comparative genomics approaches offer mechanisms for translating these raw genomics data sets into integrated knowledge that enable an informed approach to endangered species management.