Using chorioallantoic membranes for non-lethal assessment of persistent organic pollutant exposure and effect in oviparous wildlife

Abnormal persistence of the chorioallantoic membrane is associated with severe developmental abnormalities in freshwater turtles

Development in oviparous reptiles requires the correct formation and function of extra-embryonic membranes in the egg. In 2017, we incubated 2583 eggs from five species of freshwater turtle during a long-term ecological study and opened eggs that failed to hatch. We described a previously unreported developmental anomaly: the retention of an extra-embryonic membrane around 7 turtles (1 Spiny Softshell Turtle (Apalone spinifera (Le Sueur, 1827)), 1 Snapping Turtle (Chelydra serpentina (Linnaeus, 1758)), and 5 Northern Map Turtles (Graptemys geographica (Le Sueur, 1817))) that were alive but unhatched >14 days after their clutch mates had emerged. We investigated the association between retention of this membrane and the exhibition of other developmental deformities of varying severity, and we tested whether this novel abnormality was associated with reduced fertility or hatching success in affected clutches. Consultation of ∼150 years of literature suggests that we observed persistence of the chorioallantoic membrane (CAM; also called the chorioallantois). Our data suggest that clutches where at least one turtle exhibits a persistent CAM may also exhibit slightly reduced fertility or hatch success in the rest of the clutch compared with conspecific clutches that do not contain this anomaly. Future research should investigate the factors predicting CAM retention and other developmental abnormalities.

Maternal transfer and embryonic assimilation of trace elements in freshwater turtles after remediation of a coal fly-ash spill

Oviparous vertebrates maternally transfer elements to their offspring during egg production. Maternal transfer occurs because elements mimic, or are incorporated into, nutrients allocated to eggs, but likely differs among species depending on the quantities of specific nutrients allocated to eggs. Developing embryos are often assumed to assimilate all of the elements allocated to eggs, but this assumption has rarely been tested. We tested the hypothesis that maternal transfer and embryonic assimilation of trace elements differed between two species of freshwater turtles exposed to a recently-remediated coal fly-ash spill. Sternotherus odoratus transferred As, Se, and Zn, while Trachemys scripta transferred As, Hg, Se, Sr, and Zn. Logarithmic non-linear relationships between hatchling and egg concentrations indicated that turtles partially assimilated elements present in eggs. In systems contaminated with multiple trace elements, our data show that maternal transfer and embryonic assimilation are element- and species-specific, and may be inconsistent even among closely-related species.

Bioaccumulation in freshwater crabs. Endosulfan accumulation in different tissues of Zilchiopsis collastinensis P. (Decapoda: Trichodactylidae)

We examined the bioaccumulation of α- and β-endosulfan and endosulfan sulfate in tissues from the crab Zilchiopsis collastinensis. There was more endosulfan accumulated in the hepatopancreas (from <2 to 467.8 ng g(-1)) than in the gonads (from <2 to 52.1 ng g(-1)) or muscles (<2 ng g(-1)). The endosulfan concentrations in the hepatopancreas decreased over time and with the endosulfan dilution (p < 0.05). In the gonads there was little bioaccumulation, which did not vary over time (p > 0.05). The hepatopancreas is a dynamic organ that is able to depurate itself, whereas the gonads act as a sink for pesticides.

An investigation of the chick chorioallantoic membrane as an alternative model to various biological tissues for permeation studies

OBJECTIVES

The chick chorioallantoic membrane (CAM) was explored as a biological membrane for use in the study of drug permeation with a Franz diffusion cell.

METHODS

The CAM was removed from fertilized chicken eggs of embryo age 9-18 days. The permeation profiles of nicotine through the fresh CAM were first obtained with a Franz diffusion cell. The permeation profiles of nicotine through frozen CAM, snake skin, pig skin, pig retina and pig buccal mucosa were also determined and compared with those of the fresh CAM.

KEY FINDINGS

The permeability coefficient of the CAM varied with its age. The CAM at embryo age 13 was the most robust, showing the lowest standard error in permeability. It was thus chosen for comparative studies with snake skin, pig skin, retina and buccal mucosa. The CAM was found to be most similar to the buccal mucosa in terms of permeation profile and permeability coefficient values. Frozen CAM was also found to have a higher permeability coefficient than fresh CAM. The enhanced permeability was attributed to freezing, which affected the integrity of the CAM structure.

CONCLUSIONS

From the findings, CAM shows potential as an alternative to the pig buccal mucosa as an in-vitro buccal model. The robustness of the CAM for drug permeation studies is affected by its age.

Contaminant exposure in terrestrial vertebrates

Here we review mechanisms and factors influencing contaminant exposure among terrestrial vertebrate wildlife. There exists a complex mixture of biotic and abiotic factors that dictate potential for contaminant exposure among terrestrial and semi-terrestrial vertebrates. Chemical fate and transport in the environment determine contaminant bioaccessibility. Species-specific natural history characteristics and behavioral traits then play significant roles in the likelihood that exposure pathways, from source to receptor, are complete. Detailed knowledge of natural history traits of receptors considered in conjunction with the knowledge of contaminant behavior and distribution on a site are critical when assessing and quantifying exposure. We review limitations in our understanding of elements of exposure and the unique aspects of exposure associated with terrestrial and semi-terrestrial taxa. We provide insight on taxa-specific traits that contribute, or limit exposure to, transport phenomenon that influence exposure throughout terrestrial systems, novel contaminants, bioavailability, exposure data analysis, and uncertainty associated with exposure in wildlife risk assessments. Lastly, we identify areas related to exposure among terrestrial and semi-terrestrial organisms that warrant additional research.

Mercury and methylmercury accumulation and excretion in prairie voles (Microtus ochrogaster) receiving chronic doses of methylmercury

Methylmercury cation (MeHg) and divalent mercury (Hg++) accumulation in liver, kidney, and brain were quantified in prairie voles (Microtus ochrogaster) at 0, 3, 6, and 12 weeks during chronic exposure to aqueous MeHg. Dose groups received deionized water or aqueous solutions containing 9, 103, or 920 ng MeHg/ml. Our study presents temporal patterns of Hg++ and MeHg concentrations in organ tissues and makes inter-tissue comparisons at each time point to illustrate the accumulation and distribution of Hg species during the study. MeHg was accumulated in tissues for 3 weeks and then concentrations plateaued. Mercury accumulated in brain, liver, and kidney to average concentrations of 510 ng/g, 180 ng/g, and 3400 ng/g, respectively. MeHg and Hg++ concentrations were roughly equivalent in liver, kidney, and urine. MeHg concentrations in brain tissue were 2 to 20 times the concentrations of Hg++. Regression analysis was also used to demonstrate the utility of urinalysis as an indicator of Hg++ and MeHg concentrations in organ tissue (p < 0.001).

Loggerhead sea turtle (Caretta caretta) egg yolk concentrations of persistent organic pollutants and lipid increase during the last stage of embryonic development

Data are scarce describing the concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides in sea turtle eggs. The purpose of this study was to establish appropriate sample collection methodology to monitor these contaminants in sea turtle eggs. Contaminant concentrations were measured in yolk samples from eggs that failed to hatch from three loggerhead sea turtle (Caretta caretta) nests collected in southern Florida to determine if concentrations change through embryonic development. One to three egg yolk samples per nest were analyzed from early, middle, and late developmental stages (n=22 eggs total). PCB and pesticide concentrations were determined by gas chromatography with electron capture detection (GC-ECD). Geometric mean concentrations of summation operatorPCBs (52 congeners), summation operatorDDTs, summation operatorchlordanes, and dieldrin in all eggs were 65.0 (range=7.11 to 3930 ng/g lipid), 67.1 (range=7.88 to 1340 ng/g lipid), 37.0 (range=4.04 to 685 ng/g lipid), and 11.1 ng/g lipid (range=1.69 to 44.0 ng/g lipid), respectively. Early and middle developmental stage samples had similar concentrations of PCBs and organochlorine pesticides on a wet-mass basis (ng/g tissue extracted), but the concentrations doubled by the late stage. This increase is most likely attributable to the 50% increase in lipid content observed in the late-stage yolk. These findings indicate that an early-stage sample cannot be directly compared to a late-stage sample, especially from different nests. These preliminary findings also allowed us to calculate the minimum number of eggs per nest required for analysis to obtain an acceptable mean concentration per nest. More research is required to investigate geographical trends of contaminant concentrations and potential health effects (i.e., abnormalities) caused by these contaminants on sea turtle development.