Sims 4 Reptile Skin: The Best Custom Content for Scaly Sims

The animals were obtained by a private breeder and kept in a terrarium on conventional litter, through several moult cycles. The scales were mounted on a flat non-reflective substrate with double-sided tape with the outside skin surface pointing away from the surface.

Despite widespread recognition of significant data deficiencies, reptiles remain a relatively understudied taxon in ecotoxicology. To conduct ecological risk assessments on reptiles frequently requires using surrogate taxa such as birds, but recent research suggests that reptiles have significantly different exposure profiles and toxicant sensitivity. We exposed western fence lizards, Sceloporus occidentalis, to the same quantities of three model chemicals via oral (gavage) and dermal (ventral skin application) exposure for either 24 or 48 hours. Three phthalate esters (di-methyl phthalate [DMP], di-iso-butyl phthalate [DIBP], and di-n-octyl phthalate [DNOP]) were chosen as model chemicals because they represent a gradient of lipophilicity but are otherwise structurally similar. Overall, the more lipophilic phthalates (DIBP and DNOP) were found to have higher concentrations in tissues than the less lipophilic DMP. Significant differences in tissue concentrations between DIBP and DNOP were tissue-dependent, suggesting that delivery to a site of action following exposure is not only a simple function of lipophilicity. In dermal treatments, DMP usually had fewer detections (except in ventral skin samples), suggesting that lipophilicity (log Kow>2) is a requirement for uptake across the skin. In general, tissue residues were greater in oral treatments than dermal treatments (significant in adipose and liver tissue), but differences were driven strongly by differences in DMP which did not appear to be absorbed well across skin. When differences in tissue residue concentrations between oral and dermal exposure did occur, the difference was not drastic. Taken together these results suggest that dermal exposure should be considered in risk assessments for reptilian receptors. Dermal exposure may be an especially important route for reptiles as their ectothermic physiology translates to lower energetic demands and dietary exposure compared to birds and mammals.

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Reptiles appear to be declining globally, and contaminants are one of many possible stressors contributing to these declines [1]. Despite recognition that chemical contaminants can and do impact reptiles, the taxon remains understudied in ecotoxicology [2], [3] despite several calls for more research [4], [5]. One of the consequences of a lack of ecotoxicity and exposure data is that ecological risk assessments (ERA) on a reptilian species will have considerable uncertainty reducing the utility of assessment results for sound management decision-making. Because of a lack of reptile-specific data, birds are often used as surrogates for reptiles in ERAs. The use of avian surrogates in reptile ERAs, however, may be inappropriate and could result in gross underestimates of risk under certain exposure scenarios, or when reptiles are far more sensitive than birds to a particular contaminant [3]. In addition, there has been an increased interest in explicitly considering reptiles and amphibians in the risk assessment process (see, for example, [6]). Unfortunately, so few data on reptile ecotoxicity are available that even a generalized understanding of contaminant toxicity and exposure is elusive in this taxon.

The introduction of the western fence lizard (Sceloporus occidentalis) as a vetted model organism for reptile ecotoxicity studies [7] has played a large role in increasing the availability of reptile toxicity data in recent years for metals [8], pesticides [9], and compounds of military importance [10], [11]. However, both estimates of exposure and estimates of toxicity are needed to conduct meaningful ERAs. Experimental investigations of the dynamics and importance of contaminant exposure are rare for most terrestrial taxa [12] and, to our knowledge, no data on the nature and extent of contaminant exposure exist for any reptile species.

Current approaches in ERAs generally focus on dietary exposure as the sole (or dominant) route of contaminant exposure such that other routes are infrequently considered (e.g., [13]). There has been a recent surge in interest regarding the explicit incorporation of dermal exposure into ecological risk assessments [14], [15]. Dermal contaminant exposure may be more important than dietary exposure immediately following a pesticide spray, even in birds, which generally have very high dietary exposure as a result of high energetic demands [16], [17]. The relative importance of dermal exposure is likely to be especially significant for reptiles as their lower metabolic rate results in fewer daily feeding events compared with birds and mammals. Reptiles would, therefore, be expected to have less dietary exposure than birds and mammals of a similar trophic level. Importantly, because reptiles have a high percentage of body surface area potentially in contact with a contaminated substrate, the relative contribution of dermal exposure may be quite high [3].

The purpose of this research was twofold. The first objective was to determine the relative contribution of dermal and oral contaminant exposure in a model reptile, the western fence lizard, under controlled laboratory conditions. Secondly, we sought to determine the role of lipophilicity in understanding and potentially predicting the relative importance of oral and dermal exposure to total contaminant exposure. To address these objectives, we exposed western fence lizards to three phthalate esters representing a lipophilicity gradient via both oral and dermal routes. We discuss results in light of the need to improve ERAs for reptiles.

Phthalates were very rarely detected in control lizards. Out of 12 samples from control lizards, DMP, DIBP, or DNOP were not detected in adipose or liver tissues. In blood, DIBP was detected in 7 samples with a mean concentration of 207.749.74 ng/g. In skin samples, DIBP and DNOP were detected in 6 samples each with means of 188.518.7 ng/g and 364.4108.3 ng/g, respectively. Because detections were relatively infrequent and of low concentration relative to treatment samples, concentrations detected in control sample tissues were not subtracted from treatment samples. In all tissues, control residue data was always significantly lower than both diet and dermal treatments (all p

Exposure of lizards to the same quantity of phthalate via oral and dermal exposure routes resulted in greater residues for oral in some cases (adipose tissue and liver), but not blood or skin. When there were significant differences between the two exposure routes, the differences in residue concentrations were generally not large. The exception is the large difference in residue in skin samples, with dermal exposure having much greater residues than oral exposure. In addition, in liver at 48 hours, dermal exposure resulted in greater residues than oral exposure, but our statistical analysis did not allow interactive post hoc comparisons. Overall, these results suggest that similar quantities of chemicals that are delivered via oral or dermal exposure routes will result in similar uptake and subsequent body residues, at least within 48 hours. To our knowledge, this is the first study to explore the relative roles of dermal and oral exposure in contaminant uptake and distribution to tissues in any reptile species.

Blood samples had more detections than liver samples. Parent compounds in blood samples up to 48 hours after exposure suggests relatively recent absorption of the phthalates from either skin or the gastrointestinal tract. Perhaps the slower reptile ectothermic physiology allowed the phthalates to continue to circulate in the blood stream even up to 48 hours after exposure. There was no significant difference in phthalate residues between oral and dermal exposures in whole blood, despite significant differences in adipose and liver tissue. Our results suggest that both exposure routes result in similar levels of circulation in blood. Perhaps the significant differences in liver are due to the fact that oral exposures are routed to the liver prior to circulation, while dermal exposure can immediately enter circulation.

Generally, phthalate tissue residues significantly differed among congeners. In general, DMP had lower tissue concentrations than DIBP and DNOP, except in liver. This result seems fairly consistent across exposure routes suggesting that DMP is not absorbed as well as the more lipophilic phthalates, regardless of exposure route. The difference between DIBP and DNOP is more complex and is tissue dependent. DNOP concentrations were significantly greater than DIBP in liver, the reverse was found for adipose tissue. As stated earlier, very lipophilic contaminants, such as DNOP, may not behave as expected [20]. In this case, perhaps DNOP was shunted to the liver following absorption, rather than accumulating in the adipose tissue. A consistent finding was the number of detections of DMP was almost always higher in oral exposures than in dermal exposures, suggesting that an even greater lipophilicity is needed to be absorbed dermally compared to oral exposure [27]. There may be a threshold lipophilicity below which chemicals are not absorbed well across the skin.

Although ERAs for terrestrial wildlife generally focus on estimating exposure via the dietary route, there has been some interest in exploring the role of dermal exposure but the focus has been more on avian than reptilian species. For example, following an experimental organophosphate pesticide spray, dermal exposure resulted in greater cholinesterase suppression than either inhalation or oral exposure in bobwhite quail (Colinus virginianus) from 8 to 48 hours post-spray [16]. Domestic pigeons (Columba livia) exposed to three organophosphate pesticides via oral and dermal (feet application) exposure showed responses similar to those reported by Brooks et al. [28]. Pigeons exposed orally had greater mortality, but dermal exposure resulted in longer cholinesterase inhibition [32]. This pattern may be occurring in our current results as well. The concentration of DNOP in liver samples at 48 hours appears to be much higher from dermal exposure compared to oral (our statistical methods did not allow interactive post hoc comparisons, Figure 2). This is perhaps the result of continuing exposure to DNOP from external skin residues that are still being absorbed into circulation. Finally, birds inhabiting an orchard sprayed with azinphos-methyl had detectable concentrations on skin, feathers, and feet for up to 7 days post-spray [17]. Despite the evidence to suggest that dermal exposure is important for birds, regulatory assessments continue to emphasize dietary exposure over other exposure routes [15]. Dermal exposure is ignored for several reasons. First, oral exposure is often overestimated (e.g., assuming a bird feeds only in a pesticide treated field), and it is considered that the dermal exposure is taken into consideration by overestimating oral exposure. Second, there are less data and fewer established models available for dermal exposure, likely because it is often ignored in risk assessments. This results in risk assessments that may be overly conservative and with a great deal of uncertainty with regards to exposure modeling. Improving our understanding of dermal exposure will help to improve models that can be used to estimate dermal exposure and risk. 2ff7e9595c