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Introduction
Published in Lawrence V. Tannenbaum, Ecological Risk Assessment, 2017
The experimental egg-injection system raises more questions than it answers. There do not appear to be opportunities for an incubating egg in a nest to absorb a chemical load. The featherless brood patch has never been described in the literature as a rich and overflowing chemical source that generously infuses eggs through the porous shell. Soil-to-plant chemical transfer, in a general sense, is not an overriding phenomenon at contaminated sites, and thus the twigs and grasses used to fashion nests are unlikely to bear sizeable stores of site-bound contaminants to dose the eggs that might lie against these materials. While the specific egg compartment into which a chemical load is artificially delivered might well correlate with instances where developmental effects take hold, it seems unlikely that potentially harmful toxic stores that arise in nature are confined to a singular compartment. If chemicals of either category that concern us (i.e., of the type that don’t belong in eggs altogether, or that could be expected to accumulate in eggs but not necessarily in alarming quantities) become stored in multiple or all egg compartments, of what utility are compartment-specific egg-injection studies? Consider that, while the experimental exogenous introduction of estrogen induces transformation of the left testicle into an ovotestis in males, and causes persisting Mullërian ducts and duct anomalies in males and females, respectively (Brunström et al., 2009), eggs in the real world are not exogenously exposed to estrogen.
A suggested bisphenol A metabolite (MBP) interfered with reproductive organ development in the chicken embryo while a human-relevant mixture of phthalate monoesters had no such effects
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Anna Mentor, Carl-Gustaf Bornehag, Maria Jönsson, Anna Mattsson
Representative images of control and MBP-exposed embryos of both sexes are illustrated in Figure 1 and the left and right gonad sizes of all groups are shown in Figure 2. Control females exhibited a large left and a small, largely regressed, right ovary. Control males showed two testes of similar size and shape. The mean left ovary area was significantly smaller in MBP-exposed females than in control females (Figure 2(a)) and in several MBP-exposed individuals the ovary appeared thinner than controls. On average, the right testis was significantly smaller and the left testis significantly larger in MBP-exposed males than in control males (Figure 2(c)). All males exposed to MBP developed a left ovotestis, as assessed by the shape and structure of the left gonad. Four out of 12 MBP-exposed males were feminized to the degree that they were mistaken for females at the visual inspection during the dissection. These were determined to be males by genetic sex determination. In mixture-exposed embryos, the gonads appeared unaffected and the mean gonad area did not differ markedly from that of the control group in either of the sexes.