Meeting Abstract
Perchlorate (P) is a contaminant found in surface water around the globe and is known to cause health issues in vertebrates. P reduces production of thyroid hormone and masculinizes germ cell growth and adult phenotypes in threespine stickleback fish (Gasterosteus aculeatus); this effect on germ cells is not fully explained through known thyroid-hormone pathways. Our study aims to quantify P’s effects on fish development. We exposed zebrafish (Danio rerio) to 100ppm P from fertilization to 45 days post fertilization (dpf). Experiments were conducted using Nadia stock to allow for sex genotyping. We collected fish at 17, 25, and 45 dpf and analyzed histology from control and P treated (PT) groups to assess pathologies correlated with endocrine disruption. These endpoints are density of liver adipocytes, primary germ cell count, thyroid follicle count and size, and density of spleen melanomacrophages. Thyroid follicle counts were significantly higher in PT fish at 25 and 45dpf. Melanomacrophage density increased with PT at 45dpf; this effect appeared earlier in female fish. Primary germ cell counts were significantly higher in 25dpf PT females, but adipocyte density did not increase in PT fish. High germ cell number is a female trait in zebrafish, and failure to find changes in adipocyte density means that P is not an obesogen in zebrafish. We found no effect of P on sex ratio during development. Our findings differ from previous published data involving stickleback, where P caused masculinization and adipogenesis. Overall, our findings provide new insight into mechanisms and action pathways of P, but also raises questions about the species-specific response to the contaminant.
