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1. Cardiac physiology and metabolic gene expression during late organogenesis among F. heteroclitus embryo families from crosses between pollution-sensitive and -resistant parents

   https://doi.org/10.1186/s12862-022-01959-1  

   Bozinovic, Goran; Feng, Zuying; Shea, Damian; Oleksiak, Marjorie F. (December 2022, BMC Ecology and Evolution)

   Abstract Background The teleost fish Fundulus heteroclitus inhabit estuaries heavily polluted with persistent and bioaccumulative chemicals. While embryos of parents from polluted sites are remarkably resistant to toxic sediment and develop normally, embryos of parents from relatively clean estuaries, when treated with polluted sediment extracts, are developmentally delayed, displaying deformities characteristic of pollution-induced embryotoxicity. To gain insight into parental effects on sensitive and resistant phenotypes during late organogenesis, we established sensitive, resistant, and crossed embryo families using five female and five male parents from relatively clean and predominantly PAH-polluted estuaries each, measured heart rates, and quantified individual embryo expression of 179 metabolic genes. Results Pollution-induced embryotoxicity manifested as morphological deformities, significant developmental delays, and altered cardiac physiology was evident among sensitive embryos resulting from crosses between females and males from relatively clean estuaries. Significantly different heart rates among several geographically unrelated populations of sensitive, resistant, and crossed embryo families during late organogenesis and pre-hatching suggest site-specific adaptive cardiac physiology phenotypes relative to pollution exposure. Metabolic gene expression patterns (32 genes, 17.9%, at p < 0.05; 11 genes, 6.1%, at p < 0.01) among the embryo families indicate maternal pollutant deposition in the eggs and parental effects on gene expression and metabolic alterations. Conclusion Heart rate differences among sensitive, resistant, and crossed embryos is a reliable phenotype for further explorations of adaptive mechanisms. While metabolic gene expression patterns among embryo families are suggestive of parental effects on several differentially expressed genes, a definitive adaptive signature and metabolic cost of resistant phenotypes is unclear and shows unexpected sensitive-resistant crossed embryo expression profiles. Our study highlights physiological and metabolic gene expression differences during a critical embryonic stage among pollution sensitive, resistant, and crossed embryo families, which may contribute to underlying resistance mechanisms observed in natural F. heteroclitus populations living in heavily contaminated estuaries. 

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2. Stable genetic structure and connectivity in pollution-adapted and nearby pollution-sensitive populations of Fundulus heteroclitus

   https://doi.org/10.1098/rsos.171532  

   Nunez, Joaquin C.; Biancani, Leann M.; Flight, Patrick A.; Nacci, Diane E.; Rand, David M.; Crawford, Douglas L.; Oleksiak, Marjorie F. (May 2018, Royal Society Open Science)

   Populations of the non-migratory estuarine fish Fundulus heteroclitus inhabiting the heavily polluted New Bedford Harbour (NBH) estuary have shown inherited tolerance to local pollutants introduced to their habitats in the past 100 years. Here we examine two questions: (i) Is there pollution-driven selection on the mitochondrial genome across a fine geographical scale? and (ii) What is the pattern of migration among sites spanning a strong pollution gradient? Whole mitochondrial genomes were analysed for 133 F. heteroclitus from seven nearby collection sites: four sites along the NBH pollution cline (approx. 5 km distance), which had pollution-adapted fish, as well as one site adjacent to the pollution cline and two relatively unpolluted sites about 30 km away, which had pollution-sensitive fish. Additionally, we used microsatellite analyses to quantify genetic variation over three F. heteroclitus generations in both pollution-adapted and sensitive individuals collected from two sites at two different time points (1999/2000 and 2007/2008). Our results show no evidence for a selective sweep of mtDNA in the polluted sites. Moreover, mtDNA analyses revealed that both pollution-adapted and sensitive populations harbour similar levels of genetic diversity. We observed a high level of non-synonymous mutations in the most polluted site. This is probably associated with a reduction in N e and concomitant weakening of purifying selection, a demographic expansion following a pollution-related bottleneck or increased mutation rates. Our demographic analyses suggest that isolation by distance influences the distribution of mtDNA genetic variation between the pollution cline and the clean populations at broad spatial scales. At finer scales, population structure is patchy, and neither spatial distance, pollution concentration or pollution tolerance is a good predictor of mtDNA variation. Lastly, microsatellite analyses revealed stable population structure over the last decade. 

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3. Accumulation of Nanoplastics in Biomphalaria glabrata Embryos and Transgenerational Developmental Effects

   https://doi.org/10.3390/environments12010028  

   Martin, Leisha; Armendarez, Carly; Merrill, Mackenzie; Huang, Chi; Xu, Wei (January 2025, Environments)

   (1) Background: Nanoplastics are emerging environmental pollutants with potential toxic effects on aquatic organisms. This study investigates the toxicity of NPs in Biomphalaria glabrata, a freshwater snail species widely used as a bioindicator species in ecotoxicology studies.; (2) Methods: We exposed three generations (F0–F2) of B. glabrata snail embryos to different sizes of polystyrene nanoparticles and assessed responses.; (3) Results: We observed severe effects on F0 to F2 B. glabrata embryos, including size-dependent (30 to 500 nm) increases in mortality rates, size and dosage-dependent (1 to 100 ppm) effects on hatching rates with concentration-dependent toxicity in the 30 nm exposure group. The F2 generation embryos appear to be most responsive to detoxification (CYP450) and pollutant metabolism (HSP70) at 48-h-post-treatment (HPT), while our developmental marker (MATN1) was highly upregulated at 96-HPT. We also report a particle-size-dependent correlation in HSP70 and CYP450 mRNA expression, as well as enhanced upregulation in the offspring of exposed snails. We also observed significant reductions in hatching rates for F2.; (4) Conclusions: These findings indicate that F2 generation embryos appear to exhibit increased stress from toxic substances inherited from their parents and grandparents (F1 and F0). This study provides valuable insights into the impact of plastic particulate pollution on multiple generations and highlights the importance of monitoring and mitigating plastic waste. 

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4. Transcriptome profiling of the Caenorhabditis elegans intestine reveals that ELT-2 negatively and positively regulates intestinal gene expression within the context of a gene regulatory network

   https://doi.org/10.1093/genetics/iyad088  

   Williams, Robert_T_P; King, David_C; Mastroianni, Izabella_R; Hill, Jessica_L; Apenes, Nicolai_W; Ramirez, Gabriela; Miner, E_Catherine; Moore, Andrew; Coleman, Karissa; Nishimura, Erin_Osborne; et al (May 2023, GENETICS)

   Abstract ELT-2 is the major transcription factor (TF) required for Caenorhabditis elegans intestinal development. ELT-2 expression initiates in embryos to promote development and then persists after hatching through the larval and adult stages. Though the sites of ELT-2 binding are characterized and the transcriptional changes that result from ELT-2 depletion are known, an intestine-specific transcriptome profile spanning developmental time has been missing. We generated this dataset by performing Fluorescence Activated Cell Sorting on intestine cells at distinct developmental stages. We analyzed this dataset in conjunction with previously conducted ELT-2 studies to evaluate the role of ELT-2 in directing the intestinal gene regulatory network through development. We found that only 33% of intestine-enriched genes in the embryo were direct targets of ELT-2 but that number increased to 75% by the L3 stage. This suggests additional TFs promote intestinal transcription especially in the embryo. Furthermore, only half of ELT-2's direct target genes were dependent on ELT-2 for their proper expression levels, and an equal proportion of those responded to elt-2 depletion with over-expression as with under-expression. That is, ELT-2 can either activate or repress direct target genes. Additionally, we observed that ELT-2 repressed its own promoter, implicating new models for its autoregulation. Together, our results illustrate that ELT-2 impacts roughly 20–50% of intestine-specific genes, that ELT-2 both positively and negatively controls its direct targets, and that the current model of the intestinal regulatory network is incomplete as the factors responsible for directing the expression of many intestinal genes remain unknown. 

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5. Assessing the Role of Incubation Temperature as a Barrier to Successful Establishment of Coho Salmon ( Oncorhynchus kisutch ) in a Rapidly Warming Arctic

   https://doi.org/10.1002/ece3.70797  

   Lindley, Elizabeth D; Dunmall, Karen M; Westley, Peter_A H (January 2025, Ecology and evolution)

   ABSTRACT Warming associated with climate change is driving poleward shifts in the marine habitat of anadromous Pacific salmon (Oncorhynchusspp.). Yet the spawning locations for salmon to establish self‐sustaining populations and the consequences for the ecosystem if they should do so are unclear. Here, we explore the role of temperature‐dependent incubation survival and developmental phenology of coho salmon (Oncorhynchus kisutch) as a potential early life history barrier to establishment in an Arctic stream. We exposed embryos to temperatures previously recorded in the substrate of an Arctic groundwater spring‐fed spawning environment. Using a common garden experimental design, coho salmon embryos were exposed to treatments that thermally mimicked four spawning dates from August 1 to October 1 (AUG1, SEPT1, SEPT15, and OCT1). Spawning temperatures were 6°C at the warmest (AUG1) and 1.25°C at the coldest (OCT1). We observed low survival rates in SEPT1 (41%) and OCT1 (34%) and near complete mortality in the other treatments. While far below what is considered normal in benign hatchery‐like conditions, these rates suggest that temperatures experienced at these spawning dates are survivable. We detected differences in developmental rates across treatments; embryos developed 1.9 times faster in the warmest treatment (AUG1, 120 days) compared to the coldest (OCT1, 231 days). Differences in accumulated thermal units (ATUs) needed for hatching ranged from 392 ATUs in AUG1 to 270 ATUs in OCT1, revealing compensation in developmental requirements. Given these findings, the most thermally suitable spawning dates within our study are between September 15 and October 1, which facilitates hatching and projected nest emergence to occur in spring warming conditions (March–September). Broadly, our findings suggest that spawning sites within thermal tolerances that can support the survival and development of coho salmon exist in the North American Arctic. Whether the habitat is otherwise suitable for transitions through other life stages remains unknown. 

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