The effects of natural and anthropogenic stressors on the stress response and tissue-level response in teleost fish

Analysis of integrative physiological responses is a valuable approach to studying the biological impacts of natural and anthropogenic stressors in biota. By measuring fluctuations in multiple physiological characteristics, we are able to predict the impact that exogenous stressors may have on organismal health. Laboratory studies are useful in studying the effects of a single or multiple stressor interactions in a controlled environment, although field-based studies allow for the understanding of how fish are affected in situ, where multiple natural and anthropogenic stressors exist. Using laboratory and field-based experimental design, physiological indices of fish health were measured in fish exposed to natural and anthropogenic stressors in two unique incidences. First, controlled laboratory-based studies were performed where fish were exposed to larval freshwater mussels, a natural stressor found in North American freshwater environments. Unionid freshwater mussel larvae, called glochidia, must attach to a host fish in order to metamorphose into their juvenile state. This obligate stage in the unionid freshwater mussel life-cycle was found to cause a stress response in fish infected at high concentrations, where elevated cortisol in stressed fish was found to be coincident with an increase in glochidia metamorphosis to the juvenile stage. Second, both laboratory and field studies were conducted to understand the effects of the Deepwater Horizon oil spill on populations of Gulf killifish (Fundulus grandis) in oil-impacted areas in Louisiana, compared to reference sites in Louisiana, Mississippi, and Alabama. We show evidence of exposure to crude oil coincident with contamination from the Deepwater horizon oil spill in field-collected fish collected in 2010 and 2011 from oil-impacted sites, which had divergent gene and protein expression patterns compared to fish from unoiled locations. Further, controlled laboratory exposures of Gulf killifish embryos to field-collected sediments from oiled locations revealed that fish exposed to heavily oiled sediments as embryos had reduced cardiovascular defects, delayed hatching, reduced overall hatching success, pericardial edema, and were smaller at hatch. Together, these data suggest that fish were exposed to toxins in crude oil for two successive breading seasons, indicating, that contaminating oil from the Deepwater Horizon oil spill impacts organismal fitness, which may be predictive of long-term effects on Gulf killifish populations, and other biota that inhabit these areas, and also highlights the utility of combining laboratory and field-based techniques to predict the effects of natural and anthropogenic stressors on fish

Influence of cortisol on the attachment and metamorphosis of larval Utterbackia imbecillis on bluegill sunfish (Lepomis macrochirus)

The larvae of unionid freshwater mussels (i.e., glochidia) undergo a parasitic stage requiring their attachment to the external epithelia of fish hosts, where they metamorphose into free-living juveniles. We describe the physiological effects in bluegill sunfish (Lepomis macrochirus) of infection with glochidia from the paper pondshell (Utterbackia imbecillis). Glochidia accumulation on bluegill increased dramatically at concentrations of 2000 glochidia liter-1 and above, reaching a maximum attachment density of about 30 glochidia g-1 fish at 4000 glochidia liter-1. Plasma cortisol was the most sensitive indicator of biological effect to glochidial exposure, increasing significantly in hosts exposed to 2000 glochidia liter-1 or greater. Glochidia were 31% more likely to undergo successful juvenile metamorphosis when attached to bluegill with elevated plasma cortisol, largely due to the enhanced survivorship of these larvae during the first 48 h after infection. We tested the hypothesis that glochidial attachment and juvenile metamorphosis were stimulated directly by plasma cortisol in fish hosts. Bluegill were given an intraperitoneal injection of cortisol, then infected with 1000 glochidia liter-1 at 48 h after hormone supplementation. Cortisol-injected fish had a 42% increase in the number of attached glochidia g-1 fish and a 28% increase in larval metamorphosis compared to sham-injected and control fish. We provide evidence that cortisol enhances glochidial metamorphosis on hosts by improving the retention of attached glochidia. This study gives insights into the influence of host physiology on glochidial attachment and juvenile mussel transformation. © 2011 Marine Biological Laborat006Fry

Biomarkers of Aryl-hydrocarbon Receptor Activity in Gulf Killifish (Fundulus grandis) From Northern Gulf of Mexico Marshes Following the Deepwater Horizon Oil Spill

© 2017, Springer Science+Business Media New York. Following the Deepwater Horizon oil spill, shorelines throughout the Barataria Basin of the northern Gulf of Mexico in Louisiana were heavily oiled for months with Macondo-252 oil, potentially impacting estuarine species. The Gulf killifish (Fundulus grandis) has been identified as a sentinel species for the study of site-specific effects of crude oil contamination on biological function. In November and December 2010, 4–5 months after the Macondo well was plugged and new oil was no longer spilling into the Gulf waters, Gulf killifish were collected across the Barataria Basin from 14 sites with varying degrees of oiling. Fish collected from oiled sites exhibited biological indications of exposure to oil, including increase in cytochrome P4501A (CYP1A) mRNA transcript and protein abundances in liver tissues. Immunohistochemistry revealed increases in gill, head kidney, and intestinal CYP1A protein at heavily oiled sites. Intestinal CYP1A protein was a sensitive indicator of exposure, indicating that intestinal tissue plays a key role in biotransformation of AHR ligands and that ingestion is a probable route of exposure, warranting additional consideration in future studies

Multitissue molecular, genomic, and developmental effects of the deepwater horizon oil spill on resident Gulf killifish (Fundulus grandis)

The Deepwater Horizon oil rig disaster resulted in crude oil contamination along the Gulf coast in sensitive estuaries. Toxicity from exposure to crude oil can affect populations of fish that live or breed in oiled habitats as seen following the Exxon Valdez oil spill. In an ongoing study of the effects of Deepwater Horizon crude oil on fish, Gulf killifish (Fundulus grandis) were collected from an oiled site (Grande Terre, LA) and two reference locations (coastal MS and AL) and monitored for measures of exposure to crude oil. Killifish collected from Grande Terre had divergent gene expression in the liver and gill tissue coincident with the arrival of contaminating oil and up-regulation of cytochrome P4501A (CYP1A) protein in gill, liver, intestine, and head kidney for over one year following peak landfall of oil (August 2011) compared to fish collected from reference sites. Furthermore, laboratory exposures of Gulf killifish embryos to field-collected sediments from Grande Terre and Barataria Bay, LA, also resulted in increased CYP1A and developmental abnormalities when exposed to sediments collected from oiled sites compared to exposure to sediments collected from a reference site. These data are predictive of population-level impacts in fish exposed to sediments from oiled locations along the Gulf of Mexico coast. © 2013 American Chemical Society

Deepwater Horizon Oil Spill as a Case Study for Interdisciplinary Cooperation within Developmental Biology, Environmental Sciences and Physiology

This article makes the argument for interdisciplinary teams that bring together scientists with different specialties as an efficient way--and perhaps the only way--to unravel highly complex biological effects of marine oil spills

Genomic and physiological footprint of the Deepwater Horizon oil spill on resident marsh fishes

The biological consequences of the Deepwater Horizon oil spill are unknown, especially for resident organisms. Here, we report results from a field study tracking the effects of contaminating oil across space and time in resident killifish during the first 4 mo of the spill event. Remote sensing and analytical chemistry identified exposures, which were linked to effects in fish characterized by genome expression and associated gill immunohistochemistry, despite very low concentrations of hydrocarbons remaining in water and tissues. Divergence in genome expression coincides with contaminating oil and is consistent with genome responses that are predictive of exposure to hydrocarbon-like chemicals and indicative of physiological and reproductive impairment. Oil-contaminated waters are also associated with aberrant protein expression in gill tissues of larval and adult fish. These data suggest that heavily weathered crude oil from the spill imparts significant biological impacts in sensitive Louisiana marshes, some of which remain for over 2 mo following initial exposures

Prenatal hypoxia affects scaling of blood pressure and arterial wall mechanics in the common snapping turtle, Chelydra serpentina

In reptiles, exposure to hypoxia during embryonic development affects several cardiovascular parameters. These modifications may impose different mechanical stress to the arterial system, and we speculated that the arterial wall of major outflow vessels would be modified accordingly. Since non-crocodilian reptiles possess a partially divided ventricle, ensuing similar systemic and pulmonary systolic pressures, we investigated how morphological and mechanical properties of segments from the left aortic arch (LAo) and the proximal and distal segments of the left pulmonary artery (LPAp and LPAd, respectively) change as body mass (M) increases. Eggs from common snapping turtles, Chelydra serpentina, were incubated under normoxia (21% O; N21) or hypoxia (10% O; H10), hatched and maintained in normoxia thereafter. Turtles (0.11-6.85 kg) were cannulated to measure arterial pressures, and an injection of adrenaline was used to increase pressures. Portions of the LAo, LPAp and LPAd were fixed under physiological hydrostatic pressures for histology and mechanical assessment. Arterial pressures increased with M for N21 but not for H10. Although mechanical and functional characteristics from the LPAp and LPAd were similar between N21 and H10, wall thickness from LAo did not change with M in the H10 group, thus wall stress increased in larger turtles. This indicates that larger H10 turtles probably experience an elevated probability of arterial wall rupture without concomitant changes in the cardiovascular system to prevent it. Finally, collagen content of the LPAp and LAo was smaller than in LPAd, suggesting a more distensible arterial wall could attenuate higher pressures from larger turtles