Physiological responses of euryhaline marine fish to naturally-occurring hypersalinity.

Hypersaline habitats are generally defined as those with salinities in excess of 40 ppt. Well-known hypersaline regions (e.g.

Characterization of two carbonic anhydrase isoforms in the pulmonate snail (Lymnaea Stagnalis) and their involvement in Molluskan calcification.

Calcifying organisms are suffering from negative impacts induced by climate change, such as CO-induced acidification, which may impair external calcified structures. Freshwater mollusks have the potential to suffer more from CO-induced acidification than marine calcifiers due to the lower buffering capacity of many freshwater systems. One of the most important enzymes contributing to the biomineralization reaction is carbonic anhydrase (CA), which catalyzes the reversible conversion of CO to bicarbonate, the major carbon source of the calcareous structure in calcifiers.

The physiological significance of plasma-accessible carbonic anhydrase in the respiratory systems of fishes.

Carbonic anhydrase (CA) activity is ubiquitously found in all vertebrate species, tissues and cellular compartments. Most species have plasma-accessible CA (paCA) isoforms at the respiratory surfaces, where the enzyme catalyzes the conversion of plasma bicarbonate to carbon dioxide (CO) that can be excreted by diffusion. A notable exception are the teleost fishes that appear to lack paCA at their gills.

Acute toxicity testing of 6PPD-quinone on the estuarine-dependent sport fish, Sciaenops ocellatus.

Recently, large-scale fish kills in the Pacific Northwest were linked to tire wear particles (TWPs) left on roadways, with the lethality attributed to 6PPD-quinone. which has a median lethal concentration of <1 µg/L for selected salmonids. However, there remains a paucity of 6PPD-quinone toxicity values developed for estuarine fish species, which is particularly significant because estuaries receiving inflows from highly urbanized watersheds are especially vulnerable to TWP contamination.

Hypoxia acclimation improves mitochondrial efficiency in the aerobic swimming muscle of red drum (Sciaenops ocellatus).

Environmental hypoxia (low dissolved oxygen) is a significant threat facing fishes. As fishes require oxygen to efficiently produce ATP, hypoxia can significantly limit aerobic capacity. However, some fishes show respiratory flexibility that rescues aerobic performance, including plasticity in mitochondrial performance.

Recalibrating the significance of the decline effect in fish ocean acidification research.

The recently described decline effect in ocean acidification impacts on fish behaviour should not be equated with negligible effects. Here, existing mechanistic data are used to argue for continued research and cautions against "throwing the baby out with the bathwater."

Functional divergence of teleost carbonic anhydrase 4.

The functional role of membrane-bound carbonic anhydrases (CAs) has been of keen interest in the past decade, and in particular, studies have linked CA in red muscle, heart, and eye to enhanced tissue oxygen extraction in bony fishes (teleosts). However, the number of purported membrane-bound CA isoforms in teleosts, combined with the imperfect system of CA isoform nomenclature, present roadblocks for ascribing physiological functions to particular CA isoforms across different teleost lineages. Here we developed an organizational framework for membrane-bound CAs in teleosts, providing the latest phylogenetic analysis of extant CA4 and CA4-like isoforms.

The role of carbonic anhydrase-mediated tissue oxygen extraction in a marine teleost acclimated to hypoxia.

With the growing prevalence of hypoxia (O2 levels ≤2 mg l-1) in aquatic and marine ecosystems, there is increasing interest in the adaptive mechanisms fish may employ to better their performance in stressful environments. Here, we investigated the contribution of a proposed strategy for enhancing tissue O2 extraction - plasma-accessible carbonic anhydrase (CA-IV) - under hypoxia in a species of estuarine fish (red drum, Sciaenops ocellatus) that thrives in fluctuating habitats. We predicted that hypoxia-acclimated fish would increase the prevalence of CA-IV in aerobically demanding tissues to confer more efficient tissue O2 extraction.

Early life-stage Deepwater Horizon crude oil exposure induces latent osmoregulatory defects in larval red drum (Sciaenops ocellatus).

Crude oil is known to induce developmental defects in teleost fish exposed during early-life stages (ELSs). A recent study has demonstrated that zebrafish (Danio rerio) larvae acutely exposed to Deepwater Horizon (DHW) crude oil showed transcriptional changes in key genes involved in early kidney (pronephros) development and function, which were coupled with pronephric morphological defects. Given the osmoregulatory importance of the kidney, it is unknown whether ELS effects arising from short-term crude exposures result in long-term osmoregulatory defects, particularly within estuarine fishes likely exposed to DWH oil following the spill.

Pyrene drives reduced brain size during early life exposure in an estuarine fish, the red drum (Sciaenops ocellatus).

Crude oil and the constituent polycyclic aromatic hydrocarbons (PAHs) induce a consistent suite of sub-lethal effects in early life stage fishes. It has been suggested that 3-ring PAHs drive cardiotoxicity and that all other impacts are downstream consequences of these cardiac effects. However, recent studies have documented behavioral alterations that may not be linked to cardiotoxicity.

Exposure to Deepwater Horizon crude oil increases free cholesterol in larval red drum (Sciaenops ocellatus).

The 2010 Deepwater Horizon oil spill impacted over 2100 km of shoreline along the northern Gulf of Mexico, which coincided with the spawning season of many coastal species, including red drum (Sciaenops ocellatus). Red drum develop rapidly and are sensitive to crude oil exposure during the embryonic and larval periods. This study investigates the predictions from recent transcriptomic studies that cholesterol biosynthetic processes are impacted by oil exposure in fish early life stages.

Is hypoxia vulnerability in fishes a by-product of maximum metabolic rate?

The metabolic index concept combines metabolic data and known thermal sensitivities to estimate the factorial aerobic scope of animals in different habitats, which is valuable for understanding the metabolic demands that constrain species' geographical distributions. An important assumption of this concept is that the O2 supply capacity (which is equivalent to the rate of oxygen consumption divided by the environmental partial pressure of oxygen: ) is constant at O2 tensions above the critical O2 threshold (i.e.

Behavioral Changes in a Coastal Marine Fish Lead to Increased Predation Risk Following Oil Exposure.

Fishes exposed to crude oil have shown reduced sociability and poor habitat selection, which corresponded with increased predation risk. However, the contribution of oil-induced cardiorespiratory impairments to these findings is uncertain. This study explores the effect of oil exposure on predation risk in a model fish species, , across a suite of physiological and behavioral end points to elucidate the mechanisms through which any observed effects are manifested.

Osmoregulatory plasticity during hypersaline acclimation in red drum, Sciaenops ocellatus.

Prolonged drought and freshwater diversion are making periods of hypersalinity more common in coastal ecosystems. This is especially true in the Laguna Madre system along the Texas coast where salinities can exceed 60 g/kg. As such, the ability to tolerate hypersalinity is critical to the success of endemic species, such as the commercially important red drum (Sciaenops ocellatus).

Assessment of hypoxia avoidance behaviours in a eurythermal fish at two temperatures using a modified shuttlebox system.

Behavioural avoidance responses of red drum (Sciaenops ocellatus) to aquatic hypoxia were investigated at 22 and 30°C using a modified shuttlebox system. Fish movement between a control side maintained at normoxia and a hypoxic side with stepwise decreasing water oxygen tension was analysed for entries into the hypoxic side, residence time per entry into the hypoxic side and total time in the hypoxic side. Acclimation to 30°C increased the oxygen threshold for the onset of hypoxia avoidance behaviours for entries and total time, while residence time per entry was unchanged.

Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum.

Oxygen (O) and carbon dioxide (CO) transport are tightly coupled in many fishes as a result of the presence of Root effect hemoglobins (Hb), whereby reduced pH reduces O binding even at high O tensions. Red blood cell carbonic anhydrase (RBC CA) activity limits the rate of intracellular acidification, yet its role in O delivery has been downplayed. We developed an assay to manipulate RBC CA activity while measuring Hb-O offloading following a physiologically relevant CO-induced acidification.