Distinct genomic routes underlie transitions to specialised symbiotic lifestyles in deep-sea annelid worms.

Bacterial symbioses allow annelids to colonise extreme ecological niches, such as hydrothermal vents and whale falls. Yet, the genetic principles sustaining these symbioses remain unclear. Here, we show that different genomic adaptations underpin the symbioses of phylogenetically related annelids with distinct nutritional strategies.

Dining on the dead in the deep: Active NH excretion via Na /H (NH ) exchange in the highly ammonia tolerant Pacific hagfish, Eptatretus stoutii.

Aim: Pacific hagfish are exceptionally tolerant to high environmental ammonia (HEA). Here, we elucidated a cellular mechanism that enables hagfish to actively excrete ammonia against steep ammonia gradients expected to be found inside a decomposing whale carcass.

Methods: Hagfish were exposed to varying concentrations of HEA in the presence or absence of environmental Na , while plasma ammonia levels were tracked.

Hypoxemia as the mechanism of acute cationic polymer toxicity in rainbow trout and prevention of toxicity using an anionic neutralizing polymer.

Industrial operations such as surface mining, road building, and aggregate washing result in high concentrations of suspended particles (Total Suspended Solids; TSS) in surface waters which must be treated prior to discharge into fish-bearing waters. A common industrial practice is to add flocculants to improve the efficacy and speed of TSS sedimentation. A significant environmental issue even small amounts of uncomplexed cationic polymer coagulant/flocculant remaining in treated water is highly toxic to fish at very low concentrations (LC ∼ 0.

Molecular identification and postprandial regulation of glucose carrier proteins in the hindgut of Pacific hagfish, .

Hagfish are an excellent model species in which to draw inferences on the evolution of transport systems in early vertebrates owing to their basal position in vertebrate phylogeny. Glucose is a ubiquitous cellular energy source that is transported into cells via two classes of carrier proteins: sodium-glucose-linked transporters (Sglt; Slc5a) and glucose transporters (Glut; Slc2a). Although previous pharmacological evidence has suggested the presence of both sodium-dependent and -independent transport mechanisms in the hagfish, the molecular identities were heretofore unconfirmed.

A novel K -dependent Na uptake mechanism during low pH exposure in adult zebrafish (Danio rerio): New tricks for old dogma.

Aim: To determine whether Na uptake in adult zebrafish (Danio rerio) exposed to acidic water adheres to traditional models reliant on Na /H Exchangers (NHEs), Na channels and Na /Cl Cotransporters (NCCs) or if it occurs through a novel mechanism.

Methods: Zebrafish were exposed to control (pH 8.0) or acidic (pH 4.

Adrenergically induced translocation of red blood cell β-adrenergic sodium-proton exchangers has ecological relevance for hypoxic and hypercapnic white seabass.

White seabass () increasingly experience periods of low oxygen (O; hypoxia) and high carbon dioxide (CO, hypercapnia) due to climate change and eutrophication of the coastal waters of California. Hemoglobin (Hb) is the principal O carrier in the blood and in many teleost fishes Hb-O binding is compromised at low pH; however, the red blood cells (RBC) of some species regulate intracellular pH with adrenergically stimulated sodium-proton-exchangers (β-NHEs). We hypothesized that RBC β-NHEs in white seabass are an important mechanism that can protect the blood O-carrying capacity during hypoxia and hypercapnia.

Evolutionary links between intra- and extracellular acid-base regulation in fish and other aquatic animals.

The acid-base relevant molecules carbon dioxide (CO ), protons (H ), and bicarbonate (HCO ) are substrates and end products of some of the most essential physiological functions including aerobic and anaerobic respiration, ATP hydrolysis, photosynthesis, and calcification. The structure and function of many enzymes and other macromolecules are highly sensitive to changes in pH, and thus maintaining acid-base homeostasis in the face of metabolic and environmental disturbances is essential for proper cellular function. On the other hand, CO , H , and HCO have regulatory effects on various proteins and processes, both directly through allosteric modulation and indirectly through signal transduction pathways.

The importance of a single amino acid substitution in reduced red blood cell carbonic anhydrase function of early-diverging fish.

In most vertebrates, red blood cell carbonic anhydrase (RBC CA) plays a critical role in carbon dioxide (CO) transport and excretion across epithelial tissues. Many early-diverging fishes (e.g.

Ventilatory sensitivity to ammonia in the Pacific hagfish (), a representative of the oldest extant connection to the ancestral vertebrates.

Ventilatory sensitivity to ammonia occurs in teleosts, elasmobranchs and mammals. Here, we investigated whether the response is also present in hagfish. Ventilatory parameters (nostril flow, pressure amplitude, velar frequency and ventilatory index, the last representing the product of pressure amplitude and frequency), together with blood and water chemistry, were measured in hagfish exposed to either high environmental ammonia (HEA) in the external sea water or internal ammonia loading by intra-vascular injection.

Ventilatory responses of the clown knifefish, Chitala ornata, to hypercarbia and hypercapnia.

The aim of the present study was to determine the roles of externally versus internally oriented CO/H-sensitive chemoreceptors in promoting cardiorespiratory responses to environmental hypercarbia in the facultative air-breathing fish, Chitala ornata (the clown knifefish). Fish were exposed to environmental acidosis (pH ~ 6.0) or hypercarbia (≈ 30 torr PCO) that produced changes in water pH equal to the pH levels of the acidotic water to distinguish the relative roles of CO versus H.

Dropping the base: recovery from extreme hypercarbia in the CO tolerant Pacific hagfish (Eptatretus stoutii).

Hagfish are capable of tolerating extreme hypercapnia (> 30 Torr) by mounting substantial plasma [HCO] (hypercarbia) to compensate for CO-mediated acidosis. The goal of this study was to characterize the mechanistic hypercarbia-recovery strategies in the highly CO tolerant hagfish. We exposed hagfish to hypercapnia (30 Torr) for 48 h and allowed a 24 h recovery period in normocapnic seawater.

Functional redundancy of glucose acquisition mechanisms in the hindgut of Pacific hagfish (Eptatretus stoutii).

This study examined the mechanisms of glucose acquisition in the hindgut of Pacific hagfish (Eptatretus stoutii) using in vitro gut sac techniques. The intestine was determined to have the capacity to digest maltose into glucose along the entirety of the tract, including the foregut. Glucose uptake was biphasic and consisted of a high-affinity, low-capacity concentration-dependent component conforming to Michaelis-Menten kinetics (K 0.

Post-prandial physiology and intestinal morphology of the Pacific hagfish (Eptatretus stoutii).

Hagfishes are unique to the vertebrate lineage in that they acquire dissolved nutrients across multiple epithelia including the intestine, gill, and skin. This feat has been attributed to their immersive feeding behavior that likely simultaneously provides benefits (nutrient rich) and potentially adverse (hypercapnia, hypoxia, high environmental ammonia) physiological effects. Examinations have been conducted of the ex vivo transport capabilities of specific nutrients as well as in vivo effects of the hypothesized feeding environments, yet the physiological effects of feeding itself have never been elucidated.

Flexible ammonia handling strategies using both cutaneous and branchial epithelia in the highly ammonia-tolerant Pacific hagfish.

Hagfish consume carrion, potentially exposing them to hypoxia, hypercapnia, and high environmental ammonia (HEA). We investigated branchial and cutaneous ammonia handling strategies by which Pacific hagfish () tolerate and recover from high ammonia loading. Hagfish were exposed to HEA (20 mmol/l) for 48 h to elevate plasma total ammonia (T) levels before placement into divided chambers for a 4-h recovery period in ammonia-free seawater where ammonia excretion () was measured independently in the anterior and posterior compartments.

Regulation of plasma glucose and sulfate excretion in Pacific hagfish, Eptatretus stoutii is not mediated by 11-deoxycortisol.

The goal of this study was to identify whether Pacific hagfish (Eptatretus stoutii) possess glucocorticoid and mineralocorticoid responses and to examine the potential role(s) of four key steroids in these responses. Pacific hagfish were injected with varying amounts of cortisol, corticosterone or 11-deoxycorticosterone (DOC) using coconut oil implants and plasma glucose and gill total-ATPase activity were monitored as indices of glucocorticoid and mineralocorticoid responses. Furthermore, we also monitored plasma glucose and 11-deoxycortisol (11-DOC) levels following exhaustive stress (30 min of agitation) or following repeated infusion with SO.

It's all in the gills: evaluation of O2 uptake in Pacific hagfish refutes a major respiratory role for the skin.

Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, whether cutaneous O uptake is the dominant route of uptake remains under debate; all evidence supporting this hypothesis has been derived using indirect measurements. Here, we used partitioned chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific hagfish (Eptatretus stoutii) at rest and following exhaustive exercise.

ERK1 and ERK2 present functional redundancy in tetrapods despite higher evolution rate of ERK1.

Background: The Ras/Raf/MEK/ERK signaling pathway is involved in essential cell processes and it is abnormally activated in ~30 % of cancers and cognitive disorders. Two ERK isoforms have been described, ERK1 and ERK2; ERK2 being regarded by many as essential due to the embryonic lethality of ERK2 knock-out mice, whereas mice lacking ERK1 are viable and fertile. The controversial question of why we have two ERKs and whether they have differential functions or display functional redundancy has not yet been resolved.

Life stage dependent responses to the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), provide insight into glucose homeostasis and metabolism in the sea lamprey (Petromyzon marinus).

The primary method of sea lamprey (Petromyzon marinus) control in the Great Lakes is the treatment of streams and rivers with the pesticide 3-trifluoromethyl-4-nitrophenol (TFM), which targets larval sea lamprey. However, less is known about the effects of TFM on other stages of the sea lamprey's complex life cycle. The goal of this study was to determine how TFM affected internal energy stores, metabolites, and ion balance in larval, juvenile (parasitic) and adult sea lamprey.

Adaptations of a deep sea scavenger: high ammonia tolerance and active NH₄⁺ excretion by the Pacific hagfish (Eptatretus stoutii).

The Pacific hagfish (Eptatretus stoutii) has an exceptional ability to both withstand and recover from exposure to high external ammonia (HEA). This tolerance is likely due to the feeding behavior of this scavenger, which feeds on intermittent food falls of carrion (e.g.

Mechanisms of Cl(-) uptake in rainbow trout: cloning and expression of slc26a6, a prospective Cl(-)/HCO3(-) exchanger.

In fresh waters, fishes continuously acquire ions to offset diffusive losses to a more dilute ambient environment and to maintain acid-base status. The objectives of the present study were to clone slc26a6, a prospective Cl(-)/HCO3(-) exchanger from rainbow trout, investigate its expression patterns in various tissues, at different developmental stages and after differential salinity exposure, and probe the mechanisms of Cl(-) uptake in rainbow trout embryos during development using a pharmacological inhibitor approach combined with (36)Cl(-) unidirectional fluxes. Results showed that the cloned gene encoded a 783 amino acid protein with conserved domains characteristic of the SLC26a family of anion exchange proteins.

Phosphate absorption across multiple epithelia in the Pacific hagfish (Eptatretus stoutii).

Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific hagfish (Eptatretus stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill.

Defensive slime formation in Pacific hagfish requires Ca2+- and aquaporin-mediated swelling of released mucin vesicles.

Hagfishes defend themselves from fish predators via the rapid deployment of a fibrous slime that adheres to and clogs gills. The slime transforms from a thick glandular exudate to a fully hydrated product in a fraction of a second through a process that involves the swelling and rupture of numerous mucin vesicles. Here we demonstrate that the vesicle membrane plays an important role in regulating the swelling of mucin granules, and provide evidence that the membrane contains proteins that facilitate the movement of ions and water molecules.