Evidence for the involvement of branchial Vacuolar-type H-ATPase in the acidification of the external medium by the West African lungfish, Protopterus annectens, exposed to ammonia-loading conditions.

African lungfishes are obligatory air-breathers with exceptionally high environmental ammonia tolerance. They can lower the pH of the external medium during exposure to ammonia-loading conditions. This study aimed to demonstrate the possible involvement of branchial vacuolar-type H-ATPase (Vha) in the ammonia-induced acidification of the external medium by the West African lungfish, Protopterus annectens, and to examine whether its capacity to acidify the medium could be augmented after exposure to 100 mmol l NHCl for six days.

Ammonia transporter 2 as a molecular marker to elucidate the potentials of ammonia transport in phylotypes of Symbiodinium, Cladocopium and Durusdinium in the fluted giant clam, Tridacna squamosa.

Giant clams harbor coccoid Symbiodiniaceae dinoflagellates that are phototrophic. These dinoflagellates generally include multiple phylotypes (species) of Symbiodinium, Cladocopium, and Durusdinium in disparate proportions depending on the environmental conditions. The coccoid symbionts can share photosynthate with the clam host, which in return supply them with nutrients containing inorganic carbon, nitrogen and phosphorus.

Molecular characterization, immunofluorescent localization, and expression levels of two bicarbonate anion transporters in the whitish mantle of the giant clam, Tridacna squamosa, and the implications for light-enhanced shell formation.

Giant clams conduct light-enhanced shell formation, which requires the increased transport of Ca and inorganic carbon (C) from the hemolymph through the shell-facing epithelium of the whitish inner mantle to the extrapallial fluid where CaCO deposition occurs. The major form of C in the hemolymph is HCO, but the mechanisms of HCO transport through the basolateral and apical membranes of the shell-facing epithelial cells remain unknown. This study aimed to clone from the inner mantle of Tridacna squamosa the complete coding cDNA sequences of electrogenic Na-HCOcotransporter 1 homolog (NBCe1-like-b) and electrogenic Na-HCOcotransporter 2 homolog (NBCe2-like).

The colorful mantle of the giant clam Tridacna squamosa expresses a homolog of electrogenic sodium: Bicarbonate cotransporter 2 that mediates the supply of inorganic carbon to photosynthesizing symbionts.

Giant clams live in symbiosis with phototrophic dinoflagellates, which reside extracellularly inside zooxanthellal tubules located mainly in the colourful and extensible outer mantle. As symbiotic dinoflagellates have no access to the ambient seawater, they need to obtain inorganic carbon (Ci) from the host for photosynthesis during illumination. The outer mantle has a host-mediated and light-dependent carbon-concentrating mechanism to augment the supply of Ci to the symbionts during illumination.

Basolateral Na/Ca exchanger 1 and Na/K-ATPase, which display light-enhanced gene and protein expression levels, could be involved in the absorption of exogenous Ca through the ctenidium of the giant clam, Tridacna squamosa.

Giant clams perform light-enhanced shell formation (calcification) and therefore need to increase the uptake of exogenous Ca during illumination. The ctenidium of the fluted giant clam, Tridacna squamosa, is involved in light-enhanced Ca uptake. It expresses the pore-forming voltage-gated calcium channel (VGCC) subunit alpha 1 (CACNA1) in the apical membrane of the epithelial cells, and the protein expression level of CACNA1 is upregulated in the ctenidium during illumination.

Using glutamine synthetase 1 to evaluate the symbionts' potential of ammonia assimilation and their responses to illumination in five organs of the giant clam, Tridacna squamosa.

Nitrogen-deficient symbiotic dinoflagellates (zooxanthellae) living inside the fluted giant clam, Tridacna squamosa, need to obtain nitrogen from the host. Glutamine synthetase 1 (GS1) is a cytosolic enzyme that assimilates ammonia into glutamine. We determined the transcript levels of zooxanthellal GS1 (Zoox-GS1), which represented comprehensively GS1 transcripts of Symbiodinium, Cladocopium and Durusdinium, in five organs of T.

Effects of seawater acclimation on two Na/K-ATPase α-subunit isoforms in the gills of the marble goby, Oxyeleotris marmorata.

The marble goby, Oxyeleotris marmorata, is a freshwater teleost, but can acclimate progressively to survive in seawater (salinity 30). As an obligatory air-breather, it can also survive long periods of emersion. Two isoforms of Na/K-ATPase (nka) α-subunit, nkaα1 and nkaα3, but not nkaα2, had been cloned from the gills of O.

Illumination enhances the protein abundance of sarcoplasmic reticulum Ca-ATPases-like transporter in the ctenidium and whitish inner mantle of the giant clam, Tridacna squamosa, to augment exogenous Ca uptake and shell formation, respectively.

The fluted giant clam, Tridacna squamosa, can perform light-enhanced shell formation, aided by its symbiotic dinoflagellates (Symbiodinium, Cladocopium, Durusdinium), which are able to donate organic nutrients to the host. During light-enhanced shell formation, increased Ca transport from the hemolymph through the shell-facing epithelium of the inner mantle to the extrapallial fluid, where calcification occurs, is necessary. Additionally, there must be increased absorption of exogenous Ca from the surrounding seawater, across the epithelial cells of the ctenidium (gill) into the hemolymph, to supply sufficient Ca for light-enhanced shell formation.

The fluted giant clam (Tridacna squamosa) increases the protein abundance of the host's copper-zinc superoxide dismutase in the colorful outer mantle, but not the whitish inner mantle, during light exposure.

The colorful outer mantle of giant clams contains abundance of symbiotic dinoflagellates (zooxanthellae) and iridocytes, and has direct exposure to light. In light, photosynthesizing dinoflagellates produce O, and the host cells in the outer mantle would be confronted with hyperoxia-related oxidative stress. In comparison, the whitish inner mantle contains few symbiotic dinoflagellates and no iridocytes.

Symbiodiniaceae Dinoflagellates Express Urease in Three Subcellular Compartments and Upregulate its Expression Levels in situ in Three Organs of a Giant Clam (Tridacna squamosa) During Illumination.

Giant clams harbor three genera of symbiotic dinoflagellates (Symbiodinium, Cladocopium, and Durusdinium) as extracellular symbionts (zooxanthellae). While symbiotic dinoflagellates can synthesize amino acids to benefit the host, they are nitrogen-deficient. Hence, the host must supply them with nitrogen including urea, which can be degraded to ammonia and carbon dioxide by urease (URE).

The Non-ureogenic Stinging Catfish, , Actively Excretes Ammonia With the Help of Na/K-ATPase When Exposed to Environmental Ammonia.

The stinging catfish, , can tolerate high concentrations of environmental ammonia. Previously, it was regarded as ureogenic, having a functional ornithine-urea cycle (OUC) that could be up-regulated during ammonia-loading. However, contradictory results indicated that increased urea synthesis and switching to ureotelism could not explain its high ammonia tolerance.

Calcium absorption in the fluted giant clam, Tridacna squamosa, may involve a homolog of voltage-gated calcium channel subunit α1 (CACNA1) that has an apical localization and displays light-enhanced protein expression in the ctenidium.

In light, giant clams can increase rates of shell formation and growth due to their symbiotic relationship with phototrophic zooxanthellae residing extracellularly in a tubular system. Light-enhanced shell formation necessitates increase in the uptake of Ca from the ambient seawater and the supply of Ca through the hemolymph to the extrapallial fluid, where calcification occurs. In this study, the complete coding cDNA sequence of a homolog of voltage-gated calcium channel subunit α1 (CACNA1), which is the pore-forming subunit of L-type voltage-gated calcium channels (VGCCs), was obtained from the ctenidium (gill) of the giant clam, Tridacna squamosa.

Increased apical sodium-dependent glucose transporter abundance in the ctenidium of the giant clam upon illumination.

Giant clams contain phototrophic zooxanthellae, and live in nutrient-deficient tropical waters where light is available. We obtained the complete cDNA coding sequence of a homolog of mammalian sodium/glucose cotransporter 1 () from the ctenidium of the fluted giant clam, had a host origin and was expressed predominantly in the ctenidium. Molecular characterizations reveal that SGLT1-like of could transport urea, in addition to glucose, as other SGLT1s do.

Molecular characterization, cellular localization, and light-enhanced expression of Beta-Na/H Exchanger-like in the whitish inner mantle of the giant clam, Tridacna squamosa, denote its role in light-enhanced shell formation.

The fluted giant clam, Tridacna squamosa, lives in symbiosis with photosynthetic zooxanthellae, and can engage in light-enhanced growth and shell formation. Light-enhanced shell formation necessitates the elimination of excess H from the extrapallial fluid adjacent to the shell. This study aimed to clone Na/HExchanger (NHE) from the whitish inner mantle adjacent to the extrapallial fluid of T.

Light-enhanced expression of Carbonic Anhydrase 4-like supports shell formation in the fluted giant clam Tridacna squamosa.

Giant clams represent symbiotic associations between a host clam and its extracellular zooxanthellae. They are able to grow in nutrient-deficient tropical marine environments and conduct light-enhanced shell formation (calcification) with the aid of photosynthates donated by the symbiotic zooxanthellae. In light, there is a high demand for inorganic carbon (C) to support photosynthesis in the symbionts and light-enhanced calcification in the host.

Air-breathing and excretory nitrogen metabolism in fishes.

During water-land transition, ancient fishes acquired the ability to breathe air, but air-breathing engendered problems in nitrogenous waste excretion. Nitrogen is a fundamental component of amino acids, proteins, and nucleic acids, and the degradation of these nitrogen-containing compounds releases ammonia. Ammonia is toxic and must be removed.

RNA sequencing, de novo assembly and differential analysis of the gill transcriptome of freshwater climbing perch Anabas testudineus after 6 days of seawater exposure.

To obtain transcriptomic insights into branchial responses to salinity challenge in Anabas testudineus, this study employed RNA sequencing (RNA-Seq) to analyse the gill transcriptome of A. testudineus exposed to seawater (SW) for 6 days compared with the freshwater (FW) control group. A combined FW and SW gill transcriptome was de novo assembled from 169.

The ctenidium of the giant clam, Tridacna squamosa, expresses an ammonium transporter 1 that displays light-suppressed gene and protein expression and may be involved in ammonia excretion.

Ammonium transporters (AMTs) can participate in ammonia uptake or excretion across the plasma membrane of prokaryotic, plant and invertebrate cells. The giant clam, Tridacna squamosa, harbors nitrogen-deficient symbiotic zooxanthellae, and normally conducts light-enhanced ammonia absorption to benefit the symbionts. Nonetheless, it can excrete ammonia when there is a supply of exogenous nitrogen or exposed to continuous darkness.

Molecular Characterization of a Dual Domain Carbonic Anhydrase From the Ctenidium of the Giant Clam, , and Its Expression Levels After Light Exposure, Cellular Localization, and Possible Role in the Uptake of Exogenous Inorganic Carbon.

A () had been sequenced and characterized from the ctenidia (gills) of the giant clam, , which lives in symbiosis with zooxanthellae. was expressed predominantly in the ctenidium. The complete cDNA coding sequence of from comprised 1,803 bp, encoding a protein of 601 amino acids and 66.

Molecular characterization, light-dependent expression, and cellular localization of a host vacuolar-type H-ATPase (VHA) subunit A in the giant clam, Tridacna squamosa, indicate the involvement of the host VHA in the uptake of inorganic carbon and its supply to the symbiotic zooxanthellae.

The giant clam, Tridacna squamosa, represents a clam-zooxanthellae association. In light, the host clam and the symbiotic zooxanthellae conduct light-enhanced calcification and photosynthesis, respectively. We had cloned the cDNA coding sequence of a Vacuolar-type Proton ATPase (VHA) subunit A, ATP6V1A, from T.

Light exposure enhances urea absorption in the fluted giant clam, , and up-regulates the protein abundance of a light-dependent urea active transporter, DUR3-like, in its ctenidium.

Giant clams live in nutrient-poor reef waters of the Indo-Pacific and rely on symbiotic dinoflagellates ( spp., also known as zooxanthellae) for nutrients. As the symbionts are nitrogen deficient, the host clam has to absorb exogenous nitrogen and supply it to them.

Molecular characterization of a novel algal glutamine synthetase (GS) and an algal glutamate synthase (GOGAT) from the colorful outer mantle of the giant clam, Tridacna squamosa, and the putative GS-GOGAT cycle in its symbiotic zooxanthellae.

Giant clams harbor symbiotic zooxanthellae (Symbiodinium), which are nitrogen-deficient, mainly in the fleshy and colorful outer mantle. This study aimed to sequence and characterize the algal Glutamine Synthetase (GS) and Glutamate Synthase (GLT), which constitute the glutamate synthase cycle (or GS-GOGAT cycle, whereby GOGAT is the protein acronym of GLT) of nitrogen assimilation, from the outer mantle of the fluted giant clam, Tridacna squamosa. We had identified a novel GS-like cDNA coding sequence of 2325 bp, and named it as T.

Na/H Exchanger 3 Is Expressed in Two Distinct Types of Ionocyte, and Probably Augments Ammonia Excretion in One of Them, in the Gills of the Climbing Perch Exposed to Seawater.

The freshwater climbing perch, , is an euryhaline teleost and an obligate air-breather with the ability to actively excrete ammonia. Members of the Na/H exchanger (NHE) family help maintain intracellular pH homeostasis and ionic balance through the electroneutral exchange of Na and H. This study aimed to obtain, from the gills of , the full cDNA coding sequence of , and to determine the effects of exposure to seawater or 100 mmol l of NHCl in fresh water on its mRNA and protein expression levels.

Carbonic anhydrase 2-like in the giant clam, : characterization, localization, response to light, and possible role in the transport of inorganic carbon from the host to its symbionts.

The fluted giant clam, , lives in symbiosis with zooxanthellae which reside extracellularly inside a tubular system. Zooxanthellae fix inorganic carbon (C) during insolation and donate photosynthate to the host. Carbonic anhydrases catalyze the interconversion of CO and HCO3-, of which carbonic anhydrase 2 (CA2) is the most ubiquitous and involved in many biological processes.

Molecular characterization of three Rhesus glycoproteins from the gills of the African lungfish, Protopterus annectens, and effects of aestivation on their mRNA expression levels and protein abundance.

African lungfishes are ammonotelic in water. They can aestivate for long periods on land during drought. During aestivation, the gills are covered with dried mucus and ammonia excretion ceases.