The role of the antennal glands and gills in acid-base regulation and ammonia excretion of a marine osmoconforming brachyuran.

The excretory mechanisms of stenohaline marine osmoconforming crabs are often compared to those of the more extensively characterized euryhaline osmoregulating crabs. These comparisons may have limitations, given that unlike euryhaline brachyurans the gills of stenohaline marine osmoconformers possess ion-leaky paracellular pathways and lack the capacity to undergo ultrastructural changes that can promote ion-transport processes in dilute media. Furthermore, the antennal glands of stenohaline marine osmoconformers are poorly characterized making it difficult to determine what role urinary processes play in excretion.

Gene knockout of NHX-3 in the soil nematode Caenorhabditis elegans leads to broad-spectrum compensatory regulation of Na/H exchangers, antiporters, and the V-type H-ATPase.

Na/H exchangers are directly involved in a variety of an animal's essential physiological processes such as ionoregulation, acid-base regulation, nitrogenous waste excretion, and nutrient absorption. While nine NHX isoforms have been identified in Caenorhabditis elegans, the physiological importance of each isoform is not understood. The current study aimed to further our knowledge of NHX-3 which has previously been suggested to be involved in the movement of ammonia and acid-base equivalents across the nematode's hypodermis.

Identification of different physiological functions within the gills and epipodites of the American lobster: Differences in metabolism, transbranchial transport, and mRNA expression.

Transbranchial transport processes are responsible for the homeostatic regulation of most essential physiological functions in aquatic crustaceans. Due to their widespread use as laboratory models, brachyuran crabs are commonly used to predict how other decapod crustaceans respond to environmental stressors including ocean acidification and warming waters. Non-brachyuran species such as the economically-valuable American lobster, Homarus americanus, possess trichobranchiate gills and epipodites that are known to be anatomically distinct from the phyllobranchiate gills of brachyurans; however, studies have yet to define their potential physiological differences.

Postprandial nitrogen and acid-base regulation in the seawater acclimated green crab, Carcinus maenas.

The effects of feeding (meal of 3% of body mass) on acid-base and nitrogen homeostasis were investigated in the seawater acclimated green shore crab, Carcinus maenas. Feeding did not change gastric fluid pH (~pH 6); however, feeding was associated with a respiratory acidosis. Hemolymph HCO did not increase during this acidosis, although titratable and net acid efflux changed from an uptake to an excretion.

Effects of single and dual-stressor elevation of environmental temperature and P on metabolism and acid-base regulation in the Louisiana red swamp crayfish, Procambarus clarkii.

Elevation of temperature and CO levels within the world's aquatic environments is expected to cause numerous physiological challenges to their inhabitants. While effects on marine ecosystems have been well studied, freshwater ecosystems have rarely been examined using a dual-stressor approach leaving our understanding of its inhabitants upon these challenges unclear. We aimed to identify the affects of elevated temperature and hypercapnia in isolation and in combination on the metabolic and acid-base regulatory processes of a freshwater crayfish, Procambarus clarkii.

Effects of emersion on acid-base regulation, osmoregulation, and nitrogen physiology in the semi-terrestrial mangrove crab, Helice formosensis.

Emersion limits water availability and impairs the gill function of water-breathing animals resulting in a reduced capacity to regulate respiratory gas exchange, acid-base balance, and nitrogenous waste excretion. Semi-terrestrial crustaceans such as Helice formosensis mitigate these physiological consequences by modifying and recycling urine and branchial water shifting some branchial workload to the antennal glands. To investigate how this process occurs, Helice formosensis were emersed for up to 160 h and their hemolymph and urinary acid-base, nitrogenous waste, free amino acids, and osmoregulatory parameters were investigated.

Exploring the versatility of the perfused crustacean gill as a model for transbranchial transport processes.

The study of transbranchial ion and gas transport of water-breathing animals has long been a useful means of modeling transport processes of higher vertebrate organs through comparative physiology. The molecular era of biological research has brought forward valuable information detailing shifts in gene expression related to environmental stress and the sub-cellular localization of transporters; however, purely molecular studies can cause hypothetical transport mechanisms and hypotheses to be accepted without any direct physiological proof. Isolated perfused gill experiments are useful for testing most of these hypotheses and can sometimes be used outright to develop a well-supported working model for transport processes relating to an animal's osmoregulation, acid-base balance, nitrogen excretion, and respiratory gas exchange as well as their sensitivity to pollutants and environmental stress.

Specialized adaptations allow vent-endemic crabs (Xenograpsus testudinatus) to thrive under extreme environmental hypercapnia.

Shallow hydrothermal vent environments are typically very warm and acidic due to the mixing of ambient seawater with volcanic gasses (> 92% CO) released through the seafloor making them potential 'natural laboratories' to study long-term adaptations to extreme hypercapnic conditions. Xenograpsus testudinatus, the shallow hydrothermal vent crab, is the sole metazoan inhabitant endemic to vents surrounding Kueishantao Island, Taiwan, where it inhabits waters that are generally pH 6.50 with maximum acidities reported as pH 5.

Impact of climate change on the American lobster (Homarus americanus): Physiological responses to combined exposure of elevated temperature and pCO.

The physiological consequences of exposing marine organisms to predicted future ocean scenarios, i.e. simultaneous increase in temperature and pCO, have only recently begun to be investigated.

Ammonia excretion in aquatic invertebrates: new insights and questions.

Invertebrates employ a variety of ammonia excretion strategies to facilitate their survival in diverse aquatic environments, including freshwater, seawater and the water film surrounding soil particles. Various environmental properties set innate challenges for an organism's ammonia excretory capacity. These include the availability of NaCl and the respective ion-permeability of the organism's transport epithelia, and the buffering capacity of their immediate surrounding medium.

Ammonia excretion and acid-base regulation in the American horseshoe crab, .

Many studies have investigated ammonia excretion and acid-base regulation in aquatic arthropods, yet current knowledge of marine chelicerates is non-existent. In American horseshoe crabs (), book gills bear physiologically distinct regions: dorsal and ventral half-lamellae, a central mitochondria-rich area (CMRA) and peripheral mitochondria-poor areas (PMPAs). In the present study, the CMRA and ventral half-lamella exhibited characteristics important for ammonia excretion and/or acid-base regulation, as supported by high expression levels of Rhesus-protein 1 (LpRh-1), cytoplasmic carbonic anhydrase (CA-2) and hyperpolarization-activated cyclic nucleotide-gated K channel (HCN) compared with the PMPA and dorsal half-lamella.

Ammonia-independent sodium uptake mediated by Na channels and NHEs in the freshwater ribbon leech .

Freshwater organisms actively take up ions from their environment to counter diffusive ion losses due to inhabiting hypo-osmotic environments. The mechanisms behind active Na uptake are quite well understood in freshwater teleosts; however, the mechanisms employed by invertebrates are not. Pharmacological and molecular approaches were used to investigate Na uptake mechanisms and their link to ammonia excretion in the ribbon leech At the molecular level, we identified a Na channel and a Na/H exchanger (NHE) in the skin of , where the NHE was up-regulated when acclimated to extremely low [Na] (0.