High affinity, Ca2+ specific atpase and Na+K+-ATPase in the gills of a supralittoral crab Leptograpsus variegatus

La dureza total del agua afecta la muda, calcificación, crecimiento y supervivencia de Cryphiops caementarius (Palaemonidae)

El objetivo de este estudio fue evaluar los efectos de diferentes niveles de dureza total del agua en la muda, calcificación del exoesqueleto, crecimiento y supervivencia de Cryphiops caementarius. Los camarones machos fueron colectados del río Pativilca (Lima, Perú) y cultivados en recipientes individuales dentro de acuarios (55 L). Se emplearon cuatro niveles de dureza total del agua (100, 200, 300 y 400 mg CaCO3 L-1), con tres repeticiones, respectivamente. Los camarones cultivados en agua con dureza de 300 mg L-1 tuvieron menor periodo de muda (26,7 días) y mayor frecuencia de mudas (tres mudas). El contenido de calcio del exoesqueleto del camarón incrementó (p < 0,05) de 25 a 31 % en agua con dureza de 100 y 400 mg L-1, respectivamente. El mayor grosor del exoesqueleto (144 µm en cefalotórax y 131 µm en abdomen) fue obtenido en agua con dureza de 400 mg L-1 y el menor grosor (93 µm en cefalotórax y abdomen) en 100 mg L-1. El crecimiento en longitud fue mayor (p < 0,05) en agua con durezas de 200 y 300 mg L-1. El crecimiento en peso fue similar (p > 0,05) entre tratamientos. La mayor supervivencia (> 94,4 %) se mantuvo en agua con durezas de hasta 300 mg L-1 y la menor supervivencia (77,8 %) fue con 400 mg L-1. La dureza total del agua de 200 y 300 mg L-1 es conveniente para el cultivo del camarón, pero dureza del agua mayor o menor a este rango afectan la muda, el crecimiento y la supervivencia por deficiencia o exceso de calcio acumulado, respectivamente en el exoesqueleto del camarón.

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. The technique allows full control of internal hemolymph-like saline as well as the ambient environmental fluid compositions and can measure the electrophysiological properties of the gill as well as the transport rates of ions and gases as they traverse the gill epithelium. Additives such as pharmaceuticals or peptides as well as the exclusion of ions from the media are commonly used to identify the importance of specific transporters to transport mechanisms. The technique can also be used to identify the penetrance, retention, and localization of pollutants within the gill epithelium or to explore the uptake and metabolism of nutrients directly from the ambient environment. While this technique can be applied to virtually any isolatable organ, the anatomy and rigidity of the decapod crustacean gill make it an ideal candidate for most experimental designs.

Multiple functions of the crustacean gill: osmotic/ionic regulation, acid-base balance, ammonia excretion, and bioaccumulation of toxic metals

The crustacean gill is a multi-functional organ, and it is the site of a number of physiological processes, including ion transport, which is the basis for hemolymph osmoregulation; acid-base balance; and ammonia excretion. The gill is also the site by which many toxic metals are taken up by aquatic crustaceans, and thus it plays an important role in the toxicology of these species. This review provides a comprehensive overview of the ecology, physiology, biochemistry, and molecular biology of the mechanisms of osmotic and ionic regulation performed by the gill. The current concepts of the mechanisms of ion transport, the structural, biochemical, and molecular bases of systemic physiology, and the history of their development are discussed. The relationship between branchial ion transport and hemolymph acid-base regulation is also treated. In addition, the mechanisms of ammonia transport and excretion across the gill are discussed. And finally, the toxicology of heavy metal accumulation via the gill is reviewed in detail.

Long-term exposure of the freshwater shrimp Macrobrachium olfersii to elevated salinity: effects on gill (Na+,K+)-ATPase alpha-subunit expression and K+-phosphatase activity

The kinetic properties of a microsomal gill (Na+,K+)-ATPase from the freshwater shrimp, Macrobrachium olfersii, acclimated to 21 per thousand salinity for 10 days were investigated using the substrate p-nitrophenylphosphate. The enzyme hydrolyzed this substrate obeying cooperative kinetics at a rate of 123.6+/-4.9 U mg-1 and K0.5=1.31+/-0.05 mmol L-1. Stimulation of K+-phosphatase activity by magnesium (Vmax=125.3+/-7.5 U mg-1; K0.5=2.09+/-0.06 mmol L-1), potassium (Vmax=134.2+/-6.7 U mg-1; K0.5=1.33+/-0.06 mmol L-1) and ammonium ions (Vmax=130.1+/-5.9 U mg-1; K0.5=11.4+/-0.5 mmol L-1) was also cooperative. While orthovanadate abolished p-nitrophenylphosphatase activity, ouabain inhibition reached 80% (KI=304.9+/-18.3 micromol L-1). The kinetic parameters estimated differ significantly from those for freshwater-acclimated shrimps, suggesting expression of different isoenzymes during salinity adaptation. Despite the approximately 2-fold reduction in K+-phosphatase specific activity, Western blotting analysis revealed similar alpha-subunit expression in gill tissue from shrimps acclimated to 21 per thousand salinity or fresh water, although expression of phosphate-hydrolyzing enzymes other than (Na+,K+)-ATPase was stimulated by high salinity acclimation.

In vivo and in vitro cadmium accumulation during the moult cycle of the male shore crab Carcinus maenas--interaction with calcium metabolism

The effect of moult stage on cadmium accumulation and distribution was investigated in vivo in male shore crabs Carcinus maenas exposed to 1 mg Cd l(-1) for 7 days. The accumulation of cadmium in all tissues examined was markedly higher in postmoult (A(1-2) and B(1-2)) compared to intermoult (C1, C3 and C4) and premoult (D(0-3)). In addition, elevated levels of cadmium were found in gills of late premoult (D(2-3)) animals. The total amount of cadmium accumulated in the tissues (haemolymph, gills, midgut gland and muscle) increased from 43 microg Cd in early premoult (D(0-1)) to 391 microg Cd in late postmoult (B(1-2)). Gills and midgut gland were the primary cadmium accumulating tissues in C4-intermoult and premoult (D(0-3)); in early postmoult (A(1-2)) haemolymph and midgut gland were the main cadmium containing tissues, while midgut gland dominated in late postmoult (B(1-2)) and early intermoult (C1 and C3). A detailed account of calcium distribution in haemolymph, gills, midgut gland, muscle and exoskeleton during the moult cycle is presented. Mechanistic links between cadmium and calcium uptake in posterior gills of C4-intermoult and early postmoult (A(1-2)) crabs were explored using an in vitro gill perfusion technique. Calcium and cadmium influxes were markedly higher in postmoult compared to intermoult. No differences between intermoult and postmoult effluxes were found for either calcium or cadmium. From intermoult to postmoult net influx increased from 2.4 to 29 micromol Ca2+ g(-1) ww(gill) h(-1) and from 0.24 to 25 nmol Cd2+ g(-1) ww(gill) h(-1). The results indicate that the postmoult increase in cadmium influx is due to increased active transport of cadmium, at least partly, by accidental uptake via calcium transporting proteins. The in vitro net influx rates corresponded accurately to the observed in vivo accumulation of both cadmium and calcium. Although cadmium accumulation and distribution are clearly linked to changes in calcium requirements, cadmium did not interfere with calcium accumulation or distribution at any stage during the moult cycle.

Comparative studies on the energy metabolism in spermatozoa of four closely related species of sea urchins (genus Echinometra) in Okinawa

Sea urchins of the genus Echinometra are abundant on Okinawa reef flats in southern Japan. The Okinawan Echinometra is designated into four sympatric and closely related species: A, B, C, and D (Ea, Eb, Ec, and Ed). The sperm head size and shape gradually changes to become longer and more slender according to the following order: Ea, Eb, Ec, and Ed. To obtain information regarding speciation in Okinawan Echinometra, this study examined comparatively the energy production system of spermatozoa of Ea, Eb, Ec, and Ed. All spermatozoa contained cholesterol and several kinds of phospholipids. Glycogen, glucose, and triglyceride were present at extremely low levels. After incubation in sea-water, a decrease in the level of phosphatidylcholine (PC) was observed in all spermatozoa concomitantly with activation of motility and respiration. The hydrolysis of PC correlated with the activity of phospholipase A2. Interestingly, the amount of PC consumed, the respiratory rate, and the phospholipase A2 activity in spermatozoa of Ea and Eb were approximately two-fold higher than those of Ec and Ed. Ultrastructural studies showed that lipid bodies within mitochondria were present in the midpieces of all species of spermatozoa. They became small or disappeared after incubation in seawater. Thus, the results obtained strongly suggest that spermatozoa of Ea, Eb, Ec, and Ed all use PC located in the lipid bodies as a substrate for energy metabolism. Also, it seems likely that energy production activities in Ea and Eb spermatozoa are stronger than those in Ec and Ed. The properties of energy metabolism in different species of sea urchin may be related to their habitat.

Immunolocalization of NA(+),K(+)-ATPase in the branchial cavity during the early development of the European lobster Homarus gammarus (Crustacea, Decapoda)

We examined the ontogeny of the osmoregulatory sites of the branchial cavity in embryonic and early postembryonic stages of the European lobster Homarus gammarus through transmission electron microscopy, immunofluorescence microscopy, and immunogold electron microscopy using a monoclonal antibody IgGalpha(5) raised against the avian alpha-subunit of the Na(+),K(+)-ATPase. In mid-late embryos, Na(+),K(+)-ATPase was located along the pleurites and within the epipodite buds. In late embryos just before hatching, the enzyme was confined to the epipodite epithelia. After hatching, slight differentiations of ionocytes occured in the epipodites of larval stages. Na(+),K(+)-ATPase was also located in the ionocytes of the epipodites of larvae exposed to seawater (35.%o) and to dilute seawater (22.1 %o). After metamorphosis, the inner-side branchiostegite epithelium appeared as an additional site of enzyme location in postlarvae held in dilute seawater. Within the ionocytes, Na(+),K(+)-ATPase was mostly located along the basolateral infoldings. These observations are discussed in relation to the physiological shift from osmoconforming larvae to slightly hyper-regulating (in dilute seawater) postmetamorphic stages. The acquisition of the ability to hyper-osmoregulate probably originates from the differentiation, on the epipodites and mainly along the branchiostegites, of ionocytes that are the site of ion pumping as evidenced by the location of Na(+),K(+)-ATPase.

Characterization of (Na+, K+)-ATPase in gill microsomes of the freshwater shrimp Macrobrachium olfersii

To better understand the adaptive strategies that led to freshwater invasion by hyper-regulating Crustacea, we prepared a microsomal (Na+, K+)-ATPase by differential centrifugation of a gill homogenate from the freshwater shrimp Macrobrachium olfersii. Sucrose gradient centrifugation revealed a light fraction containing most of the (Na+, K+)-ATPase activity, contaminated with other ATPases, and a heavy fraction containing negligible (Na+, K+)-ATPase activity. Western blotting showed that M. olfersii gill contains a single alpha-subunit isoform of about 110 kDa. The (Na+, K+)-ATPase hydrolyzed ATP with Michaelis Menten kinetics with K5, = 165+/-5 microM and Vmax = 686.1+/-24.7 U mg(-1). Stimulation by potassium (K0.5 = 2.4+/-0.1 mM) and magnesium ions (K0.5 = 0.76+/-0.03 mM) also obeyed Michaelis-Menten kinetics, while that by sodium ions (K0.5 = 6.0+/-0.2 mM) exhibited site site interactions (n = 1.6). Ouabain (K0.5 = 61.6+/-2.8 microM) and vanadate (K0.5 = 3.2+/-0.1 microM) inhibited up to 70% of the total ATPase activity, while thapsigargin and ethacrynic acid did not affect activity. The remaining 30% activity was inhibited by oligomycin, sodium azide and bafilomycin A. These data suggest that the (Na+, K+)-ATPase corresponds to about 70% of the total ATPase activity; the remaining 30%, i.e. the ouabain-insensitive ATPase activity, apparently correspond to F0F1- and V-ATPases, but not Ca-stimulated and Na- or K-stimulated ATPases. The data confirm the recent invasion of the freshwater biotope by M. olfersii and suggest that (Na+, K+)-ATPase activity may be regulated by the Na+ concentration of the external medium.

Cadmium influx and efflux across perfused gills of the shore crab, Carcinus maenas

Cadmium influx across perfused gills of the shore crab Carcinus maenas exposed to 9.0 µM cadmium in the external medium ranged from 0.6 to 2.0 nmol Cd(2+) g(-1) gill wet wt. per h. Cadmium efflux across perfused gills exposed to 9.0 µM cadmium in the internal medium ranged from 0.3 to 0.9 nmol Cd(2+) g(-1) gill wet wt. per h. There was no significant difference between cadmium influx and efflux across the gills. Cadmium influx across the gills was not detectable after exposure to lanthanum in the external medium, whereas cadmium efflux was unaffected by external as well as internal lanthanum. Cadmium influx was not affected when the internal medium was changed to Na-free medium, whereas efflux showed a fourfold increase when the gills were perfused with Na-free medium. Low pH in the external medium did not exert any significant effect on cadmium influx and efflux.