Osmoregulatory Capacity Research Articles

Effect of Different Oxygen Concentrations on Physiological Energetics of Blue Shrimp, Litopenaeus stylirostris (Stimpson)

The influence of different oxygen concentrations on the bioenergetics parameters, osmoregulatory capacity and O:N atomic ratio of the blue shrimp, Litopenaeus stylirostris (Stimpson), was determined under laboratory conditions; shrimp were acclimated at 28 oC and 25psu and exposed to three different oxygen concentrations 2, 4 and 6 mg L -1 . The critical oxygen level (COL) was determined at 5.5 mg L -1 . Growth, oxygen consumption (R), ammonium excretion (U), scope for growth (P) and apparent heat increment (AHI) were affected significantly (P < 0.05) when the organisms were exposed at different oxygen concentrations. The highest energy invested for routine metabolism and ammonium excretion was obtained in the animals maintained at 2 mg L -1 . The exposure of organisms to oxygen concentration (2 mg L -1 ) increased three times the feces production (23.59%). The high quantity of energy channeled to scope for growth (2756 J g - 1 day -1 d.w.) was obtained in the shrimp acclimated to an oxygen concentration of 6 mg L -1 . The O:N atomic ratio calculated for the juveniles indicated a catabolism of proteins for the organisms maintained in the lowest oxygen concentration. In the oxygen concentrations of 2 and 4 mg L -1 the blue shrimp juveniles modified their osmoregulatory capacity (OC) changing the osmoregulatory pattern the isosmotic to hypo-osmotic. We recommend maintaining Litopenaeus stylirostris at 6 mg L -1 and (25psu), these conditions for blue shrimp juveniles would enhance production in

Shrimp culture in inland low salinity waters

AbstractInland aquaculture of shrimp in low salinity waters is widespread in many regions worldwide. Owing to its ability to grow and survive in low salinity environments the Pacific white shrimp, (Litopenaeus vannamei Boone) has become the candidate of choice for low salinity culture. Remediation techniques have been developed to improve the osmoregulatory capacity of shrimp reared in low salinity waters. These techniques have evaluated water modification strategies that improve low salinity waters used for production by adding potassium and magnesium fertilizers and dietary approaches that involve modification of the feeds offered to shrimp with supplements that might improve osmoregulatory capacity. Based on our own experience as well as what we found predominantly in the literature, it appears that modification of the rearing medium with potassium and magnesium fertilizers is more effective than dietary modification techniques at improving the growth, survival and osmoregulatory capacity of shrimp reared in low salinity waters.

Ontogeny of osmoregulatory patterns in the South American shrimp Macrobrachium amazonicum: Loss of hypo-regulation in a land-locked population indicates phylogenetic separation from estuarine ancestors

Ontogenetic changes in osmoregulation were compared between two geographically separate populations of a South American shrimp, Macrobrachium amazonicum, originating from the Amazon delta (A) and the Pantanal (P), respectively. Population A lives in coastal rivers and estuaries in northern Brazil, whereas population P may be considered as land-locked, spending its entire life cycle in inland freshwater (FW) habitats in southwestern Brazil. All life-history stages of population A tolerated brackish and seawater (SW) conditions, being hyper-osmoregulators at salinities <17, iso-osmotic at ca. 17, and hypo-regulators at higher concentrations. The capabilities to survive and osmoregulate in FW were in this population expressed already at hatching (zoea I), but not any longer in the subsequent larval stages (II–IX), which showed complete mortality during an experimental 24h exposure to fully limnic conditions. FW tolerance re-appeared only in the juvenile and adult life-history stages. Similarly, the ability to hyper-regulate at salinities 1–5 was strong in the zoea I, weaker in the subsequent larval stages, and increasing again after metamorphosis. The function of hypo-regulation in concentrated media including SW was present throughout ontogeny, particularly in late larval and early juvenile stages. These ontogenetic patterns of osmoregulation and FW tolerance are congruent with a diadromous life cycle, which includes larval release in FW and a subsequent downstream transport of the salt-dependent early larvae towards estuarine or coastal marine waters, where development to metamorphosis is possible. The FW-tolerant juveniles can later migrate upstream, recruiting to riverine populations. In the land-locked population P, all life-history stages tolerated FW and brackish conditions up to salinity 25, but mortality was high in SW (100% in adults). All postembryonic stages of this population were hyper-osmoregulators at salinities <17, with a strong osmoregulatory capacity in FW. Unlike in population A, all stages were osmoconformers at higher salinities, lacking the function of hypo-regulation. In summary, our results show in two hydrologically and genetically isolated shrimp populations close relationships between differential patterns of ontogenetic change in osmoregulatory functions, salinity tolerance, and the ecology of successive life-history stages. In all postembryonic stages of the hololimnetic Pantanal population, the acquisition of an increased ability to hyper-osmoregulate in FW and, in particular, the complete loss of the ability to hypo-osmoregulate at high salt concentrations represent striking differences to the diadromous population from the Amazon estuary. These differences reflect different life styles and reproductive strategies, suggesting an at least incipient phylogenetic separation.

LAJU PERTUMBUHAN, EFISIENSI PEMANFAATAN PAKAN, KANDUNGAN POTASIUM TUBUH, DAN GRADIEN OSMOTIK POSTLARVA VANAME (Litopenaeus Vannamei, Boone) PADA POTASIUM MEDIA BERBEDA

Effect of K+ concentration on growth rate, feed efficiency, potassium whole body, and osmoregulatory capacity of L. vannamei postlarvae Boone, 1931 were investigated. Treatments consisted of different concentration of K+ added to distilled water. Four treatments were set, namely A, B, C and D, where K2CO3 levels were 0, 30, 60 and 90 ppm, respectively. After the 42-days feeding trial, growth rate and potassium whole body of the shrimp under treatment D (90 ppm K2CO3) were significantly higher, while the value of osmoregulatory capacity in treatment A (0 ppm K2CO3) significantly higher than those under the other four treatments. The results indicated treatment C (60 ppm K2CO3) were the optimum K+ level for growth rate with increasing body size.

Ontogeny of osmoregulation and salinity tolerance in the gilthead sea bream Sparus aurata

The gilthead sea bream, Sparus aurata, is a euryhaline teleost that hatches in the open sea. The larvae drift to the coast and juveniles migrate into estuaries and lagoons where the salinity of the water may vary from brackish to hyper-saline. The ontogeny of osmoregulation in Sparus aurata was studied at successive stages, from day 1 (D1) post-hatch to the late juvenile stage (D300) after exposure to different salinities ranging from fresh water to 45.1‰, at 18 °C. Survival ranged from between 5.1 and 39.1‰ at D3, and from 1.0 to 45.1‰ from D75. The fish were hyper-hypo-osmotic regulators at all studied stages. The acquisition of the full ability to hypo- and hyper-regulate occurred in four steps. The osmoregulatory capacity appeared age-dependent and reached its maximum level after D96, and the localization of ionocytes in the integument and gills occurred concurrently during development of the sea bream. However, the main site of osmoregulation shifted from the integument to the gills from D30 to D70, with a corresponding sharp increase in the osmoregulatory ability. Our results suggest that the early development of osmoregulatory ability, and thus of salinity tolerance in the sea bream may provide an advantageous flexibility for the timing of the migration between sea and estuaries and lagoons.

Physiological responses of three crustacean species to infection by the dinoflagellate-like protist Hematodinium (Alveolata: Syndinea)

This is the first study comparing physiological responses of three decapod species to infection by parasites of the genus Hematodinium, which belongs to the dinoflagellate-like Syndinea. Responses varied profoundly between the crabs Carcinus maenas and Cancer pagurus (Brachyura) , but also differed to those of hermit crabs, Pagurus bernhardus (Anomura) . Osmoregulatory capacity was reduced significantly in Hematodinium-infected C. maenas, haemolymph pH increased in parasitised C. pagurus and P. bernhardus, and L-lactate concentration decreased in infected P. bernhardus. Changes to tissues and exoskeletons were observed in C. pagurus, but not in C. maenas and P. bernhardus.

Damage of the Bacterial Cell Envelope by Antimicrobial Peptides Gramicidin S and PGLa as Revealed by Transmission and Scanning Electron Microscopy

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the ultrastructural changes in bacteria induced by antimicrobial peptides (AMPs). Both the beta-stranded gramicidin S and the alpha-helical peptidyl-glycylleucine-carboxyamide (PGLa) are cationic amphiphilic AMPs known to interact with bacterial membranes. One representative Gram-negative strain, Escherichia coli ATCC 25922, and one representative Gram-positive strain, Staphylococcus aureus ATCC 25923, were exposed to the AMPs at sub-MICs and supra-MICs in salt-free medium. SEM revealed a shortening and swelling of the E. coli cells, and multiple blisters and bubbles formed on their surface. The S. aureus cells seemed to burst upon AMP exposure, showing open holes and deep craters in their envelope. TEM revealed the formation of intracellular membranous structures in both strains, which is attributed to a lateral expansion of the lipid membrane upon peptide insertion. Also, some morphological alterations in the DNA region were detected for S. aureus. After E. coli was incubated with AMPs in medium with low ionic strength, the cells appeared highly turgid compared to untreated controls. This observation suggests that the AMPs enhance osmosis through the inner membrane, before they eventually cause excessive leakage of the cellular contents. The adverse effect on the osmoregulatory capacity of the bacteria is attributed to the membrane-permeabilizing action of the amphiphilic peptides, even at low (sub-MIC) AMP concentrations. Altogether, the results demonstrate that both TEM and SEM, as well as appropriate sample preparation protocols, are needed to obtain detailed mechanistic insights into peptide function.

Na/K-ATPase activity and osmo-ionic regulation in adult whiteleg shrimp Litopenaeus vannamei exposed to low salinities

Na/K-ATPase activity and osmo-ionic regulation were examined in Litopenaeus vannamei exposed to low salinities. The hemolymph osmolality of shrimp exposed to very low salinities (0.5 ppt and 1 ppt) decreased rapidly after 6 h from 800 mOsm to 540–560 mOsm; these individuals could not survive beyond 1 day. Under exposure to 7 ppt, osmolality levels decreased rapidly to 630 and 570 mOsm after 6 h and 1 day respectively, whereas in shrimp exposed to 18 ppt, levels declined slowly from 800 mOsm to 700 mOsm after 6 h and thereafter remained stable for 7 days until the end of the experiment. Hemolymph sodium ion levels showed a pattern of change similar to that of hemolymph osmolality, with initial levels being 380 mmol/L and decreasing to 180 mmol/L under very low salinity. Changes in calcium, potassium, and magnesium ion concentrations were also investigated. Na/K-ATPase activity was 3.98 μmol ADP/mg protein/hour in the gills of control individuals maintained at 28 ppt for the experimental duration. Levels increased in individuals exposed to 18 ppt, 7 ppt and 3 ppt for 7 days to 5.06, 6.51, and 5.81 μmol ADP/mg protein/hour, respectively. Based on the above, it is suggested that L. vannamei could not survive in low salinity (< 1 ppt) due to the loss of osmoregulatory capacity when the shrimps were transferred directly from high salinities to low salinities.

Acclimation of Solea senegalensis to different ambient temperatures: implications for thyroidal status and osmoregulation

We have investigated the regulation of thyroidal status and osmoregulatory capacities in juveniles from the teleost Solea senegalensis acclimated to different ambient temperatures. Juveniles, raised in seawater at 19°C, were acclimated for 3 weeks to temperatures of 12, 19 and 26°C. Since our preliminary observations showed that at 12°C feed intake was suppressed, our experimental design controlled for this factor. The concentration of branchial Na+,K+-ATPase, estimated by measurements of enzyme activity at the optimum temperature of this enzyme (37°C), did not change. In contrast, an increase in Na+,K+-ATPase activity (measured at 37°C), was observed in the kidney of 12°C-acclimated fish. In fish acclimated to 12°C, the hepatosomatic index had increased, which correlated with increased plasma levels of triglycerides and non-esterified fatty acids. Plasma cortisol levels did not differ significantly between the experimental groups. In liver and gills, the amount of iodothyronine deiodinases that exhibit thyroid hormone outer ring deiodination was up-regulated only when fish did not feed. When assayed at the acclimation temperature, kidney deiodinase activities were similar, indicating a temperature-compensation strategy. 3,5,3′-triiodothyronine (T3) tissue concentrations in gills and kidney did not differ significantly between experimental groups. However, at 12°C, lower T3 tissue levels were measured in plasma and liver. We conclude that S. senegalensis adjusts its osmoregulatory system to compensate for the effects of temperature on electrolyte transport capacity. The organ-specific changes in thyroid hormone metabolism at different temperatures indicate the involvement of thyroid hormones in temperature acclimation.

Effects of dietary β – 1,3 – glucan on the growth, survival, physiological and immune response of marron, Cherax tenuimanus (smith, 1912)

Six isonitrogenous and isocalorific diets supplemented with five different levels of beta –1,3 – glucan (0.08%, 0.1%, 0.2%, 0.4% and 0.8%) were formulated and tested for marron ( Cherax tenuimanus) growth, survival, organosomatic indices, osmoregulatory capacity and immunological parameters (total and differential haemocyte counts, haemolymph clotting time and bacteraemia). The sixth diet without any beta – 1,3 – glucan was used as a control. Each diet was provided to 18 marron (0.47 ± 0.02 g initial weight) replicated 3 times in individual 250 L fiberglass cylindrical tanks. Each tank was provided with a biological filtration recirculating water system. After 84 days of culture, the survival and yield were higher in the marron fed 0.1% beta glucan supplemented diet. The different levels of beta glucan did not alter any of the physiological parameters of marron. However, dietary supplementation with beta glucan resulted in significantly higher ( P < 0.05) total haemocyte count (THC) and granular cells. The bacteraemia rank was lower in all diets having beta glucan supplemented with more than or equal to 0.1% compared to the control and 0.08% beta glucan supplemented diets. Results suggest that dietary beta – 1,3 – glucan at a minimum concentration of 0.1–0.2% can improve the immune system of marron.

The effects of diclofenac on the physiology of the green shore crab Carcinus maenas

In recent years there has been increasing concern regarding the influx of pharmaceuticals into aquatic environments. One group of pharmaceuticals that has been identified as being of particular concern are the non-steroidal anti-inflammatory drugs (NSAIDs). This study examined the effects of one of the most commonly reported NSAID contaminants, diclofenac, on the physiology of Carcinus maenas. Two environmentally realistic concentrations were examined in this study (10 ng/l and 100 ng/l) at two salinities (35 and 17.5 psu). Female and male crabs were exposed to these two concentrations for 7 days. Following exposure, haemolymph samples were taken from the animals. Measurements were taken for oxyhaemocyanin and lactate concentrations. The effects of this compound on osmoregulatory capacity (OC) in C. maenas were also measured. Exposure to diclofenac had no significant effect on haemolymph lactate and oxyhaemocyanin concentrations suggesting that exposure to this compound does not elicit a stress response in this species. However, exposure to this pharmaceutical did have significant effects on both the OC and the haemolymph osmolality in C. maenas. At both salinities the data suggests that the osmoregulatory ability of C. maenas is impaired when exposed to diclofenac.

Effects of cortisol and salinity acclimation on Na&lt;sup&gt;+&lt;/sup&gt;/K&lt;sup&gt;+&lt;/sup&gt;/2Cl&lt;sup&gt;–&lt;/sup&gt;- cotransporter gene expression and Na&lt;sup&gt;+&lt;/sup&gt;, K&lt;sup&gt;+&lt;/sup&gt;-ATPase activity in the gill of Persian sturgeon, &lt;i&gt;Acipenser persicus&lt;/i&gt;, fry

Na + , K + -ATPase activity and Na + /K + /2Cl – - cotransporter (NKCC) gene expression in the gills of Persian sturgeon, Acipenser persicus , fry (2-3 g, 3.30-8.12 cm total body length) in freshwater (control group), diluted Caspian Sea water (5 ppt) and after treatment with cortisol in freshwater were studied. Na + , K + -ATPase activity was lower in the 5 ppt-acclimated fish (1.07±0.05 _mol P i /mg protein/h) than in the control fish (1.19±0.05 μmol Pi/mg protein/h) but this difference was not significant. nKCC gene expression in the 5 ppt-acclimated fish (1.6±0.07) was significantly higher than in the control fish (0.8±0.00). In the cortisol treated fish, Na + , K + -ATPase activity (1.91±0.05 μmol P i /mg protein/h) and NKCC gene expression (3.2±0.1) were significantly higher than in the control group. our results show that Persian sturgeon fry (2-3 g) can tolerate 5 ppt salinity by changing their enzymatic content and activity, and that exogenous cortisol application can increase the osmoregulatory capacity of fry before release into brackish water and can reduce their mortality.

Recruitment patterns of young-of-the-year mugilid fishes in a West African estuary impacted by climate change

With the persistence of the sub-Saharan drought since the 1970s, the Sine Saloum estuary (Senegal) – the second largest coastal Biosphere Reserve of West-Africa – has become an “inverse estuary” and hypersaline (salinity > 60) in its upstream part. A one-year survey was conducted from April 2007 to March 2008 at eight sites distributed along the salinity gradient, to investigate the recruitment patterns of young-of-the-year mugilids in such an impacted ecosystem. Fishes were sampled monthly with a conical net and a beach seine in salinities ranging from 31 to 104. Samples were identified to the species level. For the smallest individuals (<20 mm SL) a PCR–RFLP technique, developed on the mitochondrial 16S ribosomal RNA region, was used for identification. A total of 8438 juveniles belonging to six of the eight species of mugilids known for the tropical Eastern Atlantic were collected: Mugil bananensis, Mugil cephalus, Mugil curema, Liza dumerili, Liza falcipinnis and Liza grandisquamis. One species, L. dumerili, represented 89% of the total catch. Length–frequency distributions revealed that M. cephalus and L. dumerili preferentially recruited during the dry season whereas the recruitment of M. curema, M. bananensis and L. falcipinnis generally occurred during the wet season. Minimal size at recruitment ranged from 9 to 19 mm SL depending on the species, the smallest size being that of L. dumerili. Despite the general salinity increase in the estuary, most parts of the Sine Saloum were suitable for the juveniles. Only the hypersaline area in the uppermost part of the estuary presented very low fish abundance for all species. According to the species, small recruits (12–20 mm SL) were collected at salinities up to 47–78, suggesting that osmoregulatory capacities had been gained early during ontogenesis, possibly resulting from an adaptation of these populations to changing environmental conditions.

Glutamine accumulation and up-regulation of glutamine synthetase activity in the swamp eel,Monopterus albus(Zuiew), exposed to brackish water

The swamp eel, Monopterus albus, is an air-breathing teleost which typically lives in freshwater but can also be found in estuaries, where it has to deal with ambient salinity fluctuations. Unlike other teleosts, its gills are highly degenerate. Hence, it may have uncommon osmoregulatory adaptations, but no information is available on its osmoregulatory capacity and mechanisms at present. In this study M. albus was exposed to a 5 day progressive increase in salinity from freshwater (1 per thousand) to brackish water (25 per thousand) and subsequently kept in 25 per thousand water for a total of 4 days. The results indicate that M. albus switched from hyperosmotic hyperionic regulation in freshwater to a combination of osmoconforming and hypoosmotic hypoionic regulation in 25 per thousand water. Exposure to 25 per thousand water resulted in relatively large increases in plasma osmolality, [Na(+)] and [Cl(-)]. Consequently, fish exposed to 25 per thousand water had to undergo cell volume regulation through accumulation of organic osmolytes and inorganic ions. Increases in tissue free amino acid content were apparently the result of increased protein degradation, decreased amino acid catabolism, and increased synthesis of certain non-essential amino acids. Here we report for the first time that glutamine is the major organic osmolyte in M. albus. Glutamine content increased to a phenomenal level of > 12 micromol g(-1) and > 30 micromol g(-1) in the muscle and liver, respectively, of fish exposed to 25 per thousand water. There were significant increases in glutamine synthetase (GS) activity in muscle and liver of these fish. In addition, exposure to 25 per thousand water for 4 days led to significant increases in GS protein abundance in both muscle and liver, indicating that increases in the expression of GS mRNA could have occurred.

Supplementation of Chelated Magnesium to Diets of the Pacific White Shrimp, Litopenaeus vannamei, Reared in Low‐salinity Waters of West Alabama

Abstract Shrimp farmers using inland low‐salinity waters in west Alabama have traditionally used agricultural fertilizers (K‐Mag®, muriate of potash) to raise pond water levels of potassium (K) and magnesium (Mg) to improve the rearing medium for Litopenaeus vannamei. Laboratory and farm trials were performed to investigate the potential of using dietary supplementation of Mg instead of costly agricultural fertilizers. A 5‐wk laboratory trial was devised to test four diets with varying levels of Mg supplementation (0, 0.15, 0.30, and 0.60% Mg chelate) using a magnesium chelate (MgC)–amino acid complex. Juvenile shrimp were stocked into artificial low‐salinity water (5 ppt) designed to contain low levels of Mg. A farm trial was also conducted to test the same diets under field conditions. Although both laboratory and on‐farm trials revealed a trend for increased growth using the diet with the highest Mg supplement, results were not significantly different. The use of magnesium chelates as dietary supplements at levels higher than the requirement level to enhance survival, growth, and osmoregulatory capacity of shrimp reared in inland low‐salinity well waters appeared to have limited potential. Until effective specialized diet formulations are produced, farmers should continue to supplement pond waters with fertilizers containing K and Mg.

Effect of sudden change in potassium concentration on Penaeus latisulcatus Kishinouye survival, osmolality and health in inland saline water cultures

The aim of the project was to determine the effects of sudden change in potassium concentration in inland saline water on the survival, osmolality and condition indices of western Australian King Prawn—Penaeus latisulcatus Kishinouye. Australia has large volumes of inland saline water that could be used for aquaculture but is often deficient in K+. Western king prawn is a candidate species for culture in inland saline water. Such waters require K+ fortification for prawn survival and growth. Trials were conducted in tanks to determine the effect of sudden change in K+ concentration in inland saline water samples on the survival, osmolality and condition indices of western king prawns. Prawns in tanks were acclimated to inland saline water procured from Wannamal—an inland location in Western Australia. After 3 days of acclimation, prawns were subjected to sudden increase in medium K+ concentration over 1 h, ranging from 80% to 100% of the marine water K+ concentration by adding potassium chloride. Identical inland saline water was added to the control tanks over the same time period. Survival, ingestion rate and osmoregulatory capacity (OC) were then recorded over 19 days. At the conclusion of the trial, survival ranged from 71% to 78% in the potassium-enriched tanks whereas 100% mortality was observed in the control tanks by day 11. Ingestion rate of prawns was significantly higher in the experimental tanks than in the control. Osmoregulatory capacity of potassium-enriched prawns was significantly lower post- than pre-ionic change and significantly higher at the conclusion of the trial than both pre- and post-ionic change. There was no significant difference in OC between water types at any time period. These results indicate that prawns can tolerate sudden increase in K+ content in inland saline water and the higher K+ concentration increases survival and OC, but other measures indicate the prawns were experiencing stressful conditions.

Salinity effects on the expression of osmoregulatory genes in the euryhaline black porgy Acanthopagrus schlegeli

Black porgy is a marine euryhaline species with a capacity to cope with demands in a wide range of salinities and thus is a perfect model-fish to study osmoregulatory responses to salinity-acclimated processes and their hormonal control. The present study was performed to understand the regulatory changes in hormone, hormone receptors and important osmoregulatory genes in pituitary, gill, intestine and kidney in response to acute salinity stress. Transcript levels were analyzed by quantitative real-time PCR following acute salinity challenge by direct transfer of seawater (SW) acclimatized fish to fresh water (FWBP) and vice versa (SWBP). SW acclimation significantly increased plasma osmolality and intestine Na +/K +-ATPase (NKA) activity while FW acclimation increased plasma cortisol and branchial NKA activity. Plasma osmolality and chloride concentration decreased in FWBP whereas GH levels remained unchanged in both FWBP and SWBP. Comparative analysis of gene profiles between FWBP and SWBP showed that pituitary prolactin transcript increased significantly in FWBP. Prolactin receptor ( PRLR) transcripts increased in gill of FWBP while it decreased in gill and kidney of SWBP. NKA transcripts increased in gill of both FWBP and SWBP, while it decreased in intestine of FWBP and increased in intestine and kidney of SWBP. Glucocorticoid receptor ( GR) transcripts decreased in intestine and kidney of FWBP while it increased in gill and intestine of SWBP. No significant changes were observed in growth hormone receptor ( GHR) transcripts of both FWBP and SWBP in pituitary, gill, intestine and kidney. Our current data demonstrated the correlation between PRLR gene expression in relation to FW adaptation, and GR gene expression in relation to SW adaptation in euryhaline black porgy. The results indicate that black porgy has an excellent osmoregulatory capacity and is capable of withstanding large variations in salinity.

Interactive Effects of Different Temperatures and Salinities on Growth, Feed Conversion Efficiency, and Blood Physiology in Juvenile Spotted Wolffish, Anarhichas minor Olafsen

Abstract The aim of this study was to investigate the effects of different salinities and temperatures and their possible interactive effect on growth performance, feeding parameters, and blood physiology in juvenile spotted wolffish, Anarhichas minor, reared at different temperature (7 and 10 C) and salinity (15, 25, and 34‰) combinations. There was a significant interactive effect between temperature and salinity on growth, as a growth‐enhancing effect was seen at intermediate and full salinities at higher temperature, whereas the reciprocal trend was seen at lower temperature. Mean total feed consumption, daily feeding rate, and feed conversion efficiency were all highest at the intermediate salinity at 10 C, whereas at 7 C, the feeding parameters were highest at low and intermediate salinities. Blood plasma sodium content was lowest at 15‰, whereas the opposite trend was seen in partial pressure of CO2 and bicarbonate in blood where the highest concentrations were seen at 15‰. This study demonstrates that spotted wolffish has a high osmoregulatory and acclimatory capacity. In an aquaculture context, growth of juvenile spotted wolffish can be improved by rearing the species at high temperature and intermediate salinity combinations at least in a limited period of the juvenile phase.

Gross morphology and surface ultrastructure of the gills of Odontesthes argentinensis (Actinopterygii, Atherinopsidae) from a Southwestern Atlantic coastal lagoon

Odontesthes argentinensis was collected from Mar Chiquita Coastal Lagoon, the Southernmost coastal Atlantic Lagoon of Argentina. The morphology of the gills was analyzed by scanning electron microscopy. The morphology of the superficial structures of the gill filaments and pharyngeal region of the gill arch was discussed and related to their functional aspects. The gills arches are structurally similar to those of other teleosts and bring out the osmoregulatory capacity of this species. The epithelium that covers the surface of the filaments and the pharyngeal region of the gill arch is formed by polygonal pavement cells with conspicuous microridges. These folds in the membrane are not denoted in the epithelium of the respiratory lamellae. Apical crypts of chloride cells are present on the afferent and interlamellar filament surfaces, but are absent elsewhere on the gill arch. The highest density of mucous cells is observed into the gill filament and the pharyngeal region which indicates the existence of a protective strategy of the respiratory lamellae and the pharynx. The epithelium of the gill arches and the rakers is studded with spines. There are taste buds along the whole pharyngeal region that may be associated with their participation in tasting at this zone.

Tertiary stress responses in Senegalese sole ( Solea senegalensis Kaup, 1858) to osmotic challenge: Implications for osmoregulation, energy metabolism and growth

The effects of three different environmental salinities (15, 25 and 39‰) on growth, osmoregulation and energy metabolism of juvenile Senegalese sole ( Solea senegalensis Kaup, 1858) after a period of 10 weeks were investigated. Immature sole ( n = 150, 39 ± 1 g mean initial body weight) were randomly divided in 6 groups of 25 fish and reared under three different environmental salinities in an open system. Growth, weight gain, specific growth rate and estimated feed intake decreased in salinities lower than 39‰, with the most profound effects observed at 15‰. Branchial Na +,K +-ATPase activity correlated positively with environmental salinity, while renal Na +,K +-ATPase activity was not altered. Plasma electrolyte concentrations did not change in the salinity range tested, indicating that osmoregulatory capacities were unaffected. Plasma cortisol levels were higher in salinities different than 39‰ (15 > 25 > 39‰). Plasma glucose, non-esterified fatty acid, triglyceride, and protein levels were decreased in the lower salinities (25 and 15‰), whereas that of lactate was increased two-fold in the 15‰-exposed group only. Measured in tissues (liver, gill, kidney, white muscle), the most profound changes in metabolite levels were generally found in the group exposed to 15‰, compared to the 25‰- and 39‰-groups. A similar pattern was found for the activities of enzymes involved in energy metabolism. Taken together, our data suggest that the poor growth rate of 15‰-exposed fish is caused by decreased feed intake and the subsequent reallocation of energy sources that was non-sufficient to keep similar growth in fish exposed to 15‰ salinity compared with fish exposed to 25 and 39‰ salinity.