Osmotic stress does not trigger brevetoxin production in the dinoflagellate Karenia brevis

With the global proliferation of toxic Harmful Algal Bloom (HAB) species, there is a need to identify the environmental and biological factors that regulate toxin production. One such species, Karenia brevis, forms nearly annual blooms that threaten coastal regions throughout the Gulf of Mexico. This dinoflagellate produces brevetoxins, potent neurotoxins that cause neurotoxic shellfish poisoning and respiratory illness in humans, as well as massive fish kills. A recent publication reported that a rapid decrease in salinity increased cellular toxin quotas in K. brevis and hypothesized that brevetoxins serve a role in osmoregulation. This finding implied that salinity shifts could significantly alter the toxic impacts of blooms. We repeated the original experiments separately in three different laboratories and found no evidence for increased brevetoxin production in response to low-salinity stress in any of the eight K. brevis strains we tested, including three used in the original study. Thus, we find no support for an osmoregulatory function of brevetoxins. The original publication also stated that there was no known cellular function for brevetoxins. However, there is increasing evidence that brevetoxins promote survival of the dinoflagellates by deterring grazing by zooplankton. Whether they have other as yet unidentified cellular functions is currently unknown.

Dehydration of prawns in tunnel dryers

This paper deals with the dehydration of prawns in a tunnel dryer. Conditions required to produce an end-product of desired colour, shape and texture as well as good reconstitution and organoleptic properties which are not obtained in the normal hot air drying, have been worked out. An initial temperature and relative humidity of 90°C. and 85%-90% respectively and an air velocity not more than 1 metre/second are the essential conditions required. Both temperature and relative humidity are to be reduced to 70°C and 40% respectively after about an hour's operation, till the drying is complete. Flavour of the reconstituted product is close to that of the fresh cooked prawns and the texture is judged to be soft. Drying time required to reduce the moisture content of fresh prawns to 15% level is about 7 hours compared to 6-7 hours in normal hot air drying and more than 36 hours in sun-drying.

Further studies on dehydration of prawns in rotary drum dryer

The paper deals with studies made to modify the process of drying of prawns in rotary drum dryer reported by the authors earlier. Prawns belonging to any species except M. monoceros can be satisfactorily dried. With M. monoceros invariably considerable adherence of shell occurs. Prawns of any size group can be dried provided in the case of medium and big size prawns they are beheaded prior to drying. In all size groups, beheading prior to drying results in better appearance of the end product in addition to the output of the dryer per charge being increased.

A preliminary survey of the helminth fish parasites in Imo River

A preliminary survey of the helminth fish parasites was carried out in Imo River (Nigeria). A total of 191 fishes belonging to 15 genera were examined and only 13.6% were infested with various species of helminth parasites which is low percentage of infection. The following helminth parasites were recorded. Wenyonia virilis, kainji; Wenyonia sp., Procamallanus laeviconchus; Procamallanus sp., Sprionoura congolense; Spironoura sp., Cucullanus sp. and Serradacnitis serrata. It was found that helminth parasites showed some degree of specificity in their distribution within their fish hosts. This specificity could be as a result of the physiochemical and physiological factors operating in the gut such as pH, osmotic tension, oxygen tension and nutrient levels. The results also revealed that age and sex influence helminth parasites infections in fishes

Observations on the physiological development of trout eggs [Translation from: Roux. Arch. f. Entwicklungsmechanik der Organismen, 114. 771, 1929]

The osmotic pressure of the perivitelline fluid and the yolk of trout (Salmo trutta) eggs were measured separately by the Drucker-Schrein method. The permeability of the egg membrane and the variations in the osmotic pressure of the eggs when placed in salt solutions were also investigated.

Some aspects of freezing and frozen storage of pomfrets

It has been observed that a better frozen product can be obtained by freezing good quality pomfrets transported in insulated containers with sufficient quantity of ice. To enhance the keeping quality and to prevent dehydration and discoloration, a dip in B H A (0.005%) for 15 minutes and subsequent storage in polythene lined gunny bag at -15°c to -I8°c can be recommended. The products treated in the above manner can be stored well over six months. Periodical glazing at an interval of 3 weeks will also prevent the dehydration to a greater extent.

Physics in fish processing technology

To design, develop and put into operation an equipment either to increase the productivity or to improve the existing technique to obtain a better quality of the product, the fishery engineer/scientist should have a comprehensive knowledge of fundamental principles involved in the process. Many a technique in fish processing technology, whether it applies to freezing, dehydration or canning, involves always a type of heat transfer, which is dependent to a certain extent on the external physical parameters like temperature. humidity, pressure, air flow etc. and also on the thermodynamic properties of fish muscle in the temperature ranges encountered. Similarly informations on other physical values like dielectric constant and dielectric loss in the design of quick trawlers and in quality assessment of frozen/iced fish, refractive index and viscosity in the measurement of the saturation and polymerisation of fish oils and shear strength in the judgement of textural qualities of cooked fish are also equally important.

A comparative study of various extenders of milkfish, Chanos chanos (Forsskal) sperm preservation

Four chemical extenders in 7 different concentrations (potassium chloride, sodium chloride, glucose, sodium citrate, Ringer s solution, cow serum and milkfish (Chanos chanos) serum) were compared in the preservation of milkfish sperm. Results showed milkfish serum to be the most suitable of the various extenders tested. This may be attributed to suitable osmotic potential and/or presence of proteins which may have directly or indirectly influenced sperm viability. The effects of milkfish serum on the motility and fertilizing capacity of sperm at different durations of storage however need to be investigated.

Effect of cooking and drying on carbonyls of oil sardine

Changes in the total as well as major individual carbonyls of oil sardine during steam cooking, oven drying, sun drying and freeze drying are presented. Carbonyls extracted with hexane were converted to their 2:4 dinitro phenyl hydrazone (DNPH) derivatives and were separated into major classes by column chromatography on celite/magnesia. Individual carbonyls were then identified by capillary gas chromatography of the DNPH derivatives. Dehydration and heating increase the carbonyl production from highly unsaturated fish lipids. The carbonyls produced react with other muscle constituents leading to complex changes. The influence of the mode of dehydration on these different aspects and their net effect on flavour are discussed.

Effect of salinity and food ration level on the growth of Nile tilapia (Oreochromis niloticus L.)

The effect of salinity (0, 10 & 20‰, water temperature 28 ± 1°C) and food ration (3 and 4.5% bw/day) on food consumption and growth of Nile tilapia, Oreochromis niloticus (10.77 ± 0.21g) were investigated. Individual food consumption was measured using X-radiography technique. Salinities (0, 10 & 20‰) did not have significant effect on the growth rate of groups of Nile tilapia fed at different ration levels (3 & 4.5% bw/day). This study showed that the growth of all-male fish was significantly better than all-female fish for all three salinities and two rations. Salinities from 0 to 20‰ had no effect on growth performance of males or female fish. In the present study, it was evident that fish fed at 3% bw/day ration ate all the food offered and fish fed at 4.5% bw/day did not consumed all amounts. Also, growth performance did not significantly differ among fish fed at 3% bw/day ration level and reared at different salinities. Fish reared under higher salinities (20‰) and fed at higher ration (4.5% bw/day) level had skin lesions and injuries on their body. It was assumed that fish fed at higher ration under higher salinities (20‰) and maintained higher osmoregulatory costs together with osmotic stress may have a negative influence on the appetite of fish. Another possibility that may have affected the appetite could be the unionized ammonia levels that were high. The high-unionized ammonia levels combined with the osmotic stress may have been the cause, or have aided, development of skin lesions and injuries on the fish at higher salinities.

Biogeochemical study of poly aromatic hydrocarbons (PAHs) and its physiological affection response in mudskipper (Boleophthalmus dussumieri) at coast of Khuzestan

Study on the biomarkers types to assess health status of marine ecosystems in environmental biomonitoring has an important value. Accordingly, accumulation of polycyclic aromatic hydrocarbons(PAHs) in sediment, water and tissues (liver and gill) of mudskipper(i.e. Boleophthalmus dussumieri) and some physiological responses like lysosomal membrane change performed on haemocytes, stability of red blood cell membrane and the Glutathione-S Transferase (GST) activity in the liver were measured in mudskipper. Samples were obtained from five sites along north western coast of the Persian Gulf (Khuzestan coast). Red blood cell membrane changes after different concentration of PAHs at different time was also studied to evaluate impact of PAHs compound on cell membrane. PAHs concentration was measured by HPLC method. The activity of GST enzyme was analysed by spectrophotometric method. Lysosomal membrane change was measured by NRR time method and stability of red blood cell membrane was evaluated by EOF test. Total PAH concentrations in the coastal sea water, the sediments, the liver and the gill tissues ranged between 0.80-18.34 μg/l, 113.50-3384.34 ng g-1 (dry weight), 3.99-46.64 ng g-1 dw and 3.11-17.76 ng g-1 dw, respectively. Highest PAHs pollution was found at Jafari while the lowest was detected at Bahrakan sampling sites. The lowest enzymatic activity was identified at Bahrakan (7.19 ± 1.541 nmol/mg protein/min), while the highest was recorded at Jafari (46.96 ± 7.877 nmol/mg protein/min). Comparative analysis of GST activity in the liver of mudskippers showed significant difference (p < 0.05) between the locations of Jafari and Bahrakan, and with other sites. Moreover, no significant difference was detected between the locations of Arvand, Zangi and Samayeli (p < 0.05). The mean RT was below 90 minutes in all sampling sites. Values of mean RT of the dye ranged from 34 (for the blood samples of mudskipper collected from Jafari site) to 78 minutes (for the blood samples of mudskipper collected from Bahrakan site). Spatial evaluation revealed the longest RT in fish from Bahrakan as compared with those from other sites. Preliminary results showed a significant difference (p < 0.05) among sampling sites except between Arvand and Zangi (p > 0.05). Osmotic fragility curves indicated that erythrocytes collected from mudskippers at Jafari were the most 009 fragile followed by Zangi> Arvand> Samayeli> and Bahrakan. The mean erythrocyte fragility was significantly higher at Jafari site (p < 0.05) when compared to other sites. Significant differences were found between the various sites (p < 0.05).The result indicated no significant differences between the control and treatments of mudskipper RBC exposed to field concentrations of PAHs (P>0.05). The results further indicated significant differences (P<0.05) between the control and treatments of mudskipper RBC exposed to acute. Potency Divisor concentrations. It is clear from the present result that chronic. Potency Divisor concentrations protect red cells against osmotic hemolysis. This study, however, showed that PAH concentrations in this region are not higher than the available standards. The findings showed that Lysosomal membrane destabilization, liver GST activities and fragility of red cell membrane are highly sensitive in the mudskipper, B. dussumieri. Thus, mudskipper perceived to be good sentinel organisms for PAH pollution monitoring. Sediment PAH concentrations were strongly correlated with biomarkers, indicating that PAH type pollutants were biologically available to fish. One of the possible risk assessment implications of this study is that biomarkers can be applied not only to characterize biological effects of pollution exposures, but also to determine the bioavailability of pollution in aquatic systems. The results also indicated that PAHs compound possess anti haemolytic property.