Reproductive Response of Penaeus stylirostris to Temperature Manipulation

The effect of temperature manipulation on the reproduction of Penaeus stylirostris was investigated as a possible method for increasing larval production. Six 3.66 m diameter black tanks were stocked with unilaterally eyestalk enucleated females and intact males. Temperature was designed to vary between 20 and 28 C at a rate of 2 C per day in the "Fast" treatment and 2 C per week in the "Slow" treatment; upper and lower temperatures were maintained for 10 days before another cycle was initiated. In the "Ambient" treatment, temperature averaged 27.8 ± 0.9 C.
During the 105 day study maturation, mating and larval production were highest in the Ambient tanks. Temperature manipulation as tested in the Fast and Slow treatments did not produce any burst of mating and spawning activity at the upper ends of the cycles to compensate for the steady production in the Ambient group. Thus, the temperature regimes examined did not afford any practical advantage.
The effect of temperature on mating was marked. In the Slow treatment which most closely mimicked natural seasonal temperature change, mating began initially when the temperature increased to 25 C. Throughout the study mating occurred more frequently at the higher temperatures, and these results suggest that the optimal temperature range was 27–29 C for reproduction. However, the shrimp did mate at all temperatures encountered. It is notable that this tropical species can successfully reproduce at temperatures as Iow as 20 C.     

A note on the effects of L-carnitine on the energy metabolism of individually reared carp, Cyprinus carpio L.

Twelve carp, Cyprinus carpio L., were grown from 30 to 120 g live mass on four diets, control (405 g kg⁻¹ crude protein, 20.6 MJ kg⁻¹ gross energy) and control + 200, 400 or 600 mg kg⁻¹ L -carnitine. The diets were designated as CONT, C200, C400 and C600, respectively. Each diet was randomly assigned three fish kept in individual open-circuit respirometers. Fish that ate diets C400 and C600 grew faster than the controls, expended less energy and retained more energy per unit of food energy intake. Average energetic efficiency, expressed as energy retained per unit of energy expended, was 30% higher in the C400 group than in the controls. However, owing to the small number of fish in each group and the large variations in all these parameters, especially within the control group, none of these differences reached statistical significance at the P = 0.1 level.     

Effect of supplemental phytase on growth, phosphorus digestibility and bone mineralization of common carp (Cyprinus carpio L)

The effect of dietary phytase on phosphorus (P) digestibility, growth, bone mineralization and plasma P of common carp (Cyprinus carpio) was investigated. Five diets, D0, DP, PHYT1, PHYT2 and PHYT4, were used. D0 contained no supplement. DP was supplemented with 2.6 g P (Na₂HPO₄× 2H₂O) kg⁻¹. PHYT1, PHYT2 and PHYT4 comprised 1000, 2000 and 4000 U phytase [Ronozyme P (CT)] kg⁻¹. D0, PHYT1, PHYT2, PHYT4 had average of 7.95 g P kg⁻¹; DP contained 10.3 g P kg⁻¹. After 126 days of feeding, fish grew from 115 to 347 g (D0), 583.7 g (DP), 352.6 g (PHYT1), 393.3 g (PHYT2) and 406.4 g (PHYT4). Addition of phytase significantly increased daily feed intake, but only led to a marginal improvement in the weight gain, SGR and FCR of fish fed PHYT2 and PHYT4 compared with fish fed D0. Fish fed DP showed the best (P<0.05) growth performances. Fish fed DP and PHYT4 significantly digested dietary P more than the fish fed D0. Fish fed D0, PHYT1, PHYT2 and PHYT4 retained higher (P<0.05) Zn in their bones than fish fed DP. However, there was no further effect on bone mineralization. Plasma P scarcely improved by between 14% and 26% in fish fed PHYT2 and PHYT4 relative to fish fed D0. P concentration of the faeces was reduced by about 9–22% in fish fed PHYT1 and PHYT4 compared with fish fed D0.     

Effect of acclimation temperature on the acute stress response in juvenile Atlantic cod, Gadus morhua L., and haddock, Melanogrammus aeglefinus L.

Juvenile Atlantic cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus L.) were subjected to 30 s air exposure stressors following acclimation to 4, 10 and 14 and 4, 8 and 14°C respectively. Both species responded to the stressor with increases in plasma cortisol at all temperatures tested. At 14°C cortisol levels peaked within 1 h post‐stressor, and returned to pre‐stressor levels within 24 h. In contrast, at 4°C, peak cortisol levels were not attained until 6 h post‐stressor in haddock and remained elevated beyond 24 h in both species. The rate of plasma glucose accumulation was greater at higher temperatures in both species and no increase was seen at 4°C. Lysozyme activity in cod, in response to the stressor, was lower than the values reported for some other species and increased slightly at 14°C. The results show that cod and haddock acclimated to different temperatures respond to common, acute stressors in a manner similar to other teleosts.     

Efficacy of egg surface disinfectants in captive spawning Atlantic cod Gadus morhua L. and haddock Melanogrammus aeglefinus L.

In an effort to optimize the efficiency of high‐density incubation of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus eggs, the per cent hatch of eggs treated with four disinfectants (3% hydrogen peroxide, 1% polyvinylpyrrolidone iodine, 0.1% sodium hypochlorite and a 0.005% antibiotic solution – penicillin/streptomycin) was compared in both species. The per cent hatch of eggs of each species was greatest after a 24 h treatment with the antibiotic solution. The hatching success of eggs treated within the different disinfectant treatments depended upon the embryonic developmental stage in both species. The sodium hypochlorite treatment had the lowest % coverage of colony growth after disinfected haddock eggs were plated onto sterile agar media, highest survival rates to the end of the embryonic period, but the lowest per cent hatch.     

Simulation of inorganic nitrogen dynamics and shrimp survival in an intensive shrimp culture system

Nitrogenous wastes are major concerns in shrimp production and as a component of total farm wastes that impact the aquatic environment. This study describes a simulation model of the role of heterotrophic and nitrifying bacteria on nitrogen dynamics in intensive Litopenaeus vannamei (Boone) culture systems using different feeds and feeding strategies. The model represents: (i) use and remineralization by heterotrophic bacteria of nitrogen wastes and ammonia excreted by shrimp; and (ii) nitrification. The model was quantified using published and unpublished information. The model is multivariate, deterministic and uses a compartment model structure based on difference equations. Evaluation of the model consisted of simulating two indoor and one outdoor experiment that examined the effects of different feeds and feeding levels on nitrogen dynamics. In summary, the model is capable of qualitatively following inorganic nitrogen dynamics. Simulations investigating the effect of heterotrophic remineralization on total inorganic nitrogen suggested that this process may contribute up to 97% of the inorganic nitrogen in the system. This indicates that strategies to increase production, such as increases in feed protein levels or feeding rates, should be carefully evaluated before they are implemented. Future studies need to address bacterial community role in these systems and inorganic nitrogen toxicity mechanisms.     

A LAT mutation that inhibits T cell development yet induces lymphoproliferation

Mice homozygous for a single tyrosine mutation in LAT (linker for activation of T cells) exhibited an early block in T cell maturation but later developed a polyclonal lymphoproliferative disorder and signs of autoimmune disease. T cell antigen receptor (TCR)-induced activation of phospholipase C-gamma1 (PLC-gamma1) and of nuclear factor of activated T cells, calcium influx, interleukin-2 production, and cell death were reduced or abrogated in T cells from LAT mutant mice. In contrast, TCR-induced Erk activation was intact. These results identify a critical role for integrated PLC-gamma1 and Ras-Erk signaling through LAT in T cell development and homeostasis.     

Identification and functional characterization of brainstem cannabinoid CB2 receptors

The presence and function of CB2 receptors in central nervous system (CNS) neurons are controversial. We report the expression of CB2 receptor messenger RNA and protein localization on brainstem neurons. These functional CB2 receptors in the brainstem were activated by a CB2 receptor agonist, 2-arachidonoylglycerol, and by elevated endogenous levels of endocannabinoids, which also act at CB1 receptors. CB2 receptors represent an alternative site of action of endocannabinoids that opens the possibility of nonpsychotropic therapeutic interventions using enhanced endocannabinoid levels in localized brain areas.     

Discovery of a new gravitational lens system

A new gravitational lens system, the triple radio source MG2016+112, has been discovered. Five emission lines at a redshift of 3.2733+/-0.0014 have been identified in the spectra of two stellar objects of magnitude 22.5 coincident with radio components 3.4 arc seconds apart. The lines are the narrowest ever observed in objects at such a large redshift. The redshift of a 23rd-magnitude extended optical object coincident with the third radio component has not been determined spectroscopically, but its known optical properties are consistent with those of a giant elliptical galaxy with a redshift of about 0.8.     

800,000 years of abrupt climate variability

We constructed an 800,000-year synthetic record of Greenland climate variability based on the thermal bipolar seesaw model. Our Greenland analog reproduces much of the variability seen in the Greenland ice cores over the past 100,000 years. The synthetic record shows strong similarity with the absolutely dated speleothem record from China, allowing us to place ice core records within an absolute timeframe for the past 400,000 years. Hence, it provides both a stratigraphic reference and a conceptual basis for assessing the long-term evolution of millennial-scale variability and its potential role in climate change at longer time scales. Indeed, we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the Middle to Late Pleistocene.