Search

Evidence suggests that dab and rainbow trout are able to quickly adjust their food intake to an appropriate level when offered novel diets. In addition day-to-day and meal-to-meal food intake varies greatly and meal timing is plastic. Why this is the case is not clear: Food intake in fish is influenced by many factors, however the hierarchy and mechanisms by which these interact is not yet fully understood. A model of food intake may be helpful to understand these phenomena; to determine model type it is necessary to understand the qualitative nature of food intake. Food intake can be regarded as an autoregressive (AR) time series, as the amount of food eaten at time t will be influenced by previous meals, and this allows food intake to be considered using time series analyses. Here, time series data were analysed using nonlinear techniques to obtain qualitative information from which evidence for the hierarchy of mechanisms controlling food intake may be drawn. Time series were obtained for a group of dab and individuals and a group of rainbow trout for analysis. Surrogate data sets were generated to test several null hypotheses describing linear processes and all proved significantly different to the real data, suggesting nonlinear dynamics. Examination of topography and recurrence diagrams suggested that all series were deterministic and non-stationary. The point correlation dimension (PD2i) suggested low-dimensional dynamics. Our findings suggest therefore that any model of appetite should create output that is deterministic, non-stationary, low-dimensional and having nonlinear dynamics.

In this paper, food intake of whiting Merlangius merlangus, in the Eastern Irish Sea is estimated using various models developed for food consumption. A new linear model for whiting is also developed and tested. The impact of whiting food consumption in the Irish Sea is considered. It was estimated that young whiting (age 0–3) eat between 1.29 and 6.57 g day−1 in February (temperature 7.8°C). By August when temperature has reached its annual maximum (18°C), these values increased by approximately 60–80%. The average recruited whiting stock in an area of approximately 150 km2 in Red Wharf Bay, UK, was estimated to be 120 000 with a biomass of 22 t. Daily intake of sprat, sandeel and crab was 0.41, 0.14 and 0.14 g, respectively, for 0+ group. This was increased to 0.70, 0.80 and 0.94 g by the age of 4. On a daily basis the long term averages of the amount of sprat, sandeel and crab consumed were estimated to be 820, 370 and 520 g km−2 day−1. The total food intake per year by the recruited whiting stock was 44.8 t of sprat (approx. 11.5 millions of sprat), 20 t of sandeel and 28.5 t of crab. The daily food consumption by whiting in this part of the Irish Sea was compared with the data from the North Sea and the rest of the Irish Sea and it was concluded that whiting eat more in the Irish Sea than they do in the North Sea.

One-year-old rainbow trout (weight range 400–700 g) were fed for 18 weeks on low-fat herring or commercial dry pellets 1, 2 or 4 times in a day. Quadratic regression analysis indicated that at least three feedings were required for maximum growth and that fish fed a dry diet could benefit from even more frequent feeding. The proportion of lipid in growth increased with increased number of feedings, but the protein content was not affected (mean 18.6% protein wet basis). Food consumption (dry weight) was affected in a similar manner for both diets and its maximum occurred at slightly higher frequency than for maximum growth. No effects of feeding frequency or type of diet on energy retention efficiency were observed (mean 42.5% of gross energy) but protein efficiency decreased with more frequent feedings. Dry diet protein was retained more efficiently than protein from herring. It is suggested that the number of feedings required for maximum growth may be dependent on the nutrient density of diet.

One-year old rainbow trout (initially 350–670 g) were fed for 15 weeks diets containing various amounts of water (23–67%). This was achieved by replacing fish meal with Baltic herring. The growth of rainbow trout, whether measured as wet weight, protein or energy, was impaired when 50–55% dietary water was fed. The fish compensated for increasing dietary water content by consuming more diet so that the dry matter intake of the diets with 23 and 67% water were equal. Partitioning of growth into protein and lipid as well as protein and energy retention efficiencies were unaffected by dietary water. It is suggested that there is a metabolic cost of consuming more food when compensating for high dietary water content.

Two-year-old rainbow trout (initial weight 695 g) were fed for 15 weeks low-fat Baltic herring diets either with or without lipid enrichment. For comparison, similar groups of trout were fed dry pellets with and without top-dressing with fish oil. Inclusion of lipid increased growth rate in a similar manner for both types of diets. For the herring-based diet, increased lipid resulted in increased dry matter consumption but for the dry diet, feed efficiency (dry weight growth per dry weight food consumption) was improved by channelling more nutrients to lipid deposition. If compared within a stated lipid level, fish fed the herring-based diets grew at a slower rate than fish fed the dry diets. This could have been because of high dietary water content and also due to changes in herring protein quality during the frozen storage since the protein retention efficiencies were lower for the herring diets.

The feeding behaviour of medium sized (155.25±27.98 cm, n =8) whiting, Merlangius merlangus , under laboratory conditions was investigated with continuous food availability. This investigation was made using both natural, Sprattus sprattus , and artificial diet which was monitored with a periodogram analysis obtained by a newly developed demand feeding unit. The return of appetite of large whiting (305.85±056.90 cm) was also studied. Medium size whiting consumed 5.29 g (wet weight)/day corresponding to 3.41% body weight, approximately three sprats of 1.88 g each. The return of appetite after a single meal was found to follow the gastric emptying curve closely. If food is not offered directly but made available through demand feeding, the whiting feed rhythmically (every 21 h); under these conditions, it was estimated that feeding activity returns when the stomach is 40% full.

The nutrient losses into the water from rainbow trout (Oncorhynchus mykiss) cage culture using locally caught low-fat Baltic herring, herring-based moist diets and fishmeal-based dry diets were estimated. Feeding with herring led to nitrogen and phosphorus losses into the water twice as high as those feeding with dry pellets (78–162 versus 37–39 g N and 15–39 versus 7–18 g P per kg growth). This was supported by direct measurements of ammonia and phosphate excretion. Increasing feeding frequencies resulted in increased nutrient losses irrespective of diet. Increasing dietary lipid level had a more pronounced effect in reducing the expected nutrient losses in dry pellets than herring. The reduction within the herring was approximately 18% on average for nitrogen and 25% for phosphorus losses. Dietary water content did not affect the nutrient losses. © Rapid Science Ltd. 1998

An advanced constitutive model is used to describe the shock and high strain rate behaviors of silicon carbide, boron carbide, and titanium diboride under impact loading conditions. The model's governing equations utilize a set of microphysically based constitutive relationships to describe the deformation and damage processes of ceramics. The total strain is decomposed into elastic, plastic, and microcracking components. The plastic strain components are calculated using conventional viscoplastic equations. The strain components due to microcracking utilize relationships derived from a penny shaped crack in an infinite elastic solid. The main features of the model include degradation of strength and stiffness under both compressive and tensile loading conditions. When loaded above the Hugoniot elastic limit (HEL), the strength is limited by the strain rate dependent strength equation. However, below the HEL, the strength variation with respect to strain rate and pressure is modeled through microcracking relationships, assuming no plastic flow. The ceramic model parameters were determined using plate impact experimental data.

The two main objectives of this paper are; (1) to present an efficient numerical scheme based on an iterative radial corrector method for solving the Bodner-Partom equations in the explicit finite element code, EPIC-2, and (2) to compare the EPIC-2 results obtained using two different viscoplastic constitutive models. Two distinctly different viscoplastic models, Johnson-Cook and Bodner-Partom, were considered. Both models predicted similar solutions in most problems.

Interspecific and intraspecific trophic resource partitioning between coexisting plaice, Pleuronectes platessa L. and dab, Limanda limanda (L.) populations were investigated at three subtidal locations in the Irish Sea: Two inshore locations off the coast of Anglesey, North Wales and one off-shore location. In shallow inshore waters, the two species had similar diets dominated by the polychaete Pectinaria koreni. Offshore dab appeared to concentrate on Ensis ensis whilst the plaice took a wider variety of prey including bivalves, polychaetes, crustaceans and sand eels. Trawls made over a 24-hour period indicated some crepuscular and nocturnal feeding by individuals of both species. The observed patterns of resource partitioning were due to the abundance of prey species which vary spatially and seasonally and are discussed in relation to current work on resource partitioning between fishes.

The density of power deposited on some surfaces of a tokamak can easily reach the level where the surface may be destroyed by thermal stress. This report is an examination of the thermal stress problem under tokamak conditions. The magnitude of the maximum power density is given for some existing and future devices. As examples which furnish a guide to power absorption limits for surfaces in high-power plasma devices, we have made estimates of thermal stress in a thick wall subjected to transient heating On one side. Also, detailed results are given for a flat plate heated on one face and cooled on the other. Comparative power density limits are tabulated for various materials of interest for plasma device construction.

One-year-old immature green turtles (500–900 g) were kept at 25°C in recirculating seawater. When deprived of food for 108 h and then offered floating trout pellets, they consumed a satiation meal (S g) described by the equation S = 0.025 W0.96 where W is wet body weight in g. When food was offered at different deprivation times after satiation, maximum meals were taken after 60–72 h and corresponded to 2.5% body weight. Longer deprivation (108 h) led to reduced intake of 1.9–2% body weight. Gastric emptying was measured using X-radiography or chromic oxide to label the faeces. Complete stomach emptying required 110 ± 11 h S.D. and maximum appetite occurred when the stomach was estimated to be 80–95% empty. The average time for a meal to be voided from the alimentary tract was 176 ± 16 h S.D. Diets containing 40–50% protein and 4.2–5 kcal/gram were assimilated with apparent efficiencies of 76 ± 6% S.D. and 86 ± 6% for energy and protein nitrogen, respectively. A preliminary estimate for an energy budget for these animals based on a 23 day growth period accounted for 90% of the daily food intake as: 100 I⋍39M + 32E where known daily intake (I calories) is compared with measures or estimates of metabolic rate (M), growth (G) and excreted wastes (E). Although this balance is similar to that of herbivorous fish, the turtle has slower feeding and digestion rates than its teleost counterparts.

As part of an investigation on the effect of natural oil seeps and oil-bearing substrata on littoral organisms, a study was made on the effect of the presence of freshly exposed Blackstone oil shale from Kimmeridge on the Dorset coast on the behaviour of the common littoral fish the blenny Blennius pholis L. in a simulated rock pool habitat. Plastic test chambers were designed with two compartments, one contained sea water and the other contaminated sea water which had been allowed to equilibrate with pieces of Blackstone oil shale and in some experiments further modified by decreasing the pH to simulate natural CO 2 build up in rock pools. The fish were allowed to enter the sea water in either compartment from one of three types of ramp positioned above the surface. The results showed that against appropriate controls, fish which are able to sample a saturated atmosphere avoid coming into contact with equilibrated shale oil-contaminated sea water. As the shale oil content decreased the aversion decreased but the oil still affected the ability of the fish to detect a decrease in pH. Apparently the presence of shale oil leachings in the sea water interferes with the ability of the blenny to discriminate certain characteristics of the physico-chemical environment which would otherwise be avoided.

1. The splanchnic motor nerve fibres innervating the plaice ( Pleuronectes platessa L. ) gastric circular muscles were investigated by electrical stimulation using in vitro Trendelenburg and in vivo intragastric balloon preparations. 2. Stimulation of the nervi splanchnici produced a biphasic response of contraction followed by inhibition, all effects of stimulation being abolished by 5 × 10 −7 g/ml tetrodotoxin. 3. Atropine (av 9.1 × 10 −6 M) abolished all splanchnic excitatory effects. 4. The β 2 adrenoceptor blocker, butoxamine (av 2.9 × 10 −5 g/ml), and reserpine blocked sympathetic inhibition. Fluorescent histochemical studies have revealed catecholamine in the splanchnic nerves. 5. The nervi splanchnici carry postganglionic cholinergic excitatory and postganglionic adrenergic inhibitory fibres to innervate the gastric circular muscles of the plaice.

The paper describes the present (end of February 1985) status of the plasma confinement studies in the TFTR tokamak with emphasis on those with neutral beam injection (NBI). Recent improvements in the device capabilities have substantially extended operating parameters: B /sub T/ increased to 4.0 T, I /sub p/ to 2.0 MA, injection power (P /sub b/ ) to /sup 5/ MW with H/sup 0/ or D/sup 0/ beams, n /sub e/ to 5 x 10/sup 19/ m/sup -3/ and Z /sub eff/ reduced to 1.4. With ohmic heating (OH) alone, the previously established scaling for gross energy confinement time (T /sub E/ /sup 0/ n /sub e/ q) has been confirmed at higher I /sub p/ and B /sub T/ , and the maximum T /sub E/ of 0.4 sec has been achieved. With NBI at P /sub b/ substantially (by factor > 2) higher than P /sub OH/ , excellent power and particle accountability have been established. This suggest that the less-than-expected increase in stored energy with NBI is not due to problems of power delivery, but due to problems of confinement deterioration. T /sub E/ is observed to scale approximately as I /sub p/ P /sub b/more » /sup 0.5/ (independent of n /sub e/ ), consistent with previous L-mode scalings. With NBI we have achieved the maximum T /sub E/ of 0.2 s and the maximum T /sub i/ (o) of 4.4 keV in the normal operating regime, and even higher T /sub i/ (o) in the energetic-ion regime with low-n /sub e/ and low I /sub p/ operation.« less

1. 1. In vitro skin pieces of the plaice dispersed their melanophore pigment in Na+-rich solution. Pigment aggregation was induced by catecholamines in the potency order dopamine > noradrenaline > adrenaline > isoprenaline. Tyramine was the most active amine tested but its actions were abolished by reserpine. 2. 2. Melanophore pigment aggregation in the presence of K+ and Ca2+ was prevented by alpha-adrenergic blockade (yohimbine > piperoxane > dibenamine > phentolamine) or by adrenergic neurone blockade (reserpine > bretylium > guanethidine). Beta-blockade with propranolol was ineffective. 3. 3. Cholinergic drugs induced slow and delayed pigment dispersion (pilocarpine > carbachol > arecoline > acetylcholine) whereas atropine and histamine were more potent and acted faster. 4. 4. Our results support the role of alpha-adrenergic receptors in melanophore pigment aggregation and indicate a possible role of histamine in dispersion.

1. The sensitivity of plaice gastric longitudinal muscle to agonist drugs decreases with time spent in aquaria. 2. The stimulant action of acetylcholine (Ach) and 5-hydroxytryptamine (5-HT) persists after treatment with tetrodotoxin (1·6 × 10−6 M) which blocks nervous conduction. 3. Dose-dependent responses to 5-HT varied between 2·2 × 10−7 and 2·3 × 10−6 M at the first test, and between 1·8 × 10−7 and 5·6 × 10−6 M at the second test. Phenoxybenzamine (up to 3 × 10−6 M) and methysergide (up to 2 × 10−6 M) blocked part of the 5-HT contraction but morphine (up to 3 × 10−6 M), ergotamine (up to 1·5 × 10−6 M) and 2-bromo- d -LSD (up to 2 × 10−6 M) were not blockers. Hemicholinium (1 × 10−6M) gave partial, non-competitive blockade. 4. On the basis of this and previous work, it is concluded that 5-HT primarily stimulates gastric longitudinal muscle by displacing Ach from cholinergic nerve endings in the enteric plexus, but a direct action on muscle cells is also present.

1. The vagal motor supply of the gut of the stomachless flatfish Ammotretis and Rhombosolea is restricted to oesophageal striated muscles and blocked by d-tubocurare (3 × 10−6 g/ml). 2. the intestine is inhibited by sympathomimetic amines (effective doses: isoprenaline 10−8, adrenaline 3 × 1010−7, noradrenaline 10−5, phenylephrine 10−4 M) which act on β-adrenoceptors since propranolol is a competitive antagonist (pA2 = 7.9). 3. Acetylcholine (pD2 = 6.1) is excitatory on intestinal muscarinic receptors since atropine (pA2 = 8.7) is a competitive antagonist; 5-hydroxytruptamine (pD2 = 6.8 is apparently an indirect stimulant since atropine (pD'2 = 6.2) is a non-competitive antagonist. 4. Paravascular sympathetic nerve stimulation activates adrenergic neurons, which are demonstrated histochemically and are blocked by propranolol, as well as cholinergic neurons which are blocked by atropine. 5. Transmural stimulation of the intestine shows that, in addition to extrinsic nerves, the enteric plexus contains a population of excitatory cholinergic neurons and non-adrenergic/non-cholinergic inhibitory neurons which inhibit the circular muscle coat.

During the recent ohmic heating experiments on TFTR, the movable limiter array, preliminary inner bumper limiter, and prototype ZrAl alloy bulk getter surface pumping system were brought into operation. This paper summarizes the operational experience and plasma characteristics obtained with these components. The near-term upgrades of these systems are also discussed.

1. Electrical stimulation of the intracranial roots of the vagus nerve of the flathead, or of the ramus intestinalis vagi, induced atropine-sensitive primary contractions of the stomach similar to those found in other acanthopterygian teleosts. 2. Paravascular sympathetic stimulation distal to the coeliac ganglion was also excitatory, was insensitive to atropine in high doses but was readily abolished by phentolamine, indicating the α-adrenoceptors mediate the response. 3. Fluorescent histochemical tests show that sympathetic adrenergic axons enter the vagal ganglion complex to form vagosympathetic trunks to gills and heart, but do not pass to the stomach in the vagal supply. 4. Adrenergic neurones in the coeliac ganglion follow blood vessels into the stomach wall and terminate in the enteric plexus.

1. 1. The chromatic activity and potency of some adrenergic drugs (sympathomimetic amines, α- and β-adrenergic blocking agents and hypotensive agents) were investigated in intact and operated minnows using the Derived Ostwald Index as a simple method for measuring melanophore responses. 2. 2. The actions of the drugs, and the changes in sensitivity of sympathomimetic amines after operations, suggest that chromatic fibres entering the autonomic chain of the fish are preganglionic and possibly cholinergic. 3. 3. Postganglionic fibres from sympathetic ganglia are adrenergic, pass straight to the skin in the mixed spinal nerves and innervate the melan directly. 4. 4. The fibres release catecholamine transmitter from an adrenergic store in or near the axon terminals which stimulates pigment aggregation by combination with an adrenergic receptor which has α-properties.

1. 1. Examination of plaice pronephros sections using chromaffin reaction and Falck's fluorescent histochemical technique shows that the chromaffin cells surrounding the blood-vessels contain a secondary catecholamine, probably adrenaline. 2. 2. Semiquantitative thin-layer chromatography on cellulose plates confirms that adrenaline is the predominant amine present, although traces of noradrenaline occur. 3. 3. Spectrofluorimetric analysis of pronephros tissue extracts indicates that adrenaline is present at a concentration of 70±10 μg./g., which corresponds to at least 350 μg.A/g. ‘adrenal medulla’. 4. 4. Reserpine in high doses (6 mg./kg.) which is known to fully deplete plaice adrenal nerve stores only reduced the chromaffin tissue store to c . 37 per cent of control values.

1. 1. Oxygen dissociation curves of diluted Crangon blood were measured at 338 mμ. 2. 2. Increase in pH and especially buffer ionic strength increased oxygen affinity and ligand binding site interaction. 3. 3. The buffer species was also found to affect oxygen affinity.

1. 1. The chromatic activity and potency of adrenergic stimulants are described for intact specimens, and specimens with lesions in the chromatic tracts, of Pleuronectes platessa L. 2. 2. Changes in sensitivity to sympathomimetic amines after spinal section, spinal nerve section, treatment with adrenergic neurone blocking agents or cocaine suggest that postganglionic, adrenergic fibres pass from the sympathetic ganglia to the melanophores by way of mixed spinal nerves. 3. 3. The adrenergic transmitter causes melanophore pigment aggregation by combining with alpha-adrenoceptors.

The effect and mode of action of substance P was studied in a perfused stomach preparation and on isolated strip preparations of the stomach wall from the rainbow trout, Salmo gairdneri . Substance P was excitatory on the stomach muscle wall in a dose-dependent manner. Two other tachykinins, physalaemin and eledoisin, excited the preparations in a similar manner and in the same dose range. The effect of substance P was not antagonized by the substance P analogues [ d -Pro 2 , d -Phe 7 , d -Trp 9 ]substance P and [ d -Pro 2 , d -Trp 7,9 ]substance P (both 10 −5 M). Tetrodotoxin reduced or abolished the effect of substance P, while no reduction of the response was obtained after atropine, chlorisondamine or phentolamine (all 10 −6 M). 5-Hydroxytryptamine excited the stomach and this effect was not antagonized by tetrodotoxin, suggesting that the action of 5-hydroxytryptamine was direct on the smooth muscle. The 5-hydroxytryptamine antagonist methysergide, in a concentration which selectively blocked the response to 5-hydroxytryptamine, also blocked the response to substance P (10 −9 −10 −8 M). The outflow of 5-[ 3 H]hydroxytryptamine from a preloaded perfused stomach was clearly increased by substance P, and this release was blocked by tetrodotoxin. Immunohistochemistry revealed the presence of nerve fibres and ganglion cells showing 5-hydroxytryptamine-like immunoreactivity in the myenteric plexus and smooth muscle layers of the stomach wall. The immunoreactive cells and nerve fibres were particularly abundant in the pyloric part of the stomach. It is concluded that the main effect of substance P on the stomach wall of the rainbow trout is indirect, via activation of a non-adrenergic, non-cholinergic neuron. The results are compatible with the view that this neuron exerts its action by release of 5-hydroxytryptamine. Supramaximal concentrations (⩾ 10 −7 M) of substance P may in addition have a direct effect on the gastric smooth muscle.

1. 1. The intense darkening following lesions in the chromatic tract of pale minnows appears to be active and lasts approximately 24 hr. 2. 2. This darkening is antagonized by sympathetic blockade and the paling actions of catecholamines are reduced. 3. 3. Although the darkening of minnows may be nervously controlled, there is no pharmacological evidence for cholinergic “parasympathetic” darkening fibres in the minnow. 4. 4. In the absence of active paling and darkening fibres, the unsupported action of paling hormone cannot bring about full pallor of white-adapted minnows.

The model C stellarator is symmetrized by applying a magnetic field B/ sub T/ transverse to the confining field B/sub O/ so as to close the flax lines of B/sub O/. The measurements of various plasma parameters in the stellarator as functions of B/sub T/ were used to calculate B/sub S/ (the particular value of B/ sub T/ required for symmetry) and thus predict the lack of closure of the confining field. It is demonstrated that a deliberate change in this lack of closure will produce a desired change in B/sub S/. (C.E.S.)

1. 1. The concentration of copper in the blood of Crangon vulgaris collected in the autumn 1967 from East Anglesey and West Anglesey ranged from 41 to 159 μg/ml respectively. Individual variation in blood copper concentration could not be correlated with sex or size. 2. 2. A significant correlation was found betwee blood copper concentration a moult stage; highest values were found in the late premoult (D 2 /D 3 ) animals and lowest values found in postmoult (A-B) animals 3. 3. Hepatopancreas (Cu) varied from 13 to 480 μg/g dry wt. for animals collected in the autumn from East Anglesey and 118 to 2900 μg/g dry wt. for West Anglesey. 4. 4. Histochemical studies revealed copper located in vacuoles within cells of the hepatopancrease of all animals examined. Wide variation was found in the sizes of these bodies, their numbers and the number of cells containing them. 5. 5. The copper content of the blood of shrimps maintained in copper-enriched sea water did not increase whereas the hepatopancreas accumulated copper. 6. 6. All the detectable copper eluted from agar electropherograms of blood was carried by haemocyanin. An estimate of approximately 0·2 per cent was found for the copper/protein ratio of unpurified Crangon haemocyanin.