Active Feeding Period Research Articles

Stress-induced effects on feeding behavior and growth performance of the sea bass (Dicentrarchus labrax): a self-feeding approach

Repetitive aquaculture-related protocols may act as cyclic stressors that induce chronic stress in cultured fish. The sea bass is particularly sensitive to stressful conditions and the mere presence of humans will disturb feeding behavior. In this paper, we study whether chronic stress induced by repetition of acute stress protocols affects long-term feeding behavior and growth performance in sea bass and whether exogenous cortisol may induce stress-like changes in these parameters. We demonstrate that both chronic stress and dietary cortisol decrease food intake and have a negative effect on feed conversion efficiency, severely impairing sea bass performance. Both experimental approaches induced changes in the daily feeding activity by lengthening the active feeding periods. Fish subjected to a cyclic stressor modify their daily feeding pattern in an attempt to avoid interference with the time of the stressor. The delay in feeding when fish are acutely and repeatedly stressed could be of substantial adaptive importance.

Application of synthetic hormone LHRH-A2 on the artificial propagation of Persian sturgeon Acipenser persicus

For studying the effect of LHRH-A2 hormone on the induction of final maturation and ovulation of Persian sturgeon, 71 matured females and 20 matured males were used. Five groups of breeders were injected with sturgeon pituitary gland hormone (50 mg per fish) and LHRH-A2 in dosages of 3.5, 7, 8 and 10 μg kg−1 for females and 3 and 5 μg kg−1 for males. Results showed that LHRH-A2 successfully induced final maturation and ovulation in females, and there was no significant difference between five groups of breeders in ovulation proportion, fertilization rate, survival rate of incubation, survival of yolk-sac absorption period and active feeding period of larvae. It can be concluded that the LHRH-A2 is a proper alternative for pituitary gland hormone in artificial propagation of Persian sturgeon.

390 ISOLATION AND ADIPOGENESIS OF GRIZZLY BEAR MESENCHYMAL STEM CELLS

During winter hibernation, grizzly bears (Ursus arctos horribilis) do not eat but instead rely on internal fat stores as a primary source of metabolic energy. The resulting seasonal fluctuations in appetite and body mass make the grizzly bear a naturally occurring animal model for human conditions such as obesity and anorexia. An in vitro model of hibernating bear stem cells might enhance our understanding of processes such as stem cell proliferation and differentiation. Mesenchymal stem cells, derived from bone marrow and adipose tissue among others, differentiate into adipocytes and might play important roles in energy metabolism. In the current study, we examined the in vitro viability and morphology of mesenchymal stem cells isolated from grizzly bear adipose tissue (ADSC) and bone marrow (BMSC); these ADSC and BMSCs underwent adipogenic differentiation for 0, 7, 14, 21, and 28 days. Bone marrow stem cells and ADSC were isolated using mechanical disaggregation, collagenase digestion, centrifugation, and plating onto tissue culture polystyrene. Cell viability and proliferation was quantified using the colony forming unit assay and a hemocytometer. Both stem cell types were differentiated into adipocytes using 10 μM insulin, 1 μM dexamethasone, and 0.5 mM isobutylmethylxanthine (all Sigma- Aldrich, St. Louis, MO, USA) with the addition of 10% fetal bovine (FBS) or bear serum from the active feeding period. Adipogenic differentiation was confirmed using Oil Red O and quantified using ImageJ. Statistical analysis was performed using an unpaired t-test between treatments of the same time point. All cells were isolated within 28 h of tissue harvest. Adipose-derived stem cells formed an average of 11 colonies (0.011%), whereas BMSC formed 1.5 colonies (0.0015%) per 100 000 cells. Doubling time forADSC was approximately 54 h in 10% FBS. BothADSC and BMSC had an initial spindle-shaped morphology, which gradually became more rounded during adipogenic differentiation. For bear serum at Day 28, ADSC had a significantly (P < 0.01) greater stained area per cell than did BMSC. In summary, both types of mesenchymal stem cells successfully differentiated into adipocytes and maintained viability. In conclusion, grizzly bear mesenchymal stem cells canbesuccessfully isolated, expanded, and differentiated in culture. These results allow for future studies using the bear as an in vitro model for fat metabolism during hibernation and active periods. This work was partially supported by the Carle Foundation Hospital, the Intel Scholar’s Research Program, USDA Multi-State Research Project W1171, and the Illinois Regenerative Medicine Institute (IDPH # 63080017). In addition, the authors would like to thank Agatha Luszpak for support with the analysis.

Feeding, growth and nutritional status of restocked salmon parr along the longitudinal gradient of a large European river: the Allier

Abstract – The feeding, growth and nutritional status of salmon parr (0+) released at fry stage in different riffles were studied in a large temperate river (Allier, France) throughout the active feeding period. Significant differences were observed along the upstream–downstream gradient. Parr growth performance and energy storage were higher in downstream riffles and low in the most upstream one. These longitudinal growth variations are discussed in the context of diet and food availability differences, habitat variables and intra‐ and inter‐species competition. The most favourable site for optimum growth and nutritional status appeared to be the intermediary riffle located in the grayling zone.

Anhydrobiosis in tardigrades and its effects on longevity traits

AbstractLiving in harsh and variable environments that are prone to periodic desiccation, tardigrades exhibit remarkable tolerance against physical extremes through a state known as anhydrobiosis. To study the effect of this state on the longevity and hence the lifecycle in the taxon Tardigrada for the first time, we exposed a tardigrade species, Milnesium tardigradum, to alternating periods of drying and active feeding periods in a hydrated state. Compared with a hydrated control, the periodically dried animals showed a similar longevity, indicating that the time spent in anhydrobiosis was ignored by the internal clock. Thus, desiccation can produce a time shift in the age of tardigrades similar to the model described for rotifers that has been termed ‘Sleeping Beauty’.

On the physiological-biochemical state of kilka Clupeonella cultriventris (Clupeidae, Clupeiformes) in Rybinsk Reservoir (Russia)

The results of studies into lipid total content and fractional composition in the tissue and wholebody levels in kilka (Clupeonella cultriventris) are given. The fish studied belonged to various size-age groups and were sampled in Rybinsk Reservoir during active feeding periods in 2002 and 2005. A trend was revealed of deterioration of the physiological-biochemical state in adult specimens of this invasive species. This was especially true of the modal (in terms of their proportion in population) two-year-old fish. This was evidenced by a decrease in contents of total and reserve (triacylglycerol) lipids in fish muscles during the whole study period. It is shown that, in young kilka caught in all reservoir stretches in autumn, the values of these parameters depend on the time and rate of the reservoir water level decrease during the active feeding period. Probable reasons for changes in the physiological-biochemical state in adult and young specimens in the kilka population are discussed. The discussion is in view of the recent state of the Rybinsk Reservoir ecosystem which undergoes successional modification of the pelagic zooplankton community both at the level of large taxa and of some dominant species.

Seasonal variations in the levels of polyhydroxysteroids and related glycosides in the digestive tissues of the starfish Patiria ( Asterina) pectinifera

Seasonal variations in the levels of polar steroids including polyhydroxylated steroids and related glycosides in digestive organs of the starfish Patiria (= Asterina) pectinifera have been studied. The concentration of polar steroids is related to the annual reproductive cycle of the starfish and periods of active feeding. Two peaks in concentrations of polar steroids in pyloric caeca and stomach were found, the first in winter during reorganization and the second in summer during intensive gametogenesis before spawning. Probable biological functions of polyhydroxysteroids and related glycosides are discussed. The data support the hypothesis these compounds are involved in digestion in the starfish.

Seasonal variations in activity concentrations of 99Tc and 137Cs in the edible meat fraction of crabs and lobsters from the central Irish Sea

Discharges of most radionuclides into the Irish Sea from the BNFL site at Sellafield have decreased over the past 20 years or so. For a few radionuclides, however, discharges have peaked more recently. Notably, operation of the Enhanced Actinide Removal Plant (EARP) since 1994 has led to an increase in discharges of 99Tc, as a result of the treatment of previously stored waste, with consequent increases in 99Tc activity concentrations in a number of marine species, particularly in crustaceans such as lobsters. Previous research has considered the significance of factors such as sex and body weight on radionuclide concentrations. The current project set out to investigate whether seasonal variations in radionuclide concentrations in crabs and lobsters occur, with particular emphasis on the dynamics of 99Tc and 137Cs. Organisms were obtained from a site off the Isle of Man, where radionuclide concentrations were measurable but the site was sufficiently distant from Sellafield that the radionuclides were well mixed in the water column and not likely to be influenced by the pulsed nature of discharges of 99Tc. Crab and lobster samples were collected monthly, between February 2000 and February 2001. Fifteen or 16 individuals (evenly split as male and female) of each species were collected on each occasion. Seawater samples were also collected over the 12-month period. Activity concentrations of 99Tc in the edible meat fraction (both brown and white meat) ranged from 0.23 to 2.46 Bq kg −1 (fresh weight (fw)) in crabs and 124 to 216 Bq kg −1 (fw) in lobsters, with no observed seasonal variations. Activity concentrations of 137Cs in both crab and lobster were lower, ranging from <0.16 to 0.85 Bq kg −1 for crab meat (fw) and <0.3 to 3.3 Bq kg −1 for lobster meat (fw). A statistically significant increase in activity concentrations of 137Cs in the meat was observed in the summer months for both crab and lobster. The cause has not been investigated but may be related to the laying down of energy reserves during the active feeding period over the summer. At all times, uptake of 99Tc is higher in the brown meat fraction of both crabs and lobsters, whilst 137Cs is more uniformly distributed. These results are used to discuss the implications for sampling and monitoring programmes.

Feeding preferences, seasonal gut repletion indices, and diel feeding patterns of the sea urchin Tripneustes gratilla (Echinodermata: Echinoidea) on a coastal habitat off Toliara (Madagascar)

The feeding biology of the echinoid Tripneustes gratilla from a seagrass bed off Toliara, on the south-west coast of Madagascar, was investigated during the summer and winter seasons. Repletion indices of the gut of T. gratilla varied seasonally, in such a way that higher amounts of food occurred in the gut in winter than in other seasons. Conversely, a more detailed analysis of one summer and one winter sample of the gut tissue dry weights revealed higher weights in summer (February) than in winter (August). This was interpreted as a varying capability of nutrient storage and closely related to the feeding activity of the echinoid. This inverse relationship between feeding activity and nutrient storage was suggested to be dependent on gonadal growth. Indeed, higher food consumption was observed during the post-spawning period (August), that is, when most of the energy accumulated was used up for gonadal growth. Low feeding activity occurred when a sufficient amount of energy was accumulated in gut tissues (February), the time corresponding to the initiation of gonadal growth. Investigations on the feeding habits, using Ivlev's electivity index, revealed preferential feeding of T. gratilla on Syringodium isoetifolium, the dominant seagrass species found in the gut. This was partly related to the higher availability of that particular seagrass species in the field. However, its soft and terete leaf blade's morphology also makes it easier to manipulate and ingest. Studies on the feeding behaviour indicated the presence of a diel feeding cycle in T. gratilla individuals in both summer and winter seasons. Yet, its pattern varied between the two studied months (one summer and one winter) as the cycle was less contrasted during period of active feeding, i.e. in winter compared to summer. This study provides novel information on how intrinsic factors, such as physiological state, can govern the feeding activity of T. gratilla living in a seagrass habitat.

High abundance of herbivorous Lepidoptera larvae (Acentria ephemerella DENIS &amp; SCHIFFERMÜLLER) on submersed macrophytes in Lake Constance (Germany)

Seasonal changes in the abundance of the herbivorous moth larvae Acentria ephemerella on submersed macrophytes in Lake Constance were studied between 1998 and 2000. Acentria were found feeding on many pondweeds (Potamogeton lucens, P. pectinatus, P. perfoliatus), Ceratophyllum demersum and Myriophyllum spicatum, but not on Chara spp., Najas marina ssp. intermedia or Elodea nuttallii. During the vegetated periods of 1998 and 2000 the abundance of larvae on P. perfoliatus and M. spicatum increased exponentially from approx. 10ind./m 2 to a maximum of 10,000 ind./m 2 or 20-165 ind./g dm. The much lower abundance in 1999 may be a result of the massive flooding of the lake in spring. Our data suggest that at least part of the Acentria population in Lake Constance may have two generations per year. Larvae use predominantly the upper shoot sections during the active feeding period and move to the lower stem sections for winter diapause. Herbivory caused substantial damage especially to the apical meristems of P. perfoliatus and M. spicatum. This study indicates that aquatic shredder-herbivores may have a stronger impact on submersed macrophytes than previously considered.

Effect of 5-HT in mianserin-pretreated rats on the structure of feeding behavior

The present study examined the effects of intra-PVN serotonin injection in mianserin-pretreated rats at the onset of the dark phase of light cycle on the structure of feeding behavior. The drugs were injected into the paraventricular nucleus (PVN) of the hypothalamus. The animals were maintained in a self-selection feeding paradigm and provided with freely available and separate sources of protein, carbohydrate, fat and water. The suppressive effect of 5-HT on carbohydrate intake was attenuated by mianserin at the beginning of the active (dark) feeding period. Mianserin-pretreatment increased the duration of carbohydrate and protein intake, but it was unable to block the effect of 5-HT on meal frequency and local rate of carbohydrate consumption. The present data suggests that carbohydrate intake may be in part mediated by postsynaptic 5-HT 2A/2C receptors. However, the temporal characteristics of carbohydrate ingestion are mediated by another subpopulation of 5-HT receptors in the PVN and indicates a possibly adrenergic influence.

Seasonal feeding patterns of the dominant Antarctic copepods Calanus propinquus and Calanoides acutus in the Weddell Sea

The diets and feeding activity patterns of two dominant Antarctic copepods, Calanus propinquus and Calanoides acutus, were studied throughout the seasonal cycle on material from several "Polarstern" cruises to the southeastern Weddell Sea. The observed differences in feeding patterns were closely linked with the peculiarities of the life-cycle strategies and changed with ambient food concentration. Calanoides acutus underwent diapause at depth and was never found feeding in winter. The winter descent of the population of Calanus propinquus was less pronounced, as some of the older copepodids stayed in the upper layer and contained food. The period of active feeding in Calanoides acutus was shorter than in Calanus propinquus. The former did not start feeding before late in spring. Feeding activity at the main study region (south of 67°S) was compared with that at the northern (60–67°S) stations with higher food abundance, where feeding activity of Calanus propinquus was high even in winter. Calanoides acutus contained a higher proportion of diatoms and unidentified mass in the gut, while the Calanus propinquus diet included more dinoflagellates, proto- and metazoan prey. The proportion of unidentified mass decreased in the older developmental stages and from winter towards autumn; it was higher in the deep layer. Gut contents of the two species were compared with seasonal distribution of the food items in the environment. The differences in feeding of the two species are directly connected to a higher degree of carnivory in Calanus propinquus, especially when phytoplankton food was scarce, and reflect the specificity in the life-cycle strategies, which is rigid in Calanoides acutus, and more flexible in Calanus propinquus.

Life Cycle ofIxodes pacificus(Acari: Ixodidae): Timing of Developmental Processes Under Field and Laboratory Conditions

The developmental timing of Ixodes pacficus Cooley & Kohls, the primary vector of the Lyme disease spirochete and the agent of human granulocytic ehrlichiosis in the far-western United States, was determined under field and laboratory conditions. During their seasonal peaks of abundance, each of the three parasitic stages of L. pacificus, both fed and unfed, was placed inside silk-screen packets. These packets were apportioned between four topographic exposures of two hilltop sites in northwestern California. The sites differed in vegetational composition and elevation: the first (elevation 390 m) was dominated by woodland-grass, the second (elevation 914 m) by chaparral. The timing of oviposition, larval eclosion, molting, and mortality were recorded in the field every 2-3 wk for 2.5 yr. Microenvironmental temperatures were measured on all four exposures at both sites. Accelerated developmental rates of all three stages were correlated with warmer soil temperatures and the time of placement in the field. In the laboratory, replete female I. pacificus maintained under uniform environmental conditions sustained constant preovipositional and prehatch periods independent of date-of-feeding. In the field, all unfed stages survived through one active feeding season with most larvae and nymphs remaining in behavioral diapause between late summer and early spring. No life stage survived through two active feeding periods which suggests that cohorts do not overlap. We concluded that I. pacificus takes a minimum of 3 yr to complete its life cycle in northwestern California.

Seasonal changes in feeding, gonad development and lipid stores in Calanusfinmarchicus and C . hyperboreus from Malangen, northern Norway

Seasonal dynamics of feeding activity, oil sac volume, gonad development, sex ratio and spawning periods in the two sibling species Calanusfinmarchicus and C. hyperboreus, the key zooplankton copepod organisms throughout the northern Atlantic waters, were studied simultaneously in Malangen, northern Norway, during 1992. We were also tracing differences in surface- and deep-dwelling components of these populations in terms of oil sac volume and gonad development during the time period when the G1 is preparing for a subsequent generation (G2) or hibernation. The main difference in the life cycle strategies of these species is the earlier maturation and spawning of C. hyperboreus. No feeding activity in either of the two species was found in February, but both commenced feeding in March, prior to the spring phytoplankton peak. The larger copepod, C. hyperboreus, had a more intensive energy deposition than C. finmarchicus. The period of active feeding was much shorter for the former species, only from March through July in copepodite stages CIV and CV, and even less in females – March and April. Basically, a similar pattern of seasonal changes in gonad length and lipids was observed in the two species. In June, oil sacs in the surface- and deep-dwelling specimens were about equal, during the rest of the year, lipids in the deep CVs exceeded those in the surface. We propose that as copepods accumulated sufficient lipid reserves, they started to descend, while others, containing less fat, stayed in the upper layers feeding. The mean length of the gonads in the surface-dwelling copepods was consistently less than in their deep counterparts from October to February, so that gonad development at the expense of accumulated reserves during resting stage was confirmed. C. finmarchicus males were found in considerable numbers only in February and March, and were only occasionally found in the upper layers (0–100 m), while adult male C. hyperboreus were present from October to March, but were never found in the surface layers. The differences in life cycle timing among the two species are discussed in relation to tradeoffs with regard to foraging strategies, generation numbers, bioenergetics and predator avoidance.

Relationships between Diurnal Variation in R-R Interval and Feeding Behavior in the Horse.

Heart rate, R-R intervals and the number of jaw movements were measured simultaneously for a 24-h period in an adult horse in a housed free-moving state. Feeding behavior was characterized by the number of jaw movements. Dropped beats could be monitored from a series of R-R intervals, and these dropped beats were regarded as second-degree A-V blocks . Thirty-eight dropped beats occurreduring a 24-h period. Second-degree A-V blocks frequently occurred in the night (p<0.001) and scarcely occurred in the active feeding periods (p<0.001). Moreover, the R-R interval periodically fluctuated at rest in the night. It was speculated that this periodical fluctuation in R-R interval is a respiratory sinus arrhythmia. This arrhythmia was not observed during feeding periods. A periodic violent fluctuation in the R-R intervals persisting for about 10 min was observed in the interval between feeding periods in the middle of the night, and this episode might occur during paradoxical sleep (REM sleep).

Intraventricular insulin reduces food intake and body weight of marmots during the summer feeding period

The study presented below describes experiments that investigate the ability of insulin to inhibit food intake in awake, active marmots during the summer season. Our results suggest that increasing intraventricular insulin concentration during the summer active feeding period will cause a decrease in food intake and body weight of marmots. When infused with insulin into their lateral ventricles (Alzet #2002 minipumps), animals had significantly lower food intake as compared to their food intake during the control period. In addition, these animals lost body weight during the period of the insulin infusion. We suggest that during the summer when marmots are not hibernating and are actively feeding, brain insulin levels may play a role in regulating food intake.

Intergeneric hybridization in Sparidae: 1. Sparus aurata ♀ × Diplodus puntazzo ♂ and Sparus aurata ♀ × Diplodus vulgaris ♂

Eggs of gilthead sea bream ( Sparus aurata) were inseminated by the sperm of sharp-snout sea bream ( Diplodus puntazzo) and common two-banded sea bream ( Diplodus vulgaris). Under controlled conditions, at 19.5°C, embryogenesis and yolk sac resorption in both intergeneric combinations took less time than embryogenesis and yolk sac resorption in Sparus aurata. Survival and growth of larvae of Sparus aurata, Sparus aurata ♀ × Diplodus puntazzo ♂ and Sparus aurata ♀ × Diplodus vulgaris ♂ were established during yolk sac resorption. During the active feeding period, between days 6 and 30 after hatching, neither growth nor survival differed significantly among the studied species and crosses. Sparus aurata ♀ × Diplodus puntazzo ♂ larvae grew slightly but not significantly faster.

Contributing factors to reduced ecdysteroid titers in Heliothis virescens parasitized by Microplitis croceipes

AbstractHeliothis virescens parasitized by Microplitis croceipes stop development at a predictable point prior to parasite emergence. The objectives of this study were to examine several factors which might contribute to the syndrome by comparing parasitized and nonparasitized larvae at specific and correspondingly similar physiological points in their development. Fifth stadium nonparasitized larvae experience a small pupal commitment burst of ecdysone followed by a large burst. In contrast, ecdysteroid titers in parasitized larvae remained at the pupal commitment level during the entire 5th stadium. Data shows that ecdysone 20‐monooxygenase and sterol precursors are not limiting factors, with the possible exception of limited hemolymph sterol at the end of parasitoid development. In addition, isolated prothoracic glands from parasitized larvae produce amounts of ecdysteroid comparable to controls when stimulated with a crude Manduca sexta prothoracicotropic hormone preparation. Juvenile hormone esterase titers in parasitized larvae are low throughout the 5th stadium. They do not show the major rapid increase in activity normally associated with the latter part of the active feeding period in the nonparasitized 5th instar. Possible explanations for the low ecdysteroid titers in parasitized larvae include failure to synthesize and release prothoracic gland stimulatory factor by the poorly developed fat body, insufficient sterol precursors at the critical time of ecdysteroid synthesis, inhibition of the release of PTTH, failure of the prothoracic gland to respond to PTTH, and the consequences of abnormally high juvenile hormone titers.

Relationship between brain trehalase activity and trehalosema during direct and diapausing development in Pieris brassicae

1. 1. Brain trehalase specific activity and trehalosemia were measured during the end of the developmental life cycle in non-diapausing and diapausing insects. 2. 2. During non-diapausing development, trehalosemia reached maximum values at the beginning of pupal life. Then a constant decrease was observed up to the end of adult life. 3. 3. The specific activity of brain trehalase was maximum when the insects were in active feeding periods, minimum activity appearing during moulting phases. 4. 4. During diapausing development, trehalosemia was very high at the beginning of pupal life, particularly when insects were exposed to wintering conditions. 5. 5. When diapause was broken, trehalosemia fell, announcing adult emergence. 6. 6. Brain trehalase activity showed the same qualitative variations as in non-diapausing larvae, but with rather lower values. 7. 7. During pupal life, brain trehalase activity decreased markedly during the long period necessary to obtain diapause breakdown. 8. 8. Wintering conditions allow a progressive increase of brain trehalase activity, which preceded the fall of trehalosemia.

Seasonal variations of insulin and some metabolites in dogfish plasma, Scyliorhinus canicula, L

Plasma levels in insulin, glucose, ketone bodies, and lactate were analyzed during a 1-year period in the lesser spotted dogfish ( Scyliorhinus canicula) in captivity. Plasma insulin levels fluctuated similarly for both sexes. The highest insulin levels were found during late prespawning (from January to March) and another increase was observed during the active feeding period (September and October). During the spawning period, insulin decreased and in the postspawning period the lowest values were reached. Glucose, however, showed a different trend. It was a minimum in late prespawning and it reached its highest values in postspawning. It decreased again in September and October. Plasma ketone body levels were highest in late prespawning and could be considered as an alternative energy source for this hypoglycemic period. In the summer months plasma lactate levels rose, with maximum levels occurring in July.