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1.
Sara Ceballos Florentina Álvarez-Marqués 《Journal of experimental marine biology and ecology》2006,339(2):189-203
The reproductive activity and the physiological state of the calanoid copepods Calanus helgolandicus and Calanoides carinatus were investigated off the coast of NW Spain during autumn to evaluate the effect of short food resources on both populations. Phytoplankton biomass was low, and neither phytoplankton size distribution nor composition was suitable to support high reproductive rates. Accordingly, egg production rates (EPR) were much lower than maximum rates for both species, pointing to food limitation. The reproductive index (RI), which represents the proportion of females with mature gonads, was < 50% at each of the three zones into which the sampling area was divided (coast, shelf and ocean). Potential recruitment rates were very low except at some nearshore stations, where the highest concentrations of chlorophyll-a (Chl-a), diatoms, dinoflagellates and large cells were found. EPR of C. helgolandicus and C. carinatus were correlated with phytoplankton biomass and unaffected by temperature. Phytoplankton carbon ingestion explained ca. 50% of the variability in EPR for both species. At most of the stations, herbivory was insufficient to cover the carbon requirements for reproduction and respiration, so females probably fed on heterotrophic prey to meet their demands. However, given the low fecundity observed, this omnivorous diet did not seem to be optimum for reproduction, and a severe food limitation is thus suggested. Furthermore, the high C/N values measured point to a notable lipid storage, but given the low EPR found, lipid reserves were probably invested into female maintenance rather than into gonad maturation. C. helgolandicus and C. carinatus populations did not mirror phytoplankton biomass distribution, but they correlated well when considering only copepodites V (CV). The CV could be preparing for the overwintering, storing lipid reserves to ensure a successful diapause, and they could also be advected by the poleward current detected during the study. Females showed a diel feeding rhythm, with highest ingestion rates during night. From our results, it follows that C. helgolandicus and C. carinatus females did not perform diel vertical migrations. We suggest that this behaviour is likely due to the food-limiting conditions, which make it more advantageous to remain at the surface during daytime. 相似文献
2.
Chien-Hung Liu Wen-Ming Chen Jo-Shu Chang 《World journal of microbiology & biotechnology》2007,23(5):633-640
Acidic lipase finds its commercial values in medical applications and bioremediation of food wastes. In this work, approaches
for rapid screening of lipase-producing bacteria were developed and the feasibility assessment of the screening methods was
performed. From food waste samples, the proposed screening procedures allowed isolation of sixteen pure bacterial strains
expressing higher lipase activity at acidic pH (pH 6.0) than at alkaline pH (pH 9.0). To enhance the accuracy of lipase activity
determination under acidic conditions, a novel assay procedure was also developed by deactivating lipase activity by microwave
treatment prior to back titration. This additional step could minimize interferences arising from residual lipase activity
during conventional direct back-titration methods in measuring lipase activity at acidic pH. Using the four strategies proposed
in this work, the best acidic-lipase-producing isolate was obtained by strategy C (SSC) and was identified as Aeromonas sp. C14, displaying an optimal lipase activity of 0.7 U/ml at an acidic pH of 6.0. 相似文献
3.
A simple linear-operator model both describes and predicts the dynamics of choice that may underlie the matching relation. We measured inter-food choice within components of a schedule that presented seven different pairs of concurrent variable-interval schedules for 12 food deliveries each with no signals indicating which pair was in force. This measure of local choice was accurately described and predicted as obtained reinforcer sequences shifted it to favor one alternative or the other. The effect of a changeover delay was reflected in one parameter, the asymptote, whereas the effect of a difference in overall rate of food delivery was reflected in the other parameter, rate of approach to the asymptote. The model takes choice as a primary dependent variable, not derived by comparison between alternatives—an approach that agrees with the molar view of behaviour. 相似文献
4.
Invertebrate predator-prey body size relationships: an explanation for upper triangular food webs and patterns in food web structure? 总被引:1,自引:0,他引:1
Summary It has been suggested by Cohen and Newman (1985) that many of the patterns in published food webs can be derived from a stochastic model in which the species are arranged in a trophic hierarchy (the cascade model). We suggest that, if predators are larger than their prey, a trophic hierarchy can be generated on the basis of body size Empirical evidence from the literature shows that there is a positive relationship between predator and prey size for a range of invertebrates and that predators are usually larger than their prey. Using experimental data on an aquatic food web we show that body size can lead to the type of trophic hierarchy used in the cascade model, suggesting that many food web patterns may be a product of body size. This conclusion is discussed with respect to the limitations of the food web data and the relationship between static and dynamic models of web structure. 相似文献
5.
Toshisada Nishida 《Primates; journal of primatology》1989,30(1):129-138
Results of a nine-day survey of the chimpanzee habitat in Ugalla area of western Tanzania in 1975 is reported. The most dominant
vegetation of the area wasJulbernardia globiflora woodland. Evidence of chimpanzees, both indirect (such as beds, faeces, and food remnants) and direct (calls and actual observation),
suggests that chimpanzees are sparsely distributed throughout the area, but that they disproportionately useBrachystegia bussei woodland along escarpments andCynometra-Albizzia riverrine forests. The hilly country of Sisegwa/Mnyangwa was the only area where chimpanzees appeared to be comparatively
abundant. Mammal hair found in faeces indicates mammal-predation by the chimpanzees in this area. Hard-shelled fruits ofStrychnos were apparently bitten open without the use of extra-somatic objects. The food repertoire included fruits of the generaAzanza, Canthium, Cordia, andTamarindus. 相似文献
6.
Bruce Vondracek Wayne A. Wurtsbaugh Joseph J. Cech 《Environmental Biology of Fishes》1988,21(1):45-57
The allocation of energy to growth and reproduction, in relation to temperature and food availability, was investigated in
laboratory experiments with the mosquitofish,Gambusia affinis. At constant temperature of 20, 25 and 30°C and ad libitum feeding, specific growth rates increased with increasing temperature
at 1.7, 3.1 and 3.4% dry mass day−1, respectively. Growth rates in a cycling temperature regime (20–30°C,
) were faster than in a 25°C constant temperature. As temperature increased from 20 to 30°C, mean age at first reproduction
decreased from 191 to 56 days and brood size and mass of offspring increased significantly. Interbrood interval was also temperature
dependent; estimates at 25 and 30°C for females >1000 mg were 22.6 and 18.6 days, respectively. Interbrood interval could
not be calculated at 20°C. Although fitness was highest at 30°C, females at 25°C invested a greater proportion of surplus
energy (growth and reproduction) to reproduction (38%) than at 20 (17%) or 30°C (36%) during the 32-week study. Fish at cooler
temperatures began reproduction at a smaller size.
Where rations were controlled at low, medium, and ad libitum levels, somatic and gonadal growth increased with increasing
temperatures and food availability. The proportion of energy invested in reproduction was highest at 25°C for each comparable
ration level. Calculated energy budgets indicated that over the 10-week study, 17–22% of the food energy was invested in growth,
0–7% in reproduction, and 75–83% in respiration and excretory losses, depending on feeding and temperature conditions. 相似文献
7.
Influence of the food plants ofHeliothis armigera (Hb.) on the degree of parasitism by exotic parasiteCotesia kazak Telenga (Hymenoptera: Braconidae) was studied in cages in the laboratory on 7 food plants such as cotton (Gossypium hirsutum L.), tomato (Lycopersicon esculentum Mill), okra [Abelmoschus esculentus (L.) Moench], Dolichos (dolichos lablab L.), pigeonpea [Cajanus cajan (L.) Millsp.], Cowpea (Vigna unquiculata (L.) and chickpea (Cicer arietium L.). To determine the preference of the parasite 2 test methods were employed. In single plant choice test cotton was most
preferred. Next in order of preference were tomato and okra. Dolichos, pigeonpea, cowpea and chickpea were least preferred.
In multiple choice test, however, cotton and okra were preferred followed by tomato. Parasites were seen visiting these plants
very frequently and high parasitism was recorded on these plants. Chick pea, pigeon pea, cowpea and Dolichos were the least
preferred food plants. There appears to be some difference in fecundity as affected by some food plants. Exposure on okra,
cotton and tomato resulted in higher cocoon production as compared to pigeonpea, Dolichos, cowpea and chickpea. There was,
however, no difference in sex-ratio and longevity of the progeny as affected by food plants. This exotic parasite should be
released first in crops such as cotton, okra and tomato on whichH. armigera is a very serious pest in India and elsewhere.
Contribution No. 140/86 of the Indian institute of Horticultural Research, Bangalore-560 089 相似文献
8.
Jörg U. Ganzhorn Jean Prospère Abraham Marlène Razanahoera-Rakotomalala 《Primates; journal of primatology》1985,26(4):452-463
Two groups ofAvahi laniger were studied in the Forêt de Analamozoatra near Perinet in the eastern rainforest of Madagascar from August to October 1984.
Overlap between the home ranges of neighbouring groups ofA. laniger was minimal. Group size ranged from one to four individuals with a median group size of two. In four out of ten groups a
baby was born between August and September.A. laniger were most active after dusk and before dawn. They had an extended resting period around midnight. Their diet consisted mostly
of leaves from at least 17 different plant species. They also ate flowers. Fruit eating was recorded twice. Leaves eaten had
high contents of protein and sugar but did not contain alkaloids. The concentration of condensed tannins did not differ between
food items and non-food items. There was no indication of competition with other prosimians that might explain their nocturnality. 相似文献
9.
The present studies were undertaken to further assess the role of plasma beta-endorphin (beta-EP) in the hyperphagia induced by the glucose antimetabolite, 2-deoxy-D-glucose (2-DG). Plasma concentrations of immunoreactive beta-EP (ir-beta-EP) were measured at the end of the first hour of feeding in all animals treated with 400 mg/kg 2-DG. Previous studies had shown a consistent, positive association between 2-DG hyperphagia and plasma ir-beta-EP concentrations, but the present data revealed dissociations between hyperphagia and plasma ir-beta-EP. Dexamethasone administration blocked the 2-DG-induced rise in plasma ir-beta-EP, but had no effect on the 2-DG hyperphagia measured at 1 hour. Forced drinking of a 2% NaCl solution decreased 2-DG hyperphagia, but not the 2-DG induced rise in plasma ir-beta-EP. Thus, elevations in plasma ir-beta-EP are not necessary for the full expression of 2-DG-induced hyperphagia in dexamethasone-treated rats. Furthermore, decreased feeding responses to 2-DG could coexist with increased levels of plasma ir-beta-EP in NaCl-treated normal rats. Elevations in plasma ir-beta-EP do not appear to be the critical opiate link in 2-DG induced hyperphagia. 相似文献
10.
Akira Inokuchi Yasunobu Tomida Chizuko Yanaihara Ryogo Yui Yutaka Oomura Hiroshi Kimura Takanobu Hase Tomoaki Matsumoto Noboru Yanaihara 《Cell and tissue research》1986,246(1):71-75
Summary Immunohistochemically, nerve fibers and terminals reacting with anti-N-terminal-specific but not with anti-C-terminal-specific glucagon antiserum were observed in the following rat hypothalamic regions: paraventricular nucleus, supraoptic nucleus, anterior hypothalamus, arcuate nucleus, ventromedial hypothalamic nucleus and median eminence. Few fibers and terminals were demonstrated in the lateral hypothalamic area and dorsomedial hypothalamic nucleus. Radioimmunoassay data indicated that the concentration of gut glucagon-like immunoreactivity was higher in the ventromedial nucleus than in the lateral hypothalamic area. In food-deprived conditions, this concentration increased in both these parts. This was also verified in immunostained preparations in which a marked enhancement of gut glucagon-like immunoreactivity-containing fibers and terminals was observed in many hypothalamic regions. Several immunoreactive cell bodies were found in the ventromedial and arcuate nuclei of starved rats. Both biochemical and morphological data suggest that glucagon-related peptides may act as neurotransmitters or neuromodulators in the hypothalamus and may be involved in the central regulatory mechanism related to feeding behavior and energy metabolism. 相似文献