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551.
Dry weight (DW), oxygen consumption, ammonia-N excretion, proximate biochemical composition (total protein, carbohydrate,
lipid, water and ash), and energy content (estimated from biochemical composition and by wet combustion) were determined in
early developmental stages of cultured Farfantepenaeus paulensis. Pooled samples from embryonic, larval and postlarval stages (at 26 ± 1 °C and 34 ± 1‰) were used for measurements. The study
focused on physiological and biochemical processes during transitional periods of ontogeny, such as hatching, lecithotrophic
and planktotrophic stages, metamorphosis, and the attainment of a benthic existence in postlarva. DW showed higher increment
between protozoea I (PZ I) and mysis I (M I) than in the next mysid and postlarval stages. Individual rates of oxygen consumption
and ammonia-N excretion increased, while weight-specific rates presented significant reduction throughout development. Higher
weight-specific oxygen consumption was registered in nauplius III (N III) and PZ I, following a decrease in subsequent stages.
Postlarval stages PL V–VI and PL X–XII exhibited the lowest values among the stages studied. Weight-specific excretion was
high in N III and protozoeal stages, with maximum values in PZ II, while the following stages were marked by lower rates.
O:N ratios indicated higher protein catabolism in the stages between egg and M I and a shift to more lipid utilization close
to metamorphosis. Water content was higher in the protozoeal stages and decreased afterwards. Higher percentages of protein,
lipid and carbohydrate (%DW) were observed in egg and nauplius stages. Protein and lipid decreased from the egg through the
naupliar and protozoeal stages, rising again in mysis stages. Lipid content (%DW) decreased in PL V–VI and PL X–XII. Lipid:protein
ratios showed an increase of the importance of lipid between PZ III and M II. Carbohydrates represented a minor fraction of
body composition, and ash percentages increased from egg to a maximum in PZ II, decreasing in subsequent stages. Energy content
determined by wet combustion or calculated by energy equivalents presented the same trend throughout development, varying
similarly to protein. Protein was the main energy contributor to body energy in all stages, while the importance of lipid
was higher in egg and early naupliar stages. Trends observed in metabolic rates and body composition may be associated to
morphological and behavioral changes during the early stages of penaeid development, such as the transition from herbivory
to omnivory, and the adoption of a benthic existence. Different ontogenetic energy strategies contribute to succeed through
such diverse type of development.
Received: 4 July 2000 / Accepted: 6 December 2000 相似文献
552.
V Pupavac 《Disasters》2001,25(4):358-372
This paper critically analyses the significance of psycho-social intervention as a new form of international therapeutic governance based on social risk management. First, the paper examines the international psycho-social model and its origins in an Anglo-American therapeutic ethos. Second, the paper argues that psycho-social approaches jeopardise local coping strategies. Third, the paper highlights the potential political, social and psychological consequences of the pathologisation of war-affected societies. Finally the paper concludes that therapeutic governance represents the reduction of politics to administration. 相似文献
553.
The predation impact of the two chaetognaths Eukrohnia hamata and Sagitta gazellae on mesozooplankton standing stock were investigated in three depth layers during two 24 h stations occupied in the vicinity
of Marion Island in late austral summer (April/May) 1986. The zooplankton community at both stations was dominated by small
copepods (Oithona spp., Microcalanus spp.), which accounted for >95% of total zooplankton abundance. Chaetognaths comprised <2% of total zooplankton abundance.
E. hamata constituted >95% of the total chaetognath stock. The general trend in both species was decreasing abundance with increasing
depth, which appeared to be correlated to the distribution of copepods (r
2 = 0.45; P <0.05). Gut-content analysis showed that copepods (mainly Oithona spp., Calanus spp. and Rhincalanus gigas) and ostracods were the main prey of both species, accounting for 87 and 61% of the total number of prey in E. hamata and S.␣gazellae stomachs, respectively. In the guts of S.␣gazellae, pteropods (Limacina spp.) and chaetognaths were also well represented. The mean number of prey items (NPC) for E. hamata ranged from 0.02 to 0.06 prey individual−1 which corresponds to an individual feeding rate (Fr) of between 0.05 and 0.12 prey d−1. For S.␣gazellae, the NPC values were higher, varying between 0.04␣and 0.20 prey individual−1, or between 0.15 and 0.76 prey d−1. The daily predation impact of the two chaetognaths was estimated at between 0.3 and 1.2% of the copepod standing stock or
between 7 and 16% of the daily copepod production. Predation by S. gazellae on chaetognaths accounted for up to 1.6% of the chaetognath standing stock per day.
Received: 26 November 1996 / Accepted: 31 October 1997 相似文献
554.
Copepod resting eggs are abundant in the seabed of many bays and estuaries where they provide a potential source of recruits
for growth of planktonic populations. In the northeastern Gulf of Mexico the copepod Centropages hamatus (Lillejeborg) occurs in the water column only during the late fall, winter and early spring. The species produces subitaneous
and diapause eggs, and both egg types have been found in the seabed. We determined the longevity of these two egg types to
ascertain their potential for contributing to the growth of the planktonic population and for sustaining a persistent egg
bank. Eggs were collected from females and incubated in the laboratory under temperature and oxygen conditions chosen to simulate
field conditions. The diapause eggs were also exposed to sulfide. The total hatching success of subitaneous eggs in two experiments
declined from highs of 78 and 97% to zero after 60 and 90 d of exposure to anoxia. The total hatching success of diapause
eggs that were exposed to anoxia for 90 d however was typically greater than 80%. Some diapause eggs hatched after being incubated
under anoxia for 437 d. Diapause eggs survived longer at ambient field temperatures when incubated under anoxia (437 d) compared
to normoxia (118 d). Exposure to sulfide did not result in greater mortality of diapause eggs compared to anoxia alone. Diapause
eggs that were incubated at ambient field temperatures did not hatch when exposed to normoxia until the temperature dropped
to <20 °C. The results of this study suggest that C.␣hamatus sustain a short-term reserve of subitaneous eggs in the seabed that provides recruits for the current year's population.
The greater longevity of diapause eggs suggests that they sustain the seasonal reappearance of the species year after year
in the northeastern Gulf of Mexico. However, the contribution of diapause eggs of C. hamatus from the Gulf of Mexico to a persistent egg bank is questionable since hatching ceased after 437 d.
Received: 30 July 1997 / Accepted: 18 January 1998 相似文献
555.
Whole-body carbon (C), nitrogen (N) and phosphorus (P) content, and stable-isotope composition (13C:12C and 15N:14N), were followed during metamorphosis of bonefish (Albula sp.) larvae (leptocephali). Metamorphosing larvae depend entirely on endogenous carbon compounds (some of which contain N and P) as an energy source. Two fundamental questions are (1) Do the demands of extensive tissue remodeling during metamorphosis require the efficient retention of N and P during the catabolism of carbon compounds? (2) What effect does the lack of feeding have on stable-isotope composition? Our results showed that both C and N decreased by ~35 to 40%, reflecting the utilization of neutral lipid (triacylglycerols) and N-containing compounds (phosphatidylethanolamine and keratan sulfate glycosaminoglycan) as energy sources, and indicating that larvae have little or no capacity to retain N. Evidence suggested that collagen breakdown, measured as a loss of hydroxyproline content, also contributed to N loss. Stable-isotope ratios, expressed as 13C and 15N, showed no statistically significant differences in early and advanced metamorphosing larvae. In contrast to C and N, phosphorus was conserved during metamorphosis and most probably is utilized in the increased bone mineralization occurring in advanced larvae. We show, however, that advanced larvae are P-limited and that normal ossification is dependent upon a supply of exogenous P obtained after the resumption of feeding. The N:P ratio of 12.3 in early larvae decreased to 8.1 in advanced larvae owing to the conservation of P as N was lost. The mean 15N value in early metamorphic larvae (11.6‰) is consistent with results from other studies, and provides further support for the view that premetamorphic leptocephali feed at a very low trophic level. 相似文献
556.
James V. Briskie Robert Montgomerie Tarmo Põldmaa Peter T. Boag 《Behavioral ecology and sociobiology》1998,43(3):181-190
In species where females copulate with more than one male during a single breeding attempt, males risk investing in offspring
that are not their own. In the polygynandrous Smith's longspur (Calcarius pictus), females copulate sequentially with one to three males for each clutch of eggs and most of these males later assist in feeding
the young. Using multilocus DNA profiling, we determined that there was mixed paternity in >75% of broods (n=31) but that few offspring (<1% of 114 nestlings) were sired by males outside the polygynandrous group. Male feeding rate
increased significantly with the number of young sired, with males siring four nestlings feeding the brood at double the frequency
of males siring only a single nestling. However, male Smith's longspurs appear to show a graded adjustment of paternal care
in response to paternity only when other males are available to compensate for reduced care: feeding rate did not vary in
relation to paternity when only one male provisioned young at the nest. There was no evidence that males could recognise their
own offspring within a brood and feed them preferentially. The number of offspring sired by each male was significantly correlated
with the number of days spent copulating with the attending female: on average, a male sired one offspring for every 2 days
of copulatory access. If males use their access to females to estimate paternity (and thereby decide on their subsequent level
of parental investment), a positive relationship is expected between the amount of female access and the subsequent feeding
rate to the nestlings. Nonetheless, male feeding effort was only weakly correlated with female access and more study is needed
to determine how males estimate their paternity in a brood.
Received: 1 June 1997 / Accepted after revision: 1 April 1998 相似文献
557.
Water blending is modelled as a combination of a linear program and a stochastic dynamic program. Optimal policies are found
for linear and integer-linear formulations using both an expected monetary value and conditional value-at-risk criterion.
The sensitivity of these solutions to the discretisation over volume and over time is investigated. 相似文献
558.
T. Ramachandramoorthy V. Sivasankar V. Subramanian 《Environmental monitoring and assessment》2010,160(1-4):127-139
The study area Rameswaram, a holy island, is famous for the sacred Ramanathaswamy temple, which cements people of the country regardless of their place, residence, or their religion or creed. This coastal tract is experiencing a chronic fresh water shortage, despite a few spring sources. The study area is selected for the characterization of physico-chemical parameters viz., pH, EC, TDS, salinity, TA, TH, CH, MH, chloride, and fluoride for 150 groundwater samples and the impact of pre- and post-monsoons on the groundwater quality is studied. The water quality index advocates the transfer of groundwater quality from unacceptable status in the pre-monsoon into an acceptable status in the post-monsoon. The Langelier saturation index reflects the scaling tendency of groundwater in the study area. The Karl Pearson correlation matrix has approved the maximum influence of calcium and chloride on the total dissolved solids. It is interesting to conclude that the groundwater in the study area has very had nature, especially of non-carbonate type. 相似文献
559.
J. Jernström J. Lehto V. A. Dauvalter A. Hatakka A. Leskinen J. Paatero 《Environmental monitoring and assessment》2010,161(1-4):93-105
Sediment cores collected from different locations of Lake Umbozero were studied with respect to concentration and mobility of trace and heavy metals Co, Cu, Fe, Mn, Ni, Pb, U, and Zn. Lake Umbozero is the second largest lake in the Murmansk Region and subjected to contamination by air-borne emissions and river transportation from the nearby metallurgical and mining industries. Unlike its neighboring, more industry-prone Lake Imandra, Lake Umbozero is relatively unexplored with respect to its state of pollution. In our study, metal distribution in sediments was found to vary with respect to the cores, although in general the concentrations were at the same level throughout the lake indicating uniform horizontal distribution of metals. When compared to Lake Imandra, the concentrations of most of the metals studied were significantly lower and represented the levels in sediments measured in lakes of Kola Peninsula located further off from industrial pollutant sources. An exception was Pb the concentration of which was at the same level as in Lake Imandra, probably due to long-distance transport. Sediment layers were subjected to four-step sequential extraction procedure to reveal the metal distribution in soluble, exchangeable, acid-soluble, and residual fractions. Indicative of their potential higher lability, Mn, U, and Zn were generally found in exchangeable fraction; as also Mn and U extensively in the acid-soluble fraction. 相似文献
560.
C. K. Jain V. V. S. Gurunadha Rao B. A. Prakash K. Mahesh Kumar Mitsuo Yoshida 《Environmental monitoring and assessment》2010,166(1-4):57-67
Hussainsagar Lake in the heart of Hyderabad City (India) receives toxic substances through five streams draining from a catchment area of 245 km2. Of particular interest are heavy metals received from urban runoff as well as municipal sewage and industrial effluents. Heavy metals entering the lake get adsorbed onto the suspended sediments, which eventually settle down in the bottom of the lake. In this study, fractionation of metal ions has been studied on the bed sediments of Hussainsagar Lake in order to determine the ecotoxic potential of metal ions. Comparison of sediments with average shale values indicated anthropogenic enrichment with copper, nickel, lead, cadmium, and zinc. The risk assessment code as applied to the present study reveals that 10–17% of manganese, 10–18% of nickel, 14–24% of chromium, 10–19% of lead, 21–30% of cadmium, and 18–28% of zinc exist in exchangeable fraction and, therefore, comes under medium risk category and may enter into food chain. The association of these metals with the exchangeable fraction may cause deleterious effects to aquatic life. The present database will help in formulating guidelines for carrying out dredging operations under restoration programs in the Hussainsagar Lake. 相似文献