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781.
J. B. Lewis 《Marine Biology》1998,130(4):651-662
Dipolydora armata (Langerhans, 1880) is a small (4 to 5 mm) spionid polychaete found burrowing in the calcareous hydrozoan Millepora complanata Lamarck, 1816, on coral reefs at Barbados, West Indies. It excavates complex networks of interconnecting burrows and forms
aggregations of worms in cavities within branches of the coral. Adult worms have a mixed feeding mode (suspension feeding
and deposit feeding). Size–frequency distributions of worms in branch samples suggest that they mature in a single year and
that reproduction occurs throughout the year. Burrow openings on the surface of the coral develop distinctive, erect spines
caused by combined growth of worm tubes and host tissue. Millepore zooids were absent in the vicinity of tube openings and
on spines, and thus the potential feeding surface of the coral will be reduced in heavily colonized branches. Burrows and
openings were densest at the bases of millepore branches where weakening of the skeleton would be expected to occur. The absence
of openings near the branch tips suggests difficulty in larval settlement there, amongst stinging zooids. Reproduction␣and
larval development of the worms were examined, and a sequence of larval stages from one to 20 segments and a juvenile stage
of 22 segments are described. Eggs are deposited in brood sacs attached to the burrow wall, and the larvae feed upon nurse
eggs (adelphophagy). The presence of larvae and juveniles occurring free in the burrows suggests that larval development may
be completed within the host coral as an alternative or in addition to a planktonic larval phase. Lack of provisional larval
setae, early development of adult capillary setae, production of special spermatophores and a protracted breeding cycle in
D. armata are all traits which would favour complete development within the host skeleton.
Received: 6 March 1997 / Accepted: 25 October 1997 相似文献
782.
Although scyphomedusae have received increased attention in recent years as important predators in coastal and estuarine
environments, the factors affecting zooplankton prey vulnerability to these jellyfish remain poorly understood. Current models
predicting feeding patterns of cruising entangling predators, such as Chrysaora quinquecirrha (Desor, 1948), fail to account for the selection of fast-escaping prey such as copepods. Nevertheless, our analysis of gastric
contents of field-collected medusae showed that this scyphomedusa fed selectively on the calanoid copepod Acartia tonsa (Dana, 1846) and preferentially ingested adult over copepodite stages. We measured feeding rates in a planktonkreisel while
simultaneously videotaping predator–prey interactions. C. quinquecirrha consumed adult A. tonsa ten times faster than copepodites. Differences in prey behavior, in the form of predator–prey encounter rates or post-encounter
escape responses, could not account for the elevated feeding rates on adults. Prey size, however, had a dramatic impact on
the vulnerability of copepods. In experiments using heat-killed prey, feeding rates on adults (1.5 times longer than copepodites)
were 11 times higher than on copepodites. In comparison, medusae ingested heat-killed prey at only two to three times the
rate of live prey. These results suggest that during scyphomedusan–copepod interactions, prey escape ability is important,
but ultimately small size is a more effective refuge from predation.
Received: 26 September 1997 / Accepted: 20 May 1998 相似文献
783.
Home range, activity and distribution patterns of a temperate rocky-reef fish, Cheilodactylus fuscus
Red morwong (Cheilodactylus fuscus; Cheilodactylidae: Perciformes), are large temperate rocky reef fish that are patchily distributed in local aggregations
of 3 to >100 fish. The home ranges and aggregating behaviour of red morwong were investigated using external tags (n = 114, over 35 mo) and ultrasonic transmitters (n = 9 over 20 d) at coastal and estuarine sites in south-east Australia. Adult red morwong had a mean home range during the
day of 1865 m2 (SE = 268). Night movement, determined by ultrasonic telemetry, indicated a significantly greater mean home range of 3639 m2 (SE = 416). Home range did not differ significantly with size or sex. Fish movements were greatest and aggregation sizes
varied most during the non-reproductive mid-summer period. Tagged fish (N = 20) displaced 200 to 900 m returned in 1 to 3 d to the point of capture, often traversing open sand habitat and other aggregations.
During the day, fish were commonly found on bouldered habitat. During the night, these site-specific aggregations fragmented
as fish dispersed over a variety of substrata, with crepuscular peaks in activity. Therefore, estimates of habitat-specificity
and feeding patterns collected only by day may give misleading results.
Received: 28 June 1996 / Accepted: 8 July 1998 相似文献
784.
We examined the temporal variation of lysosomal enzyme activities and lysosomal membrane stability in two stocks of blue
mussels (Mytilus edulis L., 1758) from the Magdalen Islands which differ in their susceptibility to summer mass-mortality. The activity of lysosomal
enzymes reflects the autolytic capacity which could be used during the transfer of reserves between storage and reproductive
tissues or for mobilisation of reserves for energy requirements. The peak of lysosomal enzyme activities in mantle tissue
in June 1992 probably was related with autolysis of storage cells to support maturation of the developing gametes. A second
peak of lysosomal enzyme activity which occurred in mid- August of 1992 and 1993 may help to cover energetic requirements
of maintenance metabolism during this period of high temperatures and reduced food quality. Measures of the destabilization
of lysosomal membranes in the digestive gland confirmed that mussels showed a significant stress response in mid-August. Mussels
from the stock with a higher susceptibility to summer mortality underwent a longer period of stress and accumulated less glycogen
between spawning and the stressful period in mid-August than mussels from the more resistant stock. In conclusion, our field
observations demonstrate high activities of lysosomes not only in spawning periods but also during stressful periods of high
temperatures and reduced food quality.
Received: 23 September 1997 / Accepted: 11 June 1998 相似文献
785.
Peter Weindler Frank Böhme Varis Liepa Wolfgang Wiltschko 《Behavioral ecology and sociobiology》1998,42(4):289-294
To assess the role of celestial rotation during daytime in the development of the magnetic compass course, pied flycatchers
(Ficedula hypoleuca Pallas, Muscicapidae) were handraised in Latvia under various celestial and magnetic conditions. Tests were performed during
autumn migration in the local geomagnetic field (50 000 nT, 73° inclination) in the absence of celestial cues. A group of
birds that had never seen the sky showed a bimodal preference for the migratory southwest-northeast axis, whereas a second
group that had been exposed to the natural sky from sunrise to sunset in the local geomagnetic field showed a unimodal preference
for the seasonally appropriate southwesterly direction. A third group that had also been exposed to the daytime sky, but in
the absence of magnetic compass information, also oriented bimodally along a southwest-northeast axis. These findings demonstrate
that observing celestial rotation during daytime enables birds to choose the right end of the migratory axis for autumn migration
at the Latvian test location. This transformation of axial behavior into appropriate migratory orientation, however, requires
the birds to have simultaneous access to information on both celestial rotation and the geomagnetic field.
Received: 19 September 1997 / Accepted after revision: 22 November 1997 相似文献
786.
In this study, variance analysis technique on unbalanced data was examined, and in this sense, Type II (fitting constants) methods were studied. The aim of this study was to show that meaningful evaluations can be performed even in unbalanced conditions and to contribute to the present investigations in biological area. In the implementation part of the study, the juvenile leaf densities of Posidonia oceanica—which is a sea grass that grows in Izmir Bay, and has very important ecological effects—in various regions and in various depths were determined. The results revealed that depth affect number of juvenile leaf (d.f.?=?3, F?=?523.90, R 2?=?0.998, p?0,01). There were significant differences among region (d.f.?=?3, F?=?41.53, p?0.01), site (d.f.?=?1, F?=?19.65, p?0.01). As a result of Tukey ANOVA test it can be said that there were significant differences among Urla–Gülbahçe (p?0.001), Urla–Foça (p?0.001), Karaburun–Gülbahçe (p?0.001), Karaburun–Foça (p?0.001). It was found that Foça had the highest juvenile leaf counts (782.15?±?435.71) whereas Urla had the lowest juvenile leaf counts (231.46?±?175.67). The mean juvenile leaf counts in Izmir was (496.23?±?377.61). it can be said that juvenile leaf counts in Karaburun(Island) had (448.13?±?250.85), and Foça(Island) had (888.65?±?497.39). 相似文献
787.
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
788.
Sezen Saçan Aysun Uğur Uğur Sunlu Baha Büyükışık Mehmet Aksu F. Sanem Sunlu 《Environmental monitoring and assessment》2010,161(1-4):575-582
Bottom sediments reflect in general the relative contamination of a sea area. Therefore, a great deal of monitoring work has been dedicated to the analysis of bottom sediments. Izmir Bay is a very important pollution centre in Turkish Aegean coast region due to a densely populated community, industrial complex and maritime transportation, and there are many streams flowing into the bay that pass through a number of industrial and agricultural areas. It had received the majority of domestic and industrial wastewaters until the wastewater treatment plant was constructed. It is well known that sediments play an important role as reservoirs of a fraction of the pollution in aquatic systems. Therefore, sediment samples were collected monthly from three stations which are located in the inner part of the bay during the period January to December 2003. Temporal variations and seasonal changes on their 210Po and 210Pb contents were examined, and the activity concentrations of 210Po and 210Pb were found to vary from 43±6 to 132±12 and 27±5 to 91±9 Bq kg???1 dry wt, respectively. The highest values of those natural radionuclides were measured at Kar??yaka Station because of the current systems of the bay. Seasonally, the 210Pb levels were found to increase during the winter time for all the stations. 相似文献
789.
Veena Chaudhary Mukesh Kumar Mukesh Sharma B. S. Yadav 《Environmental monitoring and assessment》2010,161(1-4):343-348
The study was carried out to access the fluoride, boron, and nitrate concentrations in ground water samples of different villages in Indira Gandhi, Bhakra, and Gang canal catchment area of northwest Rajasthan, India. Rural population, in the study site, is using groundwater for drinking and irrigation purposes, without any quality test of water. All water samples (including canal water) were contaminated with fluoride. Fluoride, boron, and nitrate were observed in the ranges of 0.50–8.50, 0.0–7.73, and 0.0–278.68 mg/l, respectively. Most of the water samples were in the categories of fluoride 1.50 mg/l, of boron 2.0–4.0 mg/l, and of nitrate <?45 mg/l. There was no industrial pollution in the study site; hence, availability of these compounds in groundwater was due to natural reasons and by the use of chemical fertilizers. 相似文献
790.
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