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71.
72.
Trophic ecology of Rimicaris exoculata : a combined lipid abundance/stable isotope approach 总被引:1,自引:0,他引:1
The alvinocaridid shrimp Rimicaris exoculata is an abundant component of the biota of Mid-Atlantic Ridge hydrothermal vents. To determine the nutritional strategy of
this organism, we analysed the molecular abundance and carbon isotopic composition of its phospholipid fatty acids. High abundances
of n-7 fatty acids (>40% total fatty acids) were observed in R. exoculata muscle tissues, in bacterial epibionts scraped from its gill bailers, and from the bacterially infested metal sulphides that
the shrimp ingest. The phospholipid fatty acid abundance data indicates that the bacteria in the sulphides are closely related
to the bacterial epibiota inhabiting the shrimp gill bailers, carapace and other body parts. Compound specific δ13C analyses of the phospholipid fatty acids gave average values of −12‰ for the epibiont bacteria and −21‰ for the sulphide
bacteria. This difference may be largely due to the expression of different forms of RuBisCO (Forms I and II) which fractionate
against 13C to different extents. Carbon limitation within the shrimp epibiont population may be an additional factor. The δ13C values (mean = −13‰) of the saturated and monounsaturated fatty acids isolated from the muscle tissues of R. exoculata were very close to those of the epibionts, indicating that the predominant source of dietary carbon for the shrimp is their
epibionts, with a lesser contribution from free-living bacteria. The δ13C values (−26‰) of shrimp cholesterol were much more negative than those of the fatty acids, and this cholesterol is likely
to have derived from the oceanic photic zone.
Received: 26 June 1997 / Accepted: 6 November 1998 相似文献
73.
Moerisia lyonsi Boulenger (Hydrozoa) medusae and benthic polyps were found at 0 to 5‰ salinity in the Choptank River subestuary of Chesapeake
Bay, USA. This species was introduced to the bay at least 30 years before 1996. Medusae and polyps of M. lyonsi are very small and inconspicuous, and may occur widely, but unnoticed, in oligohaline waters of the Chesapeake Bay system
and in other estuaries. Medusae consumed copepod nauplii and adults, but not barnacle nauplii, polychaete and ctenophore larvae
or tintinnids, in laboratory experiments. Predation rates on copepods by medusae increased with increasing medusa diameter
and prey densities. Feeding rates on copepod nauplii were higher than on adults and showed no saturation over the range of
prey densities tested (1 to 64 prey l−1). By contrast, predation on copepod adults was maximum (1 copepod medusa−1 h−1) at 32 and 64 copepods l−1. Unexpectedly, M. lyonsi colonized mesocosms at the Horn Point Laboratory during the spring and summer in 4 years (1994 to 1997), and reached extremely
high densities (up to 13.6 medusae l−1). Densities of copepod adults and nauplii were low when medusa densities were high, and estimated predation effects suggested
that M. lyonsi predation limited copepod populations in the mesocosms. Polyps of M. lyonsi asexually produced both polyp buds and medusae. Rates of asexual reproduction increased with increasing prey availability,
from an average total during a 38 d experiment of 9.5 buds polyp−1 when each polyp was fed 1 copepod d−1, to an average total of 146.7 buds polyp−1 when fed 8 copepods d−1. The maximum daily production measured was 8 polyp buds and 22 medusae polyp−1. The colonizing potential of this hydrozoan is great, given the high rates of asexual reproduction, fairly wide salinity
tolerance, and existence of a cyst stage.
Received: 29 October 1998 / Accepted: 3 March 1999 相似文献
74.
Frequency and timing of extrapair fertilisation in the polyandrous red phalarope (Phalaropus fulicarius) 总被引:1,自引:0,他引:1
James Dale Robert Montgomerie Denise Michaud Peter Boag 《Behavioral ecology and sociobiology》1999,46(1):50-56
In sequentially polyandrous bird species, where females mate with different males in succession during a single breeding
season, sperm stored by females can occasionally lead to extrapair fertilisations (EPFs) in clutches cared for by the second
and subsequent males. Thus, we predicted that in red phalaropes (Phalaropus fulicarius) – a sex-role-reversed, sequentially polyandrous, arctic breeding shorebird – EPFs would occur more frequently in clutches
laid later in the breeding season. We used multilocus DNA profiling to examine the frequency and timing of EPFs in a population
of red phalaropes breeding in the Canadian high arctic. Using a technique to determine parentage without maternal DNA, we
inferred that 6 of 70 chicks in 18 broods resulted from EPFs – one extrapair chick in each of 6 broods. These results were
supported by a further analysis using microsatellite DNA. As predicted, broods containing EPFs hatched from clutches laid
significantly later in the season than did broods containing no EPFs. The difference in median hatch dates between broods
with and without EPFs was 9.0 days, or 38% of the entire egg-laying period in that season. For the whole breeding season,
we estimated that 6.5% of chicks were sired by extrapair males, which is similar to extrapair paternity estimates for other
sex-role-reversed birds, but relatively low compared to the majority of socially monogamous species studied so far.
Received: 24 August 1998 / Received in revised form: 18 January 1999 / Accepted: 24 January 1999 相似文献
75.
Andrés González Frank C. Schroeder Athula B. Attygalle Aleš Svatoš Jerrold Meinwald Thomas Eisner 《Chemoecology》1999,9(3):105-112
Summary. Female Photuris fireflies sequester defensive steroidal pyrones (lucibufagins) from male fireflies of the genus Photinus. Lucibufagin analyses of Photuris females and Photinus ignitus males show that the lucibufagin mixtures of predator and prey differ in their composition. Analyses of whole body extracts
showed that P. ignitus males contain a mixture of eight non-glycosylated lucibufagins, composed mostly of compounds with two oxygenated positions
in the steroidal A-ring (C-3, C-5). After feeding on P. ignitus males, Photuris females contain six major lucibufagins. Three of these compounds are not present in the prey, including the novel lucibufagin
glycoside 5β,11α-dihydroxy-12-oxo-3β-O-β-D-xylopyranosylbufalin, and two other lucibufagins with a trioxygenated A-ring (C-2,
C-3, C-5). These results indicate that Photuris females transform the sequestered lucibufagins both by glycosylation and oxidation, which could affect the systemic transportability
of these compounds due to an increase in their polarity.
Received 18 February 1999; accepted 19 April 1999. 相似文献
76.
Summary. Female Photuris fireflies contain defensive chemicals of two types. They sequester steroidal pyrones (lucibufagins) from male fireflies of
the genus Photinus that they eat, and themselves produce the defensive betaine N-methylquinolinium 2-carboxylate. Chemical analyses of Photuris eggs showed that females that fed on Photinus males endow their eggs with both lucibufagin and the betaine, while those that did not feed on Photinus lay eggs that contain betaine, but virtually no lucibufagin. Photuris females collected in the field during the Photinus flight season laid eggs that invariably contained betaine, but lucibufagin only at times. Predation experiments showed that
Photuris eggs are essentially unacceptable to larvae of a coccinellid beetle (Harmonia axyridis) and an ant (Leptothorax longispinosus), but moderately acceptable to an earwig (Forficula auricularia). When applied experimentally to palatable insect eggs, lucibufagin proved deterrent to these three predators, while the
betaine proved deterrent to the ant and coccinellid larva only. Both types of defensive compound decreased egg predation in
the field. By endowing their eggs with both exogenous and endogenous chemicals, Photuris females are essentially “maximizing their options”– when feeding on Photinus, their eggs are doubly protected, but they are not entirely defenseless when the females are unable to procure lucibufagin.
Received 12 August 1999; accepted 27 August 1999 相似文献
77.
《Atmospheric Environment. Part A. General Topics》1992,26(16):2975-2982
Source and sink processes of phosgene (COCl2) in the troposphere are reviewed. Sources are identified as decomposition of chlorinated hydrocarbons in both troposphere and stratosphere, which can be expected to increase in the future. Sinks are dry deposition and hydrolysis which, within clouds, is of the time scale of hours, and photolysis, which will not be of importance in the troposphere. Though above the cloud layer the lifetime of phosgene is expected to be greater than 10 years, hydrolysis during the transit through clouds and dry deposition will be the dominant sink, leading to an estimated residence time of approximately a few days. 相似文献
78.
《Atmospheric Environment. Part A. General Topics》1992,26(12):2227-2236
An indoor air quality model, MAVRIQ, has been developed for use with a personal computer (PC) to simulate the air concentration of organic compounds due to volatilization of chemicals originating in the domestic water supply. MAVRIQ also simulates the inhalation exposure of individuals based on their location and water use behavior. An application of MAVRIQ, presented in this paper, demonstrates the effect of various water uses on the air concentrations in a test house, and on the inhalation exposure of the inhabitants. The occupants' activities, location and water-use patterns are shown to affect their inhalation exposure. In the case of a person who spends the majority of his or her time in a home (such as the primary child-care adult) with contaminated water supply, the daily inhalation exposure is likely to exceed the exposure from ingestion of the same water. A large part of the inhalation exposure occurs during showering and post-showering activities, but other water uses also contribute. In addition, it is shown that a simple remedial action, the installation of a bathroom exhaust fan, can result in significant reductions of the inhalation exposure. 相似文献
79.
《Atmospheric Environment. Part A. General Topics》1992,26(2):287-298
Using the 1988 and 1989 experimental results obtained for two loblolly pine half-sibling families (GAKR 15–23 and GAKR 15–91) at the Auburn University intensive field research site, we: (1) explored the performance of a set of exposure indices; (2) characterized the ambient air and charcoal-filtered air treatments at Auburn and compared the values of the O3 exposure indices with those values calculated for ambient O3 monitors for a select set of sites; (3) identified and characterized O3 treatments in the Auburn open-top exposure chambers where an adverse effect was noted; and (4) identified where such experimental exposure regimes occurred under ambient conditions. We found that the SUMO exposure index did not perform adequately. We were unable to distinguish among the performances of the SUM06, W126, and SUM08 exposure indices. The results of the analyses of six estimated logistic parameters for a model of diameter2 × height (d2h) vs time indicated O3 effects for both families. At pH 4.3 (near ambient conditions), a response to O3 was detected in the NF × 2.5 treatments for both families for t2, the approximate time of maximum growth during the second year. Using ln (final d2h), family 23 did not show O3 effects. A comparison of the exposures experienced in the NF × 2.5 treatments with those occurring under ambient conditions at other locations showed that in 1983 and 1986, the San Bernardino County (CA) site experienced O3 exposures similar to those values experienced at the NF × 2.5 treatments in 1989. 相似文献
80.
《Atmospheric Environment. Part A. General Topics》1991,25(8):1649-1656
Junge's (Junge C.E., 1977, in Fate of Pollutants in the Air and Water Environments, pp7–25, John Wiley, New York) aerosol/vapor adsorption algorithm for organic air pollutants is extended to account for the water vapor content in air. A model, based on classical competitive adsorption theory and supported by ancillary data, is proposed to quantify the role of relative humidity (r.h.) on the equilibrium distribution of semivolatile organic chemicals (SOCs) between the aerosol (solid) and vapor phases. In general the model shows that aerosols contain significantly less SOCs for r.h. in the range of 10–90%. Quantitative predictions are made and one calculation shows that as air r.h. increases to 60% the aerosol associated SOC fraction is reduced by 80%. The model also suggest that dry aerosols and those with complete water films have the highest SOC content. 相似文献