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1.
Besides diatoms Demospongiae are the most important consumers of dissolved silica in the sea. They can play an important
role for the silica budget especially in the shallow water areas of the Baltic Sea. The dependence of the silica uptake rate
on the silica concentration of the seawater was measured for the sponge Halichondria panicea (Pallas, 1766). The sponges were collected in Kiel Bight. The uptake conformed to Michaelis–Menten kinetics with a half-saturation
constant of 46.41 μM and a saturated uptake rate of 19.33 μmol h−1 g−1 ( p < 0.01). In the red algae zone of Kiel Bight the sponges depend on silica supply from the surrounding waters and may be silica-limited
rather than food-limited in growth. Because of the much faster uptake of silica by diatoms and their lower saturation point,
as well as the difference in spatial distribution of the two main silica consumers, a competition for silica between sponges
and diatoms seems unlikely.
Received: 21 June 1997 / Accepted: 15 July 1997 相似文献
2.
In situ measurements of photosynthetic irradiance responses of two Red Sea sponges growing under dim light conditions 总被引:6,自引:0,他引:6
Photosynthetic responses to irradiance by the photosymbionts of the two Red Sea sponges Theonella swinhoei (Gray) and Clionavastifica (Hancock) growing under dim light conditions were measured in situ (in September 1997) using a newly developed underwater
pulse amplitude modulated (PAM) fluorometer. Relative rates of photosynthetic electron transport (ETR) were calculated as
the effective quantum yield of photosystem II (Y ) multiplied with the photosynthetic photon flux (PPF). Photosynthesis versus irradiance (P-I ) curves, obtained within minutes, showed that individual specimens of both sponges, growing under very low light conditions,
feature lower light saturation points as well as lower maximal ETRs than individuals growing under higher light. Evaluations
of such curves using low irradiances of the actinic light source (20 to 130 μmol photons m−2 s−1) showed a general decrease in Y, with a shoulder from the lowest irradiance applied till 20 to 30 μmol photons m−2 s−1. Point measurements yielded ETRs close to what could be estimated from the P-I curves. These point measurements also revealed good correlations between the diurnally changing ambient irradiances (1 to
50 μmol photons m−2 s−1) and average ETR values for both species. Further analysis showed that although Y values varied considerably between the different point measurements, they did not decrease significantly with light under
these very low irradiances. Therefore, PPF rather than Y seems to determine the in situ diel photosynthetic performance at the low ambient irradiances experienced by these sponges.
Received: 22 November 1997 / Accepted: 8 April 1998 相似文献
3.
We performed an intensive year-round sampling with the aim of studying the abundance of sponge larvae in four Mediterranean
benthic communities: photophilic algae, sciaphilous algae, semi-obscure (i.e. low light-intensity) caves and sandy bottoms.
We record here for the first time, a larval bloom of Cliona viridis (Schmidt 1862), the most common excavating sponge in the Mediterranean, which took place simultaneously in several rocky
communities of the Blanes sub-littoral (NE Spain), and discuss the role of restricted larval dispersal in the distribution
of adult sponges. In the communities studied, C. viridis larvae bloomed synchronously once, in June. Spawning and consequent embryo development presumably occurred in May, when water
temperature was 16 °C. The free larva is a small, evenly ciliated, weakly swimming parenchymella with low dispersal capabilities.
The number of larvae m−3 and sponge abundance (as percent cover and biomass) were significantly higher in the community of sciaphilous algae than
in the other communities studied. Because of limited larval dispersal, larval and adult abundance in the communities were
positively correlated. Larvae developed into juvenile sponges 10 to 15 d after settlement. Settlers displayed distinctive
features: a peripheral cuticle, vacuolar etching-like cells at the sponge base, absence of oscular chimneys, and the presence
of zooxanthellae, which were presumably transmitted during oocyte maturation.
Received: 24 January 2000 / Accepted: 4 July 2000 相似文献
4.
Mytilus edulis L., Ruditapes philippinarum (Adams & Reeve) and Tapes decussatus L. were fed particles of the same shape (spherical), the same density (2.1 g cm−3) and the same chemical composition (SiO2), but which varied in diameter from 5 to 37 μm. Findings obtained at different particle concentrations (mean ± SD) of 51 ± 2,
105 ± 18 and 171 ± 17 mg l−1 invariably indicate that significant proportions of all particles with diameters larger than from between 7.5 and 22.5 μm
were preferentially rejected as pseudofaeces. We define the preferential ingestion index (PII) as the ratio between average
particle volume in pseudofaeces and average particle volume in food. Whatever the particle concentration or the species, this
PII was always statistically higher than 1. Irrespective of particle concentration, PII values in M. edulis were lower than in T. decussatus (averages of 1.2 and 2, respectively). PII values in M. edulis were also lower than in R. philippinarum maintained at particle concentrations above 171 ± 17 mg l−1. We suggest that preferential size-dependent rejection of larger particles could be of significant adaptive value in the
natural environment, either if there are large inorganic particles, or if the average organic content of smaller particles
is higher.
Received: 11 January 1997 / Accepted: 8 March 1997 相似文献
5.
In the Red Sea, the zooxanthellate sponge Cliona vastifica (Hancock) is mainly present at >15 m depth or in shaded areas. To test whether its scarcity in unshaded areas of shallower
waters is linked to the functional inefficiency of its photosymbionts at high irradiances, sponges were transferred from 30 m
to a six times higher light regime at 12 m depth, and then returned to their original location. During this time, photosynthetic
responses to irradiance were measured as rapid light curves (RLCs) in situ by pulse amplitude modulated (PAM) fluorometry
using a portable underwater device, and samples were taken for microscopic determinations of zooxanthellar abundance. The
zooxanthellae harboured by this sponge adapted to the higher irradiance at 12 m by increasing both their light saturation
points and relative photosynthetic electron transport rates (ETRs). The ETRs at light saturation increased almost fourfold
within 15–20 days of transfer to the shallower water, and decreased back to almost their original values after the sponges
were returned to 30 m depth. This, as well as the fact that the photosynthetic light responses within an individual sponge
were in accordance with the irradiance incident to specific surfaces, shows that these photosymbionts are highly adaptable
to various irradiances. There was no significant change in the number of zooxanthellae per sponge area throughout these experiments,
and the different photosynthetic responses were likely due to adaptations of the photosynthetic apparatus within each zooxanthella.
In conclusion, it seems that parameters other than the hypothesised inability of the photosymbionts to adapt adequately to
high light conditions are the cause of C. vastifica's rareness in unshaded shallow areas of the Red Sea.
Received: 25 April 2000 / Accepted: 13 October 2000 相似文献
6.
Friederike Hoffmann Hans Røy Kristina Bayer Ute Hentschel Martin Pfannkuchen Franz Brümmer Dirk de Beer 《Marine Biology》2008,153(6):1257-1264
The Mediterranean sponge Aplysina aerophoba kept in aquaria or cultivation tanks can stop pumping for several hours or even days. To investigate changes in the chemical
microenvironments, we measured oxygen profiles over the surface and into the tissue of pumping and non-pumping A. aerophoba specimens with Clark-type oxygen microelectrodes (tip diameters 18–30 μm). Total oxygen consumption rates of whole sponges
were measured in closed chambers. These rates were used to back-calculate the oxygen distribution in a finite-element model.
Combining direct measurements with calculations of diffusive flux and modeling revealed that the tissue of non-pumping sponges
turns anoxic within 15 min, with the exception of a 1 mm surface layer where oxygen intrudes due to molecular diffusion over
the sponge surface. Molecular diffusion is the only transport mechanism for oxygen into non-pumping sponges, which allows
total oxygen consumption rates of 6–12 μmol cm−3 sponge day−1. Sponges of different sizes had similar diffusional uptake rates, which is explained by their similar surface/volume ratios.
In pumping sponges, oxygen consumption rates were between 22 and 37 μmol cm−3 sponge day−1, and the entire tissue was oxygenated. Combining different approaches of direct oxygen measurement in living sponges with
a dynamic model, we can show that tissue anoxia is a direct function of the pumping behavior. The sponge-microbe system of
A. aerophoba thus has the possibility to switch actively between aerobic and anaerobic metabolism by stopping the water flow for more
than 15 min. These periods of anoxia will greatly influence physiological variety and activity of the sponge microbes. Detailed
knowledge about the varying chemical microenvironments in sponges will help to develop protocols to cultivate sponge-associated
microbial lineages and improve our understanding of the sponge-microbe-system. 相似文献
7.
The benthic crustacean Saduria entomon occurs frequently in deeper parts of the Gulf of Gdańsk. It is one of a few species able to survive oxygen deficiencies in
its natural environment. The anaerobic heat production of S. entomon during 40 h of anoxia was determined. Additionally, the effects of size, sex and activity of the organism on its heat production
were investigated. Average heat production of S. entomon was 0.25 ± 0.16 mJ g−1 wet wt s−1 (n=55, avg. length 39 ± 6 mm). The amount of heat produced decreased with increasing body size. The heat production of S. entomon males was greater than that of females ( p<0.05). Specimens kept in chambers with glass beads and water were less active and had lower metabolic rates than those placed
in chambers containing water only (more active). During 40 h of anoxia S. entomon gradually decreased its heat production to 5–16% of aerobic level, demonstrating the high adaptation of this species to changeable
oxygen conditions in the Baltic Sea.
Received: 31 July 1997 / Accepted: 21 January 1998 相似文献
8.
Silica content and spicule size variations in Pellina semitubulosa (Porifera: Demospongiae) 总被引:1,自引:0,他引:1
The variations in both silica content and spicular size were studied in two populations of the demosponge Pellina semitubulosa (Lieberkühn). Samples were collected over a period of 1 year (June 1994 to May 1995) in two Mediterranean coastal basins:
Porto Cesareo (southwestern Apulia) and Marsala (northwestern Sicily). The values of spicule size (length and width) and sponge
silica content were significantly higher in the population of Porto Cesareo, where the highest water silica concentration
was recorded. In both Porto Cesareo and Marsala the sponge silica content showed a seasonal trend, positively correlated with
water temperature values. In both populations, the smallest spicules were found in specimens collected from summer to late
autumn, after sexual reproduction. Secretion of new spicules may be connected with the process of remodelling occurring in
sponges after gamete and larval release.
Received: 10 October 1999 / Accepted: 13 April 2000 相似文献
9.
When symbiotic dinoflagellate algae (Symbiodinium sp., isolated from the coral Plesiastrea versipora) were incubated with NaH14CO3 in the light in seawater, they released 22.69±9.16 nmol carbon/106 algae. Release of photosynthetically fixed carbon was stimulated more than six-fold for algae incubated in host-tissue homogenate
(148.54±97.03 nmol C/106 algae) and more than four-fold (102.00±49.16 nmol C/106 algae) for algae incubated in a low molecular weight fraction (≤1 000 M
r
) prepared from host homogenate. Soluble released 14C-labelled products, as determined by chromatography and autoradiography, were the same when algae were incubated in either
host homogenate or the low molecular weight fraction. After 4 h incubation in the light (300 mol photons m−2 s−1),␣intracellular␣glycerol increased in algae incubated with the low molecular weight fraction (an increase of 0.39 to␣0.67 nmol glycerol/106 algae) compared with little or no increase in algae incubated in seawater (0 to 0.12 nmol glycerol/106 algae). Partial inhibition of triglyceride synthesis (up to 51%) was also observed when algae were incubated in the low molecular
weight fraction. All these effects are the same as those observed when algae were incubated in host homogenate. These data
indicate that the “host release-factor” activity of P.␣versipora is a compound of low molecular weight.
Received: 13 February 1997 / Accepted: 24 October 1997 相似文献
10.
Nutrients were added separately and combined to an initial concentration of 10 μM (ammonium) and/or 2 μM (phosphate) in a series of experiments carried out with the giant clam Tridacna maxima at 12 microatolls in One Tree Island lagoon, Great Barrier Reef, Australia (ENCORE Project). These nutrient concentrations
remained for 2 to 3 h before returning to natural levels. The additions were made every low tide (twice per day) over 13 and
12 mo periods for the first and second phase of the experiment, respectively. The nutrients did not change the wet tissue
weight of the clams, host C:N ratio, protein content of the mantle, calcification rates or growth rates. However, ammonium
(N) enrichment alone significantly increased the total population density of the algal symbiont (Symbiodinium sp.: C = 3.6 · 108 cell clam−1, N = 6.6 · 108 cell clam−1, P = 5.7 · 108 cell clam−1, N + P = 5.7 · 108 cell clam−1; and C = 4.1 · 108 cell clam−1, N = 5.1 · 108 cell clam−1, P = 4.7 · 108 cell clam−1, N + P = 4.5 · 108 cell clam−1, at the end of the first and second phases of the experiment, respectively), although no differences in the mitotic index
of these populations were detected. The total chlorophyll a (chl a) content per clam but not chlorophyll a per cell also increased with ammonium addition (C = 7.0 mg chl a clam−1, N = 13.1 mg chl a clam−1, P = 12.9 mg chl a clam−1, N + P = 11.8 mg chl a clam−1; and C = 8.8 mg chl a clam−1, N = 12.8 mg chl a clam−1; P = 11.2 mg chl a clam−1, N + P = 11.3 mg chl a clam−1, at the end of the first and second phases of the experiment, respectively). The response of clams to nutrient enrichment
was quantitatively small, but indicated that small changes in inorganic nutrient levels affect the clam–zooxanthellae association.
Received: 2 June 1997 / Accepted: 9 June 1997 相似文献
11.
Variability in the chemical defense of the sponge Chondrilla nucula against predatory reef fishes 总被引:2,自引:0,他引:2
Chondrilla nucula is a common Caribbean demosponge that grows in a range of habitats, from coral reefs to mangrove swamps. On reefs, C. nucula grows as a thinly encrusting sheet, while in mangrove habitats it surrounds submerged mangrove roots as fleshy, lobate clumps.
Previous feeding experiments using predatory reef fish revealed a high degree of variability in the chemical defenses of C. nucula. The present study was undertaken to determine whether a relationship exists between habitat, growth form, and chemical defense
of C. nucula. Both laboratory and field feeding-assays of crude extracts confirmed that C. nucula possesses a chemical defense with high intercolony variability, but there was no significant variation in feeding deterrency
between reef and mangrove habitats at either geographic location (Bahamas and Florida). Extracts of C. nucula collected during September and October 1994 from the Bahamas were significantly more deterrent than those collected during
August 1993, May 1994, and May 1995 from Florida, and extracts of these spring and summer Florida collections were more deterrent
than extracts of C. nucula collected in December 1994 and February 1995 in the same locations. There was no evidence that deterrent compounds were concentrated
in the surface tissues of the sponge, or that chemical defense could be induced by simulated predation. Laboratory and field
assays of the fractionated crude extract revealed that feeding deterrency was confined to the most polar metabolites in the
extract. Field transplants were used to determine whether predation influenced the growth form of C. nucula. Uncaged sponges transplanted from the mangrove to the reef were readily consumed by spongivorous reef fishes. Lobate mangrove
sponges became thinner after being caged on the reef for 3 mo, but encrusting reef sponges did not become thicker after being
caged in the mangroves for the same period of time. Reef sponges that were caged for 3 to 15 mo thickened by only a small
amount (<1 mm) compared to uncaged and open-caged (i.e. in cages lacking tops) sponges. Simulated bite marks on both reef
and mangrove sponges were repaired at a rapid rate (0.8 to 1.6 mm d−1). Fish predation has an important impact on the distribution and abundance of C. nucula, but the thin growth form common to reef environments may be more the result of hydrodynamics than of grazing by spongivorous
fishes.
Received: 6 October 1997 / Accepted: 19 March 1998 相似文献
12.
Anne Marie Power Karen McCrann David McGrath Ruth M. O’ Riordan Christina Simkanin Alan A. Myers 《Marine Biology》2011,158(10):2149-2160
This study examined how the species composition of an intertidal barnacle guild varied according to physical gradients in
the environment at small scales governed by microclimates, medium scales of wave exposure and large scales of latitude. Barnacle
distributions at small and medium scales were sampled in Ireland between 51°29′ and 52°44′N and 6°50′ and 10°08′W. Sampling
on European shores spanned ~18° latitude from 37°05′ to 55°16′N. Barnacle surveys mainly took place in 2003–2004. An index
of wave fetch was calculated along the wave exposure gradient using a digital coastline-based model that was supported by
a biological exposure scale. A ‘dryness’ index was defined according to mean monthly wind speed, fetch along the average wind
direction and mean monthly air or sea surface temperatures for 2 years (January 2001–December 2002) which is the period when
the most recent adults in the barnacle community would have settled and grown to adulthood. The proportion of the dry-loving
barnacle Chthamalus montagui Southward increased within the barnacle guild at all scales as the habitat became warmer and drier. Barnacle densities were
high in all habitats, mean densities ranged from a minimum of 4.16 cm−2 on moderately exposed shores to a maximum of 6.27 cm−2 in sunlit or south-facing microclimates. Percentage cover of barnacles across the gradient of latitudes was usually >70%.
The results suggest that the distribution and abundance of interacting barnacle species on European coasts is strongly controlled
by abiotic factors, most likely temperature and desiccation. 相似文献
13.
Redwood of the reef: growth and age of the giant barrel sponge Xestospongia muta in the Florida Keys 总被引:1,自引:0,他引:1
The growth of animals in most taxa has long been well described, but the phylum Porifera has remained a notable exception.
The giant barrel sponge Xestospongia muta dominates Caribbean coral reef communities, where it is an important spatial competitor, increases habitat complexity, and
filters seawater. It has been called the ‘redwood of the reef’ because of its size (often >1 m height and diameter) and presumed
long life, but very little is known about its demography. Since 1997, we have established and monitored 12 permanent 16 m
diameter circular transects on the reef slope off Key Largo, Florida, to study this important species. Over a 4.5-year interval,
we measured the volume of 104 tagged sponges using digital images to determine growth rates of X. muta. Five models were fit to the cubed root of initial and final volume estimates to determine which best described growth. Additional
measurements of 33 sponges were taken over 6-month intervals to examine the relationship between the spongocoel, or inner-osculum
space, and sponge size, and to examine short-term growth dynamics. Sponge volumes ranged from 24.05 to 80,281.67 cm3. Growth was variable, and specific growth rates decreased with increasing sponge size. The mean specific growth rate was
0.52 ± 0.65 year−1, but sponges grew as fast or slow as 404 or 2% year−1. Negative growth rates occurred over short temporal scales and growth varied seasonally, significantly faster during the
summer. No differences in specific growth rate were found between transects at three different depths (15, 20, 30 m) or at
two different reef sites. Spongocoel volume was positively allometric with increasing sponge size and scaling between the
vertical and horizontal dimensions of the sponge indicated that morphology changes from a frustum of a cone to cylindrical
as volume increases. Growth of X. muta was best described by the general von Bertalanffy and Tanaka growth curves. The largest sponge within our transects (1.23 × 0.98 m
height × diameter) was estimated to be 127 years old. Although age extrapolations for very large sponges are subject to more
error, the largest sponges on Caribbean reefs may be in excess of 2,300 years, placing X. muta among the longest-lived animals on earth. 相似文献
14.
The ability of endosymbioses between anthozoans and dinoflagellate algae (zooxanthellae) to retain excretory nitrogen and
take up ammonium from seawater has been well documented. However, the quantitative importance of these processes to the nitrogen
budget of such symbioses is poorly understood. When starved symbiotic Anemonia viridis were incubated in a flow-through system in seawater supplemented with 20 μM ammonium for 91 d under a light regime of 12 h light at 150 μmol photons m−2 s−1 and 12 h darkness, they showed a mean net growth of 0.197% of their initial weight per day. Control anemones in unsupplemented
seawater with an ammonium concentration of <1 μM lost weight by a mean of 0.263% of their initial weight per day. Attempts to construct a nitrogen budget showed that, over
a 14 d period, ≃40% of the ammonium taken up could be accounted for by growth of zooxanthellae. It was assumed that the remainder
was translocated from zooxanthellae to host. However, since the budget does not balance, only 60% of the growth of host tissue
was accounted for by this translocation. The value for host excretory nitrogen which was recycled to the symbionts equalled
that taken in by ammonium uptake from the supplemented seawater, indicating the importance of nitrogen retention to the symbiotic
association.
Received: 23 December 1997 / Accepted: 12 September 1998 相似文献
15.
A distinct smell of dimethylsulfide (DMS) was noted at the edge of the intertidal mudflat of Marennes-Oléron Bay, at the
French Atlantic coast, where dense populations of the marine flatworm Convoluta roscoffensis Graff (Platyhelminthes: Turbellaria) were present. DMS is the cleavage product of dimethylsulfoniopropionate (DMSP). DMSP
was shown to be present in high amounts in sediment containing the flatworm as well as in axenic cultures of the symbiotic
alga Tetraselmis sp. that was isolated from the flatworm. In untreated sediment samples containing C. roscoffensis the concentration of DMS was as high as ∼55 μmol l−1 sediment, and in samples that were fixed with glutaraldehyde the concentration of DMS was even three orders of magnitude
higher (∼66 mmol l−1 sediment). This rapid cleavage of DMSP to DMS in fixed samples was unexpected. Pure DMSP was stable in glutaraldehyde, and
it was therefore concluded that a DMSP-lyase was responsible for cleavage in the field samples. The isolated symbiotic alga,
Tetraselmis sp., did not show DMSP-lyase activity, indicating that DMSP-lyase may have been present in the flatworm, although the role
of bacteria could not be excluded. The Chl a-specific DMSP content of C. roscoffensis (∼200 mmol g−1) was much higher than that of Tetraselmis sp. (∼30 mmol g−1). Possibly, DMSP was not only present in the symbiotic alga, but was also incorporated in the body tissue of the flatworm.
It remains unclear what the function of DMSP is in C. roscoffensis. In Tetraselmis sp., but not in C. roscoffensis, DMSP increased with increasing salinity. It was concluded that salinity probably does not play an important role in the
dynamics of DMSP and DMS in sediment containing C. roscoffensis.
Received: 21 January 2000 / Accepted: 29 August 2000 相似文献
16.
When aseptically-cultured sea anemones, Aiptasia pulchella, were incubated with 14C-labelled glucose, aspartate and glutamate, radioactivity was incorporated into animal protein. Radioactivity was recovered
from all amino acids in the protein hydrolysates of A. pulchella bearing the symbiotic alga Symbiodinium sp., and from all but seven of the amino acids in A. pulchella experimentally deprived of their algae. These data suggest that these seven amino acids (histidine, isoleucine, leucine,
lysine, phenylalanine, tyrosine and valine) may be synthesized by the symbiotic algae and translocated to the sea anemone's
tissues; and that methionine and threonine, two amino acids traditionally considered as dietary essentials for animals, are
synthesized by A. pulchella. Essential amino acid translocation from the symbiotic algae to the animal host is a core element in symbiotic nitrogen-recycling.
Its nutritional value to the animal host is considered in the context of the amino acid biosynthetic capacity of the host.
Received: 26 October 1998 / Accepted: 28 June 1999 相似文献
17.
Reduced take-off ability in robins (Erithacus rubecula) due to migratory fuel load 总被引:11,自引:0,他引:11
Lind Johan Fransson Thord Jakobsson Sven Kullberg Cecillia 《Behavioral ecology and sociobiology》1999,46(1):65-70
Recent studies have shown that large fuel loads in small birds impair flying ability. This is the first study to show how
migratory fuel load affects flying ability, such as velocity and height gained at take-off in a predator escape situation,
in a medium-distance migrant, and whether they adjust their take-off according to predator attack angle. First-year robins
(Erithacus rubecula) were subjected to simulated attacks from a model merlin (Falco columbarius), and take-off velocity and angle were analysed. Robins with a wing load of 0.19 g cm−2 took off at a 39% lower angle than robins with a wing load of 0.13 g cm−2, while velocity remained unaffected. The robins did not adjust their angle of ascent in accordance with the predator's angle
of attack. Since many predators rely on surprise attacks, a difference in flight ability due to varying fuel loads found in
migrating robins can be important for birds' chances of survival when actually attacked.
Received: 28 October 1998 / Received in revised form: 12 January 1999 / Accepted: 30 January 1999 相似文献
18.
Halogenated metabolites in two marine polychaetes and their planktotrophic and lecithotrophic larvae
This study investigated the occurrence and ontogenetic changes of halogenated secondary metabolites in planktotrophic and
lecithotrophic larvae and adults of two common, infaunal polychaetes, Streblospio benedicti (Spionidae) and Capitella sp. I (Capitellidae), with different life-history traits. S. benedicti contains at least 11 chlorinated and brominated hydrocarbons (alkyl halides) while Capitella sp. I contains 3 brominated aromatic compounds. These halogenated metabolites are potential defense compounds benefiting
both larvae and adults. We hypothesized that: (1) planktotrophic larvae contain halogenated metabolites because they are not
protected by adult defenses, (2) quantitative and qualitative variation of planktotrophic larval halogenated metabolites parallels
that of adults, and (3) brooded lecithotrophic larvae initiate the production of halogenated metabolites only after metamorphosis.
To address these hypotheses, volatile halogenated compounds from polychaete extracts were separated using capillary gas chromatography
and identified and quantified using mass spectrometry with selected ion monitoring. All four life stages (pre- and post-release
larvae, new recruits, adults) of both S. benedicti and Capitella sp. I contained the halogenated metabolites previously identified from adults. This is the first report of halocompounds
identified and quantified in polychaete larvae. Allocation of potential defense compounds to offspring varied as a function
of species, feeding type and developmental stage. Pre-release larvae of S. benedicti with planktotrophic development contained the lowest concentration of total halogenated metabolites (1.75 ± 0.65 ng mm−3), post-release and new recruits contained intermediate concentrations (8.29 ± 1.72 and 4.73 ± 2.63 ng mm−3, respectively), and planktotrophic adults contained significantly greater amounts (28.9 ± 9.7 ng mm−3). This pattern of increasing concentrations with increasing stage of development suggests synthesis of metabolites during
development. Lecithotrophic S. benedicti post-release larvae contained the greatest concentrations of halometabolites (71.1 ± 10.6 ng mm−3) of all S. benedicti life stages and developmental types examined, while the amount was significantly lower in new recruits (34.0 ± 15.4 ng mm−3). This pattern is consistent with a previously proposed hypothesis suggesting a strategy of reducing potential autotoxicity
during developmental transitions. Pre-release lecithotrophic larvae of Capitella sp. I contained the highest concentration of total halogenated metabolites (1150 ± 681 ng mm−3), whereas the adults contained significantly lower total amounts (126 ± 68 ng mm−3). All concentrations of these haloaromatics are above those known to deter predation in previously conducted laboratory and
field trials. As a means of conferring higher larval survivorship, lecithotrophic females of both species examined may be
expending more energy on chemical defenses than their planktotrophic counterparts by supplying their lecithotrophic embryos
with more of these compounds, their precursors, or with energy for their synthesis. This strategy appears common among marine
lecithotrophic larval forms.
Received: 14 July 1999 / Accepted: 20 January 2000 相似文献
19.
Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa 总被引:1,自引:0,他引:1
Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminifer Orbulina universa and its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2 and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2 concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured
at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness
decreased the O2 concentration at the shell surface to <70% of the oxygen content in the surrounding air-saturated water. The pH at the shell
surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2 h−1 foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2 h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2 h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2 h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross
photosynthesis versus scalar irradiance curves (P vs E
o curves) showed light saturation irradiances (E
k) of 75 and 137 μmol photons m−2 s−1 in two O. universa specimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2 s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2 s−1. Radial profile measurements of scalar irradiance (E
o) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (E
d).
Received: 26 January 1998 / Accepted: 11 April 1998 相似文献
20.
Zooplankton responses to hypoxia: behavioral patterns and survival of three species of calanoid copepods 总被引:2,自引:0,他引:2
Seasonally recurrent and persistent hypoxic events in semi-enclosed coastal waters are characterized by bottom-water dissolved
oxygen (d.o.) concentrations of < 2.0 ml l−1. Shifts in the distribution patterns of zooplankters in association with these events have been documented, but the mechanisms
responsible for these shifts have not been investigated. This study assessed interspecific differences in responses to hypoxia
by several species of calanoid copepods common off Turkey Point, Florida, USA: Labidocera aestiva (Wheeler) (a summer/fall species), Acartia tonsa (Dana) (a ubiquitous year-round species), and Centropages hamatus (Lilljeborg) (a winter/spring species). Under conditions of moderate to severe hypoxia 24-h survival experiments were conducted
for adults and nauplii of these species from August 1994 to October 1995. Experiments on adults used a flow-through system
to maintain constant d.o. concentrations. Adults of A. tonsa showed no decline in survival with d.o. as low as 1.0 ml l−1, sharp declines in survival at d.o. = 0.9 to 0.6 ml l−1, and 100% mortality with d.o. = 0.5 ml l−1. Adults of L. aestiva and C. hamatus were more sensitive to oxygen depletion: both species experienced significant decreases in survival for d.o. = 1.0 ml l−1. Nauplii of L. aestiva and A. tonsa showed no significant mortality with d.o. = 1.1 to 1.5 ml␣l−1 and d.o. = 0.24 to 0.5 ml l−1, respectively. In addition, experiments investigating behavioral avoidance of moderate to severe hypoxia were carried out
for adults of all three species. None of the three species effectively avoided either severely hypoxic (d.o. < 0.5 ml l−1) or moderately hypoxic (d.o. ≈ 1.0 ml l−1) bottom layers in stratified columns. These results suggest that in␣nearshore areas where development of zones of d.o. < 1.0 ml
l−1 may be sudden, widespread, or unpredictable, patterns of reduced copepod abundance in bottom waters may be due primarily
to mortality rather than avoidance.
Received: 31 August 1996 / Accepted: 24 September 1996 相似文献