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1.
Suspension-feeding molluscs are important members of coastal communities and a large body of literature focuses on their feeding
processes, including the efficiency of particle capture. Some molluscs, such as bivalves, capture individual picoplankton
cells (0.2–2.0 μm) with a retention efficiency of less than 50%, leading to the assumption that such particles are not an
important food resource. Picoplankton, however, are often concentrated in particle aggregates of much larger size. This study
investigates the ability of suspension feeders to ingest picoplankton-size particles (0.2–2.0 μm) bound in marine aggregates.
We fed clams (Mercenaria mercenaria), mussels (Mytilus edulis), oysters (Crassostrea virginica), scallops (Argopecten irradians) and slipper snails (Crepidula fornicata) 1.0- and 0.5-μm fluorescent particles (either polystyrene beads or bacteria) that were (1) dispersed in seawater, or (2)
embedded within laboratory-made aggregates. Dispersed 10-μm beads were also delivered so that feeding activity could be determined.
Ingested fluorescent particles were recovered in feces or isolated digestive glands and quantified. Results indicate that
aggregates significantly enhance the ingestion of 1.0- and 0.5-μm beads by all species of bivalves, and enhance the ingestion
of bacteria (greatest cell dimension ca. 0.6 μm) by all suspension feeders examined. Differences among species in their ability
to ingest aggregates and picoplankton-size particles, however, were evident. Compared to mussels and clams, scallops and oysters
ingested fewer aggregates with 1.0-μm beads or bacteria, and slipper snails ingested the most dispersed beads and bacteria.
These differences may be a consequence of variations in gill structure and mechanisms of particle processing. Our data demonstrate
that suspension feeders can ingest picoplankton-size particles that are embedded within aggregates, and suggest that such
constituent particles may be an important food resource. 相似文献
2.
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
3.
Laboratory culture experiments were performed to study the changes in size-fractionated Fe concentrations during the growth
of the oceanic diatom Chaetoceros sp. Fe concentration was estimated for three size fractions: large labile particles (>0.2 μm), small colloidal particles
(0.2 μm to 200 kDa) and soluble species (<200 kDa). The size-fractionated Fe concentration in the nutrient-enriched filtered
seawater medium without diatom cells became stable within 4 d after the spike of FeCl3 solution. Light irradiation by white fluorescent tubes with a 14 h light:10 h dark cycle did not significantly alter concentrations
of the size-fractionated Fe. For the phytoplankton culture experiment, Fe-starved diatom cells were inoculated into the nutrient-enriched
media aged for 19 d after the addition of FeCl3. With the growth of diatom cells, total acid-labile Fe concentrations decreased from 0.60 to 0.46 nM during 7 d of incubation. However, only the concentration of the small colloidal particles showed a significant decrease;
the concentration of the other size fractions remained relatively constant. Although the media still contained sufficient
amounts Fe as large labile particles and soluble species, diatom cells appeared to be Fe-limited once Fe as small colloidal
particles had been used up. These results suggest that Fe in the small colloidal particle fraction was the most dynamic size
fraction during the growth of the diatom Chaetoceros sp. In addition, to better understand Fe dynamics in the ocean, we must consider the influence of phytoplankton growth on
small colloidal Fe [which is typically included in the dissolved Fe fraction (<0.2 μm)].
Received: 9 December 1999 / Accepted: 5 May 2000 相似文献
4.
D. Raby M. Mingelbier J. J. Dodson B. Klein Y. Lagadeuc L. Legendre 《Marine Biology》1997,127(4):665-672
Epifluorescence microscopy was used to analyze the stomach contents of bivalve larvae collected in the Baie des Chaleurs
(western Gulf of St. Lawrence, Canada) in order to document food-particle sizes, compare feeding among taxa, and compare the
diet with the in situ phytoplankton community. Stomach contents were mainly composed of small autotrophic flagellates (<5
μm) and cyanobacteria (<2 μm), reflecting the microbial food web which characterizes these waters. More than half (55%) of
all veligers examined contained algal cells of 5 to 15 μm, whereas only 3% had cells of 15 to 25 μm. Differences in the size
ranges of ingested algal cells among similar-sized larvae of different species suggests that veligers actively selected food
particles. Among the smallest veligers (185 to 260 μm), scallops (Placopecten magellicanus) and mussels (Mytilus edulis) ingested more <5 μm and 5 to 15 μm algae than clams (Mya arenaria). Among larger veligers (261 to 405 μm), clams contained significantly more <5 μm cells than mussels, whereas mussels contained
significantly more 5 to 15 μm algae than clams. Algal cells of 15 to 25 μm were preferentially ingested by mussel veligers.
Feeding also differed between different-sized veligers within taxa, i.e. the smallest clam veligers ingested fewer of 5 to
15 μm algae than the larger size classes. Mussel veligers ingested significantly more 15 to 25 μm and fewer <5 μm cells as
their size increased. The dominance of ultraplankton in the nearshore waters of Baie des Chaleurs and in the stomach contents
suggests that veliger larvae may be an important export path for carbon produced by small phytoplankton.
Received: 17 July 1996 / Accepted: 20 September 1996 相似文献
5.
The toxicity of fenitrothion was determined in larvae (nauplii, Zoeae 1 to 3, Mysis 1 to 3), postlarvae (PL stages) and juvenile
shrimp (Penaeus japonicus Bate), in two media, seawater (SW) and diluted seawater (DSW) (1100 and 550 mosM kg−1, ≃ 37 and 19‰ S). The effects of fenitrothion on the osmoregulatory capacities (OC) of juveniles were recorded. A gill and
epipodite histopathological study was also conducted. For larvae in seawater, 24 and 48 h LC50s ranged from 32.9 μg l−1 (Zoeae 2) to 10.7 μg l−1 (Mysis 3), and from 3.9 μg l−1 (Zoeae 3) to 2.0 μg l−1 (Mysis 3), respectively; 48 and 96 h LC50s in postlarvae (PL) at the same salinity ranged from 1.8 μg l−1 (PL1) to 0.6 μg l−1 (PL5), and from 0.3 μg l−1 (PL7) to 0.4 μg l−1 (PL15). In juveniles, 96 h LC50s were 0.8 μg l−1 in seawater and 1.5 μg l−1 in diluted seawater. From hatching to juvenile stages, the overall trend was a rapid decrease (from nauplii to PL5–PL7) followed
by a slight increase (from PL7 to PL15 and juveniles) in the shrimp's ability to tolerate the insecticide. In juveniles kept
in seawater and in diluted seawater, fenitrothion decreased the osmoregulatory capacity (OC = difference between the hemolymph
osmotic pressure and the osmotic pressure of the medium) at both lethal and sublethal concentrations. This effect was time-
and dose-dependent. In SW, the decrease in hypo-OC was ˜ 25% at sublethal concentrations and ˜ 35% at the 96 h LC50. In DSW, the decrease in hyper-OC was ˜ 10 to 15% at sublethal concentrations. In SW, shrimp were able to recover their OC
in less than 48 h when transferred to water free of pesticide. In DSW, recovery at 48 h was only possible after exposure to
the lowest tested sublethal concentration. Haemocytic congestions (thrombosis) of the gills, lamellae necrosis and other alterations
of gills and epipodites (breakage of the cuticle, reduction of the hemolymph lacunae) were noted in juveniles exposed to lethal
and sublethal concentrations of fenitrothion.
Received: 7 October 1996 / Accepted: 13 November 1996 相似文献
6.
S. K. Wilson 《Marine Biology》2000,136(3):431-437
An evaluation of the dietary resources available to, and selected by, blennies of the tribe Salariini was used to assess
their trophic status on the Great Barrier Reef. Gut-content analysis of nine species of blennies found detrital aggregates
to be the dominant item ingested. Samples of the dietary resources available to one of these species, Salarias patzneri, were compared biochemically. Of the two main dietary categories (detrital aggregates and filamentous algae), detrital aggregates
were the major resource available, accounting for 53 ± 4.6% (SE) of the organic matter present. The mean C:N values for detrital
aggregates (17.2 ± 0.8) and filamentous algae (20.0 ± 1.8) were very similar, as were protein concentrations (1.8 ± 0.1 and
2.1 ± 0.1 μg mg−1, respectively). However, mean carbohydrate concentrations were much lower in the aggregates than the filamentous algae (19 ± 2
and 76 ± 13 μg mg−1, respectively). Comparison of the inorganic particles ingested to those available indicated that S. patzneri selectively fed on particles <125 μm, (predominantly detrital aggregates) and avoided particles >250 μm, (predominantly algal
filaments). The patterns of resource availability, nutritional quality and selectivity suggest that salariin blennies utilise
detrital aggregates as their primary dietary resource.
Received: 24 May 1999 / Accepted: 29 November 1999 相似文献
7.
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
8.
Suspension feeding by a stalkless crinoid (Oligometra serripinna) was studied at Lizard Island, Australia, in 1985. The crinoids were placed in a laboratory flume with a slow, unidirectional current of seawater. Nutritive and non-nutritive particles (15 to 180 m) were introduced upstream from the crinoid, and feeding behavior was recorded at high magnifications on videotape for frame analysis. These direct observations showed that each intercepted particle (whether a dejellied clam egg, Sephadex bead or latex sphere) contacts a single, evidently adhesive tube foot and is rapidly transferred to the pinnular food groove by a bend of the tube foot. The tube foot bends in about 0.1 s and returns to its extended position in 1 to 2 s. Spheres less than 20 m in diameter cause only the intercepting tube foot to bend. In contrast, larger spheres cause the coordinated bending of the intercepting tube foot plus many of the neighboring tube feet: the stimulus spreads through the reacting group of tube feet at about 1 cm s-1. After transfer to the pinnular food groove, the nutritive particles (dejellied clam eggs) travel at about 1 cm min-1 to the arm axis and thence down the arm food groove at about 4 cm min-1 to the mouth; in contrast, non-nutritive particles (Sephadex beads and latex spheres) are discarded from the pinnular food groove between 1 and 30 s after capture. Tube-foot bending is presumably triggered when arriving particles (whether nutritive or non-nutritive) are detected by sensory cells in the tubefoot epithelium: mechanoreception by itself appears sufficient to initiate bending, although chemoreception may modify the reaction. Then, soon after captured particles have been transferred to the pinnular food groove, the crinoid discards those judged unsuitable (probably by contact chemoreceptors in the food-groove epithelium). Clam eggs with intact jelly layers temporarily hang up on tube feet they contact and then float away in the curent: the jelly evidently interferes with mechanoreception and/or chemoreception by the tube-foot epithelium. Some previous studies of crinoid feeding have suggested that particles are trapped in extensive nets or strands of mucus: we found no evidence for this in O. serripinna, which captures particles predominantly be the direct interception method of the aerosol filtration model. 相似文献
9.
Y. Shrivastava G. G. Mahambre C. T. Achuthankutty B. Fernandes S. C. Goswami M. Madhupratap 《Marine Biology》1999,135(4):663-670
The cladoceran Diaphanosoma celebensis Stingelin is reported on for the first time from Indian waters (Mandovi estuary, Goa). Amictic females were maintained in
the laboratory (temperature 24 ± 1 °C and salinity 17 psu) for three successive generations in order to follow the parthenogenetic
reproductive behaviour, growth, survival and neonate production. The mean life span and body length of adult females in the
three generations showed some variations and ranged from 9 to 12.5 d and 842 to 932 μm, respectively. The mean length of the
neonates produced also varied (283 to 446 μm) in the three generations. Cladoceran preference for three phytoplankton food
sources, i.e. Isochrysis galbana (Parke), Chaetoceros calcitrans (Paulsen) and Tetraselmis gracilis (Kylin), was determined. Growth was faster in the initial stage with all three diets but slowed down in later life. Increased
food concentrations resulted in higher neonate production but reduced the life span of females. However, long-term feeding
experiments revealed that the percentage survival was high with I. galbana and low with C. calcitrans.
Received: 23 June 1999 / Accepted: 20 September 1999 相似文献
10.
Life history of Gonatus onyx (Cephalopoda: Teuthoidea): deep-sea spawning and post-spawning egg care
A reproductive strategy consisting of deep- water spawning and egg-care was inferred for the midwater squid Gonatus onyx Young, 1972. Brooding females and associated eggs and hatchlings, captured between 1250 and 1750 m depth off southern California,
are described. Brooding females appear to be senescent and lack tentacles. Large eggs of this species (3 mm) at cold temperatures
(3 °C at capture depth) may require as long as 9 mo to develop. The high lipid content of the digestive gland in adult females
of this species may provide fuel to support such an extended “brooding” period.
Received: 22 February 1999 / Accepted: 25 May 2000 相似文献
11.
Feeding, metabolism and growth in the Antarctic limpet, Nacella concinna (Strebel 1908) 总被引:2,自引:0,他引:2
Post-prandial increases in metabolism, the specific dynamic action of feeding (SDA), were evaluated in the Antarctic limpet
Nacella concinna. O2 consumption rose to a peak value 2.3 times higher than pre-feeding standard metabolic rates. This peak rise is low for marine
ectotherms, but is typical of polar species. There were three peaks in the SDA, the first lasted only for the 1st day, was
caused by handling, and was minor. The second was the major peak. It lasted from post-prandial days 4–9 inclusive, and accounted
for around 70% of the SDA response. The third peak lasted from day 11 to day 15 and accounted for 30% of the total SDA. A
15-day SDA is much longer than values for temperate species, but is again typical for polar marine ectotherms. NH3 excretion declined post-prandially from around 0.4 μmol animal−1 h−1 to values between 0.025 and 0.223 μmol animal−1 h−1 throughout the SDA. The total O2 consumed in the SDA was 90.2 μmol O2, which converts to 44.7 J of energy. This was 45–50% of the energy consumed in the meal (93.5 J). Pre-feeding O:N ratios,
after 26 days without food, were around 1, indicating protein as the sole metabolic substrate prior to initiating the SDA.
After feeding, O:N ratios rose to between 2.5 and 19, indicating significant use of lipid or carbohydrate from the food. Experiments
were conducted in ambient seawater with enhanced levels of Sr (SrCl added at 800 mg kg−1), and limpets were fed microalgal films also grown in enhanced Sr media. Sr incorporated in the shells during the experiment
allowed the measurement of shell increments deposited during the SDA. Between five and eight microgrowth bands were present
in the Sr-enhanced increments, which was similar to the number of days in the second SDA peak. The mean shell increment laid
down was 17.6 μm. Estimating tissue deposition from measured growth increments and published ash-free dry mass (AFDM) to length
relationships produced a value of 0.81 mg AFDM, which converted to 26.4 J of energy, or 25–30% of the energy ingested in the
meal. Estimates of growth increments associated with a single SDA have not previously been possible. Overall energy used in
the SDA and tissue deposition accounted for 75–80% of the energy ingested; the remainder was probably accounted for by unmeasured
costs such as mucus production.
Received: 6 June 2000 / Accepted: 20 September 2000 相似文献
12.
During commercial handling of Nephropsnorvegicus (L.) there are a number of situations when the prawns may be exposed to very high ambient ammonia levels. These experiments
evaluated the effects of increased levels of ambient total ammonia (TA = NH3 + NH4
+) on␣blood ammonia, ammonia efflux rates and on the cardio-ventilatory performance of N. norvegicus. When prawns were taken from <1 to 2000 μmol TA l−1 medium, blood TA concentrations increased rapidly for the first 2 h but tended to drop thereafter. Original blood TA levels
were restored 6 h after the prawns were transferred back from seawater containing 2000 to <1 μmol TA l−1. Sudden exposure to 500, 1000, 2000 or 4000 μmol TA l−1 medium induced blood TA concentrations to increase respectively to 50, 30, 33 and 36% of external concentrations (normally,
internal TA values are much higher than external levels). Immediately after transfer back to seawater with low ammonia concentration
( <1 μmol TA l−1), excretion rates were higher than those of control prawns, and the absolute amounts of TA excreted were considerably higher
than those calculated to have accumulated in the haemolymph. Heart rate (HR) and scaphognathite rate (SR) were not altered
when prawns were subjected to sudden alterations in ambient ammonia ( <1 to 2000 to <1 μmol TA l−1). When water ammonia concentrations were altered more gradually, both rates increased, but only at 4000 μmol TA l−1. These results show that N. norvegicus is able to remove ammonia from the haemolymph and/or transform ammonia into some other substance when subjected to increased
levels of ambient ammonia. Possible mechanisms involved (e.g. active transport across the gills; storage in some other tissue;
glutamate synthe sis) are discussed.
Received: 20 May 1996 / Accepted: 1 July 1996 相似文献
13.
S. Mayer 《Marine Biology》1994,119(4):571-582
An experimental setup was designed for in situ videotape recording of the particle capture process in the crown of the polychaete Sabella penicillus. Intact individuals of S. penicillus (collected in the Gullmornfjord, Sweden in 1992) were exposed to either 6 m Latex spheres or Rhodomonas sp. flagellate cells (6 m). The capture of the added particles was recorded on video. From frameby-frame analyses particle velocities were estimated and the shape of the three-dimensional particle paths was inferred. The mean velocity of particles approaching the crown was estimated to be ca. 1 mm s-1, increasing to ca. 1.7 mm s-1 in the interpinnule channel. At the moment of capture the particles were seen to follow a curved, near circular path close to the tips of the latero-frontal cilia. The transport velocities on the frontal side of the pinnules and filaments were estimated to be up to 0.15 and 0.5 mm s-1, respectively. Counting captured particles relative to particles arriving within the area of the pinnules gave a rough, direct estimate of nearly 100% retention rate when the polychaete was feeding undisturbed. Together with results from clearance measurements in the literature this implies that the worm is able to capture particles down to 3 m entering the interpinnule channel almost 100% effectively. In view of the 80-m wide interpinnule channel and 40-m spacing between the tips of the latero-frontal cilia on both sides of the channel, this result cannot be explained by mechanisms based solely on direct mechanical contact between cilia and particles but must involve fluid mechanical mechanisms. The present work is the experimental basis for ongoing numerical simulations of the particle motion in the interpinnule channel. 相似文献
14.
Sexuality and cyst formation of the spring-bloom dinoflagellate Scrippsiella hangoei in the coastal northern Baltic Sea 总被引:3,自引:0,他引:3
The temporal sequence and the magnitude of the sexual reproduction and subsequent cyst deposition of the common spring-bloom
dinoflagellate Scrippsiella hangoei (Schiller) Larsen was studied during spring 1996 on the SW coast of Finland, Baltic Sea. The abundances of the different
size of fractions of S. hangoei (14 to 18 μm, 18 to 22 μm and >22 μm) were monitored in the water column, and the deposition of resting cysts was measured
using moored sediment traps. Cyst sedimentation rates were measured throughout the seasonal cycle in order to estimate cyst
resuspension rates for the quantitative assessment of the fraction of population undergoing encystment. The onset of sexual
reproduction, indicated by a significant increase of the small cells (14 to 18 μm) representing gametes, occurred in a nutrient
replete environment well before the exponential growth phase and peak abundances of vegetative cells. Gamete formation was
followed by high abundances of large cells (>22 μm) representing planozygotes, and subsequent sedimentation of resting cysts.
Approximately 60% of the asexually growing bloom population was estimated to form planozygotes, suggesting that encystment
was an important factor in bloom termination and possibly plays a role in the regulation of the magnitude of the bloom. Finally
encystment accounted for 40% of the entire S. hangoei population, resulting in a considerable loss of the bloom population and an input of the vernal phytoplankton biomass to
the benthos.
Received: 11 December 1998 / Accepted: 8 April 1999 相似文献
15.
A. Cornils S. B. Schnack-Schiel M. Böer M. Graeve U. Struck T. Al-Najjar C. Richter 《Marine Biology》2007,151(4):1261-1274
A total of 12 feeding experiments were conducted in the northern Gulf of Aqaba during spring (March/April) and autumn (September/October)
2002 at the Marine Science Station (MSS) in Aqaba. Females of three species of clausocalanids were selected: Clausocalanus
farrani, C. furcatus and Ctenocalanus vanus. Natural occurring particle (NOP) larger than 5 μm were investigated as food source. The ambient chlorophyll a concentration at sampling depth (∼70 m) ranged between 0.15 and 1.00 μg chl a l−1 and NOP concentrations ranged between 1.78 and 14.0 × 103 cells l−1 during the sampling periods. The division of particles into five size classes (5–10, 10–20, 20–50, 50–100 and >100 μm) revealed
that most of the particles were found in the size classes below 50 μm (81–98%), while most of the natural occurring carbon
(NOC) was concentrated in the size classes larger than 20 μm (70–95%). Ingestion rates were food density dependent rather
than size dependent ranging between 0.02 and 1.65 × 103 NOP ind−1 day−1 and 0.01 and 0.41 μg NOC ind−1 day−1, respectively, equivalent to a body carbon (BC) uptake between 0.4 and 51.8% BC day−1. The share of the size classes to the total ingestion resembled in most cases the size class composition of the natural particle
community. 相似文献
16.
Particle size distribution and pollutants in road-deposited sediments in different areas of Zhenjiang,China 总被引:2,自引:0,他引:2
An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant
washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were
collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City,
China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations
of pollutants. The samples are found to consist predominantly of fine particles (60–80%, <250 μm). The maximum mean concentrations
of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in
samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus
(5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest
particle size fraction analysed (63 μm). The organic matter and nitrogen content generally increased with decreasing particle
sizes in the <500-μm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the
finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer
particles (down to 125 μm for TN). 相似文献
17.
Knowing how far away animals can detect food has important consequences for understanding their foraging and social behaviors.
As part of a broader set of field experiments on primate foraging behavior, we set out artificial feeding platforms (90 × 90 cm
or 50 × 50 cm) throughout the home range of one group of 22 brown capuchin monkeys, at sites where they had not seen such
platforms previously. Whenever the group approached such a new platform to within 100 m, we recorded the group's direction
and speed of approach, and the identity and distance from the platform of the group member that detected the platform or came
closest to it without detecting it. We used logistic regression on these data to examine the effects of group movement speed,
platform size and height, and focal individual age and sex on the probability of detecting the platform as a function of distance.
Likelihood of detecting a platform decreased significantly at greater distances – the probability of detecting a platform
reached 0.5 at 41 m from the group's center and 25.5 m from the nearest group member. These results show that detectability
of platforms by the entire group (9 adults, 13 juveniles) was less than twice that for single group members. Detectability
at a given distance decreased severely as the group moved faster; at their fastest speed, individuals had to approach a platform
to within less than 10 m to find it. The large platforms were significantly more likely to be detected than the small ones,
suggesting that increased use of larger food patches by wild primates may not necessarily reflect foraging preferences.
Received: 20 May 1996 / Accepted after revision: 5 April 1997 相似文献
18.
Phytoplankton blooms are strongly impacted by microzooplankton grazing in coastal North Pacific waters 总被引:1,自引:0,他引:1
Phytoplankton growth and microzooplankton grazing were measured in two productive coastal regions of the North Pacific: northern
Puget Sound and the coastal Gulf of Alaska. Rates of phytoplankton growth (range: 0.09–2.69 day−1) and microzooplankton grazing (range: 0.00–2.10 day−1) varied seasonally, with lowest values in late fall and winter, and highest values in spring and summer. Chlorophyll concentrations
also varied widely (0.19–13.65 μg l−1). Large (>8 μm) phytoplankton cells consistently dominated phytoplankton communities under bloom conditions, contributing
on average 65% of total chlorophyll biomass when chlorophyll exceeded 2 μg l−1. Microzooplankton grazing was an important loss process affecting phytoplankton, with grazing rates equivalent to nearly
two-thirds (64%) of growth rates on average. Both small and large phytoplankton cells were consumed, with the ratio of grazing
to growth (g:μ) for the two size classes averaging 0.80 and 0.42, respectively. Perhaps surprisingly, the coupling between microzooplankton
grazing and phytoplankton growth was tighter during phytoplankton blooms than during low biomass periods, with g:μ averaging 0.78 during blooms and 0.49 at other times. This tight coupling may be a result of the high potential growth
and ingestion rates of protist grazers, some of which feed on bloom-forming diatoms and other large phytoplankton. Large ciliates
and Gyrodinium-like dinoflagellates contributed substantially to microzooplankton biomass at diatom bloom stations in the Gulf of Alaska,
and microzooplankton biomass overall was strongly correlated with >8 μm chlorophyll concentrations. Because grazing tended
to be proportionally greater when phytoplankton biomass was high, the absolute amount of chlorophyll consumed by microzooplankton
was often substantial. In nearly two-thirds of the experiments (14/23), more chlorophyll was ingested by microzooplankton
than was available for all other biological and physical loss processes combined. Microzooplankton were important intermediaries
in the transfer of primary production to higher trophic levels in these coastal marine food webs.
Received: 12 November 1999 / Accepted: 4 October 2000 相似文献
19.
B. A. Kerrigan 《Marine Biology》1997,127(3):395-402
The effects of food availability, female size, and social interactions on the quality of Pomacentrus amboinensis larvae at hatching were examined using two field-based experiments. In Experiment 1, food availability and female size significantly
influenced size, eye diameter and levels of yolk reserves of larvae at hatching. Small females (47 to 52 mm standard length,
SL) whose diets were not supplemented, produced the longest larvae (3.0 ± 0.01 mm total length, TL) with the least yolk reserves
(50.1 ± 1.04 μm2). Irrespective of female size, those that received additional food produced larvae with the largest yolk-sacs (large females:
87.60 ± 1.53 μm2; small females: 80.14 ± 1.24 μm2). In Experiment 2, interactions with conspecifics had a greater affect on the somatic development of larvae at hatching than
food availability. Increased social interactions resulted in larvae that were ⋍3% longer, with 2% greater head depth, than
larvae from females that spawned in isolation on the experimental reefs. Fed females produced larvae with ⋍20% more yolk than
larvae from females whose diets were not supplemented. All three factors (food availability, female size, and intensity of
social interactions) tested within these experiments vary spatially and temporally among reefs. There is the potential, therefore,
for larvae at the onset of the planktonic stage to vary in quality, level of development, and probability of survival.
Received: 12 August 1996 / Accepted: 26 August 1996 相似文献
20.
Juvenile squids were grown in individual 2.6-l floating enclosures and were fed either a high- or a low-ration diet of fish
and the crustacean Acetes. Squids were maintained for a maximum of 44 days in two experiments. The high-ration individuals reached a significantly
larger size in both experiments (27, 25.5 mm mean mantle length, ML) compared to their low-ration siblings (19 mm mean ML)
in both experiments. The statolith increment widths prior to the start of the experiment were significantly wider (between
3 and 4 μm) compared to the increment widths after the start of the experiment (between 2 and 3 μm) both for the low- and
the high-ration squids. High-ration squids also had significantly wider increments and larger statoliths than their low-ration
siblings. Even though we detected consistent trends in daily statolith increment widths for the different feeding regimes,
we could not detect variation in increment widths at a daily level of resolution (i.e. as a result of differences in day-to-day
food intake at an individual level). This was probably due to the relatively consistent diet experienced by each individual.
These experiments revealed that ration level influences squid growth rate, statolith size and daily statolith increment width.
Received: 30 March 2000 / Accepted: 30 October 2000 相似文献