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1.
Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) 总被引:7,自引:0,他引:7
To elucidate roles of cysts in occurrences of Heterosigma akashiwo blooms, cyst dynamics were studied in northern Hiroshima Bay, the Seto Inland Sea of Japan, where H. akashiwo regularly forms red tide in June. Monthly measurements of seasonal changes in the densities of vegetative cells of H. akashiwo and their germinable cysts in surface sediments (top 1-cm layer) were made for 2 years at three stations. Vegetative cells
of H. akashiwo could be detected from April through December throughout the water column, and the existence of vegetative cells was confirmed
in surface waters even in winter after incubation of sampled seawater in culture medium. Germinable cysts, enumerated by the
extinction dilution method, existed in sediments in all seasons, even before and after the seasonal bloom. The effects of
incubation temperature on the germination of natural cysts of H. akashiwo in sediments were examined. Germination was not observed at 5 °C, was low at 10 °C, while it increased at 15 °C, and maintained
a high level to 25 °C. The bottom water temperature reached 15 °C (suitable for the germination of cysts) and the surface
about 18 °C or more (suitable for the growth of vegetative cells) 2 to 3 weeks before the blooms. The dark survival of H. akashiwo cysts was tested, and it was found that the cysts were viable for at least 650 d at 11 °C, and for 165 d at 25 °C, indicating
a significant role of cysts in the survival during winter and summer seasons. The cysts presumably also play an important
role in seeding primary populations into water columns when the bottom water reaches a suitable temperature (around 15 °C);
thereafter the populations develop with great annual regularity to bloom in June. These results suggest that initiation of
H. akashiwo red tides in the Seto Inland Sea could be triggered by bottom water temperature.
Received: 3 July 1998 / Accepted: 12 January 1999 相似文献
2.
The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time
these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained
in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the
majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning.
Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential
for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species
studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced
and relatively isolated.
Received: 27 May 1997 / Accepted: 27 November 1997 相似文献
3.
The morphology and ultrastructure of the otolith settlement-mark was examined in 44 tropical reef-fish species spanning nine
families. A classification scheme based on similar otolith characteristics is presented. Three major categories are identified
based on changes in increment width and optical qualities of the settlement-mark. Of the 44 species examined, 39 possessed
“abrupt” settlement-marks (Type I) characterised by a rapid decrease in increment width (up to 50% reduction) over settlement.
Type I settlement-marks were found in all nine families examined. The 39 species spanned the whole range of possible larval
durations (Pomacentrus moluccensis, 15 d ± 0 SE; Naso hexacanthus, 91.2 d ± 2.97 SE). Four of the 44 species possessed “zonal” settlement-marks (Type II), featuring a band of increments that
are wider than pre-settlement increments. Species in this category are the labrids Corisaygula, Thalassoma bifasciatum, T. lunare and an unidentified acanthurid (Acanthurus sp. 2). One species of acanthurid (N. brevirostris) possessed a “gradual” settlement-mark (Type III), manifest as a gradual decrease in increment width during the settlement
period. A possible fourth type was identified from the literature. Gnatholepis thompsoni and Coryphopterus glaucofraenum possessed a settlement-mark with increment widths that increased post-settlement. Available data suggest a poor relationship
between the structure of the settlement-mark and the magnitude of metamorphosis (previously reported as internal and external
morphological change). Evidence suggests that the increment profile over early development and the increment transitions associated
with the settlement event are taxon-specific and may enable late-larval stage fishes to be identified to species level.
Received: 21 May 1997 / Accepted: 3 February 1999 相似文献
4.
Differential increment-deposition rate in embryonic statoliths of the loliginid squid Loligo vulgaris 总被引:2,自引:0,他引:2
R. Villanueva 《Marine Biology》2000,137(1):161-168
Apart from one study that reported growth of less than one increment per day in statoliths of the squid Alloteuthis subulata, most studies so far have presumed that one increment was laid down per day in the statoliths of the squid species they examined.
The present study provides evidence of differential daily growth rates in embryonic statoliths of the squid Loligo vulgaris Lamarck, 1798, thus confirming a previous report for A. subulata. Incremental growth rates of L. vulgaris statoliths differ as a function of temperature. Squid embryos were incubated in the laboratory at three temperatures (12.0,
15.5 and 21.1 °C), and tetracycline staining was used to follow statolith growth. This growth slowed in squid exposed to the
lowest temperature, but recovered when the squid were returned to warm conditions, indicating statolith adaptation. Statolith
growth rate after incubation at 12 °C was 1.3% d−1 and reached 6.1% d−1 for squids exposed to 21.1 °C. Statoliths from embryos incubated at 15.5 °C yielded a rate of 1 increment d−1 and a mean daily growth of 2.2 μm in the dorsal dome area of the statolith. In contrast, the slow growth of statoliths incubated
at 12 °C yielded a mean daily growth of only 0.9 μm in the dorsal dome and the readings resulted in a less-than-daily increment-deposition
rate.
Received: 9 October 1999 / Accepted: 30 March 2000 相似文献
5.
This study investigates the reproductive periodicity and reproductive output of the seagrass Zostera novazelandica on two intertidal reefs. Peak numbers of flowering shoots occurred during March (late summer) of two years at both sites
and no flowering shoots occurred during the winter months of July to September. There were greater numbers of flowering shoots
in seagrass patches in the low intertidal zone (up to an average of 55 per 0.1 m2) compared to the middle (up to 20 per 0.1 m2) and upper (up to 9 per 0.1 m2) zones, and about three times greater reproductive output in patches associated with tidepools compared to those not bordering
tidepools. The average number of inflorescences per shoot was 3.1 (±0.25) at one site vs 1.2 (±0.08) at the other, and showed
a progressive decrease from the lower shore to the upper shore. Patches associated with tidepools had twice the number of
inflorescences per shoot (2.8 ± 0.24) than patches not bordering tidepools (1.5 ± 0.16). The number of flowering shoots was
highly correlated with leaf width, leaf length, and ramet density, while the leaf-area index decreased from the lower shore
to the upper shore. The reproductive effort of plants, as measured by the percent biomass invested in flowering shoots during
peak reproduction, was significantly different between sites, tidepool associations, and shore level. For all the variables
measured, there was considerable spatial variation, with significant interaction terms between most factors investigated.
In laboratory experiments, more inflorescences were produced at light intensities of 30 and 300 μE m−2 s−1 than at 100 μE m−2 s−1. At a salinity of 17‰, 1.5 × the number of flowers was produced than at 33‰, while none was formed at 70‰. Plants cultured
at 5 °C had about three times the number of inflorescences than those at 15 °C, while none was formed at 25 °C.
Received: 25 June 1997 / Accepted: 24 September 1997 相似文献
6.
Oxygen transport by the hemocyanin of the protobranch mollusc Solemya reidi Bernard was studied in native hemolymph samples. Clams were collected from two different reducing environments, beneath log
booms in Alberni Inlet, British Columbia, Canada, and from the sewage effulent in Santa Monica Bay, California, USA. The hemocyanin
concentration in a pooled hemolymph sample (n = 10 individuals) was 33.5 mg ml−1. The mean hemolymph pH of five Alberni clams maintained for 3 wk in mud was 7.96 ± 0.06. No significant variation in hemocyanin
oxygen-affinity or cooperativity was found for hemocyanin in whole hemolymph samples from these five individually studied
clams. There was a significant difference only at 15 °C in the oxygen affinity of hemocyanin in pooled whole-hemolymph samples
from S. reidi collected from Alberni Inlet compared with clams collected from Santa Monica Bay. Little effect of temperature on hemocyanin
oxygen-affinity was found for temperatures below 20 °C; above 20 °C, the oxygen affinity was reduced for clams from both sites.
Temperature and pH had no apparent affect on hemocyanin cooperativity. Moderate Bohr shifts were found at all temperatures
examined. The presence of physiologically relevant concentrations of thiosulphate in hemocyanin samples resulted in a decrease
in hemocyanin oxygen-affinity, opposite to the effect on hemocyanin found for the hydrothermal vent crab Byth-ograea thermydron, but thiosulphate had no effect on hemocyanin cooperativity.
Received: 2 September 1997 / Accepted: 6 February 1998 相似文献
7.
Cell growth of a coastal marine diatom, Chaetoceros sociale, in the presence of different premixed organic-Fe(III) complexes [EDTA-Fe(III) (100:1 and 2:1), citric-Fe(III) (100:1) and
fulvic-Fe(III) (0.1, 0.2 and 1 ppm C)] and solid amorphous hydrous ferric oxide [am-Fe(III) or Fe(III) hydroxide] were experimentally
measured in culture experiments at 10 °C under 3000 lux fluorescent light. Fulvic-Fe(III) (0.1 and 0.2 ppm C) and citric-Fe(III)
(100:1) induced maximal cell yields of C. sociale. The order of cell yields was: fulvic-Fe(III) (0.1 and 0.2 ppm C) ≥ citric-Fe(III) (100:1) > EDTA-Fe(III) (2:1) ≫ solid am-Fe(III) > EDTA-Fe(III)
(100:1) ≫ fulvic-Fe(III) (1 ppm C). The short-term iron uptake rates by C. sociale in fulvic-Fe(III) (0.1 and 0.2 ppm C) and citric-Fe(III) (100:1) media were about five to six times faster than those in
EDTA-Fe(III) (100:1) and solid am-Fe(III) media. The dissociative precipitation rates of premixed organic-Fe(III) complexes
in seawater at 10 °C were determined by simple filtration (0.025 μm) involving γ-activity measurements of 59Fe. The order of estimated initial Fe(III) dissociative precipitation rates of these organic-Fe(III) complexes in seawater
were nearly consistent with those of cell yields in the culture experiments and short-term iron uptake rates by C. sociale [except for fulvic-Fe(III) (1 ppm C) medium]. In fulvic-Fe(III) (0.1 and 0.2 ppm C), citric-Fe(III) (100:1) and EDTA-Fe(III)
(2:1) media, the concentrations of dissolved organic-Fe(III) complexes in initial culture experiments are prone to supersaturate
under the culture conditions. The supersaturated dissolved organic-Fe(III) complex in seawater supplies biologically available
inorganic Fe(III) species in culture media through its dissociation at high pH and high levels of seawater cations. Therefore,
the natural dissolved organic-Fe(III) complexes supplied by riverine input may play an important role in supplying bioavailable
iron in estuarine mixing system and coastal waters.
Received: 6 September 1998 / Accepted: 8 April 1999 相似文献
8.
Abundance and temporal distribution of viable (able to germinate) resting stage cells of planktonic diatoms in bottom sediments
have been investigated almost monthly during 1989 to 1992 in Hiroshima Bay, western part of Seto Inland Sea, Japan. The abundance
of viable resting stages in bottom sediments was enumerated with the extinction dilution method (most probable number method,
MPN). In bottom sediments of Hiroshima Bay, dominantly distributed species and/ or genera of the diatom resting stages were
Skeletonema costatum, Chaetoceros spp. and Thalassiosira spp. Viable resting stages of these diatoms were densely distributed on the orders of 103 to 106 (MPN g−1 wet sediments), and persisted in bottom sediments throughout the investigation period. Conversely, vegetative cells of these
diatoms fluctuated remarkably in the water column and disappeared sporadically. Survival of the resting stages in a collected
sediment sample was also determined with the MPN method, at different storage temperatures (5, 10, 15, 20, 25 °C). The survival
test demonstrated that the diatom resting stages could survive in the dark for several months or years in sediments. Resting
stages survived longer at the lower storage temperature, and the order of longevity was consistent within three diatoms (Chaetoceros spp. > Thalassiosira spp. > S. costatum) at each storage temperature. The present study suggests that these diatom resting stages in the coastal bottom sediments
could serve as a “seed bank”, analogous to those of terrestrial plants. The seed bank would ensure the survival of diatoms
within highly fluctuating coastal environments, while it would also be the source of sporadic and autochthonous diatom blooms
in coastal waters.
Received: 29 November 1996 / Accepted: 16 December 1996 相似文献
9.
Environmental preferences of yellowfin tuna (Thunnus albacares) at the northern extent of its range 总被引:5,自引:0,他引:5
B. A. Block J. E. Keen B. Castillo H. Dewar E. V. Freund D. J. Marcinek R. W. Brill C. Farwell 《Marine Biology》1997,130(1):119-132
We used acoustic telemetry to examine the small-scale movement patterns of yellowfin tuna (Thunnus albacares) in the California Bight at the northern extent of their range. Oceanographic profiles of temperature, oxygen, currents and
fluorometry were used to determine the relationship between movements and environmental features. Three yellowfin tuna (8
to 16 kg) were tracked for 2 to 3 d. All three fish spent the majority of their time above the thermocline (18 to 45 m in
depth) in water temperatures >17.5 °C. In the California Bight, yellowfin tuna have a limited vertical distribution due to
the restriction imposed by temperature. The three fish made periodic short dives below the thermocline (60 to 80 m), encountering
cooler temperatures (>11 °C). When swimming in northern latitudes, the depth of the mixed layer largely defines the spatial
distribution of yellowfin tuna within the water column. Yellowfin prefer to spend most of their time just above the top of
the thermocline. Oxygen profiles indicated that the tunas encountered oceanic water masses that ranged most often from 6.8
to 8.6 mg O2 l−1, indicating no limitation due to oxygen concentrations. The yellowfin tuna traveled at speeds ranging from 0.46 to 0.90 m
s−1 (0.9 to 1.8 knots h−1) and frequently exhibited an oscillatory diving pattern previously suggested to be a possible strategy for conserving energy
during swimming.
Received: 14 February 1997 / Accepted: 14 April 1997 相似文献
10.
Survival, developmental and consumption rate (Artemia nauplii ingested per day) as well as predation efficiency (ingested per available Artemia nauplii) were studied during the larval development of the shallow-water burrowing thalassinid Callianassa tyrrhena (Petagna, 1792), which exhibits an abbreviated type of development with only two zoeal stages and a megalopa. The larvae,
hatched from berried females from S. Euboikos Bay (Aegean Sea, Greece), were reared at 10 temperature–food density combinations
(19 and 24 °C; 0, 2, 4, 8 and 16 Artemia nauplii d−1). Enhanced starvation resistance was evident: 92 and 58% of starved zoeas I molted to zoea II, while metamorphosis to megalopa
was achieved by 76 and 42% of the hatched zoeas at 19 and 24 °C, respectively. The duration of both zoeal stages was affected
by temperature, food density and their interaction. Nevertheless, starvation showed different effects at the two temperatures:
compared to the fed shrimp, the starved zoeae exhibited accelerated development at 19 °C (8.4 d) but delayed metamorphosis
at 24 °C (5.9 d). On the other hand, both zoeal stages were able to consume food at an increased rate as food density and
temperature increased. Predation efficiency also increased with temperature, but never exceeded 0.6. Facultative lecithotrophy,
more pronounced during the first zoeal stage of C.tyrrhena, can be regarded as an adaptation of a species whose larvae can respond physiologically to the different temperature–food
density combinations encountered in the wide geographical range of their natural habitat.
Received: 28 February 1998 / Accepted: 21 October 1998 相似文献
11.
The accumulation of lipofuscin, which is an indictor of physiological age, in the brain of juvenile European lobster (Homarus gammarus L.) was monitored for 22 mo in three experimental temperature regimes that simulated seasonal variation in temperature in
the geographic range of this species. Metabolic rate responses to changes in temperature were estimated by measuring the activity
of the electron transport system (ETS) in muscle tissue and in vivo rates of oxygen consumption. Lipofuscin accumulation oscillated
with simulated seasonal changes in temperature and was described by seasonalised von Bertalanffy growth functions. The incremental
accumulation in lipofuscin between sampling dates was linearly related to the number of degree days that accumulated between
dates, irrespective of the amplitude of temperature fluctuation that had occurred. ETS activity increased with acclimation
temperature and was modelled using a polynomial function. This indicated a lower temperature sensitivity in the temperature
mid-range (12 to 16 °C), although the Q10 for this mid-range was 2.1. ETS activity in lobsters acclimated to 8 and 18 °C and assayed at 13 °C was similar, indicating
no compensation for changes in environmental temperature. Oxygen consumption rate was significantly higher at 14 °C than at
10.5 °C and had a Q10 of 3.6, again suggesting no compensation to temperature change. The absence of metabolic compensation in response to temperature
change in H. gammarus is consistent with the predictability of changes in temperature and food availability in the sub-littoral environment of
this species. As lipofuscin accumulates according to metabolic rate, and metabolic rate in H. gammarus is directly correlated with temperature, geographic differences and long-term temporal trends in temperature will need to
be considered when converting physiological age indices, obtained from lipofuscin estimates, to a chronological scale.
Received: 27 April 2000 / Accepted: 21 July 2000 相似文献
12.
To assess the effects of both temperature and food ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), individuals collected December 1996 (winter experiment) and June 1997 (summer experiment) were maintained
for 3 months in one of four experimental treatments: (1) 3 °C and fed ad libitum (high ration), (2) 3 °C and fed one-seventh of the maximum ration (low ration), and (3) 12 °C and fed the high ration; (4) 12 °C and fed
the low ration. All individuals were fed an artificial diet and exposed to only 1 h of light every day. At the end of both
experiments, mean gonad indices of sea urchins fed the high ration had increased significantly (11–24% and 6–19% in the winter
and summer experiments, respectively), while the gonad indices of individuals fed the low ration did not change. At the high
ration (both experiments), the increase in gonad index of sea urchins occurred primarily as the result of a significant increase
in the mass of nutritive phagocytes, as revealed by histological analyses. Primary oocytes were significantly larger in individuals
held at 3 °C than at 12 °C throughout the winter experiment, regardless of food ration; during the summer experiment, primary
oocytes were significantly larger in individuals receiving the high ration, regardless of the temperature at which they were
held. These results suggest that: (1) food availability is the most important factor regulating energy storage and the relative
size of gonads throughout the year, (2) temperature affects the rate of growth and maturation of primary oocytes during the
later stages of oogenesis, and (3) once gametogenesis has been initiated, mature ova will be produced, even under conditions
of low food availability. Conditions of high food availability in summer and low temperature in winter would thus favor reproductive
output in sea urchin populations.
Received: 1 March 2000 / Accepted: 4 October 2000 相似文献
13.
The diet of juvenile pink shrimp (Farfantepenaeus duorarum Burkenroad, previously Penaeus duorarum) from Long Key Bight, Florida Keys, was studied using stomach content examination, pigment measurements, and stable isotope
(δ13C and δ15N) analysis. Samples were taken over approximately 24 h on four occasions from December 1997 to June 1998. Juvenile F. duorarum fed nocturnally, the main prey being the seagrass shrimp Thor floridanus (Decapoda: Caridea: Hippolytidae), which accounted for 34% of the stomach content volume. Other common components of the
diet were bivalves (mainly Tellina sp.) with 15% volume, calcareous algae (8%), plant detritus (5%), copepods (3%), and seagrass fragments (2%). Pigment concentrations
(chlorophyll a plus phaeopigments) in F. duorarum stomachs ranged from 7 to 73 mg l−1 or 40 to 310 ng stomach−1. The exponential gastric evacuation rate was determined experimentally at 1.3 ± 0.5 h−1. Daily rations (in percent body weight) calculated from time series of stomach fullness ranged between 11 and 16% d−1. Total consumption by the population (in wet weight) ranged between 0.05 and 0.3 g m−2 d−1. Stable isotope measurements confirmed that T. floridanus was the main food source for F. duorarum. δ13C-values of whole animals of both species were identical at −10.0 ± 1.6‰ PDB. δ15N-values of both species were also not significantly different (pooled mean: 5.9 ± 1.7‰). Stomach contents of wild-caught
F. duorarum and stomach contents of F. duorarum fed T. floridanus also showed similar stable isotope values.
Received: 12 August 1999 / Accepted: 21 March 2000 相似文献
14.
The euryhaline mysid Neomysis integer (Peracarida: Mysidacea) is a common member of the hyperbenthos of the upper reaches of European estuaries. In the East Looe
River Estuary (Cornwall, England), this species experiences extensive tidal and seasonal changes in temperature (3 to 15 °C)
and salinity (1 to 34‰). In this investigation, the effects of temperature (5, 10 and 15 °C) and salinity (1, 10, 20 and 30‰)
on the oxygen consumption of male and female N. integer are reported, and are related to field measurements to identify the adaptive responses of the respiratory physiology to such
a variable environment. The general responses were similar for each sex; however, at any given temperature/salinity combination,
male N. integer consumed more oxygen than females. The general trends were increased oxygen consumption with increasing temperature (Q10 values ranged from ∼1.7 to 2.5) and decreased oxygen consumption with increasing salinity. Temperature and salinity interacted
at high water antagonistically to minimise changes in mysid oxygen-consumption. When related to tidal fluctuations in temperature
and salinity experienced by N. integer inhabiting the East Looe River Estuary, the results reveal how the respiratory physiology of this species is adapted to its
variable environment.
Received: 16 June 1998 / Accepted: 15 December 1998 相似文献
15.
The contents of free amino acids (FAA) and total protein, together with growth and gut-content, of turbot (Scophthalmus maximus L.) larvae reared at 14, 18 and 22 °C were studied from first-feeding to approximately 140 effective day-degrees post hatch
(Deff
∘). Artemia franciscana nauplii and two species of rotifers were used as prey. Protein content accounted for about 42 and 26% of dry body mass in
the A. franciscana nauplii and the rotifers, respectively. The FAA pool constituted 5.6 and 4.8% of the total amino acids in the same animals.
The dry body mass of turbot larvae was exponentially related to Deff
∘. Protein and FAA contents were linearly related to dry body mass, and were independent of rearing temperature between 14
and 18 °C. At the end of the experiment, however, turbot larvae at 22 °C had lower gut content values, retarded growth rates,
and decreased FAA contents and concentrations. Thus, at this high temperature, turbot larvae seem unable to catch and ingest
sufficient prey, or to sustain an amino acid assimilation rate from the intestine sufficient to meet metabolic demands.
Received: 2 January 1997 / Accepted: 25 September 1998 相似文献
16.
The cosmopolitan polychaete Capitella capitata, known as a complex of opportunistic sibling species, usually dominates the macrobenthos of polluted or unpredictable environments.
A population of C. capitata, termed Capitella sp. M, was found in a shallow water hydrothermal vent area south of Milos (Greece). Here, this population occurs close to
vent outlets (termed the “transition zone”), an environment with steep gradients of temperature, salinity and pH and increased
sulphide concentrations of up to 710 μM. The field distribution of C. capitata in relation to sulphide concentrations around the vent outlets was investigated and sulphide tolerance experiments were conducted
on laboratory-cultured worms to elucidate possible adaptations of Capitella sp. M to these extreme environmental conditions. In order to investigate whether the population from the Milos hydrothermal
vent area can be considered a distinct sibling species within the C. capitata complex, crossbreeding experiments and analysis of general protein patterns were conducted with Capitella sp. M and three other C. capitata populations of different ecological ranges. Capitella sp. M showed high resistance (median survival time: 107 ± 38 h) to anoxia plus high sulphide concentrations of 740 μM. It seems that the ability to survive high-sulphide conditions in combination with reduced interspecific competition enables
the polychaete to maintain a continuous population in this rigorous habitat. From the extremely high tolerance to anoxia and
sulphide, shown in both the crossbreeding experiments and the analysis of total proteins, it can be concluded that Capitella sp. M from the Milos hydrothermal vent area represents a separate sibling species within the C. capitata complex.
Received: 3 March 1997 / Accepted: 12 September 1997 相似文献
17.
An experiment under laboratory conditions was conducted to test the hypothesis that development and growth of copepodite
stages in Calanus chilensis are temperature-dependent and not subject to food shortage in the upwelling area of the Humboldt Current, northern Chile.
Field data obtained from June 1994 to May 1995 in Bahía Mejillones (23°S) were used to define four combinations of temperature
and food under which copepodites were reared from Stage CIII to adulthood. The high temperature was 18.1 °C and the low temperature
13.1 °C, whereas the high food level was in the range of 6.8 to 24.8 μg l−1 chlorophyll a and the low level 1.0 to 6.8 μg l−1 chlorophyll a. As food a mixture of three unknown species of phytoflagellates and the diatom Navicula cryptocephala was used. This phytoplankton was initially obtained from the same sampling sites as copepods and kept in f/2 media at stable levels and composition throughout the experiment. The development rate (1/t), estimated from the time (t) elapsing between Stage CIV and adult, was significantly affected by both temperature and food, although low-food effects
were much more remarkable. Low-food conditions also significantly reduced body length and “structural” (lipid-discounted)
body mass at adulthood, while temperature only affected body length. The weight-specific growth rate was also affected by
food and temperature, but again food effects were much more drastic. The results indicate that C. chilensis is a highly sensitive species to lack of food, and is possibly subject to food shortage during its annual cycle in the coastal
upwelling area of northern Chile. Food limitation may help explain the seasonal pattern of adult size reported by previous
studies in the area and the lack of consistence between the number of generations predictable from a temperature-dependent
model and that observed in the field during the annual cycle.
Received: 10 September 1996 / Accepted: 29 October 1996 相似文献
18.
Need and nestmates affect begging in tree swallows 总被引:3,自引:0,他引:3
We conducted an experiment on nestling tree swallows (Tachycineta bicolor) to examine predictions from signalling models for the evolution of conspicuous begging behaviour. Specifically, we examined
the relationship between (1) nestling begging intensity and hunger, (2) begging intensity and parental provisioning and (3)
begging intensity and nestmate condition. Forty broods of 9-day-old nestlings were removed from their nests for 1 h and assigned
to one of the following three treatments: (1) all nestlings in the brood deprived of food (n = 13), (2) all nestlings in the brood fed (n = 11) or (3) half the nestlings in the brood deprived and half fed (n = 16). Videotapes before and after the treatments showed that begging intensity increased in broods in which all of the nestlings
had been deprived and decreased in broods in which all of the nestlings had been fed. Deprived nestlings in the half-and-half
treatment did not change their begging intensity in response to treatment, while fed nestlings in this treatment group showed
a decrease in begging intensity. Parent tree swallows increased their feeding rate to deprived broods and decreased their
rate to fed broods. Within broods, parents decreased their feeding rate to fed nestlings, but showed no significant change
in feeding to deprived nestlings. Our results suggest that begging intensity is influenced by hunger and that parents appear
to respond to variation in begging intensity. The begging of nestmates also appears to influence begging independently of
need. These results are consistent with predictions derived from signalling models of begging.
Received: 20 June 1997 / Accepted after revision: 19 January 1998 相似文献
19.
Three marine diatoms Lauderia annulata Cleve, Odontella sinensis (Greville) Grunow and Thalassiosira rotula Meunier were exposed to ultraviolet (UV) radiation of different wavebands under controlled laboratory conditions (0.035 vol%
CO2, 18 °C). Several changes in the patterns of pigments in these organisms were seen depending on the waveband of UV radiation
and species examined. UV-B and UV-B plus UV-A radiation led to a reduction in the overall pigment content of all three diatoms.
The uptake of 15N-ammonium was less affected by 5-h UV-A (WG 320) but significantly reduced after UV-B and UV-B plus UV-A exposure. The pattern
of free amino acid pools varied depending on the applied UV wavebands and the tested diatom. The main protein-bound amino
acids of T. rotula decreased after 5-h UV irradiance except leucine. Contents of adenosine 5′-mono-, di-, and triphosphate (AMP, ADP and ATP)
were affected differently by UV radiation; ATP values increased at the end of UV-B and UV-B plus UV-A exposure. These results
have been discussed with reference to the impact of the different UV sources and the influence on the nitrogen metabolism
in connection to pigments and supply with energy.
Received: 13 May 1997 / Accepted: 11 October 1997 相似文献
20.
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