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1.
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
2.
Understanding the nutritional requirements of Lytechinus variegatus is essential to define its role in the marine environment and necessary for successful culture of this species. Protein is an essential component for growth, yet the requirements for protein in most marine organisms are not known. Small Lytechinus variegatus (ca. 14 mm diameter, n=160) were collected at St. Joseph Bay, Florida in March 2000. They were held in aquaria and fed ad libitum one of four diets varying in protein concentration (9, 15, 21, or 33% dry weight) for 14 weeks. Diets 21% dry weight protein were sufficient for maximal growth and survivorship. Individuals fed a diet low in protein compensated by consuming higher quantities of food per gram wet weight. However, the protein was insufficient to support maximal growth and survivorship. Total dry matter absorption, protein absorption, and carbohydrate absorption of the prepared feeds were higher than reported for natural diets. Total production and production efficiency was lowest in those fed the low-protein diet. Gonad production occurred in individuals with test diameters smaller than reported previously in field populations and was lowest in those fed the low-protein diet. The acini of both females and males were predominantly composed of nutritive phagocytes, suggesting that growing L. variegatus use the gonad primarily as a nutrient storage organ and not for reproduction. In females the growth rate of oocytes increased with dietary protein. In males, protein concentration 21% resulted in an increase in the volume of germinal epithelium and a decrease in the volume of nutritive phagocytes. The minimal requirement for protein in L. variegatus from approximately 1 g to 15 g total weight is >15% dry weight for the conditions of this experiment. The requirement for a diet >15% protein corroborates with field studies that indicate L. variegatus consumes epibionts and animal tissues preferentially to seagrass, and that the microbial, microfloral, and microfaunal community living on the seagrass may provide the extra protein required for growth and survival of small L. variegatus.Communicated by P.W. Sammarco, Chauvin 相似文献
3.
Green sea urchins, Strongylocentrotus droebachiensis OF Müller, collected off the coast of New Hampshire, USA, in late February 1995, were brought into the laboratory and fed
an artificial diet ad libitum, and subjected to a photoperiod advanced by 4 months. During this study, temperatures and salinities
for experimental urchins mirrored those recorded at the collection site. We examined the effects of changes in feeding regime
and photoperiod on gametogenesis and compared the experimental urchins with those from the source population. During the 7-month
period, experimental urchins showed no detectable changes in mean test height or diameter. Experimental urchins had a significantly
higher gonad index (GI) in March, April and May (18 ± 6%) compared with field urchins in March (11 ± 3%). Subsequently, experimental
urchins had a mean monthly GI of 25 to 30%, while the mean GI for field urchins was 11 to 13%. Gonial cell mitosis and gametogenesis
occurred earlier in experimental male and female urchins compared with field urchins. Stereological and histological observations
and stage–frequency data showed that the ovaries of experimental urchins were large because of the accelerated development
of nutritive phagocytes, the volume fraction (V
v) of which was 89 to 90% of the gonad, while new vitellogenic primary oocytes occupied <1% V
v. In males, stereological and histological observations and stage–frequency data suggested a mobilization of materials from
the nutritive phagocytes beginning between June and August, i.e. earlier than in females, and, by September, new gametes occupied
a V
v of 49 ± 3% of the testes. Oocyte size–frequency distributions demonstrated that most primary oocytes were <80 μm in diameter
between March and September, suggesting that cold temperatures may be needed for completion of vitellogenesis. We describe
changes in the two principal cell types in the germinal epithelium of urchin gonads and indicate how knowledge of their population
dynamics may be useful in aquaculture applications.
Received: 21 February 1997 / Accepted: 3 June 1998 相似文献
4.
To determine the effects food ration and feeding regime on growth and reproduction of Strongylocentrotus droebachiensis (Müller), sea urchins in laboratory aquaria were fed kelp (Laminaria longicruris) supplied at either a high (H, ad libidum daily) or a low (L, ad libidum 1 d wk−1) ration in two successive 12-wk intervals during the reproductive period. After 24 wk, urchins fed the high ration continuously
(HH) or for the last 12 wk only (LH) had a significantly greater mean gonad index [(gonad weight/total body weight) × 100]
and body weight than urchins fed the low ration continuously (LL) or for the last 12 wk only (HL). Urchins in the HL treatment
had a significantly greater gonad index than those in the LL treatment; there was no significant difference in gonad index
between the LH and HH treatments. Females had a greater gonad index than males in the low ration (LL and HL) treatments at
the end of the experiment; there was no significant difference between sexes in the high ration (LH, HH) treatments. Gametogenesis
proceeded to maturation in all treatments and some individuals spawned at the end of the experiment. Females in the high ration
(HH and LH) treatments had a greater proportion of nutritive phagocytes in their ovaries than females in the low ration treatments,
but there was no effect of feeding treatment on oocyte or ovum size. Feeding treatment had no effect on the relative abundance
of nutritive phagocytes in the testes, although the proportion of spermatocytes was higher (and that of spermatozoa lower)
in the high ration than in the low ration treatments. Urchins in the high ration treatments had a lower mean jaw height index
[(jaw height/test diameter) × 100] and greater mean test diameter than those in the low ration treatments at the end of the
experiment, although these differences were not statistically significant. Feeding rate on kelp at the end of the experiment
was significantly greater for urchins in the low ration than in the high ration treatments. Our experimental results show
that even relatively low rations of kelp support somatic and gonadal growth in S. droebachiensis. Increasing the supply of kelp, particularly during the period of active gametogenesis, results in maximal rates of growth
and reproduction. These results suggest that populations of S. droebachiensis in barrens may derive a substantial proportion of their nutrition from drift kelp, which may contribute to their persistence
in these habitats. They also explain the large body size, high reproductive effort and fecundity of urchins grazing on kelp
beds. These findings have important implications for understanding the dynamics of natural populations of S. droebachiensis and for development of effective aquacultural practices.
Received: 17 February 1997 / Accepted: 5 March 1997 相似文献
5.
Effects of food type and ration on reproductive maturation and growth of the sea urchin Strongylocentrotus droebachiensis 总被引:1,自引:0,他引:1
We investigated the effects of food quality and quantity on reproductive maturation and growth of juveniles of Strongylocentrotus droebachiensis (Müller) in a 22 month laboratory experiment in which we fed sea urchins four diets: (1) kelp (Laminaria spp.) for 6 d wk−1 and mussel (Mytilus spp.) flesh for 1 d wk−1 (KM); (2) kelp for 7 d wk−1 (high ration, KH); (3) kelp for 1 d wk−1 (low ration, KL) and (4) no food other than encrusting coralline algae (NF). At their first and second opportunity for reproduction,
all sea urchins in the KM and KH treatments, and most in the KL treatment were reproductively mature, whereas all sea urchins
in the NF treatment remained immature. Gonad index differed significantly among all fed treatments at first and second reproduction,
and was highest in the KM and lowest in the KL treatment. Gonad index was similar in both sexes at first reproduction, but
it was higher in females than in males at second reproduction. Diet had little or no effect on the relative abundance of spermatocytes,
spermatozoa, or nutritive phagocytes in testes at first and second reproduction. In ovaries, nutritive phagocytes were significantly
more abundant in females in the KM and KH treatments than in the KL treatment at first reproduction, and significantly more
abundant in unfed (NF) than fed (KM, KH, KL) females at second reproduction. Mean oocyte size was similar in all fed females
at first reproduction, but significantly larger in fed than unfed females at second reproduction. Mean ovum size was similar
in all fed females in both reproductive periods. Increase in test diameter was greatest in the KM treatment and smallest in
the KL treatment; sea urchins in the NF treatment decreased slightly in size. Survival was 95 to 100% in all fed sea urchins
but significantly lower in unfed ones. The feeding rate on kelp was significantly greater in the KL than the KM and KH treatments.
In the KM treatment, the feeding rate on kelp increased significantly over a 6 d period after mussel flesh was provided. Our
results demonstrate that a diet of high food quality and quantity accelerates reproductive maturation and growth rate, and
enhances gonad production and survival in juvenile and young adult S. droebachiensis. These findings contribute to our understanding of the reproductive ecology of S. droebachiensis in habitats with differing food supplies (e.g., kelp beds and barrens). Our results also can be used to improve aquacultural
practices for sea urchins.
Received: 3 June 1998 / Accepted: 2 February 1999 相似文献
6.
The sea urchin Lytechinus variegatus is capable of surviving chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg l−1, and triethyl phosphate (organic phosphate) concentrations of 1,000 mg l−1. However, chronic exposure to low (0.8 mg l−1 inorganic and 10 mg l−1 organic phosphate), medium (1.6 mg l−1 inorganic and 100 mg l−1 organic phosphate) or high (3.2 mg l−1 inorganic and 1,000 mg l−1 organic phosphate) sublethal concentrations of these phosphates inhibits feeding, fecal production, nutrient absorption and
allocation, growth and righting behavior. Food consumption and fecal production declined significantly in individuals exposed
to medium and high concentrations of inorganic phosphates and all levels of organic phosphates. Feeding absorption efficiencies
for total organics and carbohydrates decreased significantly in individuals held in the highest concentration of organic phosphate.
Feeding absorption efficiencies for lipids were significantly reduced in the highest inorganic phosphate concentration only,
while they decreased significantly for protein with increasing phosphate exposure. Carbohydrate and lipid levels in gonad
and gut tissues decreased significantly with exposure to increasing phosphate concentrations, potentially impairing both gametogenesis
and nutrient storage in the gut. Moreover, gonad indices significantly decreased in individuals exposed to the highest concentrations
of either phosphate. Growth rates decreased significantly under the influence of all phosphate concentrations, while increasing
in seawater alone. Individuals exposed to increasing phosphate concentrations showed reduced righting responses (a measure
of stress) and no acclimation in righting times during chronic exposure to phosphates over a 4 week period. These findings
indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress and be inhibited in their growth and performance
due to reductions in feeding, nutrient absorption and allocation of nutrients to key somatic and reproductive tissues.
Received: 10 April 2000 / Accepted: 2 October 2000 相似文献
7.
Experiments were conducted to determine the effect of four algal diets (Corallina spp., Gelidium pristoides, Ulva rigida and an equal volume mixture of these seaweeds) on growth and reproduction of the South African gastropod Turbo sarmaticus Linnaeus, 1758. The best growth rate of juveniles (up to 13.8 mm shell length and 34.26 g wet body weight increase in 12
months), reproductive fitness of mature specimens (gonad index up to 33%) and energy reserves (up to 4.76 mg glycogen/100 mg
foot tissue) were achieved when T. sarmaticus was fed U. rigida or a mixed diet. In addition, the gonad index of individuals fed these diets was almost twice that of similar-sized field
specimens. Juveniles fed Corallina spp. only, grew very little (only 2.4 mm shell length and 4.23 g wet body weight increase in 12 months). The reproductive
fitness of adults fed on such a diet was also poor (gonad index <4.5%) and energy reserves were low (<3.5 mg glycogen/100 mg
foot tissue). Along the southeastern coast of South Africa, T. sarmaticus has a distinct reproductive cycle with gametogenesis occurring from March/April until August/September, whilst maturity (gonad
index = 15%) was maintained until December, after which spawning occurred until March.
Received: 6 July 1998 / Accepted: 8 March 1999 相似文献
8.
Reproduction of the sea anemone Anthopleura dixoniana (Haddon and Shackleton) from the high intertidal zone of southern Taiwan (120°41 E; 22°01N) was studied from April 1987 through March 1989. A. dixoniana spawns once a year, in July, and divides asexually by longitudinal fission throughout the year, with a peak in July. During the spawning season, sea anemones>3 mm pedal dise diameter can be sexed, and display a 1:1 sex ratio. Dividing sea anemones are significantly larger than non-dividing individuals, and increase in body size before fission. Under laboratory conditions, individuals kept at 28 C and fed had larger oocytes and a higher division rate than those kept at 18, 22, 25 or 32°C or starved. The division rate significantly influenced the oocyte diameter. The present study revealed for the first time, that a long photoperiod (14 h hight:10 h dark) significantly enhances the growth of oocytes in A. dixoniana under laboratory conditions. 相似文献
9.
Influence of cadmium accumulation and dietary status on fatty acid composition in two colour forms of shore crabs, Carcinus maenas 总被引:2,自引:0,他引:2
The effects of cadmium exposure and dietary status on cadmium accumulation, fatty acid (FA) content and profiles were investigated
in two colour forms of the shore crab Carcinus maenas. Groups of shore crabs were either starved or fed with blue mussels, Mytilus edulis, during a 40 d exposure period to 2 or 6 μM Cd2+ (as CdCl2). Starved green individuals accumulated more cadmium in haemolymph and hepatopancreas than did red crabs and green crabs
fed during the experiments. In the red colour form, no difference in cadmium accumulation was observed between starved and
fed individuals. In both colour forms, hepatopancreas contained more FA than gills and muscle. The FAs often present in the
largest amounts in the tissues were 16:0, 16:1ω7, 18:1ω7, 18:1ω9, 20:4ω6, 20:5ω3 and 22:6ω3. However, saturated (SAFA) and
mono-unsaturated fatty acids (MUFAs) were dominant in hepatopancreas, whereas poly-unsaturated fatty acids (PUFAs) were dominant
in gills and muscles. At the beginning of the experiment, the total FA content in the hepatopancreas was 111.6 mg g−1 (dry weight) for red crabs and 78.4 mg g−1 for green shore crabs. During the experiment, however, the FA content decreased in red crabs. This decrease was more pronounced
for starved individuals than for fed individuals. Also, the decrease in FA content was more pronounced in crabs exposed to
6 μM cadmium compared to crabs exposed to 2 μM or crabs not exposed to cadmium. No change in FA content was observed in green shore crabs, irrespective of diet and cadmium
exposure. For both colour forms, no change in FA content was observed for gills and muscle. In red crabs, a decrease was observed
for all FAs in the hepatopancreas. This decrease, however, was more pronounced for SAFAs and MUFAs than for PUFAs, indicating
that the metabolism of FAs during starvation and cadmium exposure is selective. The experiments indicate that green colour
forms of shore crabs are more tolerant of natural stress such as starvation and anthropogenic stress, e.g. cadmium exposure,
than are red colour forms of shore crabs.
Received: 23 September 1999 / Accepted: 29 April 2000 相似文献
10.
Field sampling and laboratory experiments examined whether ultraviolet radiation (UVR) affects the reproduction or the accumulation
of mycosporine-like amino acids (MAAs) and ascorbic acid in ovaries of the green sea urchin Strongylocentrotus droebachiensis (Müller). Ovaries of sea urchins sampled across a depth gradient (0.5–10 m) in March 1998 did not differ in their gonadal
index, or in concentrations of MAAs, or ascorbic acid. Concentrations of MAAs and ascorbic acid in ovaries were higher in
sea urchins collected from a kelp bed compared with those collected from a community of crustose coralline algae. The concentrations
of MAAs in ovaries varied seasonally, peaking in March, when sea urchins had high gonadal indices just before spawning. Ovaries
of sea urchins maintained on controlled diets from October 1997 to April 1998 accumulated significantly higher concentrations
of MAAs when fed a diet rich in MAAs than did ovaries of sea urchins fed an alga lacking MAAs, but the gonadal indices did
not differ between diets. Sea urchins accumulated principally one MAA, shinorine, but not others that were available in high
concentrations in their diet. Neither the gonadal index nor the ovarian concentrations of MAAs were affected by daily exposure
of adult urchins to UVR for 6 months. Concentrations of ascorbic acid in ovaries did not differ among diets or UV-treatments.
The percentages of nutritive phagocytes and gametic cells were not affected by diet or UVR, and did not co-vary with concentrations
of MAAs or ascorbic acid in ovaries. These data support previous demonstrations that female sea urchins accumulate MAAs from
their diet of macroalgae, but further show that the accumulation is selective for specific MAAs, particularly shinorine, and
that adult S. droebachiensis do not accumulate MAAs in their ovaries or eggs in response to UV-exposure. These are also the first experimental studies
to address whether MAAs are affected by or regulate gametogenesis, and indicate that they do not.
Received: 5 May 2000 / Accepted: 29 September 2000 相似文献
11.
The reproductive biology of 5 species of echinothuriid (Phormosoma placenta, Calveriosoma hystrix, Araeosoma fenestrum, Sperosoma grimaldii and Hygrosoma petersii) and 2 species of cidarid (Cidaris cidaris and Poriocidaris purpurata) sea urchins from the deep sea (Rockall Trough) has been examined from samples collected during 1973–1983. In all species the gonads lie within the interambulacrum attached to aboral gonopores and when fully developed occupy most of the test not occupied by the gut or Aristotle's lantern. In all the species, initial oocyte development takes place along the germinal epithelium embedded in nutritive tissue. In all the echinothuriids and in Poriocidaris purpurata, the oocyte grows to ca. 200 to 450 m, at which stage vitellogenesis begins. Oocyte growth continues until a maximum egg size of 1 100 to 1 500 m is attained. In the echinothuriids, two types of nutritive tissue are found. In the carly stages of gametogenesis the oocyte is surrounded by well-structured periodic acid Schiff (PAS)-positive tissue. As the oocyte grows this tissue becomes vacuolated, suggesting that there is a transfer of nutriment to the developing oocyte. In Phormosoma placenta, unspawned oocytes are phagocytosed. There is no evidence of seasonality in any of the echinothuriid species or in Poriocidaris purpurata. Extrapolation with shallow-water echinothuriids suggests that larval development is lecithotrophic, omitting any planktotrophic phase. Of the species examined, only Cidaris cidaris has a reproductive strategy which produces a known larva, although the limited samples did not permit any determination of seasonality in this deep-sea population. 相似文献
12.
M. Byrne 《Marine Biology》1990,104(2):275-289
Reproduction of the commercial sea urchinParacentrotus lividus (Lamarck) from contrasting habitats on the west coast of Ireland was examined from May 1986 through August 1988. Urchins were collected intertidally from an exposed rocky shore and subtidally from a protected bay. Monthly measurements of the gonad index and histological examination of the gonads demonstrated thatP. lividus has an annual reproductive cycle. Although the two populations exhibited similar reproductive patterns over three breeding seasons, there were inter-annual and inter-population differences in the amplitude of gonadal growth and in the time when spawning started. The subtidal urchins had significantly larger gonads and exhibited a longer period of reproductive maturity compared with the intertidal urchins. This difference was also evident in the histology of the ovaries at the beginning of breeding, when most of the subtidal females contained mature ovaries, whereas most of the intertidal females contained premature ovaries. An inter-annual difference in the onset of spawning was observed, with the start of gamete release differing by as much as four weeks between years. It appears that inter-annual differences in sea temperature influence the temporal variation in spawning byP. lividus and that increasing temperature may serve as an exogenous cue for gamete release. The inter-annual variability in the onset of spawning suggests that photoperiod does not cue gamete release. Gonadal growth, on the other hand, occurs during the coldest months of the year and during the period of shortest days, suggesting that temperature and photoperiod may both influence gonadal growth during the winter. Oogenesis and spermatogenesis ofP. lividus were examined histologically. During the post-spawning recovery and growth stages, the gonads gained weight through growth of the nutritive phagocytes and the accumulation of periodic acid Schiff (PAS) + droplets by these cells. The PAS + material appears to play a nutritive role in gametogenesis. For the females, the frequencies of six ovarian maturity stages was assessed at approximately monthly intervals. Small oocytes were present throughout the year and clusters of early oocytes were most apparent during the spent and recovery stages. With the onset of vitellogenesis and subsequent accumulation of ova, the nutritive phagocytes and their PAS + droplets became depleted. The ovarian condition at the onset of breeding was variable, due to differences in the number of vitellogenic oocytes, differences in the number of ova in storage, and differences in the amount of PAS + material. In general, the nutritive phagocyte tissue is reduced by the onset of spawning and is exhausted by the termination of breeding. A similar series of events occurs during spermatogenesis. The relevance of this study for the use ofP. lividus as a brood-stock organism for mariculture is discussed. 相似文献
13.
Una Andersone Ieva Druva-Lūsīte Baiba Ieviņa Andis Karlsons Jevgenija Ņečajeva Ineta Samsone Gederts Ievinsh 《Journal of Coastal Conservation》2011,15(4):509-522
Eryngium maritimum is a perennial species growing exclusively in a coastal littoral zone both on sand dunes and shingle beach and indicated
as declining in Northern Europe. The objective of the present study was to prove the use of nondestructive physiological measurement
methods to access physiological status of endangered plants, using E. maritimum as a model species. Plants from two Latvian sites were studied in comparison with other populations in Northern Europe (Estonia,
Lithuania, Poland, United Kingdom) to find out if local differences in environmental factors affect vitality of E. maritimum individuals. Noninvasive chlorophyll analysis and chlorophyll a fluorescence measurements were used as indicators of plant physiological status through characterization of various aspects
of photochemistry of photosystem II activity. Dynamics and morphology of individuals were investigated for evaluation of clonal
growth potential of E. maritimum in natural conditions. Highly fluctuating trend of dynamics of individuals (within 40 groups at two Latvian sites) was established
for E. maritimum in natural conditions over a five-year period. Disturbance of individuals lead to formation of new shoots from nodal root
meristems. An exponential regression between fluorescence parameters FV/FM and Performance Index and summary monthly precipitation was found indicating that E. maritimum plants had significant tolerance to water shortage together with susceptibility to increased precipitation. Negative correlation
between leaf chlorophyll content and more northern localization of individuals was found (r = 0.95 and r = 0.94, for generative and vegetative shoots, respectively). Northern populations of E. maritimum are endangered by high precipitation in conditions of low air temperature, leading to decrease of photosynthetic productivity
and overall physiological status. High developmental plasticity at the root level leads to clonal growth and an efficient
survival and relatively long life span of E. maritimum individuals. Chlorophyll a fluorescence is a useful method to search for the effect of suboptimal conditions on physiological status of endangered plant
species without elimination and disturbance of individuals. 相似文献
14.
The vertical distribution and population dynamics of the chaetognath Parasagitta elegans Verrill were determined in the water column and hyperbenthic zone of Conception Bay, Newfoundland from April 1997 to June
1998. The water column depth at the study site (47°32.2′N; 53°07.9′W) was 235 m. The temperature below the thermocline was
<0 °C the year round. Chaetognath samples from the water column were collected with a Tucker Trawl. Those from the hyperbenthic
zone, were collected with an epibenthic sledge. Depending upon whether the hyperbenthic zone was assumed to extend either
1 m or 10 m above bottom, the grand mean, areal abundance of chaetognaths in the hyperbenthic zone ranged from 6% to 40% of
the total abundance in the water column (including the hyperbenthic zone), and the grand mean, areal biomass ranged from 25%
to 77%. Large, mature individuals were collected only in the hyperbenthic zone, whereas small, immature individuals were collected
primarily in the water column. According to body length and ovary maturity data, three cohorts were identified in the hyperbenthic
zone during the study period. Within each cohort, the length frequency of reproductively mature individuals was bimodal, with
groups of mean length 33 mm and 41 mm reproducing from May to October. The recruitment period of juvenile chaetognaths extended
from July to February, coinciding with the recruitment period of copepods. The estimated individual growth rate of P. elegans was 1.0 mg C year−1. The approximate generation time of the two groups of individuals with mean length at maturity of 33 mm and 41 mm was 450
and 780 days, respectively. This study demonstrates that a failure to sample the large, mature P. elegans living in the hyperbenthic zone leads to serious underestimates of the total abundance and biomass of chaetognaths and an
inaccurate picture of seasonal population dynamics.
Received: 8 September 1999 / Accepted: 15 September 2000 相似文献
15.
The distribution of Pleurobrachia pileus Müller, 1776 in the Black Sea was determined using plankton samples collected above the anoxic zone (maximum of 200 m) in
the winter, spring, and summer of 1991 to 1995. The summer samples were collected in 1991 to 1993 (for a previous) and are
included in this paper for comparative purposes. High concentrations of P. pileus were found at the northern edges of anticyclonic eddies along the southern coastal regions. The biomass and abundance of
P. pileus increased from winter through spring to a peak in summer. The highest mean wet weight during a sampling period was 250 g m−2, while the maximum wet weight was 1429 g m−2. P. pileus was mostly found in a layer extending from the lower parts of the thermocline down to the anoxic zone, where the temperature
was <8 °C. The vertical distribution of P. pileus biomass had two clear maxima at night: an upper maximum at 20 to 40 m was less pronounced than the lower maximum at 90 to
120 m depth. Mean body length of P. pileus did not exceed 12 mm. Smaller individuals (9 to 10 mm length) occurred in winter. P. pileus had two length classes in early spring (March 1995) and late summer (August 1993), indicating the presence of both newly
hatched and larger individuals. Overall, the stomach contents of P. pileus consisted mainly of Copepoda (90%), Cladocera (1%), Mollusca (1%), fish eggs and larvae (1%), and other taxa (7%). The preferred
food of P. pileus (frequency of occurrence) was: Calanus euxinus (39%), Pseudocalanus elongatus (30%), Acartia clausi (28%), Oithona similis (2%), and Paracalanus parvus (1%). The endoparasite Hysterothylacium aduncum was commonly found in P. pileus. Abundances of Mnemiopsis leidyi and P. pileus were either negatively correlated (r = −0.5 to −0.7) or positively correlated at a low significance level (r = 0.25 to 0.3) with abundance of A. clausi in different months of the year. Aurelia aurita abundance was correlated mainly with the abundance of C. euxinus from June 1991 to March/April 1995. Over the same period the abundance of P. pileus was significantly correlated with the abundance of P.
elongatus, an important prey species.
Received: 1 November 1997 / Accepted: 30 August 1999 相似文献
16.
Cristiano Bertolucci Mauro Leorati Augusto Innocenti Augusto Foà 《Behavioral ecology and sociobiology》1999,46(3):200-209
The daily pattern of locomotor activity of Podarcis sicula in the field changes from unimodal in spring to bimodal in summer, becoming unimodal again in autumn. Short-term experiments
in which P. sicula collected in different months were tested under constant conditions immediately after capture showed that the activity pattern
typical of each season is retained in the lizard circadian locomotor rhythm. In constant conditions, the bimodal pattern is
associated with a short free-running period (τ) of the circadian locomotor rhythm and a long circadian activity (α), while
the unimodal pattern is associated with a long τ and short α. To test whether seasonal changes in circadian locomotor rhythms
are driven by a circannual clock, we recorded locomotor activity of lizards over 12–15 months in constant temperature and
darkness. The present results demonstrate, for the first time in a vertebrate, the existence of circannual changes in constant
darkness of both τ and α. In most lizards, the longest τ along its circannual cycle is associated with a short α, and the
shortest τ in the same cycle with a long α, so that the pattern of mutual association between τ and α is the same as in short-term
experiments. Most lizards, however, stayed unimodal all the time. This shows that changes in activity pattern from unimodal
to bimodal (and vice versa) are induced by seasonal changes in environmental factors, instead of being incorporated into a
circannual rhythm. Circannual changes in τ and α of locomotor rhythms may adaptively predispose the circadian system of P. sicula to a change in activity pattern as soon as seasonal changes in the environment demand it.
Received: 22 January 1999 / Received in revised form: 14 April 1999 / Accepted: 19 April 1999 相似文献
17.
Seasonal variation in reproduction and population size structure was investigated for the suspension-feeding bivalve Limopsis tajimae Sowerby inhabiting the upper bathyal zone (300 m deep) of Suruga Bay, central Japan. The bivalve was collected at 1- to 4-month
intervals for a period of 22 months, and bottom environment was monitored concurrently to detect factors affecting seasonality
in the bivalve. Bottom water temperature, organic carbon and nitrogen contents in the sediments did not exhibit seasonal variation.
Size-adjusted soft-tissue weight varied slightly, but statistically significantly between stations and months. However, its
seasonal pattern was not obvious, and the pattern of temporal variation was totally different between stations. The sex ratio
did not deviate from 1:1, and there was no significant difference between shell lengths of females and males. Females possess
both immature small oocytes and large developed oocytes in their ovaries throughout the year, suggesting that they can potentially
undergo year-round continuous reproduction. The proportion of developed oocytes in each female varied greatly from month to
month, although no seasonal cycle was obvious. Population size structure of L. tajimae was polymodal. A mode of the smallest size class occurred in most months, suggesting long periods of bivalve recruitment.
These findings indicate that seasonal variation in reproduction of the bivalve was negligible, probably reflecting constant
physical and nutritive conditions of the bottom environment.
Received: 6 January 1998 / Accepted: 19 May 1998 相似文献
18.
Age and growth of Electrona antarctica (Pisces: Myctophidae), the dominant mesopelagic fish of the Southern Ocean 总被引:1,自引:0,他引:1
Numerically and in biomass, the lanternfish Electrona antarctica is the dominant fish in the vast pelagic region of the Southern Ocean bounded on the north by the Antarctic Convergence and
in the south by the Antarctic continental shelf. It is an important krill predator, and in turn is important in the diets
of flighted and swimming seabirds. Further, it is the southernmost and coldest-dwelling representative of the globally distributed
fish family Myctophidae. The present study was undertaken to estimate the species' growth rate and average life span, to incorporate
the information in a basic energy budget, and to compare the growth of E. antarctica with more northerly confamilials. Fishes were aged using primary growth increments that were resolved on sagittal otoliths
using three sequential techniques: thin-section grinding and polishing, etching, and scanning electron microscopy (SEM). Based
on increment width (0.8 to 1.2 μm), continuity, and previous studies on confamilials, the microincrements were assumed to
be deposited on a daily basis. Montages of SEM photomicrographs were constructed for each sagitta to allow the daily rings
to be counted over the entire life span of 31 individuals representing the entire size range of the species. Results suggest
a larval stage of 30 to 47 d and a maximum life span of 3.5 yr, with females growing faster than males in the last 1.5 yr
of life and reaching a larger maximum size. Construction of a simple energy budget using the best information available suggests
that a surplus of energy is available to support the observed growth rates (0.05 to 0.07 mm d−1). The results of the present study contrast markedly with previous estimates of an 8 to 11 yr maximum age for E. antarctica. These results provide important data addressing the ecology and population dynamics of the pelagic Antarctic ecosystem.
E. antarctica is the end-member species in the continuum of vertically migrating myctophids that extend from the equator to the polar circle.
Its growth rate is consonant with that of all other myctophid species examined using primary growth increments to determine
age. The present study, in conjunction with earlier studies, suggests that growth rates of mesopelagic species are far higher
than previously thought.
Received: 12 September 1997 / Accepted: 25 July 1998 相似文献
19.
Four species of microalgae (Chaetoceros muelleri, Tetraselmis suecica, Tahitian Isochrysis sp. (T-iso) and Dunaliella tertiolecta) with distinctly different fatty acid profiles were grown in continuous culture and fed to prawn larvae (Penaeus japonicus, P. semisulcatus and P. monodon) as monospecific diets. The best two diets (C. muelleri and T. suecica) were also fed as a mixed diet. Experiments were run until the larvae fed the control diet of C. muelleri metamorphosed to Mysis 1. The survival and development (i.e. performance) of the larvae were affected by algal diet, and
the diets were ranked in the order of decreasing nutritional value: C. muelleri ≥ T. suecica > T-iso > D. tertiolecta. Larvae fed a mixed diet of C. muelleri and T. suecica (2:3 by dry weight) performed as well or better than those fed C. muelleri, and the performance of both these groups of larvae was better than those fed T. suecica. The lipid and carbohydrate compositions of the algae had little or no effect on the lipid and carbohydrate compositions
of the larvae or their performance. However, the larvae that performed best (i.e. those fed C. muelleri) had significantly more lipid and carbohydrate than those that performed worst (i.e. those fed D. tertiolecta). Larvae fed C. muelleri or the mixed-algae diet had higher proportions of the essential fatty acids eicosapentaenoic acid [EPA, 20:5(n-3)] and arachidonic acid [ARA, 20:4(n-6)] than the larvae fed on other diets. Furthermore, the larvae fed T. suecica, which showed intermediate performance between larvae fed C. muelleri and T-iso or D. tertiolecta, also had higher proportions of EPA and ARA. Both C. muelleri and T. suecica contained EPA and ARA, but T-iso and D. tertiolecta did not, except for trace amounts of EPA in T-iso. The fatty acid ARA appears to be much more important in the diet of larval prawns than has so far been considered. The level
of the essential fatty acid docosahexaenoic acid [DHA, 22:6(n-3)] in the algal diet and the larvae was not related to the performance of the larvae; only C. muelleri and T-iso contained DHA. However, the nauplii contained large proportions of DHA, suggesting that these were sufficient to meet the
larval requirements for DHA during their development to Mysis 1. Mixed-algae diets could improve the performance of larvae
by providing a more comprehensive range of fatty acids.
Received: 22 April 1998 / Accepted: 3 December 1998 相似文献
20.
The transparent goby Aphia minuta (Risso, 1810) is one of the main target species of the small-scale fishery off the Island of Majorca. Otolith microstructure
and length-frequency analysis were used to study the age and growth of this species during the 1982/1983 and 1992/1993 fishing
seasons. Daily periodicity of increment formation was determined by experiments with marked otoliths in individuals maintained
in captivity. The length range of the catches during the 11 yr period was between 12 and 49 mm, with a main distribution (89%)
between 24 and 40 mm. Otolith age-readings indicate that the population exploited in the commercial fishery consists of seven
age-groups (2 to 8 mo old), with a very high proportion of individuals (95%) between 3 and 6 mo old. Population growth-curves
revealed no differences between males and females. The growth parameters for the whole population are: asymptotic length,
L
∞ = 53.69 mm; growth coefficient, K = 2.23 yr−1; theoretical age at length zero, t
0 = −0.005 yr. Those individuals of A. minuta caught in Majorca during the winter period reached a maximum age of 7 or 8 mo.
Received: 30 December 1996 / Accepted: 16 April 1997 相似文献