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1.
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
2.
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
3.
Green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), populations are being depleted rapidly in the Gulf of Maine and there is justified concern that the potential
of this free-spawner to produce larvae may be severely inhibited. We evaluated the opposing effects of different population
densities on gonad development and fertilization success, using population surveys and fertilization experiments. We determined
gonad indices (gonad mass/body mass) over a range of population densities (0.1 to 250 ind. m−2) at seven sites in coastal Maine, USA, sampled at two depths (5 and 15 m). At shallow sites, we found that gonad indices
declined by 50% over the 1500-fold range in adult population density. At 15 m deep locations, gonad mass was consistently
low and did not vary significantly with density. Patterns of macroalgal abundance suggest urchins at high density and in deeper
water were food limited. Because macroalgal cover co-varies inversely with sea urchin density, we designed field experiments
to determine the interaction between sea urchin density and kelp canopy on fertilization success. On square arrays we manipulated
the spacing of simulated urchins, but held their numbers constant (five sperm-filled syringes interspersed with four Nitex
mesh egg containers permeable to sperm). These experiments, simulating the observed range of natural density, suggested that
(1) fertilization rates decreased many times faster than individual gamete production increased over the same range in density,
and (2) kelp increased fertilization success at high density when eggs were within 25 cm of a sperm source, but not when spaced
1 m apart. Additional laboratory fertilization experiments at ambient temperatures (3 to 5 °C) indicated that diluted sperm
were viable for <1 h, but egg viability was virtually unchanged for >8 h. In short, to the individual the reproductive benefits
of aggregating appear to outweigh the costs; and while sperm may be limiting at low population density, eggs may remain viable
long enough to be fertilized by sperm from more distant males.
Received: 10 February 1998 / Accepted: 22 January 1999 相似文献
4.
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
5.
Effect of temperature fluctuations and food supply on the growth and metabolism of juvenile sea scallops (Placopecten magellanicus) 总被引:1,自引:0,他引:1
On the eastern shore of Nova Scotia late summer atmospheric systems cause upwelling of shelf water; the associated temperature
variations of 10 °C with a 6 to 8 d period are comparable in magnitude to the seasonal variation. A laboratory study was undertaken
to assess the effects of these temperature fluctuations on sea scallop (Placopecten magellanicus) growth and metabolism. In a factorial design, scallops were subjected to constant (10 °C) or a variable (6 to 15 °C) 8 d
temperature cycle, and either a low (seston in filtered seawater) or high (seston supplemented with cultured phytoplankton)
food diet. During the 48 d experiment scallop mortality was low and growth positive in all treatments. Shell and total tissue
growth rate did not differ between temperature treatments, but growth in the high food treatments was 40 to 50% higher than
in the low food treatments. However, soft tissue (excluding adductor) growth did show a temperature treatment effect; growth
rates were significantly higher in the fluctuating temperature treatment, due in part to greater gonad development. Weight-standardized
rates of scallop oxygen consumption (V
sO2 , μmol O2 g−1 h−1) were 20 to 25% higher in high food than in low food treatments, consistent with the expected increase in respiration due
to the higher growth rates. Scallop metabolism did not acclimate to the fluctuating temperature cycle; V
sO2 and ammonium excretion (V
sNH+
4, μmol O2 g−1 h−1) remained dependent on ambient temperature throughout the experiment. V
sNH+
4 Q10 (2.77) was higher than V
sO2 Q10 (2.01) which was reflected in a decrease in the O:N ratio at 15 °C, indicating a shift toward increased protein catabolism
and a stressed state. At 10 °C, V
sO2 and V
sNH+
4 in the variable temperature treatments were 15 to 18% lower than in the constant temperature treatments, a difference that
was not detected in growth measurements. Results demonstrate that the metabolism of Placopecten magellanicus, unlike some bivalve species, is tightly coupled to fluctuations in ambient temperature. Although an absence of compensatory
acclimation had a minimal effect on growth in this study, if high temperatures were combined with low food conditions a reduction
in scallop production could result.
Received: 23 June 1998 / Accepted: 8 February 1999 相似文献
6.
Clément Dumont Christopher M. Pearce Cathy Stazicker Yu Xin An Laurie Keddy 《Marine Biology》2006,149(2):365-378
A laboratory experiment was conducted in the winter of 2003–2004 to assess the effect of varying photoperiod regime on consumption rate, assimilation rate, absorption efficiency, and gonad development of the green sea urchin, Strongylocentrotus droebachiensis. Adult individuals were collected from the wild after they had been exposed to the ambient autumn photoperiod cue (which is the extraneous trigger thought to elicit gametogenesis in this species) and placed at ambient temperature for 12 weeks under five different photoperiod regimes: (1) 24 h light:0 h dark=“0D”, (2) 16 h light:8 h dark=“8D”, (3) 8 h light:16 h dark=“16D”, (4) 0 h light:24 h dark=“24D”, and (5) ambient photoperiod (range: 10.50–15.25 h dark). Urchins in these five treatments were fed ad libitum with bull kelp, Nereocystis luetkeana. A sixth treatment consisted of starved individuals held under 0D conditions. Various gonad factors including gonad index, percent gonad water, gonad colour (CIE lightness or L*, CIE hue or a*, and CIE chroma or b*), percent area occupation of the gonad by various cell types (nutritive phagocytes, spermatozoa, and secondary oocytes/ova), and stage of development were assessed at the beginning of the experiment and at weeks 4, 8, and 12 of the study. Consumption and assimilation rates were assessed at weeks 4 and 12 and absorption efficiency at week 12 of the experiment. Urchins were predominantly in the growing and premature stages at the beginning of the experiment, but by week 4 at least 20% of individuals in all treatments receiving food were classified as mature. Spawning occurred during all these treatments between weeks 4 and 8, as evidenced by significant decreases in spermatozoa and secondary oocytes/ova and a significant decrease in percent gonad water, but was not accompanied by major declines in gonad indices. Greater than 90% of individuals in all five of the fed treatments were in the recovering and growing stages at the end of the experiment. The 16D treatment had by far the greatest percentage of urchins in the growing stage. In contrast, individuals that were starved were predominantly in the mature stage at weeks 4, 8, and 12, with only ~30% reaching the spawning stage by the end of the experiment. Photoperiod significantly affected gonad indices at the termination of the experiment with gonad index being the highest in the 16D treatment; this was significantly greater than in the 8D and ambient treatments. Photoperiod did not significantly affect gonad percent water, gonad lightness, or gonad hue. Gonad chroma was significantly affected by photoperiod, urchins held under ambient conditions having significantly lower b* readings than individuals in any other treatment. Photoperiod had little or no affect on consumption rate, assimilation rate, or absorption efficiency. Thus, differences among treatments in regards to gonad index, gonad chroma, and stage of development cannot be attributed to variations in feeding, absorption, or assimilation. The results of this experiment indicate that once gametogenesis is initiated, photoperiod manipulation cannot prevent ultimate spawning. However, photoperiod regime can affect the rate at which urchins move through the various stages of the gametogenic cycle. Urchins placed on short days under artificial lighting (16D) moved through the spawning stage into recovering and growing stages the fastest. This photoperiod regime also produced the highest gonad index at the end of the experiment. Since the commercial urchin market prefers large gonads in the growing and premature stages (i.e. before the mature stage is reached and gonads start leaking sperm and eggs), short day-lengths under artificial lighting (16D) appear to be the best photoperiod conditions for optimizing marketability. 相似文献
7.
In many vertebrates, environmental factors influence gamete differentiation and growth of the mature gonad through alteration
of sex steroid production or action; however, it is unclear how gamete differentiation and gonadal growth are regulated in
echinoids. The purpose of this study was to examine the influence of dietary administration of estradiol (E2), progesterone
(P4), testosterone (T) and finasteride (F, a 5α-reductase inhibitor) on the ovaries and testes of mature Lytechinus variegatus (Lamarck) during gonadal growth. Echinoids were fed a formulated diet supplemented with steroids or steroids in combination
with finasteride for 36 d. The effects of dietary administration of steroids on L. variegatus were both steroid- and sex-specific. The mean ovary index was 54% greater in individuals fed E2 than from individuals fed
the control (C) diet (10.0 ± 1.1 vs 6.5 ± 0.7, respectively; P < 0.05). Individuals fed E2, P4, E2/P4, and P4 in combination with F had significantly smaller oocytes (P < 0.005) than individuals fed C. The volume fraction occupied by nutritive phagocytes in ovarian tubules from individuals
fed E2/P4 or P4 were significantly larger than the volume fraction occupied by nutritive phagocytes from individuals fed C,
indicating that E2 and 5α-reduced progestins may promote nutrient allocation to nutritive phagocytes. Although oocytes from
the individuals fed T alone were significantly smaller than those fed T in combination with F, oocytes from individuals in
both treatments were significantly larger compared to oocytes from individuals fed C. These data suggest that upon removal
of 5α-reduced androgens, T is able to promote an increase in oocyte diameters. In contrast, the mean testis index was 56%
greater in individuals fed P4 than in individuals fed C (8.9 ± 0.6 vs 5.7 ± 0.9, respectively; P < 0.05); the testis index did not increase in individuals fed P4/F, suggesting that 5α-reduced progestins stimulate testicular
growth. Testes growth in the presence of 5α-reduced progestins was accomplished by significant increases in the volume fraction
occupied by nutritive phagocytes and by a significant reduction in the volume fraction occupied by spermatogenic columns in
testicular tubules. These data further indicate that 5α-reduced progestins (or 5α-reduced androgens) may inhibit spermatogenic
column formation. In conclusion, E2 stimulated ovarian growth but inhibited oocyte growth, whereas T had no affect on ovarian
growth but promoted oocyte growth in L. variegatus. We hypothesize that the E2 (or E2 metabolites) and/or 5α-reduced androgens in combination with T regulate oocyte growth
in the echinoid L. variegatus. In addition, 5α-reduced progestins promoted nutrient accumulation in nutritive phagocytes within the ovaries and the testes.
Furthermore, 5α-reduced progestins stimulated growth of the testes and inhibited spermatogenic column formation, suggesting
that 5α-reduced progestins regulate nutrient accumulation into nutritive phagocytes and spermatogenic column formation in
L. variegatus. The differences in estrogen effects between echinoids and asteroids may be related to differences in gonad morphology and,
ultimately, the differences in cellular signalling pathways (paracrine vs endocrine).
Received: 22 May 1999 / Accepted: 24 May 2000 相似文献
8.
Previous studies have shown that large numbers of ciliated and nonciliated epithelial cells (diam.: 6 to 15 μm) are released
by adult sea scallops, Placopecten magellanicus (Gmelin), during summer months in Newfoundland when water temperatures are at a maximum and gonads are well developed. Such
exfoliation of cells could be a response to stresses associated with elevated water temperatures and/or spawning activity.
In the present study an electronic particle counter/sizer was used to further investigate the factors that influence exfoliation
of epithelial cells by juvenile and adult scallops throughout the year. We observed release of epithelial cells from juveniles,
and from adults collected in months when gametogenic activity was minimal, indicating that exfoliation does not occur as a
result of reproductive activity alone. SEM analysis revealed little difference in surface characteristics of the gills, mantle
and gonad between scallops that had released cells and those that had not, suggesting that exfoliation of small numbers of
cells may be a consequence of cellular turnover and normal physiological function. Adult scallops were monitored in a second
experiment to determine the effects of raising water temperatures from 8.5 to 14.7 and to 21.0 °C on the frequency (proportion)
and rate of cellular exfoliation. Only at the highest experimental temperature (21.0 °C) were exfoliation rates significantly
higher than rates recorded at 8.5 or 14.7 °C. SEM analyses revealed some damage to gill, mantle and gonad tissues when scallops
were exposed to 14.7 and then to 21.0 °C for a total of 8 d.
Received: 21 August 1996 / Accepted: 13 September 1996 相似文献
9.
Two laboratory experiments were conducted on Ophiocoma echinata (Lamarck, 1816) collected from Missouri Key, Florida, USA, to ascertain the effects of arm regeneration on energy storage
and gonad production. In each experiment individuals were divided into non-regenerating (all arms intact) and regenerating
(three arms autotomized) groups and maintained together in a re-circulating seawater system for 2 mo. In Experiment 1, individuals
were fed once a week, and in Experiment 2 once every 2 wk. The amount of food energy required for maintenance was estimated
to be 0.172 kJ d−1. The lower feeding level (Experiment 2) was below maintenance ration and both groups lost material relative to an initial
group. At the higher feeding level (Experiment 1), regeneration of three arms resulted in less storage of organic material,
mainly lipid in the stomach, and less gonad production. Thus, regeneration may reduce energy reserves and reproductive output.
Received: 23 April 1998 / Accepted: 11 January 1999 相似文献
10.
The amount of food and when it is available affect both the timing of reproduction and the number of gametes produced by purple
sea urchins, Strongylocentrotus purpuratus. To investigate this further, the effects of food availability on feeding rates, gonad growth, and gamete development were
examined in S. purpuratus collected from the Point Loma kelp forest near San Diego, California, USA (32.69° N, 117.26° W) in September (Fall) 2007,
and February (Spring) and July (Summer) 2008, using laboratory mesocosms. Each seasonal laboratory feeding experiment lasted
3 months, and different levels of food availability were established with different feeding frequencies (from 1 to 7 days
week−1). Gonad tissues of male and female urchins were staged at the end of each experiment using histological analyses. Reduced
food availability resulted in increased daily consumption rates, especially in the Fall when gamete development began. Food
limitation at this time resulted in failure to produce viable gametes, suggesting there is a critical period early in gonad
development when food limitation affects reproductive competency. Food limitation later in gonad development did not stop
viable gamete production, although it did reduce gamete output. 相似文献
11.
E. Mutlu 《Marine Biology》2001,138(2):329-339
The distribution of moon jellyfish (Aurelia aurita Linnaeus, 1758) in the Black Sea was determined from plankton samples collected above the anoxic zone (maximum depth 200 m)
in the summer, winter and spring during 1991–1995. Distribution was patchy. Average biomass ranged from 98 to 380 g m−2, and abundance varied from 2 to 14 individuals m−2. Biomass and abundance peaked in late spring and summer. The distribution was correlated with hydrographic features in the
Black Sea, with higher concentrations occurring at the peripheries of anticyclonic eddies. Centers of the two main cyclonic
gyres generally had a low biomass of A. aurita. From July 1992 to March 1995, the populations were largely concentrated in offshore regions. A. aurita were confined to the upper part of the mixed layer. Smaller A. aurita (≤1 cm) were present in early spring (March), and individuals reached maximum size in the summer. Release of the epyhrae
occurred in spring on the northwestern shelf of the sea when the seawater temperature was 11–12 °C. Microscopic analysis of
stomach contents showed that copepods and mollusks form their main diet.
Received: 3 September 2000 / Accepted: 29 September 2000 相似文献
12.
M. D. Herrero-Pérezrul H. Reyes Bonilla F. García-Domínguez C. E. Cintra-Buenrostro 《Marine Biology》1999,135(3):521-532
The reproduction and growth of Isostichopus fuscus (Ludwig, 1875) at Isla Espíritu Santo, Baja California Sur, México from July 1992 to September 1993 and from August 1996
to July 1997 were analyzed. The reproductive cycle was monitored by using histological analysis. Five gonadal stages were
described according to cell types present in the gonad; undetermined, gametogenesis, maturity, spawning and post-spawning.
This holothurian reproduces annually during summer (July to September), when sea surface temperature reaches 27 °C. The gonad
index is related to the gonadal stages. The first sexual maturity for I. fuscus was calculated at 367 g (4 to 5 years old) according to the von Bertalanffy equation, and nearly all the specimens at Isla
Espíritu Santo were 5 to 7 years old (including some individuals over 35 years old). Data of the length–weight relationship
showed that I. fuscus grows allometrically at the studied site (b = 1.83). The mortality rate was relatively high (M = 0.51), indicating that in a typical cohort, 40% of the recruits does not survive the first year, and less than 20% reaches
maturity.
Received: 15 July 1998 / Accepted: 19 August 1999 相似文献
13.
A multi-factorial experiment on heart rate variations in the intertidal crab Pachygrapsus marmoratus
A multi-factorial experiment was designed to investigate the effect of the following factors on the cardiac activity of the
intertidal crab Pachygrapsus marmoratus: respiratory medium (air, water), temperature (four levels, 10, 17.5, 25, 32.5 °C), season (winter, summer) and body size
(two levels, carapace ≤21 mm and carapace >21 mm). The results showed that the heart rate of P. marmoratus increased linearly with temperature and decreased when the specimens were exposed to air rather than water. Moreover, the
heart rate values in summer were lower than those in winter at the corresponding temperature and body size. The summer heart
rate–temperature regression line was laterally (to the right) shifted with respect to the winter line, suggesting a seasonal
acclimation. Body size affected heart rate only at the acclimation temperature (17.5 °C), while no significant effect was
detected at lower or higher temperatures. During the reproductive season a separate experiment was carried out to assess the
effect of sex and reproductive status on heart rate. No significant difference was found among mean values of males, berried
females and females without eggs. The results of the present study confirm the high physiological plasticity of this species,
suggesting that P. marmoratus is a truly amphibious crab, able to deal with both water- and air-breathing during its activity.
Received: 5 January 1999 / Accepted: 7 July 1999 相似文献
14.
We determined the temporal evolution of amylase, cellulase, laminarinase and protease in the digestive gland and crystalline
style of cockles Cerastoderma edule held over 9 to 12 d in the presence and absence of food. Cockles were fed a constant diet of 1.5 mm3 l−1 of Tetraselmis suecica for 9 to 12 d and were then starved for 6 to 8 d in late summer (September 1992) and in winter (January 1993). Feeding increased
the dry weight and total cellulase, laminarinase and protease activities of the digestive gland irrespective of season, whereas
amylase activity remained unchanged. In winter (i.e. when cockles are metabolically weak) the response was faster and stronger,
especially for protease. An additional experiment in September starved cockles for 20 d before resuming feeding. In agreement
with the seasonal differences, the presence of food after prolonged starvation induced a rapid and marked increase in protease
in the digestive gland of the cockles. In winter, the possible effects of the biochemical composition of food on their enzymatic
response were tested by feeding two groups of cockles with the same ration of T. suecica but harvested at different growth phases. A compensatory induction of cellulases occurred in cockles fed on T. suecica with a lower carbohydrate content. In the crystalline style, the protein level and carbohydrase fell during the first day
of feeding and increased during the first day of subsequent starvation. These results indicate that the release of enzymes
from the style prevails over the incorporation of enzymes during the early stages of feeding, whereas the opposite occurs
during starvation.
Received: 15 February 1998 / Accepted: 22 February 1999 相似文献
15.
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
16.
A mass synchronous spawning of the sea urchin Evechinus chloroticus (Valenciennes) was observed in situ in Doubtful Sound, a large New Zealand fiord. Spawning occurred between 17:30 hrs and
18:30 hrs on 27 January 1994 and coincided with a full moon, spring tides and a period of decreasing sea temperatures. During
spawning, the sea urchins formed a dense spawning aggregation of both sexes, with >90% of the urchins observed spawning at
the time. Spawned gametes clouded the water column, and some were eaten by small labrid fish species. The spawning, which
may have been as widespread as 40 km, marked a 42 to 50% decrease in gonad indices and resulted in a widespread, dense cohort
of E. chloroticus larvae within the fiord.
Received: 25 September 1997 / Accepted: 6 March 1998 相似文献
17.
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
18.
Effect of temperature on statolith growth of the European squid Loligo vulgaris during early life 总被引:1,自引:0,他引:1
R. Villanueva 《Marine Biology》2000,136(3):449-460
Over the past decade, statolith interpretation has resulted in a major advance in our knowledge of squid population-dynamics,
but the way in which environmental conditions affect the statolith increment-deposition ratio remains virtually unknown. The
object of the present study was to determine the effect of temperature on this process, using tetracycline marks to validate
statolith growth in Loligo vulgaris Lamarck, 1798 under rearing conditions equivalent to severe winter (11 °C) and summer (19 °C) temperature regimes. Tetracycline
marking was performed every 10 d (at 10, 20, 30, 40, 50 and 60 d of age). The newly hatched squid paralarvae were slightly
smaller in summer than those hatched in winter. Survival rates were similar in both cultures, but growth rates (wet mass)
of summer squids were double those in winter. At hatching, statoliths were already longer in the summer squids, and growth
rates were 2% d−1 as opposed to 0.9% d−1 for winter statoliths. For the dorsal dome area of the statolith, where more increment counts were made, statolith growth
was of 3.25 μm d−1 in summer, and daily increment deposition was confirmed in 87% of the statoliths. The slow growth of statoliths at winter
temperatures yielded a mean growth of 1.1 μm d−1– insufficient to discern the increments using light microscopy. Subsequent SEM observation enabled only 21% of the winter
statoliths to be read; these also indicated a deposition rate of one increment d−1. Since the life span of L. vulgaris is ≃1 yr, squids will experience at least one winter during their life cycle, and this might be visible on the statolith.
Received: 28 June 1999 / Accepted: 20 December 1999 相似文献
19.
E. Sala 《Marine Biology》1997,129(3):531-539
Direct observations of predation on 436 individuals of the sea urchin Paracentrotus lividus (Lamarck) were carried out in infralittoral rocky bottoms (between 5 and 20 m deep) in three Mediterranean marine reserves.
The predator guild was composed of six fish species, the sparids Diplodus sargus and D. vulgaris being the main predators, and the labrid Coris julis a major predator of juvenile sea urchins. Four species attempted but failed to open sea urchins. The scavenger guild was
most rich in species, with 17 species observed. Predation was size-dependent; the size of predators increased with increasing
size of the sea urchins. The presence of two feeding guilds is suggested, one composed of sparids (Diplodus spp.), able to kill juvenile and adult sea urchins, and the other composed of labrids (mainly C. julis), which feed on juvenile sea urchins. To avoid the extension of overgrazed, barren areas created by P. lividus populations, fisheries' regulations should focus on major sea-urchin predators, chiefly D. sargus, D. vulgaris and C. julis.
Received: 23 April 1997 / Accepted: 30 May 1997 相似文献
20.
From September to November 1991, UV-absorbing mycosporine-like amino acids (MAAs) were monitored in a natural population of
the sea urchin Sterechinusneumayeri from a coastal area of Anvers Island (Antarctic Peninsula). MAA concentrations were determined for specific tissues (gonad,
digestive tract and body wall) from adults collected at four depths (intertidal, 8, 15 and 24 m). Four MAAs were identified:
mycosporine-glycine, shinorine, porphyra-334 and paly-thine. Concentrations of MAAs among replicate individuals varied considerably.
Ovaries had high concentrations of MAAs (84 to 1389 μg g−1 dry wt), while testes had non-detectable levels. The relative abundance of specific MAAs in ovaries appeared to be related
to the spawning cycle. Digestive-tract samples had MAA concentrations as high as 3000 μg g−1 dry wt, but the mean MAA content in intertidal individuals decreased by 70% over 3 mo during spring. The body walls of sea
urchins had very low amounts of MAAs (≤ 0.08 μg g−1 dry wt). There were significant depth differences in the␣total MAA content of the ovary ( p <0.001), ( p <0.015), digestive tract ( p <0.001), and body wall with organisms from the intertidal and 8 m depth having the highest concentrations of MAAs. Biological
dosimetry indicated that UV-B (280 to 320 nm) wavelengths penetrated 3 to 7 m below the sea ice during the study period. The
total MAA content in ovaries decreased with depth on all sample dates; however, the MAA content of the digestive tract and
body wall did not exhibit a consistent pattern of change with depth. The MAA content of tissues did not change significantly
with the temporal gradient of light exposure that was established by both ozone depletion and increasing photoperiod, except
in the digestive tract sampled from intertidal specimens. Adult urchins are probably well-protected from UV exposure by the
water column and a calcareous test; however, the results of this study suggest that, even under ice cover, depth of habitation
is a determinant of MAA content in S. neumayeri. Large daily and seasonal fluctuations in the light regime, which are characteristic of Antarctic coastal environments, apparently
do not provide reliable cues to elicit a detectable, temporal, biochemical response.
Received: 19 February 1997 / Accepted: 26 March 1997 相似文献