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1.
Otolith microstructure and microchemistry of the tropical eel Anguilla bicolor pacifica Schmidt were examined in glass eels collected at the mouth of the Dumoga River, North Sulawesi Island, Indonesia. Ages of
the glass eels examined (age at recruitment) ranged from 124 to 202 d (167 ± 19.3 d; mean ± SD), hatching being estimated
as having occurred between November 1995 and March 1996. Otolith increment widths markedly increased from age 101 to 172 d
(135 ± 18.2 d; mean ± SD), coincident with a drastic decrease in otolith Sr:Ca ratios, suggesting that metamorphosis began
during that period. The duration of metamorphosis was estimated as 20 to 40 d, on the basis of otolith microstructural characteristics.
The fluctuation patterns in otolith increment widths and Sr:Ca ratios were similar to those of the temperate Japanese eel
A. japonica.
Received: 20 May 1998 / Accepted: 7 October 1998 相似文献
2.
Otolith microstructure and microchemistry were examined in juveniles of American (Anguilla rostrata) and European (A. anguilla) eels. Otolith increment width markedly increased from age 132 to 191 d (156 ± 18.9 d; mean ± SD) in A. rostrata and 163 to 235 d (198 ± 27.4 d; mean ± SD) in A. anguilla, both of which were coincident with drastic decreases in otolith Sr:Ca ratios, suggesting that metamorphosis from leptocephalus
to glass eel began at those ages in each species. The duration of metamorphosis was estimated to be 18 to 52 d from otolith
microstructure, for both species studied. Ages at recruitment were 171 to 252 d (206 ± 22.3 d; mean ± SD) in A. rostrata and 220 to 281 d (249 ± 22.6 d; mean ± SD) in A. anguilla. In these two species, positive linear relationships were found in ages between the beginning of metamorphosis and recruitment,
suggesting that early metamorphosing larvae recruited at younger ages. Duration of the leptocephalus stage to recruitment
in A. anguilla was about 40 d longer than that in A. rostrata. The geographical segregation between the two species in the Atlantic Ocean seems to be involved in the differences in the
duration of the leptocephalus stage (age at metamorphosis).
Received: 8 November 1999 / Accepted: 8 May 2000 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.
Larvae of the marine cheilostomatid bryozoan Bugula neritina (L.) were prevented from settling for 1, 4 and 8 h by mechanical agitation, following which settlement and metamorphosis
success were examined. Settlement rates were significantly affected by swimming time, which decreased from 100% after 2 h
to 93.7 ± 4.3% after 8 h. Similarly, metamorphosis to the feeding ancestrula was significantly impaired following a swimming
time of 8 h, declining from 93.7 ± 4.3% after 1 h to 65.9 ± 7.0% after 8 h. The resultant colonies grew well for the first
3 wk, following which time, growth patterns became erratic. Growth rate was in all cases highly variable, and did not correlate
with enforced swimming times. Larval protein composition was examined after 1, 4 and 8 h swimming time, and post-larval composition
1, 2, 5, 24 and 48 h after settlement using sodium-dodecyl-sulphate polyacrylamide-gel electrophoresis (SDS-PAGE). Individual
protein content was measured using a densitometer. Larvae did not consume protein during swimming, however a protein measuring
170 kdaltons was consumed during metamorphosis. These results are discussed in the context of larval settlement and energetics.
Received: 19 July 1998 / Accepted: 3 December 1998 相似文献
5.
J. M. Kalish J. M. Johnston D. C. Smith A. K. Morison S. G. Robertson 《Marine Biology》1997,128(4):557-563
Accelerator mass-spectrometry was used to measure radiocarbon in the earliest formed portions of selected blue grenadier,
Macruronus novaezelandiae, otoliths to provide a validation of fish-age estimates based on the quantification of opaque and translucent zones in otolith
thin-sections. Δ14C data from blue grenadier otoliths were compared with previous estimates of Δ14C in seawater-dissolved inorganic carbon at similar latitutes, longitudes, and depths to link variation in otolith Δ14C to time. Minimum otolith Δ14C was −76.9 ± 7.7‰, indicative of pre-bomb radiocarbon levels below the surface mixed-layer at latitudes where juvenile blue
grenadier are found. When plotted versus fish age estimated from otolith sections, the majority of the Δ14C data combined to define a curve reflecting the increase in bomb radiocarbon in temperate oceans of the Southern Hemisphere,
indicating that age-estimation procedures based on otolith thin-sections are satisfactory for determining blue grenadier age.
If otolith-section age estimates were correct, peak otolith Δ14C of 106.8 ± 7.9‰ occurred during the late 1960s, i.e. earlier than expected. This may be a manifestation of an increase in
the mixed-layer depth associated with increased frequency of zonal westerly winds at this time.
Received: 3 December 1996 / Accepted: 17 December 1996 相似文献
6.
Strontium (Sr) and calcium (Ca) contents in the otoliths of yellow and silver European eels [Anguilla anguilla (L.)] collected from coastal waters of the Baltic Sea and a freshwater lake in Sweden were examined by wavelength dispersive
X-ray spectrometry with an electron microprobe. The mean Sr/Ca ratios from elver check to otolith edge were significantly
higher for the eels from coastal waters (5.39 ± 1.09‰) than for those from the lake (0.71 ± 0.89‰). The evidence indicates
that European eels in the Baltic Sea do not necessarily migrate into freshwater streams during the growth phase.
Received: 30 September 1999 / Accepted: 6 April 2000 相似文献
7.
Use of otoliths and eye lenses for measuring trace-metal incorporation in fishes: a biogeographic study 总被引:1,自引:0,他引:1
The otoliths and lenses of the temperate damselfish Parma microlepis (Günther) (Pomacentridae) showed similar differences in trace-metal profile for selected locations along the coast of New
South Wales, Australia. Otoliths and lenses displayed a differential ability to accumulate metals. Metal concentrations were
ranked differently in the two structures (e.g. Sr > Ba > Pb > Rb > Hg in otoliths, and Hg > Sr ≃ Rb > Pb > Ba in lenses),
and where similar metals were accumulated, they were accumulated at vastly different concentrations (e.g. Ba concentrations
in otoliths are a thousand-fold greater than in lenses). Analyses of the otoliths and lenses of P. microlepis from locations close to Sydney and up to 100 km from the city were able to distinguish amongst these locations with respect
to a number of metals, namely Ba, Mn and Hg. Multivariate analyses of otolith and lens data gave similar results among locations
(agreement was obtained for 11 out of 15 pair-wise comparisons), and differences were attributable to the differential ability
of the two structures to accumulate metals such as Mn and Hg. Trace-metal differences between locations were found to coincide
with the proximity of sewage (including industrial waste) and petroleum storage facilities to the different locations.
Received: 23 June 1997 / Accepted: 4 August 1997 相似文献
8.
The relationship between somatic growth and incremental growth of otoliths of Pacific saury, Cololabis saira (Brevoort), larvae under different temperature conditions was studied in the laboratory for three age groups (0 to 9, 10
to 20 and 20 to 30 d posthatch). Larvae were incubated from hatching to 9 d at 24, 20, and 16 °C. Further, larvae initially
reared at an ambient temperature of 21.7 °C were transferred to experimental temperatures of 22, 18, and 14 °C on Day 10 and
reared to Day 20 and similarly from Day 20 and reared to Day 30 posthatch. Growth trajectories of larvae sampled at the end
of the three experiments were back-calculated using the biological intercept method and compared to the measured values 0
and 5 d after the start of each experiment. Back-calculated knob length at the different temperatures indicated no significant
difference to the measured knob lengths except for the cases at 20 °C from hatching to 9-d-old larvae and at 14 °C from 20-
to 30-d-old larvae. The close correlation between somatic and otolith growth shown in this study indicated the feasibility
of estimating the growth history of Pacific saury larvae using otolith readings.
Received: 14 April 1999 / Accepted: 27 October 1999 相似文献
9.
The talitrid amphipod Uhlorchestia spartinophila lives in close association with standing-dead leaves of the smooth cordgrass Spartina alterniflora Loisel in salt marshes along the Atlantic coast of North America. This study probed the strength of the trophic link between
the amphipod population and the decomposition process in this detrital-based ecosystem. We measured survival, growth and reproductive
output in groups of amphipods reared for 6 wk on five diets derived from sheath and blade portions of S. alterniflora leaves just prior to (senescent) and during (dead) decomposition. In unfed treatments, the daily specific mortality rate
was 0.391 and starved amphipods survived no longer than 11 d. Among the fed treatments, a diet of senescent sheaths resulted
in the lowest survival (20%) and yielded no offspring. Groups fed senescent blades, dead sheaths, dead blades and unwashed
dead sheaths had survival rates of 56 to 84% and produced 5.0 to 12.5 offspring replicate−1. Sex ratio usually favored females, but approached unity in treatments with high overall survival, suggesting that quality
of available food resources may influence sex ratio in this species. Mean specific growth rates (mm mm−1 d−1) ranged from 0.013 to 0.016, and matched previous estimates of growth from field populations. Overall ecological performance
(survival + growth + reproduction) was similar for all food treatments, except senescent sheaths, which yielded a final mean
(±SD) dry biomass (0.4 ± 0.42 mg replicate−1) of amphipods significantly lower than that of other diets (1.7 ± 0.81 to 2.6 ± 0.69 mg replicate−1). Natural diets derived from decomposing cordgrass leaves can fulfill the nutritional requirements of U. spartinophila populations, but variation in initial amounts of living fungal biomass among the five experimental diets only partially explained
the responses of amphipods in our experiment. Structural characteristics and variation in rates of fungal occupation within
different portions of cordgrass leaves may affect the amphipod's ability to access plant production made available by decomposers.
Received: 12 December 1996 / Accepted: 18 December 1996 相似文献
10.
Dry weight (DW), oxygen consumption, ammonia-N excretion, proximate biochemical composition (total protein, carbohydrate,
lipid, water and ash), and energy content (estimated from biochemical composition and by wet combustion) were determined in
early developmental stages of cultured Farfantepenaeus paulensis. Pooled samples from embryonic, larval and postlarval stages (at 26 ± 1 °C and 34 ± 1‰) were used for measurements. The study
focused on physiological and biochemical processes during transitional periods of ontogeny, such as hatching, lecithotrophic
and planktotrophic stages, metamorphosis, and the attainment of a benthic existence in postlarva. DW showed higher increment
between protozoea I (PZ I) and mysis I (M I) than in the next mysid and postlarval stages. Individual rates of oxygen consumption
and ammonia-N excretion increased, while weight-specific rates presented significant reduction throughout development. Higher
weight-specific oxygen consumption was registered in nauplius III (N III) and PZ I, following a decrease in subsequent stages.
Postlarval stages PL V–VI and PL X–XII exhibited the lowest values among the stages studied. Weight-specific excretion was
high in N III and protozoeal stages, with maximum values in PZ II, while the following stages were marked by lower rates.
O:N ratios indicated higher protein catabolism in the stages between egg and M I and a shift to more lipid utilization close
to metamorphosis. Water content was higher in the protozoeal stages and decreased afterwards. Higher percentages of protein,
lipid and carbohydrate (%DW) were observed in egg and nauplius stages. Protein and lipid decreased from the egg through the
naupliar and protozoeal stages, rising again in mysis stages. Lipid content (%DW) decreased in PL V–VI and PL X–XII. Lipid:protein
ratios showed an increase of the importance of lipid between PZ III and M II. Carbohydrates represented a minor fraction of
body composition, and ash percentages increased from egg to a maximum in PZ II, decreasing in subsequent stages. Energy content
determined by wet combustion or calculated by energy equivalents presented the same trend throughout development, varying
similarly to protein. Protein was the main energy contributor to body energy in all stages, while the importance of lipid
was higher in egg and early naupliar stages. Trends observed in metabolic rates and body composition may be associated to
morphological and behavioral changes during the early stages of penaeid development, such as the transition from herbivory
to omnivory, and the adoption of a benthic existence. Different ontogenetic energy strategies contribute to succeed through
such diverse type of development.
Received: 4 July 2000 / Accepted: 6 December 2000 相似文献
11.
Thirty-eight yellowfin tuna (Thunnus albacares) were tagged with coded ultrasonic beacons between 6 March and 4 December 1996 near two buoys off the western coast of Oahu,
Hawaii. Two to four tuna were captured, tagged, and released on the same day in as rapid succession as possible in an effort
to tag members of the same school. Automated “listening” monitors attached to the buoys recorded when these marked individuals
entered within a radius of ≤1.1 km of the buoys during a 13 mo period. Twenty-seven of the tuna returned to the site of tagging.
The mean number of returns was 4.2 per tuna (max. = 17), and visits ranged from 1 to 910 min (median = 2.7 min, mean = 40.1 min).
The intervals between successive returns varied from 1 to 257 d (median = 3.0 d, mean = 17.4 d). Seventy-three percent of
the tuna returned together with tunas tagged on the same day, exceeding the frequency of returns of tuna tagged on another
day or arriving alone. This social cohesion is supported by the pattern of return visits by five tuna tagged on 6 March at
Monitoring Station R. Two or more of these tuna arrived together on 24 of 35 d when tagged tuna were detected. All five individuals
visited R on 11 April, a month after tagging, three arrived together 5 mo later on 4 August, and three returned 6 mo later
on 1 December 1996. Tuna often arrived at the same time of day, e.g. Individuals 1 and 3 visited R at 09:15 hrs on 12 April
and at 09:00 hrs 8 mo later. The returns were also site-specific. The 22 tuna tagged at R made 182 return visits to R (92.4%)
and only 15 visits to Monitoring Station K (7.6%), 10 km away. An allegiance of tuna to one school, a predilection for returning
to the site of tagging, and precise timing when visiting sites, are consistent with tuna having migratory pathways consisting
of “way-points” that are visited with temporal regularity.
Received: 30 April 1998 / Accepted: 27 October 1998 相似文献
12.
Tae Won Lee Michael J. Miller Hak Bin Hwang Sam Wouthuyzen Katsumi Tsukamoto 《Marine Biology》2008,153(3):285-295
Leptocephali of the widely distributed tropical marine eels of the genus Kaupichthys (family Chlopsidae) were collected around Sulawesi Island during a sampling survey in the Indonesian Seas in late September
and early October 2002, and the otolith microstructure of 24 of the 59 specimens captured was examined to learn about the
larval growth rates and spawning times of these small sized eels. Leptocephali ranging in size from 25 to 60 mm were collected
in Makassar Strait and the Celebes Sea, but they were most abundant in the semi-enclosed Tomini Bay of northeast Sulawesi
Island. The Kaupichthys leptocephali examined had 39–161 otolith growth increments. Their back-calculated hatching dates indicated that five age
groups were present and each group appeared to have been spawned around the full moon of previous months. Average growth rate
estimates of the first two age groups were 0.65 and 0.54 mm/day for the 27.4–30.4 and 37.6–45.6 mm age classes. The growth
rates of the oldest three age groups (52.0–60.8 mm) appeared to have slowed down after they reached their approximate maximum
size. An increase in increment widths at the outer margin of the otoliths of those larger than 53 mm suggested that the process
of metamorphosis had begun even though there were few external morphological changes indicating metamorphosis. It is hypothesized
that chlopsid leptocephali have an unusually short gut that may not need to move forward during early metamorphosis. The presence
of four age classes in Tomini Bay suggests that the Togian Islands region may be productive habitats for Kaupichthys juveniles and adults. 相似文献
13.
Using a biopsy dart system, samples of skin tissue were collected from southern right whales (Eubalaena australis) in 1995 on two wintering grounds, southwest Australia (n = 20) and the Auckland Islands of New Zealand (n = 20); and on offshore feeding grounds at Latitudes 40 to 43°, south of Western Australia (n = 5). A variable section of the mitochondrial DNA control-region (289 nucleotides) was amplified and sequenced from these
45 individuals (21 males, 20 females and 4 of unknown sex), distinguishing a total of seven unique sequences (i.e. mtDNA haplotypes).
Two haplotypes were found on both wintering grounds (including a common type representing 45% of each sample), and five types
were unique to only one wintering ground. An analysis of variance adapted for molecular information revealed significant genetic
differentiation between the two wintering grounds (p = 0.017). The feeding-ground sample was too small for statistical comparison with the wintering grounds, but included two
haplotypes found only in the Auckland Islands as well as the common haplotype found on both wintering grounds. The nucleotide
diversity and differentiation of mtDNA among the right whales was similar to that among humpback whales (Megaptera novaeangliae) from the same regions (Baker et al. 1998), but haplotype diversity was significantly reduced, perhaps as a result of more
intensive hunting during the last century and continued illegal hunting during this century.
Received: 16 March 1998 / Accepted: 18 December 1998 相似文献
14.
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
15.
Growth trajectories of individual larvae of Japanese sardine, Sardinops melanostictus, caught in the coastal waters off western Japan were back-calculated from the first feeding stage up to date of capture (approximate
size of 20 to 35 mm total length; TL) based on individually determined allometric relationships between otolith daily ring
radii and fish total lengths. The larvae in January-, February-, and March-hatched cohorts in the coastal waters grew faster
and more uniformly than those in the oceanic waters offshore of the Kuroshio current. Growth trajectories of the three hatch-month
cohorts were similar and could be expressed by the Gompertz model. The inflection points of the growth curves were reached
at 9 to 11 d after hatching, when larvae were 10.8 to 11.8 mm TL. Maximum growth rates at these points were 0.80 to 0.85 mm
d−1. Growth rates gradually declined after the inflection points, and larval TLs converged into the infinite length of 29 to
32 mm, the sizes at which metamorphosis from larvae to juveniles is initiated. This asymptotic growth pattern in the larval
stage resulted in the narrow ranges in TLs in spite of the wide range of ages of the larvae caught by boat seiners in the
coastal waters. Slow growth and therefore long duration of the metamorphosing stage could be influential in determining the
cumulative total mortality in the early life stages of the Japanese sardine.
Received: 14 July 1996 / Accepted: 20 August 1996 相似文献
16.
Juveniles of the planehead filefish Stephano-lepishispidus (Pisces: Monacanthidae) (Linnaeus, 1766) are a major component of the Sargassum spp. community, yet little is known of their ecology. In this study, the otolith record of age, growth, and ontogeny in S.
hispidus was examined. Juveniles caught off Beaufort Inlet, North Carolina (USA) on 30 June 1996 were marked with alizarin complexone
and reared in a flow-through, outdoor tank for up to 19 days. Examination of marked otoliths at several time intervals showed
that increment formation was not significantly different than one increment per day, and thus, increment number was used to
estimate age. Depth-distribution, morphology, and meristics of larvae and juveniles collected (1990–1992) between Cape Romain,
South Carolina, and Cape Hatteras, North Carolina, were examined to identify the timing of the larval to juvenile transition.
All indicators suggested the transition occurred between 17 and 20 days. Mean otolith increment widths exhibited a marked
change at about 20 days, coinciding with the timing of the larval to juvenile transition and a change in the depth distribution
from bottom to surface waters. Increment width of individual juveniles, however, did not exhibit the same pattern; only 40%
conformed to the pattern identified for all fish. Thus, the record of the larval to juvenile transition is clear at the population
level, but unresolved at the individual level.
Received: 1 November 1999 / Accepted: 18 December 2000 相似文献
17.
Arm damage is a widely reported but superficially investigated aspect of the biology of the starfish Asterias rubens L. In the present study, the incidence of arm damage was surveyed in populations of A.
rubens at two sites in the Firth of Clyde, Scotland, and three sites in Gullmarsfjorden, Sweden. The mean (±SD) incidence across
all sites of individuals with basal arm damage (resulting from detachment at the basal autotomy plane) was 19.69 ± 8.86%,
the incidence of those with distal arm damage (resulting from amputation at more distal levels) was 7.74 ± 10.01%. The mean
incidence of arms with basal damage was 5.28 ± 4.12%, of those with distal damage 1.83 ± 2.45%. There was a significant negative
correlation between size and the incidence of basal damage at all but one site, but no significant correlation between size
and distal damage at any site. Mechanical tests on specimens of the aboral body wall from the basal region of the arm (which
included the autotomy plane) and from a more distal region revealed that with increasing body size there was a significant
increase in yield stress, ultimate stress and Young's modulus (stiffness) but no significant change in yield strain and ultimate
strain. There was no significant difference between the relationships for basal and distal specimens. It is hypothesised that
in larger individuals increased mechanical toughness replaces autotomy as an effective antipredator strategy. Using two methods
to induce autotomy, a significant positive correlation between size and the delay between the onset of stimulation and arm
detachment was found; this may represent a size-related decline in the efficiency of the autotomy mechanism through the relaxation
of selection pressure. Since size is an unreliable indicator of age in A.
rubens, the trends identified herein can be interpreted only tentatively as age-associated phenomena.
Received: 4 September 1999 / Accepted: 17 February 2000 相似文献
18.
Halogenated metabolites in two marine polychaetes and their planktotrophic and lecithotrophic larvae
This study investigated the occurrence and ontogenetic changes of halogenated secondary metabolites in planktotrophic and
lecithotrophic larvae and adults of two common, infaunal polychaetes, Streblospio benedicti (Spionidae) and Capitella sp. I (Capitellidae), with different life-history traits. S. benedicti contains at least 11 chlorinated and brominated hydrocarbons (alkyl halides) while Capitella sp. I contains 3 brominated aromatic compounds. These halogenated metabolites are potential defense compounds benefiting
both larvae and adults. We hypothesized that: (1) planktotrophic larvae contain halogenated metabolites because they are not
protected by adult defenses, (2) quantitative and qualitative variation of planktotrophic larval halogenated metabolites parallels
that of adults, and (3) brooded lecithotrophic larvae initiate the production of halogenated metabolites only after metamorphosis.
To address these hypotheses, volatile halogenated compounds from polychaete extracts were separated using capillary gas chromatography
and identified and quantified using mass spectrometry with selected ion monitoring. All four life stages (pre- and post-release
larvae, new recruits, adults) of both S. benedicti and Capitella sp. I contained the halogenated metabolites previously identified from adults. This is the first report of halocompounds
identified and quantified in polychaete larvae. Allocation of potential defense compounds to offspring varied as a function
of species, feeding type and developmental stage. Pre-release larvae of S. benedicti with planktotrophic development contained the lowest concentration of total halogenated metabolites (1.75 ± 0.65 ng mm−3), post-release and new recruits contained intermediate concentrations (8.29 ± 1.72 and 4.73 ± 2.63 ng mm−3, respectively), and planktotrophic adults contained significantly greater amounts (28.9 ± 9.7 ng mm−3). This pattern of increasing concentrations with increasing stage of development suggests synthesis of metabolites during
development. Lecithotrophic S. benedicti post-release larvae contained the greatest concentrations of halometabolites (71.1 ± 10.6 ng mm−3) of all S. benedicti life stages and developmental types examined, while the amount was significantly lower in new recruits (34.0 ± 15.4 ng mm−3). This pattern is consistent with a previously proposed hypothesis suggesting a strategy of reducing potential autotoxicity
during developmental transitions. Pre-release lecithotrophic larvae of Capitella sp. I contained the highest concentration of total halogenated metabolites (1150 ± 681 ng mm−3), whereas the adults contained significantly lower total amounts (126 ± 68 ng mm−3). All concentrations of these haloaromatics are above those known to deter predation in previously conducted laboratory and
field trials. As a means of conferring higher larval survivorship, lecithotrophic females of both species examined may be
expending more energy on chemical defenses than their planktotrophic counterparts by supplying their lecithotrophic embryos
with more of these compounds, their precursors, or with energy for their synthesis. This strategy appears common among marine
lecithotrophic larval forms.
Received: 14 July 1999 / Accepted: 20 January 2000 相似文献
19.
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
20.
M. E. Lutcavage R. W. Brill G. B. Skomal B. C. Chase J. L. Goldstein J. Tutein 《Marine Biology》2000,137(2):347-358
Ultrasonic, depth-sensitive transmitters were used to track the horizontal and vertical movements, for up to 48 h, of 11
adult (136 to 340 kg estimated body mass) North Atlantic bluefin tuna (Thunnus thynnus Linnaeus). Fish were tracked in October 1995, September and October 1996, and August and September 1997 in the Gulf of Maine,
northwestern Atlantic. The objective was to document the behavior of these fish and their schools in order to provide the
spatial, temporal, and environmental information required for direct (i.e. fishery-independent) assessment of adult bluefin
tuna abundance using aerial surveys. Transmitters were attached to free-swimming fish using a harpoon attachment technique,
and all fish remained within the Gulf of Maine while being followed. Most of the bluefin tuna tagged on Stellwagen Bank or
in Cape Cod Bay (and followed for at least 30 h) held a predominately easterly course with net horizontal displacements of
up to 76 km d−1. Mean (±SD) swimming depth for all fish was 14 ± 4.7 m and maximum depth for individuals ranged from 22 to 215 m. All but
one fish made their deepest excursions, often single descents, at dawn and dusk. In general, adult bluefin tuna spent <8%
of their time at the surface (0 to 1 m), <19% in the top 4 m, but >90% in the uppermost 30 m. Mean (±SD) speed over ground
was 5.9 km h−1, but for brief periods surpassed 20 to 31 km h−1. Sea surface temperatures during tracking were 11.5 to 22.0 °C, and minimum temperatures encountered by the fish ranged from
6.0 to 9.0 °C. Tagged bluefin tuna and their schools frequented ocean fronts marked by mixed vertebrate feeding assemblages,
which included sea birds, baleen whales, basking sharks, and other bluefin schools.
Received: 19 July 1999 / Accepted: 25 March 2000 相似文献