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1.
A series of laboratory (short-term exposure in small beakers) studies and a 19 d mesocosm (6 m3 polyethylene bags filled with fjord water) study were conducted on blue mussel, Mytilus edulis, larvae and plantigrades exposed to a concentration gradient of the detergent linear alkylbenzene sulphonate (LAS, 0 to 39 mg l−1). LAS is increasingly found in nearshore environments receiving wastewater from urban treatment plants. The aims were to
observe physiological effects on swimming, grazing and growth in the laboratory and effects on settling and population development
at in situ conditions (in field mesocosms) in order to evaluate the damages on ciliated meroplankton caused by LAS. In the
laboratory the larvae showed a 50% mortality at 3.8 mg LAS l−1 after 96 h exposure whether or not food was provided. Additionally the swimming behaviour was affected at 0.8 mg LAS l−1 (i.e. a more compact swimming track, a smaller diameter of the swimming tracks, and reduced swimming speed). The larval particle
grazing was reduced 50% at 1.4 mg LAS l−1. The specific growth rate of the larvae was reduced to half at 0.82 mg LAS l−1 over 9 d. During the mesocosm experiment, the larval population showed a dramatic decrease in abundance within 2 d at concentrations
as low as 0.08 mg LAS l−1, both due to a significantly increased mortality, but also due to settling. The settling success was reduced at the same
LAS concentration as that at which mortality was observed to increase significantly. In addition to reduced settling rate,
the larvae showed delayed metamorphosis and reduced shell growth as a response to LAS. Our hypothesis that the larval ciliary
apparatus, crucial for normal swimming, orientation, and settling behaviours and for particle uptake, was damaged due to LAS
exposure is supported by our results. This is confirmed by the physiological data (grazing, growth) and in the direct video-based
observations of larval performance (swimming) and provides a reasonable explanation for what was observed in the bags (abundance,
settling, mortality). These physiological effects on blue mussel larvae/plantigrades occurred at LAS concentrations reported
to occur in estuarine waters.
Received: 15 January 1997 / Accepted: 12 February 1997 相似文献
2.
J. Gilmour 《Marine Biology》1999,135(3):451-462
Laboratory and field experiments were used to determine whether high (≃100 mg l−1), low (≃50 mg l−1) and control (≃0 mg l−1) levels of suspended sediment affected fertilisation, larval survival, and larval settlement in the scleractinian coral Acropora digitifera (Dana, 1846). Both high- and low-sediment treatments significantly decreased fertilisation, but post-fertilisation embryonic
development was not inhibited by suspended sediments. Larval survival and larval settlement were significantly reduced in
high- and low-sediment treatments. No difference was found between high- and low-sediment treatments in any of the three post-spawning
processes investigated, suggesting that they are susceptible to sediment concentrations which are not exceptionally high even
under natural conditions (>50 mg l−1). The introduction of an additional stress in the form of high levels of suspended sediments coupled with naturally high
variability in recruitment may have a considerable effect on the successful supply and settlement of coral larvae to a reef.
Given that many coral communities are open reproductive systems, the consequences of disturbance events are not likely to
be restricted to the impact area. Recruitment to a population may be reduced significantly in the presence of high levels
of suspended sediments because of effects on larval survival and settlement. Recruitment of larvae to adjacent populations
may also be affected due to a decreased fertilisation success and potential increases in mortality of larvae passing through
the affected site.
Received: 13 August 1998 / Accepted: 22 July 1999 相似文献
3.
Detailed inventories of the benthos and field studies of the settlement and recruitment processes of marine benthic invertebrates
require accurate identification of newly settled larvae and early juvenile stages. We provide morphological criteria, visible
under a good quality dissecting stereomicroscope, by which to discriminate between species of the settling larval and early
postlarval stages (∼250 to 700 μm shell length) of mussels of the genus Mytilus on the west coast of Vancouver Island and Southern California. Compared to the bay mussel (M. trossulus), the sea mussel (M. californianus) has: (i) a shallower and flatter umbo, the latter corresponding to a significantly less pronounced prodissoconch I (PI)
curvature and (ii) a greater PI length; as well as (iii) a wider separation between the provincular lateral teeth (PLT). The
PLT distance is a new term denoting the separation between the midpoint of two reddish pigment spots of the provinculum (larval
hinge apparatus) region of settling larvae and early postlarvae of Mytilus spp. from the East Pacific Coast. These spots mark the larger provincular lateral teeth, situated at either end of the provinculum.
We confirmed the validity of morphological criteria by comparing PCR products of genomic DNA of provisionally identified postlarvae.
Furthermore, measurements of PI lengths and PLT distance from well-preserved postlarvae of sea mussels (M. californianus) and of bay mussels (M. galloprovincialis) from Southern California indicate that the PI morphology and morphometry, and PLT distance criterion apply for that region
as well. The criteria presented here can also apply to the advanced (competent) veliger stages, as the latter may settle (i.e.
become the “settling” stage) upon encountering a suitable substrate. Our present and previously published work provide economical
and effective identification methods that can be used to discriminate among early life history stages (∼250 μm to 5.0 mm shell
length) of Mytilus spp. along the west coast of North America.
Received: 10 November 1999 / Accepted: 6 September 2000 相似文献
4.
Late larvae of the serranid coral trout Plectropomus leopardus (Lacepède), captured in light traps, were released during the day both in open water and adjacent to two reefs, and their
behaviour was observed by divers at Lizard Island, northern Great Barrier Reef. Coral trout larvae (n = 110) were present in light-trap catches from 18 November to 3 December 1997, including new moon (30 November). The swimming
speed of larvae in open water or when swimming away from reefs was significantly greater (mean 17.9 cm s−1) than the speed of larvae swimming towards or over reefs (mean 7.2 cm s−1). Near reefs, larvae swam at average depths of 2.7 to 4.2 m, avoiding 0 to 2 m. In open water, swimming depth varied with
location: larvae >1 km east of Lizard Island swam steeply downward to >20 m in 2 to 4 min; larvae >1 km west oscillated between
2.6 and 13 m; larvae 100 to 200 m east of Lizard Island oscillated between 0.8 and 15 m. Nearly all larvae swam directionally
in open water and near reefs. In open water, the average swimming direction of all larvae was towards the island, and 80%
(4 of 5) swam directionally (p < 0.05, Rayleigh's test). Larvae swam directionally over the reef while looking for settlement sites. The frequency of behaviours
by larvae differed between two reefs of different exposure and morphology. Depending on site, 26 to 32% of larvae released
adjacent to reefs swam to open water: of these, some initially swam towards or over the reef before swimming offshore. In
some cases, offshore-swimming seemed to be due to the presence of predators, but usually no obvious cause was observed. Depending
on the reef, 49 to 64% of the larvae settled. Non-predatory reef residents aggressively approached 19% of settlers. Between
5 and 17% of the larvae were eaten while approaching the reef or attempting to settle, primarily by lizardfishes but also
by wrasses, groupers and snappers. A higher percentage of larvae settled in the second week of our study than in the first.
Average time to settlement was short (138 s ± 33 SE), but some larvae took up to 15 min to settle. Average settlement depth
was 7.5 to 9.9 m, and differed between locations. No settlement took place on reef flats or at depths <4.2 m. Larvae did not
appear to be selective about settlement substrate, but settled most frequently on live and dead hard coral. Late-stage larvae
of coral trout are capable swimmers with considerable control over speed, depth and direction. Habitat selection, avoidance
of predators and settlement seem to rely on vision.
Received: 7 July 1998 / Accepted: 26 January 1999 相似文献
5.
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
6.
Larval settlement in the marine polychaete Hydroides elegans (Haswell) is induced by certain bacteria in marine biofilms. The exact nature of the settlement cue that larvae of H. elegans receive from these bacteria remains unknown. In this study, we revealed some properties of the bacterially derived larval
settlement cue by investigating the larval settlement inductive activity of two bacterial strains after various treatments.
These two bacterial strains, Roseobacter sp. and an α-subclass Proteobacteria, are highly inductive to larval settlement of H. elegans. The larvae responded similarly to Roseobacter and Proteobacteria in all the larval settlement bioassays, suggesting that the larval settlement-inducing substances produced by these bacteria
may share common characteristics. First of all, the larvae did not settle in the seawater conditioned by the bacteria attached
as a film or by the bacteria that were freely suspended in seawater. The results suggest that the putative larval settlement
cue is not released into seawater and, therefore, should be associated with the surface of the bacteria. Secondly, formaldehyde
treatment entirely eliminated the larval settlement induction activity of the bacterial films, and streptomycin treatment
reduced the percentage of larval settlement on the bacterial films in a concentration-dependent manner. Since both treatments
can kill bacteria with little damage to the surface chemistry of bacterial cells, the decline in larval settlement is suggested
be due to a reduction of the viable bacterial population in the bacterial films. In fact, the reduction of larval settlement
in the streptomycin treatments coincided with the decrease in viable bacterial populations in broth cultures containing respective
concentrations of streptomycin. These results suggest that the viability of Roseobacter and Proteobacteria is important to their settlement induction effect. Since the larval settlement induction activity of the bacterial strains
appears to correlate with their viability, we suggest that the putative larval settlement cue is derived from a metabolic
pathway in the bacteria and that the cue is exported to and concentrated at the extracellular polymer matrix of the bacterial
cell, at which the larvae establish contact with the bacteria. The larval settlement cue may be highly susceptible to degradation
so that a metabolically active bacterial film is needed to maintain the putative cue at a concentration that surpasses the
threshold for induction of larval settlement.
Received: 14 October 1998 / Accepted: 5 September 2000 相似文献
7.
It has been hypothesized that marine fish larvae in the advanced stages of starvation would show increased density (ρ = mass
volume−1) from water loss due to osmoregulation failure. Changes in larval buoyancy are currently attributed to swim bladder regulation
and protein synthesis or catabolism. Osmoregulation-related changes in density is an alternative mechanism, the importance
of which remains untested in the laboratory and the influence of which on vertical distributions is unknown. We provide evidence
that loss of osmotic control is a plausible mechanism for increased density of larval cod (Gadus morhua L.). Furthermore, our results show that this mechanism is not restricted to larvae in the advanced stages of starvation.
“Relative” larval densities are estimated using a modified density gradient. We use a gravimetric method to separate the effects
of nutrition from osmoregulation failure. We assessed the importance of sampling strata on estimates of larval density. Proportional
sampling within three depth strata (stratified sample) produced the least biased method for determining the “average” density
of a population of larvae in laboratory culture. Larvae sampled from the bottom third of the culture tank were significantly
more dense then those sampled from the surface. This was true for larvae of all ages. The average change in density from hatching
till death from starvation for larvae sampled in the surface stratum was nominal (Δρ = 5.0 × 10−4 g cm−3), while the change for those sampled from the bottom stratum was large (Δρ = 3.8 × 10−3 g cm−3). These large density differences suggest that larvae sampled from the bottom stratum were either osmotically stressed or
were facultatively changing their density via regulatory pathways. Preliminary observations suggest that vitality is lower
amongst those larvae which are sampled near the bottom. The small change in average density of larvae sampled from the surface
stratum was due to starvation. The density differences we observed between “osmotically stressed” and “starving” larvae could
readily have been misconstrued as differences in feeding and growth experienced by individual larvae. The potential bias of
increased density from osmoregulation failure must be considered as a factor in experimental designs developed to assess the
effect of fed and starved treatments on buoyancy for larvae of all ages. The simple bioassay we describe may prove useful
both as a means of assessing larval condition and as a mechanism for evaluating factors affecting larval vertical distributions
in the field.
Received: 13 January 1997 / Accepted: 3 February 1997 相似文献
8.
The blue mussels Mytilus edulis L. and M. galloprovincialis Lmk. hybridize in western Europe. Within hybrid populations nuclear alleles specific to M. galloprovincialis increase in frequency with age and size. This relationship changes with tidal height; alleles from M. galloprovincialis occur more frequently high in the intertidal zone, while M. edulis alleles predominate in the low intertidal zone. We tested the hypotheses that larvae with M. galloprovincialis alleles tend to settle higher in the intertidal zone, or that mussels redistribute themselves with respect to tidal height
after initial larval settlement. We sampled recently metamorphosed mussels every 2 weeks in a hybrid mussel population at
Whitsand Bay in southwest England throughout the summer of 1996. We observed four cohorts of newly settled mussels. There
was no evidence of differential settlement of mussels with different genotypes in connection with tidal height, or into shaded
versus unshaded microsites. Therefore, we rejected the preferential settlement hypothesis. There was substantial movement
of juvenile mussels in the first 4 weeks following initial settlement, but this “secondary settlement” did not result in genetic
differentiation with respect to tidal height. Further, significant differences in allele frequencies were found between primary
and secondary spat. This allele frequency change was in the opposite direction of that seen in the adult population, suggesting
newly settled larvae may be experiencing different selective pressures than adults. We propose that the genetic structure
of hybrid mussel populations with respect to tidal height is the consequence of differences in selection intensity.
Received: 30 April 1999 / Accepted: 5 May 2000 相似文献
9.
To examine the impact of development rate on swimming performance, escape response, and morphology, yolk-sac larvae of American
plaice (Hippoglossoides platessoides, Fabricius) were reared at two temperatures (5 and 10 °C). Videomicroscopy and silhouette collimation videography were used
to examine swimming, escape behaviour, and morphology (standard length, finfold area, and yolk-sac area) of individual larvae.
Larvae were examined from 0 d post hatch (dph) to 14 dph for the 5 °C treatment group and from 0 to 6 dph for the 10 °C treatment
group (3 August to 17 August 1996). Since larvae were not fed, yolk-sac reserves were essentially exhausted by 14 and 6 dph
for the 5 and 10 °C treatment groups, respectively. To control for the effect of testing temperature on behaviour, larvae
from each temperature treatment were tested at both 5 and 10 °C. Testing temperature had an effect on some swimming parameters
but not on escape response. Swimming performance, escape response, and morphology varied with age, while only morphology and
escape response varied with development rate. Morphology and swimming performance, and morphology and escape response were
found to be correlated as determined by canonical correlation. This study suggests that both types of swimming behaviours
should be examined when developing models of the impacts of predation on the early life history of larval fish.
Received: 13 September 1999 / Accepted: 21 June 2000 相似文献
10.
We tested the hypothesis that regional differences in oceanic productivity have led to the evolution of predictable patterns
of regional variation in life-history traits of pelagic larvae of tropical reef fishes. To do so we compared larval traits
(egg and hatchling size, larval growth rate and duration, and size at settlement) among closely related reef fishes from the
Atlantic and Pacific coasts of the Isthmus of Panama. This comparison provides a control for phylogenetic effects because
those regions shared a common fauna prior to the rise of the Isthmus ˜3.5 million years ago, subsequent to which each fauna
evolved independently under a very different productivity regime. We measured larval traits of 12 benthic-spawning damselfishes
(Pomacentridae: Abudefduf, Chromis and Stegastes) and 13 pelagic-spawning wrasses (Labridae: Bodianus, Halichoeres and Thalassoma). These included members of each genus on each side of the Isthmus and four sets of transisthmian sister species of pomacentrids.
Among the pomacentrids we found consistent transisthmian differences in hatchling size, but not in other larval traits. Essentially
the reverse pattern occurred among the labrids – larval growth and duration differed consistently among congeners in the two
regions, but without consistent differences in hatchling size or size at settlement. Neither relationship is predicted by
the regional-productivity hypothesis. Most of the differences were quite small. Stronger phylogenetic effects on larval traits
(inter- and intrageneric variation within regions) occur in both families and evidently overwhelm any effect of regional variation
in productivity. Reassessment of data that takes into account such phylogenetic effects questions previous conclusions about
the existence of regional differences in larval traits among damselfishes in the West Pacific and the Caribbean.
Received: 19 January 2000 / Accepted: 26 September 2000 相似文献
11.
Influence of substratum heterogeneity and settled barnacle density on the settlement of cypris larvae 总被引:3,自引:0,他引:3
On the Atlantic coast of Canada, Semibalanus balanoides (L.) is widely distributed in the mid-intertidal zone, whereas in the Gulf of St. Lawrence, this species is mostly limited to crevices. We tested the hypothesis of regional differences in microhabitat selection by barnacle larvae at settlement in 1984 and 1985 at St. Andrews, New Brunswick, Canada. Since larvae settle in microhabitats already colonized by adults, the relative influence of settled barnacle density and of different scales of substratum heterogeneity on settlement were evaluated experimentally at Capucins, Québec, (Gulf of St. Lawrence) and at St. Andrews, New Brunswick (Atlantic coast). On a large scale (>10 cm deep crevices) of heterogeneity, results show that, in the Gulf, cypris larvae settled nearly exclusively (93%) in natural crevices rather than on adjacent horizontal surfaces. On the Atlantic coast, settlement was more important outside than inside of crevices, when the substrata were either natural or artificial. This result is unique and contrasts sharply with all known reports on barnacle settlement in relation to surface contour. The influence of barnacle density on settlement was greater than that of large scale heterogeneity. On a small scale (<1.5 cm deep cracks), the presence of conspecifics had a stronger effect on settlement than heterogeneity in both regions. Field observations showed a relationship between larval settlement density and percentage of adult cover. Settlement increased up to 22 or 30% (Gulf and Atlantic coast) of adult cover and decreased afterwards. The results confirm the hypothesis of larval selection for cryptic habitats in the Gulf and the opposite behaviour (preferences for horizontal surfaces) on the Atlantic coast. This microhabitat selection is apparent at large scales of heterogeneity, whereas at small scales, the presence of conspecifics is the predominant factor.Contribution to the programme of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec) 相似文献
12.
Larval growth rate and settlement of the European flat oyster Ostrea edulis were experimentally studied as a function of the composition of dietary fatty acids. Diets differing in fatty acid composition
were composed by mixtures of the microalgae Isochrysis galbana, Pavlova lutheri and Chaetoceros calcitrans. Fatty acid content in the tissue of the feeding larvae, analyzed by gas chromatography and mass spectrometry, reflected
the composition in the diet. Larval growth rate was significantly correlated to the three omega-3 polyunsaturated fatty acids
(PUFA) C18:3, C18:4 and C22:6, with minor differences for neutral and polar lipids. No relation between growth rate and the
omega-3 PUFA C20:5 was detected, a PUFA often implied as essential for bivalves. It is suggested that naturally occurring
variability in fatty acid composition may constrain larval growth. In settlement experiments in both still water and flume
flow little substrate selectivity was found for some contrasting substrates. It is concluded that differences in dietary fatty
acids may explain as much of settlement success as the variability of substrates.
Received: 12 October 1998 / Accepted: 6 April 1999 相似文献
13.
Larvae of a colonial ascidian use a non-contact mode of substratum selection on a coral reef 总被引:2,自引:0,他引:2
D. S. Stoner 《Marine Biology》1994,121(2):319-326
The rate at which larvae successfully recruit into communities of marine benthic invertebrates is partially dependent upon how well larvae avoid benthic predators and settle on appropriate substrata. Therefore, to be able to predict recruitment success, information is needed on how larvae search for settlement sites, whether larvae preferentially settle on certain substrata, and the extent to which there are adequate cues for larvae to find these substrata. This article describes how larvae of the colonial ascidian Diplosoma similis find settlement sites on a coral reef. Direct field observations of larval settlement were made on a fringing reef in Kaneohe Bay, Oahu, Hawaii, between September 1985 and April 1986. A comparison of the substrata that larvae contacted prior to settlement relative to the percentage cover of these substrata on the study reef suggests that larvae are using a non-contact mode of substratum identification to locate suitable settlement sites. This mode of substratum identification allowed 74% of larvae to evade predation by benthic organisms who would otherwise have eaten larvae if they had been contacted. Of those larvae that evaded predation, 88% subsequently settled on the same two substrata upon which most adults are found (dead coral or the green alga Dictyosphaeria cavernosa). This pattern of settlement was probably a result of active selection, since the two substrata cover only 14.4% of the reef's surface and currents had little effect on the direction in which larvae swam. An important contributing factor to the high success rate of larval settlement on suitable substrata was the lack of any temporal decay in substratum preference. It is concluded that for Diplosoma similis larval supply is a sufficient predictor of larval settlement rate. However, for marine invertebrates whose larvae are passively dispersed and exhibit a greater temporal decay in substratum preference, larval settlement should generally have a greater dependency on spatial variation in the abundance of benthic predators and suitable substrata. 相似文献
14.
The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time
these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained
in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the
majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning.
Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential
for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species
studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced
and relatively isolated.
Received: 27 May 1997 / Accepted: 27 November 1997 相似文献
15.
H. Zenitani 《Marine Biology》1999,134(4):645-652
The size-specific nutritional conditions of larval sardines, Sardinops melanostictus, from the main Kuroshio Current and its offshore waters off eastern Japan were assessed by lipid analysis. A rapid lipid
analysis technique (diagnostic kits for human serum lipids) was used to measure the different lipid components of individual
sardine larvae as indicators of their nutritional condition. Size-specific growth trajectories of individual larvae were estimated
by the biological intercept method, and the recent daily growth rate of standard length (SL) was calculated from the 3 d outer increment width on the otolith. Relationships between the amount of larval phospholipid
(PL; tissue weight indicator) and SL, and the recent daily growth rate of larva (Gr) and SL, could be expressed by the equations PL = 0.459 SL
1.77 and Gr = 0.0809 SL − 0.341, respectively. There was no notable difference in these values between the two survey areas. The relationship between
the amount of triglyceride (TG) and SL could be expressed allometrically (TG = 0.013 SL
2.63). The relationship between the index of starvation tolerance (TG/PL) and SL could be expressed by the allometric equation TG/PL = 0.0288 SL
0.865, suggesting that larger sardine have a higher starvation tolerance than smaller sardine. The TG of the 8 to 9 mm SL size-class larvae in the offshore area was higher than in the main Kuroshio Current. To test whether
the TG for each larval sardine in the 8 to 9 mm SL size-class could be correlated with variables (temperature, chlorophyll a and distribution density of the sardine larvae) measured at the sampling stations, correlation analyses were performed. A
highly significant negative correlation between TG and distribution density of the sardine larvae was found. A density-dependence effect seemed to influence the fluctuation
of the larval storage energy component for short-term needs.
Received: 12 March 1998 / Accepted: 26 March 1999 相似文献
16.
We performed an intensive year-round sampling with the aim of studying the abundance of sponge larvae in four Mediterranean
benthic communities: photophilic algae, sciaphilous algae, semi-obscure (i.e. low light-intensity) caves and sandy bottoms.
We record here for the first time, a larval bloom of Cliona viridis (Schmidt 1862), the most common excavating sponge in the Mediterranean, which took place simultaneously in several rocky
communities of the Blanes sub-littoral (NE Spain), and discuss the role of restricted larval dispersal in the distribution
of adult sponges. In the communities studied, C. viridis larvae bloomed synchronously once, in June. Spawning and consequent embryo development presumably occurred in May, when water
temperature was 16 °C. The free larva is a small, evenly ciliated, weakly swimming parenchymella with low dispersal capabilities.
The number of larvae m−3 and sponge abundance (as percent cover and biomass) were significantly higher in the community of sciaphilous algae than
in the other communities studied. Because of limited larval dispersal, larval and adult abundance in the communities were
positively correlated. Larvae developed into juvenile sponges 10 to 15 d after settlement. Settlers displayed distinctive
features: a peripheral cuticle, vacuolar etching-like cells at the sponge base, absence of oscular chimneys, and the presence
of zooxanthellae, which were presumably transmitted during oocyte maturation.
Received: 24 January 2000 / Accepted: 4 July 2000 相似文献
17.
Role of bacteria in larval settlement and metamorphosis of the polychaete Hydroides elegans 总被引:1,自引:0,他引:1
The serpulid polychaete Hydroides elegans Haswell, 1883 is an early colonist of new substrata in Pearl Harbor, Oahu, Hawaii. When metamorphically competent, larvae
of H. elegans will settle rapidly upon an acceptably biofilmed surface, but not on a clean surface. In this study we found the ability
of larvae to respond selectively to inductive surfaces to be retained for at least 3 wk. Of a series of bacterial strains
isolated from Hawaiian marine biofilms, 13 induced larval settlement, 11 gave moderate or mixed results, and 10 others did
not stimulate the settlement of H. elegans. The amount of settlement induced by monospecific strains was rarely as great as with natural, multispecies films. Most of
the isolated bacteria were motile Gram-negative rods, but Gram-positive strains were also present, and diverse metabolic types
were represented in the study. Biofilms killed by treatment with heat, ultraviolet radiation or chemical fixatives were no
longer inductive. Soluble, dialyzable, heat-stable bacterial products induced settlement and metamorphosis more slowly. The
range of bacteria producing an inductive signal suggests either that there are multiple cues, or that the cue is common to
many bacteria. Chemical signals characteristic of early microbial biofilms may indicate freshly available substrata with optimal
potential for the growth and survival of H. elegans.
Received: 30 January 1998 / Accepted: 12 September 1998 相似文献
18.
Carl Van Colen J. Lenoir A. De Backer B. Vanelslander M. Vincx S. Degraer T. Ysebaert 《Marine Biology》2009,156(10):2161-2171
The role of multi-species benthic diatom films (BDF) in the settlement of late pediveliger larvae of the bivalve Macoma balthica was investigated in still-water bioassays and multiple choice flume experiments. Axenic diatom cultures that were isolated
from a tidal mudflat inhabited by M. balthica were selected to develop BDF sediment treatments characterized by a different community structure, biomass, and amount of
extracellular polymeric substances (EPS). Control sediments had no added diatoms. Although all larvae settled and initiated
burrowing within the first minute after their addition in still water, regardless of treatment, only 48–52% had completely
penetrated the high diatom biomass treatments after 5 min, while on average 80 and 69% of the larvae had settled and burrowed
into the control sediments and BDF with a low diatom biomass (<3.5 μg Chl a g−1 dry sediment), respectively. The percentage of larvae settling and burrowing into the sediment was negatively correlated
with the concentration of Chl a and EPS of the BDF. This suggests higher physical resistance to bivalve penetration by the BDF with higher diatom biomass
and more associated sugar and protein compounds. The larval settlement rate in annular flume experiments at flow velocities
of 5 and 15 cm s−1 was distinctly lower compared to the still-water assays. Only 4.6–5.8% of the larvae were recovered from BDF and control
sediments after 3 h. Nonetheless, a clear settlement preference was observed for BDF in the flume experiments; i.e., larvae
settled significantly more in BDF compared to control sediments irrespective of flow speed. Comparison with the settlement
of polystyrene mimics and freeze-killed larvae led to the conclusion that active selection, active secondary dispersal and,
at low flow velocities (5 cm s−1), passive adhesion to the sediment are important mechanisms determining the settlement of M. balthica larvae in estuarine biofilms. 相似文献
19.
Cod (Gadus morhua L.) eggs may develop and hatch within temperatures of −1.5 to 12 °C, but little is known about the effects of very low temperatures
on larval characteristics. Eggs of the Northeast Arctic cod (Gadus morhua) were incubated at 1, 5 or 8 °C from Day 1 after fertilisation until hatching, and transferred to 5 °C after hatching. Histological
samples of the axial musculature were taken at hatching and 5 d after hatching, and the data on muscle cellularity from these
samples were related to survival and hatching, size, developmental data and viability of the yolk sac larvae. All larvae hatched
at the same developmental stage. Incubation of eggs at 1 °C produced shorter larvae with a larger yolk sac and more, small
deep fibres at hatching than larvae from eggs incubated at 5 or 8 °C. The larval size difference was still present 5 d after
hatching, a time at which the larvae from 1 °C-incubated eggs were less developed and less resistant to an acute viability
stress test (65 ppt salinity). Although there were no differences between temperature groups in number and size of muscle
fibres 5 d after hatching, the deep fibres of the 1 °C-group contained less myofibrils than the two other groups. The phenotype
of the larvae at hatching was thus affected within these incubation temperatures. Although all groups were transferred to
the same temperature after hatching, the lowest egg incubation temperature (1 °C) still had a negative effect 5 d after hatching,
as these larvae were both smaller, less resistant to stress and had less functional muscles at the time of first feeding.
Our conclusion is therefore that 1 °C is close to, or below, the lower thermal tolerance limit for normal functional development
of Northeast Arctic cod. The results are discussed in relation to larval viability and recruitment of this species in the
wild.
Received: 4 February 1998 / Accepted: 10 July 1998 相似文献
20.
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