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1.
The life cycle of Lychnorhiza lucerna (Scyphozoa: Rhizostomeae) and the settlement preferences of its larvae were studied using laboratory-based rearing experiments.
Mature medusae of L. lucerna were collected from the beach of the Río de la Plata estuary, Argentina. This species displayed the typical metagenetic,
(i.e. medusoid and polypoid), life cycle reported for other rhizostomes. The fertilized eggs developed into motile and short
lived planulae. The majority of planulae settled on the air-water interface (p < 0.001). Of those that settled on the settlement plates provided, no significant differences were observed between styrene
slides, glass slides and shells of the bivalve Mactra isabelleana (p > 0.05). No planulae settled on stones. Several hours after planulae settled, they metamorphosed into sessile four-tentacled
scyphistomae. Most scyphistomae attached onto the air-water interface. At 19–22°C, the scyphistomae grew up to 22 tentacles
and reached 1,500 μm height. The scyphistomae increased their numbers by means of formation of podocysts from which new polyps
emerged and strobilated. Strobilation occurred 46 days after settlement. Only polydisk strobilation was observed and each
strobila always produced three ephyrae. After releasing ephyrae, strobilae returned to normal scyphistomae and were capable
of repeating strobilation. A single founder polyp was estimated to produce up to 60 ephyrae over 4 months. Ephyrae developed
into metephyrae 15 days after release at 19–22°C. In this paper we describe the morphological and some behavioural features
of L. lucerna in the polypoid and early medusoid stages. 相似文献
2.
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
3.
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
4.
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
5.
Distributions of serotonin and catecholamines in larvae of the marine bryozoan Bugula neritina (Bryozoa: Cheilostomatida) were investigated using immunohistochemistry with anti-serotonin antiserum and glyoxylic acid–induced
fluorescence histochemistry. Anti-serotonin immunoreactive substances and glyoxylic acid–induced fluorescent substances had
similar distributions in the equatorial neuromuscular ring, the neural plexus, the paired axial neuromuscular cords, and tracts
connecting the neural plexus to ciliated cells bordering the pyriform organ. The effects of dopamine, noradrenaline, adrenaline,
tyramine, octopamine, synephrine and serotonin, at 10−4, 10−5 and 10−6
M, on settlement were analysed. In filtered seawater, 98% of larvae settled in 3 h, but only 11%, 3% and 6% total settlement
was observed after 8 h in 10−4
M dopamine, 10−4
M serotonin and 10−5
M serotonin, respectively. Total settlement was 70% in 10−4
M noradrenaline, 80% in 10−4
M adrenaline and 60% in 10−4
M tyramine. Less than 60% settlement was observed in 10−4 and 10−5
M octopamine and synephrine. Serotonin's inhibitory effect on settlement was mimicked by a range of serotonin receptor agonists
and antagonists, among which 5-carboxamidotryptamine was the most potent.
Received: 19 March 1999 / Accepted: 11 October 1999 相似文献
6.
Andrew Storfer 《Behavioral ecology and sociobiology》1999,46(4):273-279
There is increasing evidence that populations may not be well adapted to their local environments, and as a result, recent
interest has focused on understanding factors that constrain adaptive evolution. This study presents data suggesting gene
flow may constrain the ability of larvae of the streamside salamander Ambystoma barbouri to avoid predation by fish via escape behavior and life history tactics. Streamside salamander larvae face conflicting selection
pressures in different streams. Some streams are ephemeral, where larvae should be active to feed, grow, and reach metamorphosis
before stream drying. Other streams contain predatory fish, where larvae should be generally inactive to avoid predation.
Previous work has shown that streamside salamander larvae exhibit ineffective antipredator behavior by having inappropriately
high activity levels with fish, resulting in high predation in laboratory and field experiments. This study investigated the
possibility that gene flow from larvae in ephemeral habitats may reduce the escape performance of larvae from populations
with fish and alter their life history characteristics to increase their susceptibility to fish predation. I assayed escape
behavior (speed, acceleration, and duration of escape) and life history characteristics (hatching date, size, stage) associated
with predator avoidance among laboratory-reared larvae from four populations. As predicted, two populations (one with fish
and the other fishless and ephemeral) connected by gene flow were not significantly different in almost all assays. In contrast,
larvae from an isolated population with fish had significantly stronger escape behaviors and delayed hatching than both an
isolated population that lacked a history of fish co-occurrence and the population with fish but gene flow from a fishless
population. These results support theory suggesting that gene flow can constrain adaptive evolution.
Received: 22 February 1999 / Received in revised form: 4 April 1999 / Accepted: 26 April 1999 相似文献
7.
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
8.
The corallimorpharian Rhodactis rhodostoma (Ehrenberg, 1934) forms aggregations that dominate patches on some coral reef flats in the Red Sea. The outcomes and mechanisms
of competition for space between this corallimorpharian and other sessile organisms are poorly understood. Polyps of R. rhodostoma were observed to overgrow zoanthids, hydrozoan corals, sponges and encrusting macroalgae on a fringing reef at Eilat, northern
Red Sea. R. rhodostoma polyps also damaged, and in some cases overgrew, reef-building corals in the families Poritidae, Acroporidae and Pocilloporidae,
most of which form branching colonies with small polyps that are subordinate in coral competitive hierarchies. In contrast,
most stony corals in the families Faviidae and Mussidae had standoff interactions with R. rhodostoma, in which they prevented the corallimorpharians from damaging them or approaching closer than 1 to 3 cm. The latter corals
are ranked at the top of competitive hierarchies for Indo-Pacific corals, and they form massive colonies of large polyps which
may develop aggressive organs termed sweeper tentacles. Some soft corals that exude allelopathic chemicals also avoided overgrowth
by the corallimorpharians. Tentacles along the oral disk margin of R. rhodostoma polyps were swollen and bulbous during contacts with cnidarians. These bulbous marginal tentacles had significantly thicker
ectoderm and a higher proportion of holotrichous nematocysts than did the normally filiform marginal tentacles of R. rhodostoma polyps. It is concluded that, on the reef flat at Eilat, this corallimorpharian damages and overgrows a variety of sessile
competitors, including branching stony corals, via the application of specialised marginal tentacles filled with penetrating
nematocysts. R. rhodostoma is an intermediate competitor in the aggressive hierarchy among Indo-Pacific Anthozoa, including the reef-building corals.
Received: 1 July 1998 / Accepted: 24 March 1999 相似文献
9.
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
10.
Sessile marine invertebrate larvae can recognize suitable settlement substrata by using various environmental cues, including
organic/microbial biofilms. In laboratory choice assays, the effect of biofilms of varying ages on the settlement behaviour
of two fouling organisms was assessed. The species included the arborescent cheilostome bryozoan Bugula flabellata (Thompson) and the solitary ascidian Ciona intestinalis (L.), both of which are characteristic of temperate sublittoral hard substratum assemblages in northwest Europe. Experiments
were carried out using polystyrene petri dish substrata preconditioned with multispecies biofilms from natural laboratory-aquarium
seawater for 1, 3, 6 or 12 d. Unfilmed (new, initially sterile) dishes were used as control substrata. Whereas the coronate
larvae of B. flabellata generally were inhibited by biofilming, irrespective of film age, the settlement of tadpole larvae of C. intestinalis was facilitated on biofilmed substrata, and numbers of settled larvae generally increased with biofilm age: the highest mean
numbers were counted on 12 d-old biofilms. In C. intestinalis, settlement and metamorphosis are processes which can be temporally separate and are possibly induced by different environmental
cues. This study therefore distinguished between C. intestinalis larvae which were attached to the biofilm surface by the anterior, and those larvae entrapped by the biofilm but not settled
in the conventional meaning of the term. As reported in previous studies, we did observe that such entrapped larvae could
subsequently attach and develop successfully into sessile juveniles. Both the numbers of “attached” and “trapped” tadpoles
increased with biofilm age. Assuming that “settlement” is essentially a process involving the active behavioural response
of larvae to environmental cues, it seems that the facilitated attachment of C. intestinalis onto biofilmed substrata is due to the combined effect of active habitat selection and passive deposition/“entrapment” of
larvae onto the “sticky” substratum.
Received: 21 August 1996 / Accepted: 21 November 1996 相似文献
11.
Despite the importance of the gills in the acquisition of food by suspension-feeding bivalve mollusks, there is almost no
information on gill organogenesis. By means of a series of stereoscan electron micrographs, this paper describes gill development
in the Chilean oyster, Ostrea chilensis, from the brooded larval stages to 1-month-old spat. A single gill rudiment was observed on each side of the mantle at a
shell length of 320 μm, and the rudiments increased in number and size until the end of the brooding period. During metamorphosis
the gill filaments increased in number from 5 or 6 to between 7 and 9. The loss of the velum and the absence of functional
gill filaments during metamorphosis are consistent with previous observations of weight loss during this critical period of
the life history, because the newly settled juvenile lacks the ability to remove particles from suspension. The end of metamorphosis
(100% of spat with dissoconch edge) was reached 36 h after larval settlement, when the gill filaments began to grow cilia,
which increased in density and differentiated as the spat developed and acquired the capability of suspension-feeding, accounting
for the increase in body weight previously recorded during this stage. The larval rudiments gave rise to the inner demibranchs.
The outer demibranchs were observed 10 days after settlement, located between the inner demibranch and the mantle. In 1-month-old
spat, the gill did not show differentiation between primary and secondary filaments, indicating that the heterorhabdic condition
characteristic of adult oysters had yet to be attained.
Received: 11 December 1998 / Accepted: 21 August 2000 相似文献
12.
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
13.
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
14.
Polyps of the corallimorpharian Rhodactis rhodostoma (Ehrenberg, 1934) form aggregations that monopolise patches of space on the shallow reef flats of some Red Sea coral reefs.
Some of these polyps bear specialised bulbous marginal tentacles (BMTs) where they contact cnidarian competitors. BMTs differ
from the normally filiform marginal tentacles (FMTs) of R. rhodostoma, and appear to develop from them. However, their morphogenesis and long-term impacts on spatial competition with reef corals
are unknown. We experimentally induced contacts between R. rhodostoma polyps and colonies of the branching stony coral Acropora eurystoma on a shallow coral reef at Eilat, northern Red Sea. During the first 24 d of contact, the A. eurystoma colonies extruded mesenterial filaments that damaged the tissues of the corallimorpharian polyps. After 18 d,>90% of R. rhodostoma individuals had developed BMTs, which resulted in a reversal in the direction of competitive damage. During the subsequent
1.5 years of observation, the corallimorpharians maintained well-developed BMTs, unilaterally damaged the tissues of A. eurystoma, and in some cases moved onto the stony coral skeletons and partially overgrew them. BMTs developed from FMTs in a series
of four distinct stages, accompanied by significant changes in their morphology, cnidom, and density of nematocysts. Isolated
control polyps did not develop BMTs or show any signs of damage. In contrast, corallimorpharian polyps transplanted into contact
with colonies of the massive stony coral Platygyra daedalea began to develop sporadic BMTs, but were unilaterally and severely damaged by the corals, and started to disappear within
21 d, after the corals developed sweeper tentacles. We conclude that long-term outcomes of competition between R. rhodostoma and reef-building corals depend largely on the relative aggressive reach of the competitive mechanisms developed by each
species. As a consequence, this corallimorpharian is an intermediate competitor in the aggressive hierarchy among Indo-Pacific
reef corals. This study confirms that R. rhodostoma polyps may actively damage and overgrow some stony corals, leading to the formation of an almost continuous blanket of polyps
in large patches of some shallow reef flats.
Received: 15 July 1998 / Accepted: 24 March 1999 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.
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
17.
We have assessed the secondary-metabolite chemistry of freshly metamorphosed coral polyps, with and without zooxanthellae,
using extremely sensitive electro-spray and Fourier-transform mass spectrometry. Coral larvae of the soft coral Lobophytum compactum of the same genetic background were reared, then inoculated with zooxanthellar strains of different taxonomic and geographic
origin, and their terpenoid chemistry analysed. The identification of isolobophytolide in individuals of all treatment groups,
including aposymbiotic control polyps, demonstrates that control of terpene production lies with the host coral and not their
symbiotic algae.
Received: 29 November 1999 / Accepted: 22 November 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.
Acroporid corals are the main reef-building corals that provide three-dimensional habitats for other reef organisms, but are
decreasing on many reefs worldwide due to natural and anthropogenic disturbances. In this study, temporal patterns of larval
settlement and survivorship of two broadcast-spawning acroporid coral species, Acropora muricata and A. valida, were examined through laboratory rearing experiments to better understand the potential for larval dispersal of this important
coral group. Many larvae were attached (but not metamorphosed) to settlement tiles on the first examination 3–4 days after
spawning (AS). The first permanent larval settlement (i.e. metamorphosed and permanently settled juvenile polyps) occurred
at 5–6 days AS, and most larval settlement (85–97% of total) occurred within 9–10 days AS. Larval survivorship decreased substantially
to around 50% by the first week of the experiment and to approximately 10% by the second to third week. The rates of larval
attachment, settlement, and the initial drop in survivorship of larvae suggest that effective dispersal of some acroporid
species may largely be completed within the first few weeks AS. 相似文献
20.
Stages in the life cycle of the rhizostome jellyfish Rhizostoma octopus (L.) were reared in the laboratory from planula to young medusa and are described here. Fertilization of eggs was external,
and planulae, 110–150 μm in length, appeared after 2 days. These settled and developed into the scyphistoma stage. Scyphistomae
reached a maximum size of 2.3 mm, bore up to 24 tentacles, and had a large manubrium. Polyps reproduced asexually mainly by
podocysts. Strobilation was induced by temperature change. Each strobila released up to five ephyrae that measured 2.7–5.8 mm
in diameter at liberation. During transformation from newly released ephyra to young medusa, velar lappets appeared and increased
in number, the manubrium developed eight branched oral arms with epaulettes, and a marginal gastric network arose. Only one
cnidocyst type, the “a”-atrichous haploneme, was present in the planula. In addition to these haplonemes, heterotrichous microbasic
euryteles were observed in polyps, ephyrae, and medusae. Statoliths, located in the rhopalia, had a characteristic compact
shape. These sensory structures increased in number and size with the growth of ephyrae and medusae. 相似文献