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1.
T. Soltwedel 《Marine Biology》1997,129(4):747-756
To test the extent to which sea surface productivity governs the distribution pattern of benthic organisms, meiobenthic standing
stocks were investigated on the shelf, continental margin and the adjacent abyssal plains off the western African coast between
Guinea (10°N) and Angola (18°S). The area of investigation is characterized by gradients in surface productivity due to spatially
and seasonally varying coastal upwelling. Reflecting the dependency of deep-sea organisms on organic matter input from the
euphotic zone, similar gradients ought to be expected within the benthos. Meiofaunal abundances and biomasses (including Foraminifera)
from a total of 57 stations along 13 transects across the continental margin showed a fairly close correlation with sediment-bound
chloroplastic pigment concentrations, indicating the sedimentation of particulate organic matter from phytoplankton production.
However, certain discrepancies in faunal and pigment distribution patterns were found in regions apart from the centres of
enhanced primary␣productivity, i.e. apart from the upwelling centres: whereas pigment concentrations in the sediments were
still comparably high, meiofaunal numbers in those peripheral areas were generally lower. It is suggested that smaller/lighter
phytodetritial matter, transported over long distances by subsurface currents and exposed to ongoing microbial degradation
during its passage, probably does not have the same energy content as the relatively fast-sinking, larger phytodetritus aggregates
(“marine snow”), which are found in centres of enhanced primary productivity and support extensive benthic stocks. Thus, meiobenthic
abundances in relation to sediment-bound pigment concentrations on the western African continental margin may indicate fractionated
sedimentation of organic matter to the sea floor.
Received: 28 May 1997 / Accepted: 14 July 1997 相似文献
2.
Abundance and temporal distribution of viable (able to germinate) resting stage cells of planktonic diatoms in bottom sediments
have been investigated almost monthly during 1989 to 1992 in Hiroshima Bay, western part of Seto Inland Sea, Japan. The abundance
of viable resting stages in bottom sediments was enumerated with the extinction dilution method (most probable number method,
MPN). In bottom sediments of Hiroshima Bay, dominantly distributed species and/ or genera of the diatom resting stages were
Skeletonema costatum, Chaetoceros spp. and Thalassiosira spp. Viable resting stages of these diatoms were densely distributed on the orders of 103 to 106 (MPN g−1 wet sediments), and persisted in bottom sediments throughout the investigation period. Conversely, vegetative cells of these
diatoms fluctuated remarkably in the water column and disappeared sporadically. Survival of the resting stages in a collected
sediment sample was also determined with the MPN method, at different storage temperatures (5, 10, 15, 20, 25 °C). The survival
test demonstrated that the diatom resting stages could survive in the dark for several months or years in sediments. Resting
stages survived longer at the lower storage temperature, and the order of longevity was consistent within three diatoms (Chaetoceros spp. > Thalassiosira spp. > S. costatum) at each storage temperature. The present study suggests that these diatom resting stages in the coastal bottom sediments
could serve as a “seed bank”, analogous to those of terrestrial plants. The seed bank would ensure the survival of diatoms
within highly fluctuating coastal environments, while it would also be the source of sporadic and autochthonous diatom blooms
in coastal waters.
Received: 29 November 1996 / Accepted: 16 December 1996 相似文献
3.
Temporal fluctuations of abundance (or emergence) in small benthic and planktonic crustaceans were studied in shallow subtidal
waters (1.5 to 3.5 m in tide height). The abundances were more or less rhythmic, and showed wide diversity ranging from very
clear nocturnal patterns to patterns in sychrony with the tidal cycle alone. These abundance patterns were classified into
categories relating to the degree of synchrony with day/night and tidal cycles. Nocturnal patterns were especially strong
in benthic crustaceans, which would be inactive during the daytime, being attached to algae and stones or disappearing into
rock crevices, and actively swim in the water at night. Mysis larvae also showed a clear nocturnal pattern. Their lifestyle
might be similar to that of many benthic animals. Other planktonic crustaceans drifting in the water showed weak nocturnal
patterns. In some planktonic crustaceans (e.g., Calanoida), the ratio of abundance in the surface and bottom samples was reversed
between day and night. Their pattern might be a manifestation of weak diel vertical movement between day and night. Furthermore,
most patterns of zooplankton and benthos were modified in synchrony with tides to various degrees. Small crustaceans may respond
to changes of hydrologic variables fluctuating with the tides, which may exogenously produce a weak tidal component in their
emergence patterns.
Received: 12 January 1998 / Accepted: 29 August 1998 相似文献
4.
Copepod grazing impact on planktonic communities has commonly been underestimated due to the lack of information on naupliar
feeding behaviour and ingestion rates. That is particularly true for small cyclopoid copepods, whose nauplii are mainly in
the microzooplankton size range (<200 μm). The trophic role of Oithona spp. nauplii was investigated off Concepción (central Chile, ~36°S) during the highly productive upwelling season, when maximum
abundances of these nauplii were expected. Diet composition, ingestion rates, and food-type preferences were assessed through
grazing experiments with different size fractions of natural planktonic assemblages (<3, <20, <100, and <125 μm) and cultures
of the nanoflagellate Isochrysis galbana. When the Oithona spp. nauplii were offered a wide range of size fractions as food (pico- to microplankton), they mostly ingested small (2–5 μm)
nanoflagellates (5–63 × 103 cells nauplius−1 day−1). No ingestion on microplankton was detected, and picoplankton was mainly ingested when it was the only food available. Daily
carbon (C) uptake by the nauplii ranged between 28 and 775 ng C nauplius−1, representing an overall mean of 378% of their body C. Our relatively high ingestion rate estimates can be explained by methodological
constraints in previous studies on naupliar feeding, including those dealing with “over-crowding” and “edge” effects. Overall,
the grazing impact of the Oithona spp. nauplii on the prey C standing stocks amounts up to 21% (average = 13%) for picoplankton and 54% (average = 28%) for
nanoplankton. These estimates imply that the nauplii of the most dominant cyclopoid copepods exert a significant control on
the abundances of nanoplankton assemblages and, thereby, represent an important trophic link between the classical and microbial
food webs in this coastal upwelling system. 相似文献
5.
Offspring size can have pervasive effects throughout the life history stages of many marine invertebrates. Although maternal
offspring investment is largely determined by the environmental conditions experienced by the mother, egg size might additionally
vary in response to the number and quality of previous mating partners. Positive effects of mating multiply with several different
males (polyandry) have been confirmed for a variety of species, whereas such investigations are lacking for marine invertebrates.
Here we differentiated between the effects of ejaculate amount (repeatedly mated) and ejaculate diversity (polyandry) on maternal
offspring investment in the simultaneously hermaphroditic sea slug Chelidonura sandrana. We found that focal “females” mated with four different “males” produced significantly larger egg capsules and larger veligers,
while focal “females” mated four times with the same “male” suffered from reduced mid-term fecundity. We found no effect of
veliger size on veliger survival. Our results show that female mating patterns are an important addition to understanding
the variation in offspring size in internally fertilizing marine invertebrates. 相似文献
6.
A simple density separation technique for quantitative isolation of meiobenthos using the colloidal silica Ludox-TM 总被引:6,自引:0,他引:6
A simple, quantitative density separation method is described. The method is based on differences in specific weight between meiobenthos and sediment. Nematodes and copepods could be separated from sediment and detritus when samples were suspended in Ludox-TM, a colloidal silica. Organisms float at the surface, while sediment particles sink. Results obtained with this new method were compared with the well-known decantation method. For a quantitative isolation of nematodes from sediments, rich in coarse detritus, a maximum volume of 7 cm3 sample could be used. For copepods this maximum was 13 cm3. For such sediments the density method is more reliable than the decantation method. The time needed for sorting the meiobenthic organisms is reduced to about 30% compared with the former method. The new method can be used for preserved as well as for fresh sediment samples and can also be applied for the disolation of small polychaetes, small oligochaetes, larvae of some macrofaunal groups and net-zooplankton.Publication No. 10 of the project Biological Research in the Ems-Dollard Estuary. 相似文献
7.
Jochanan Aronowicz 《Marine Biology》2007,151(3):1137-1141
The “agitator”, a device designed for culturing lecithotrophic echinoderm larvae, is described. The unit consists of an open
system which is easily constructed and is made up of a base which holds the culturing baskets as well as a lid or manifold
carrying a tube which transports fresh seawater into each culture, gently stirring it and eliminating any decaying embryos.
The device is scalable and water flow can be adjusted for laminar flow or slow dripping. The method has been used to successfully
rear large numbers of lecithotrophic larvae of the starfish Solaster stimpsoni. The agitator could be used to culture any fragile planktonic organisms that require an extended rearing time. 相似文献
8.
The biochemical composition of vegetative cells and resting spores of Chaetoceros pseudocurvisetus Mangin was compared in cultures under various nutrient and light conditions. The cellular content of major nucleotides such
as AMP, ADP, ATP and UTP decreased in the order: vegetative cells, nutrient-starved (vegetative) cells and resting spores,
indicating that the general metabolism of resting spores is relatively inactive. ADP-glucose was only abundant in nutrient-starved
vegetative cells, suggesting metabolic imbalance in these cells. The chl a–specific fluorescence yield of vegetative cells grown under all culture conditions was low, but very high in resting spores.
The ratios of the cellular contents of diadinoxanthin to chl a and of diatoxanthin to chl a were higher in resting spores and nutrient-starved vegetative cells than in nutrient-replete vegetative cells. The diadinoxanthin–diatoxanthin
xanthophyll cycle was active in resting spores; the xanthophyll cycle was synchronized with a 14 h light:10 h dark photoperiod.
Also, the ratios of cellular content of diadinoxanthin and diatoxanthin to cellular content of chl a in resting spores were relatively high in high irradiance, and decreased gradually in conditions of darkness over long culture
periods. Under conditions of strong light and high temperature, most resting spores survived more than 40 d while nutrient-starved
vegetative cells died within 33 d. These results suggest that resting spore formation is a strategy for enhancing protection
and lowering metabolic rate for survival. These physiological changes accompanying spore formation enable resting spores not
only to overwinter but also to “oversummer” in the coastal euphotic layer.
Received: 23 March 1999 / Accepted: 11 August 1999 相似文献
9.
Julia Bartmess-LeVasseur Carrie L. Branch Sheri A. Browning Jessica L. Owens Todd M. Freeberg 《Behavioral ecology and sociobiology》2010,64(7):1187-1198
Evidence from different chickadee species (Poecile genus) indicates that birds can modify the note composition of their “chick-a-dee” calls in the presence of predator stimuli.
Here, we tested the effects of predator models and the distance of those models on calls of three species foraging together
at feeding stations: Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor), both members of the Paridae family, and white-breasted nuthatches (Sitta carolinensis), a member of the Sittidae family. Model and distance affected seed-taking rates in all three species. “Chick-a-dee” calling
rates were higher in the predator context for both chickadees and titmice, but we detected no predator context effects on
“quank” call rates for nuthatches. Predator and distance contexts affected acoustic parameters of notes of the “chick-a-dee”
calls of chickadees and titmice; no such effects were detected for nuthatch “quank” calls. These results suggest species differences
in encoding of information in the primary social calls of these three species that commonly occur in multi-species flocks.
Chickadees and titmice are “nuclear” species and nuthatches are “satellite” species, and these different roles might be related
to the differences in vocal signaling that we detected. 相似文献
10.
M. Antonio Todaro Francesca Leasi Nicoletta Bizzarri Paolo Tongiorgi 《Marine Biology》2006,149(5):1079-1091
During the past 5 decades, the large-sized biota inhabiting dark marine caves has attracted the attention of many marine biologists; in contrast, studies concerning the meiofaunal organisms of these peculiar biotopes remain scanty and mostly with a taxonomic aim. In this study, the nature and abundance of meiofaunal taxa living in a Mediterranean, semi-submerged sea cave was surveyed in relation to distance from the entrance and over two different seasonal periods. Particular attention was paid to the Gastrotricha taxocene. Research was carried out in a cave along the Ionian coast of Apulia (southern Italy), the “Grotta Piccola del Ciolo” which opens for approximately 120 m on the north-eastern side of a shallow fjord and has a bottom blanketed by fine to very fine sand, occasionally rich in detritus. Quantitative samples in four replicates were collected by SCUBA diving, in November 2000 and June 2001, coring the sediment with a hand-held piston corer in three light-free sites (stations 1–3) located at increasing distances from the entrance. At each site, two additional 500-ml sediment samples were collected for an in vivo study of the Gastrotricha. Faunistic analysis found a fairly high meiobenthic diversity, identifying representatives of more than 12 major groups, with total abundances ranging from 656 ind./10 cm2 (10 cm2) in November to 1,069 ind./10 cm2 in June. Station 1, the closest to the entrance invariably hosted the most abundant meiofaunal community (851 ind./10 cm2 in November and 1932 ind./10 cm2 in June), followed by station 2 or 3 depending on the season. While nematodes and harpacticoids appear as the most abundant taxa when the cave is considered as a whole, other taxa may prevail numerically in selected stations, e.g. priapulids, which are the second most abundant taxon at station 1 (30 ind./10 cm2 in November and 83 ind./10 cm2 in June). Although the density of total meiofauna and that of the single groups may not be very high, the cave is interesting by virtue of the peculiarity of the hosted fauna, e.g., species and genera new to science or new to the Mediterranean Sea. Regarding the Gastrotricha, we found 16 species, accounting for 1.3–2.6% of the total meiobenthos (density = 8.4 ind./10 cm2 in November and 27.4 ind./10 cm2 in June). Analysis of the gastrotrich community found, particularly in June, an assemblage of taxa quite different from those found in open habitats, even at the family level; differences that are probably due to the exploitation of different food resources by animals populating the two environments, i.e. algae in the open sea versus bacteria in the caves. Results indicate that for meiofauna, as happens for macrofauna, the marine caves may represent hotspots of biodiversity and endemism; the driving forces at the base of the trophic depletion hypothesis seem to be responsible for structuring the meiofauna community inside the cave. 相似文献
11.
C. S. McFadden 《Marine Biology》1999,133(2):171-184
Species boundaries among taxa of colonial marine organisms are often obscured by intraspecific morphological and ecological
variation; genetic comparisons of recognized “ecotypes” frequently reveal them to be reproductively isolated species. Based
on morphological similarities, it has been proposed that the Mediterranean soft coral Alcyonium (=Parerythropodium) coralloides Pallas, 1766 and its Atlantic congener A. hibernicum belong to one highly variable and geographically widespread species, A. coralloides. I collected A. coralloides from ten Atlantic and three Mediterranean locations in 1990 and 1994, and used differences in colony form, substrate use
and color to separate them into five distinct morphotypes. Two occur sympatrically in the Mediterranean (M1, M2) and three
have overlapping distributions in the Atlantic (A1, A2, A3). I used allozyme electrophoresis to compare morphotypes genetically
at 14 enzyme loci. Where two morphotypes occurred sympatrically, fixed allelic differences at 4 to 6 loci indicated reproductive
isolation. In all but one pairwise comparison (M1 and A2), morphotypes whose ranges did not overlap were also separated by
large genetic distances. From these results I suggest that the five morphotypes represent four distinct species. A. coralloides comprises two morphotypes (M1, A2) with relatively high genetic identity. A. hibernicum (=A1) is reproductively isolated from A. coralloides and should be retained as a valid species; levels of genetic diversity and heterozygosity within populations support the
absence of outcrossing in this reportedly asexual species. Morphotypes M2 and A3 are also reproductively isolated from A. coralloides; they are taxonomically distinct from but belong to the same phylogenetic clade as A. hibernicum. Although preliminary observations suggest that differences in reproductive timing maintain species boundaries in sympatry,
wider geographic sampling will be required to elucidate the events leading to speciation within this species complex.
Received: 8 May 1998 / Accepted: 8 October 1998 相似文献
12.
Duccio Lambardi Francesca R. Dani Stefano Turillazzi Jacobus J. Boomsma 《Behavioral ecology and sociobiology》2007,61(6):843-851
Some social parasites of insect societies are known to use brute force when usurping a host colony, but most use more subtle
forms of chemical cheating either by expressing as few recognition cues as possible to avoid being recognized or by producing
similar recognition cues to the host to achieve positive discrimination. The former “chemical insignificance” strategy represents
a more general adaptive syndrome than the latter “chemical mimicry” strategy and is expected to be characteristic of early
evolutionary stages of social parasitism. We tested this hypothesis by experimentally analyzing the efficiency by which Acromyrmex echinatior leaf-cutting ants recognize intruding workers of the incipient social parasite Acromyrmex insinuator. The results were consistent with the parasite being “chemically insignificant” and not with the “chemical mimicry” hypothesis.
Gas chromatography–mass spectrometry analysis of cuticular hydrocarbon profiles showed that social parasite workers produce
significantly fewer hydrocarbons overall and that their typical profiles have very low amounts of hydrocarbons in the “normal”
C29–C35 range but large quantities of unusually heavy C43–C45 hydrocarbons. This suggests that the C29–C35 hydrocarbons are
instrumental in normal host nestmate recognition and that the C43–C45 compounds, all of which are dienes and thus more fluid
than the corresponding saturated compounds, may reinforce “chemical insignificance” by blurring any remaining variation in
recognition cues. 相似文献
13.
Crayfish are excellent model organisms to study the proximate mechanisms underlying the maintenance of dominance hierarchies
in invertebrates. Our aim here was to investigate whether Procambarus clarkii males use social eavesdropping to discriminate dominant from subordinate crayfish. To this end, we conducted an experiment
composed of a “passive” and an “active” phase. In the passive phase, “focal” individuals were allowed (treatment 1) or not
(treatment 2) to see and smell two size-matched crayfish fighting while, in the subsequent active phase, they were allowed
to freely interact with the fighting dyad. None of the recorded variables showed any significant difference between the two
treatments, but, invariably, focal individuals were able to promptly discriminate dominant from subordinate crayfish. This
study provides evidence that male crayfish recognize the social status of a conspecific without the need of direct or indirect
experience with it and avoid dominants—and thus dangerous opponents—by means of a badge of status. A form of “winner and loser
effects” could also contribute to the structuring of dominance/subordinate relationships. The implication of these results
in understanding the maintenance of dominance hierarchies in invertebrates are discussed and compared with findings previously
achieved in the context of mate choice by P. clarkii females, who do appear to use eavesdropping to identify dominants and subordinates. 相似文献
14.
Five hypotheses have been proposed to explain polygyny in the red-winged blackbird (Agelaius phoeniceus). We categorized the hypotheses into three groups based on female preference for unmated versus monogamously mated males:
(1) the “polygyny threshold” model, “sexy son” hypothesis and the “asynchronous settlement” model, which assume that females
prefer unmated males to mated males on breeding situations of homogeneous quality; (2) the “neutral mate choice” hypothesis,
which assumes that females have no preference; and (3) the “cooperative female choice” model, which assumes that females prefer
monogamously mated males to unmated males. We tested the direction of female preference in two field experiments. In both
experiments, newly settling females were given a choice of two adjacent territories, one defended by an unmated male and the
other by a monogamously mated male. Male mating status was randomized with respect to the variation in territory quality and
male quality. Early in the breeding season, significantly more females settled with the unmated males than with the mated
males. Although more females settled with the unmated males than with the mated males late in the breeding season, the difference
was no longer significant. Female settlement late in the season appeared to be related to the tenure of the resident females:
the new females avoided territories where the resident females were in early stages of their nesting, but settled on territories
where the resident females were in late stages. The pattern of female settlement shows that females prefer unmated males to
mated males. The preference is consistent with the polygyny threshold model, sexy son hypothesis and the asynchronous settlement
model, and inconsistent with the neutral mate choice hypothesis and the cooperative female choice model. For this reason,
the latter two hypotheses are unlikely to explain the occurrence of polygyny in our population of red-winged blackbirds.
Received: 1 December 1994 / Accepted after revision: 28 October 1995 相似文献
15.
The flow of particulate nitrogen from marine net pen fish farm effluents to the surrounding biofouling community was quantified by means of stable isotopes of nitrogen. Plastic mesh substrates were deployed at 8 m depth near a sea bream fish farm and at a nearby reference site in the northern Gulf of Aqaba (Red Sea) to assess whether natural fouling organisms could sequester substantial quantities of farm-derived particulate nitrogen waste. A mixing equation, incorporating differences in nitrogen stable isotope composition, δ15N, between particulate organic matter (“source”) and fouling organisms (“sink”) at the fish farm and reference site, was used to estimate the amount of farm-derived nitrogen that was incorporated by the fouling community. Among the conspicuous fouling organisms examined, sponges, tunicates and polychaetes showed greatest uptake of fish farm N, where the mean fractions of farm-derived N estimated over the 2-year period of observation were 19±7, 22±6 and 31±8% of total organisms’ N content, respectively, with maximal recorded seasonal values of 68, 85 and 57%, respectively. Mean N uptake by mixed fouling communities (conspicuous + cryptic organisms) was as much as fivefold higher than that calculated for the sum of conspicuous taxa, suggesting that the retention efficiency is greater in mixed than in mono-specific biofouling communities. 相似文献
16.
Genetic heterogeneity among adult and recruit red sea urchins, Strongylocentrotus franciscanus 总被引:1,自引:1,他引:0
Allozyme electrophoresis was used to characterize genetic variation within and among natural populations of the red sea urchin
Strongylocentrotus franciscanus. In 1995 to 1996, adult urchins were sampled from twelve geographically separated populations, seven from northern California
and five from southern California (including Santa Rosa Island). Significant population heterogeneity in allelic frequencies
was observed at five of six polymorphic loci. No geographic pattern of differentiation was evident; neighboring populations
were often more genetically differentiated than distant populations. Northern and southern populations were not consistently
distinguishable at any of the six loci. In order to assess within-population genetic variation and patterns of recruitment,
large samples were collected from several northern California populations in 1996 and 1997, and were divided into three size
classes, roughly representing large adults (>60 mm), medium-sized individuals (31 to 60 mm, “subadults”) and individuals <2 yr
of age (≤30 mm test diam, referred to as “recruits”). Comparisons of allelic counts revealed significant spatial and temporal
differentiation among size-stratified population samples. Recruit samples differed significantly from adult samples collected
at the same locale, and showed extensive between-year variation. Genetic differentiation among recruit samples was much higher
in 1997 than in 1996. Between-year differences within populations were always greater for recruits than for adults. Potential
explanations for the differentiation of recruit samples include pre- and post-settlement natural selection and high interfamily
variance in reproductive success or “sweepstakes” recruitment. Unless recruit differentiation can be attributed to an improbable
combination of strong and spatially diverse selection, such differentiation across northern California populations indicates
that the larval pool is not well mixed geographically (even on spatial scales <20 km), despite long planktonic larval duration.
Received: 6 July 1999 / Accepted: 25 January 2000 相似文献
17.
Physiological studies were made on the crabs Ucides cordatus (L.) and Callinectes danae sampled from populations living in “polluted” mangroves on the southeast littoral of Brazil. Analysis of Cu, Cd, Zn, and
Fe of sediments and crab tissues showed interspecific differences in tissue concentrations, and significantly higher levels
of Cu, Cd, and Zn in “polluted” populations compared to “unpolluted” crabs living in uncontaminated mangrove in the same geographical
area. Individuals of both species from the polluted site showed significantly greater capacities for regulating blood osmotic
concentrations at low salinity (9‰). However, U. cordatus showed a reduced hypo-regulatory ability in 34‰S. Differences in ionoregulation were also seen. “Polluted”C. danae showed significantly higher Na/ K-ATPase levels in posterior gills compared to “unpolluted” crabs. Oxygen consumption rates
(M˙
O2) were elevated in U. cordatus, but depressed in C. danae from the “polluted” population. Individuals of both species from this site showed significantly lower O:N ratios, mainly
because of an increased net efflux of ammonia. Adenylate energy charge (AEC) values of muscle and hepatopancreas in “unpolluted”
and “polluted” populations of both species were not significantly different. These physiological differences are discussed
in relation to the known acute physiological and metabolic effects of heavy metals in crustaceans, and interpretated in the
light of possible adaptive changes following long-term exposure to contamination.
Received: 6 August 1999 / Accepted: 22 June 2000 相似文献
18.
D. M. Alongi 《Marine Biology》1987,95(3):447-458
Intertidal zonation and seasonality of tropical meiobenthic communities were examined within five mangrove estuaries along the northeastern coast (Cape York peninsula) of Australia from May 1985 to January 1986. Partial correlation analysis revealed that environmental cues such as temperature and sediment granulometry were the most important factors regulating the zonation patterns of meiofauna. Seasonality was greatly influenced by monsoonal rains. During austral summer, prolonged monsoonal rains occurred along the coast north of 18°S latitude (Hinchinbrook Island), resulting in increased river discharge and scouring of surface silts and clays, organic matter and bacteria from most tidal sediments. Despite scouring, meiofaunal densities increased in the summer wet season, probably due to warmer temperatures and the high resilience of meiobenthos to sediment disturbance. In mangrove sediments not subjected to torrential rains (Hinchinbrook Island), meiofaunal densities were highest in austral autumn and winter (sediment temperature: 23 to 27°C) and lowest in austral spring and summer (28° to 40°C). Turbellarians were the dominant meiofaunal group, accounting for 58 to 67% of total faunal densities which generally decreased with elevation in all of the estuaries. Meiofauna in tropical Australian mangroves, as in other organic-rich muds and in coral reefs, appear to exert little impact on microbial standing stocks when intercorrelated variables are accounted for. The abundances of hard-bodied meiofauna were low compared with temperate communities, lending further support to Moore's (1972) contention that tropical intertidal communities are subjected to greater physical stress than their temperate counterparts. 相似文献
19.
M. Thiel 《Marine Biology》2000,137(4):661-674
The population dynamics and reproductive biology of an ascidian- and a sponge-dwelling amphipod were examined. The two undescribed
amphipod species, Leucothoe“ascidicola” and L.“spongicola”, are closely related to each other, and occur in ascidians and sponges, respectively, along the Florida Atlantic coast.
L. “ascidicola” was abundant in solitary ascidians during fall 1997, disappeared during spring/early summer, and became abundant again in
September 1998. During the time when L. “ascidicola” were absent from their hosts, a copepod became a frequent inhabitant of the ascidians but disappeared again when L.“ascidicola” returned to the ascidians in September 1998. The numbers of L.“spongicola” in sponges increased substantially during spring, when high reproductive activity was observed. Following this reproductive
peak, both adult and juvenile amphipods apparently left the sponges, and during the summer amphipod numbers in the sponges
were very low. Another small amphipod species, which often co-occurred with L.“spongicola”, showed less seasonal variation and was found in sponges throughout the whole study period. The percentage of ovigerous
females per host unit was usually lower in the ascidian-dwelling than in the sponge-dwelling amphipods. In solitary ascidians,
L.“ascidicola” amphipods usually occurred in groups of several adults, yet there never was more than one ovigerous female per ascidian.
In contrast, several ovigerous L.“spongicola” females were found to cohabit in the same spongocoel. This suggests that intrasexual aggression may be stronger among reproductive
amphipod females in the ascidians than in sponges. The size distributions of juvenile cohorts indicate that juvenile L.“ascidicola” remain for relatively long time periods in the parental ascidian, where they may reach sexual maturity. In contrast, in
L.“spongicola”, only cohorts of very small juveniles could be identified, indicating that juveniles disperse shortly after emerging from
the female's brood pouch. It is concluded that extended parental care is of very short duration or does not occur in the sponge-dwelling
amphipod L. “spongicola”, possibly because fast-growing sponges with a highly branched spongocoel system do not allow long-lasting coexistence of
parent-offspring groups. In contrast, the discrete character of the solitary ascidians may enhance the potential for exclusion
of other species, resource monopolization by reproductive females, and furthermore for long-lasting extended parental care
in the ascidian-dwelling amphipod. Groups of single parents together with cohorts of large juveniles are reported in the literature
for amphipods and isopods from brachiopods, bivalves and ascidians, suggesting that these discrete biotic microhabitats may
favor the evolution of extended parental care in peracarid crustaceans.
Received: 30 July 1999 / Accepted: 8 May 2000 相似文献
20.
E. A. Widder S. Johnsen S. A. Bernstein J. F. Case D. J. Neilson 《Marine Biology》1999,134(3):429-437
To learn how organisms apportion space in the open ocean, biological oceanographers have sought to improve temporal and spatial
resolution of ocean sampling systems. Their objectives are to simultaneously measure physical, chemical and biological structure
in the water column in order to find significant correlations that may reveal underlying processes. Here we report one such
correlation between intense peaks of bioluminescence and density discontinuities in the water column. Intensified video recordings
made in these bioluminescent “hot spots” were analyzed with a computer image-recognition program that identifies organisms
based on the temporal and spatial characteristics of their luminescent displays. Based on this analysis, the source of the
“hot spots” was found to be very thin layers (0.5 m) of the bioluminescent copepod Metridia lucens present at from 5 to 100 times average background concentrations. Given the recent discovery that the vertical distribution
of marine snow is also strongly correlated with density discontinuities in the water column, we suggest that this finding
may provide a possible explanation for the disparity between estimated energy requirements of marine copepods and measurements
of average in situ food concentrations. The energy costs associated with locating food-rich micro-patches is greatly reduced
if those patches are spread out into very thin layers, because the search strategy can be reduced from three dimensions to
one.
Received: 28 December 1998 / Accepted: 12 April 1999 相似文献