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1.
Sexual reproduction in the azooxanthellate octocoral Dendronephthya hemprichi Klunzinger, 1877 was studied in Eilat (Red Sea) for 2 years beginning March 1989. D. hemprichi is a gonochoric broadcasting species. Gonads at all developmental stages were found throughout the year. Small-sized oocytes
and sperm sacs, 51 to 100 μm in diameter, are highly abundant, accompanied by numerous smaller primordial gonads. These features
result from continuous gametogenesis, and lead to year-round oocyte and sperm maturation and release. Gamete release was observed
in the laboratory on all monitoring dates, and most of the female colonies spawned repeatedly for several successive nights.
The reproductive features of D. hemprichi constitute an exception to the generalization that free-spawning reef-corals have brief and synchronized broadcast-spawning
episodes. This species demonstrates early onset of first reproduction, which further increases its reproductive output.
Received: 7 May 1997 / Accepted: 15 May 1997 相似文献
2.
Antimicrobial activity of Red Sea corals 总被引:1,自引:0,他引:1
Dovi Kelman Yoel Kashman Eugene Rosenberg Ariel Kushmaro Yossi Loya 《Marine Biology》2006,149(2):357-363
Scleractinian corals and alcyonacean soft corals are the two most dominant groups of benthic marine organisms inhabiting the coral reefs of the Gulf of Eilat, northern Red Sea. Antimicrobial assays performed with extracts of six dominant Red Sea stony corals and six dominant soft corals against marine bacteria isolated from the seawater surrounding the corals revealed considerable variability in antimicrobial activity. The results demonstrated that, while the majority (83%) of Red Sea alcyonacean soft corals exhibited appreciable antimicrobial activity against marine bacteria isolated from the seawater surrounding the corals, the stony corals had little or no antimicrobial activity. From the active soft coral species examined, Xenia macrospiculata exhibited the highest and most potent antimicrobial activity. Bioassay-directed fractionation indicated that the antimicrobial activity was due to the presence of a range of compounds of different polarities. One of these antibiotic compounds was isolated and identified as desoxyhavannahine, with a minimum inhibitory concentration (MIC) of 48 μg ml−1 against a marine bacterium. The results of the current study suggest that soft and hard corals have developed different means to combat potential microbial infections. Alcyonacean soft corals use chemical defense through the production of antibiotic compounds to combat microbial attack, whereas stony corals seem to rely on other means. 相似文献
3.
The reproductive biology of Antipathes fiordensis Grange, a species endemic to south-western New Zealand, was followed from April 1994 to May 1995. Ten colonies were individually
tagged in Doubtful Sound and sampled on a monthly basis in order to determine their reproductive activity. The fecundity of
each of the five tagged female colonies was determined by estimating the total number of polyps per colony from photographs
of each colony and by planimetry, the proportion of gravid polyps per colony, and the mean number of oocytes per gravid polyp.
In addition, 56 colonies were sampled in March 1995 to estimate the sex ratio, height at sexual maturity, and mean sizes of
females and males. A. fiordensis was found to be a dioecious species which, in the absence of gonads in the polyps, has no obvious external morphological
differences between the sexes. Broadcast spawning of gametes is the likely mode of reproduction. Gametogenesis began in November
1994 and was highly synchronous within and between colonies, with spawning occurring in March 1995. The sex ratio in adults
was 1:1. Colonies reached sexual maturity between the heights of 70 and 105 cm which, based on existing estimates of growth
rate, corresponds to a minimum age for sexual maturity of about 31 yr. The largest oocytes measured ranged from 100 to 140 μm
in size. Female colonies produced between 1.3 and 16.9 million oocytes, with the larger colonies dominating the reproductive
output of the population.
Received: 23 June 1997 / Accepted: 1 August 1997 相似文献
4.
Although coral dwelling fishes are common on coral reefs, the nature of their effect on the host corals is poorly understood. The present study, conducted in the Gulf of Eilat (Red Sea) between July 1989 and August 1990, demonstrated that the branching coral Stylophora pistillata (Esper) benefits, in two components of coral fitness, from the presence of the damselfish Dascyllus marginatus (Rüppell), an obligate coral dweller. The growth rate of damselfish-inhabited corals was significantly higher than that of corals without damselfish. This was observed, using two growth assessment methods, in long-term (>7 mo) comparisons between: (1) corals where the damselfish were experimentally removed versus corals with unaltered fish groups; and (2) naturally inhabited versus non-inhabited corals. The presence of damselfish did not affect the coral's specific (per surface area) reproductive output, whether it was assessed by the number of female gonads per polyp or by the number of planulae released cm-2 surface area d-1. However, the more rapid increase in branch size in damselfish-inhabited corals resulted in an apparent increase in the total reproductive output, with age, in growing corals. These findings demonstrate that the association between the damselfish D. marginatus and its host coral, S. pistillata, is mutualistic. 相似文献
5.
O. Barneah I. Brickner M. Hooge V. M. Weis T. C. LaJeunesse Y. Benayahu 《Marine Biology》2007,151(4):1215-1223
Epizoic worms were found to occur on certain coral colonies from reefs off the coast of Eilat (Red Sea). We identified 14
coral species infested by acoelomorph worms at a depth range of 2–50 m. The host corals were all zooxanthellate and included
both massive and branching stony corals and a soft coral. Worms from all hosts were identified as belonging to the genus Waminoa and contained two distinct algal symbionts differing in size. The smaller one was identified as Symbiodinium sp. and the larger one is presumed to belong to the genus Amphidinium. Worm-infested colonies of the soft coral, Stereonephthya cundabiluensis, lacked a mucus layer and exhibited distinct cell microvilli, a phenotype not present in colonies lacking Waminoa sp. In most cases, both cnidarian and Acoelomorph hosts displayed high specificity for genetically distinctive Symbiodinium spp. These observations show that the epizoic worms do not acquire their symbionts from the “host” coral. 相似文献
6.
The mode of reproduction in Pocillopora verrucosa Ellis and Solander, 1786 varies between geographically isolated regions. This scleractinian coral is common along the KwaZulu-Natal
coast, and its reproductive mode and period of reproduction were assessed using histological preparations. The study was undertaken
from 1992 to 1994 and showed that P. verrucosa is a simultaneous hermaphrodite and broadcast spawner in KwaZulu-Natal. Gametogenesis occurs from October to January, with
the gametes maturing simultaneously so that spawning can be synchronised at new moon in January (mid-summer). Zooxanthellae
are present in the mature oocytes.
Received: 10 September 1997 / Accepted: 6 July 1998 相似文献
7.
Reproductive success among clonal taxa is often portrayed as a simple function of clone size, but reproduction in Pseudoplexaura porosa (Houtuyn), a common Caribbean gorgonian, reflects a more complex relationship between size and gamete production. Tagged
colonies were sampled at two reefs in the San Blas Islands, Panama during the 1995 spawning season to determine the colony
size at first reproduction, size-dependent polyp fecundities, and whole colony gonad production, and to follow the gametogenic
cycle. Additional data were obtained during non-spawning months in 1984 and 1985. Of 120 colonies ranging in height from 20
to 250 cm, only colonies taller than 50 cm were reproductive. An average of 4.33 oocytes polyp−1, 560 to 800 μm in diameter, were released during monthly synchronous spawning events from June to September. Oocytes released
each month developed from a group of intermediate size oocytes present at the end of the preceding month. Almost all oocytes
>560 μm were released during each spawning event. Spermatogenesis was a shorter process than oogenesis. During each spawning
month, mature spermaries developed from a group of <125 μm spermaries. Virtually all spermaries >190 μm were released each
month, and most of the spermary volume in mature male polyps was generated anew each month of spawning. Among reproductive
colonies, polyp fecundity increased with colony height from 50 to 200 cm. Per capita fecundity of >200 cm tall female colonies
was lower than for 150 to 200 cm colonies, but whole colony fecundity of large colonies was greater due to the exponential
increase in the number of polyps that occurs with increasing colony height. In male colonies, both polyp and colony reproductive
output increased with colony height. The large amounts of sperm produced by large male colonies probably contributes to the
high rates of in situ fertilization observed in P. porosa. Differences in fecundity as a function of colony size and sex suggest differences in some combination of the cost of reproduction
and/or allocation of resources to reproduction.
Received: 9 September 1998 / Accepted: 7 June 1999 相似文献
8.
The sexuality, reproductive mode, and timing of reproduction of Pocillopora verrucosa from the Republic of Maldives, Indian Ocean, were assessed using serial histological sections. These showed that P. verrucosa is an annual simultaneous hermaphrodite, with gonads arranged in two opposing arcs of alternating testes and ovaries, six gonads in each arc. No planulae were observed in any dissection or histological analysis carried out, therefore making brooding unlikely. Broadcast spawning is inferred from the disappearance of mature gametes from samples collected between late March and April 1991. Mean oocyte size at spawning was 53.5 m and mean potential fecundity was 7300 ooctyes cm-2yr-1. The reproductive pattern of P. verrucosa in the Maldives is compared to that of the same species in different locations, the short breeding season in March to April occurring earlier in the Maldives than in Red Sea populations. The maximum mean oocyte diameter found in Maldivian specimens was much smaller than elsewhere. The year-to-year variation in numbers of oocytes/polyp within single colonies, and the variation between colonies within the population was significant (p<0.01). Therefore, it is possible that fecundity is not a good variable to use when monitoring stress on coral reefs unless larger numbers of estimates can be routinely made. Some colonies contained immature oocytes at spawning that were not released and continued to grow to approximately twice the size of the spawned oocytes that were presumed to be mature. These unspawned oocytes were oosorbing, and were characterised by the presence of zooxanthellae and large numbers of vacuoles in their cytoplasm. This gradual expansion and oosorption of unspawned oocytes has not been documented previously for corals. 相似文献
9.
Mucus released by scleractinian corals can act as an important energy and nutrient carrier in coral reef ecosystems, and a
distinct isotopic signature would allow following the fate of this material. This study investigates the natural C and N stable
isotopic signatures of mucus released by four scleractinian coral genera (Acropora, Fungia, Pocillopora and Stylophora) in comparison with those of suspended particulate organic matter (POM) in seawater of a Northern Red Sea fringing coral
reef near Aqaba, Jordan. The natural δ13C and δ15N signatures of coral mucus differed significantly from seawater POM for the majority of seasonal comparisons, but were inappropriate
for explicit tracing of mucus in the coral reef food web. Thus, a labeling technique using stable isotope tracers (13C and 15N) was developed that produced δ13C values of up to 122 ± 5‰ (mean ± SE) and δ15N of up to 2,100 ± 151‰ in mucus exuded by Fungia corals. 13C and 15N-enriched compounds were rapidly (within 3 h) and light-dependently transferred from the endosymbiotic zooxanthellae to the
mucus-producing coral host. The traceability of 15N-labeled mucus was examined by evaluating its uptake and potential utilization by epizoic acoelomorph Waminoa worms naturally occurring on a range of scleractinian coral taxa. This tracer experiment resulted in uptake of coral mucus
by the coral-associated acoelomorphs and further demonstrated the possibility to trace stable isotope-labeled coral mucus
by revealing a new trophic pathway in coral reef ecosystems. 相似文献
10.
The global decline in reef health has prompted the need for effective management methodologies, including the development
of active restoration measures. One such approach is the ‘gardening concept’ that involves use of underwater nurseries where
coral fragments are farmed before their transplantation into denuded reefs. Here we document enhanced sexual reproduction
in colonies of the coral Stylophora pistillata cultured in mid-water floating nursery situated in nutrient enriched water, near the fish farms in Eilat, Red Sea. We found
that after 2 years of nursery, the average number of oocytes per polyp in farmed colonies was ca. 35% higher than in corresponding
naturally growing colonies. Small branches in the nursery developed gravid colonies that released equal (or more) numbers
of planula larvae as compared to similar size, 5-year old naturally growing colonies. These nursery-borne planulae possessed
more zooxanthellae and contained more chlorophyll per larva. While settled and metamorphosed in equal rates compared to planulae
originated from reef-grown colonies, the nursery borne planulae developed faster growing young colonies. We estimate that
a coral nursery could generate, during the reproductive season, tens of millions of planula larvae and therefore should be
regarded as a ‘larval dispersion hub’ that can be used as a management tool for natural recruitment enhancement. 相似文献
11.
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
12.
P. W. Glynn N. J. Gassman C. M. Eakin J. Cortes D. B. Smith H. M. Guzman 《Marine Biology》1991,109(3):355-368
Reproductive ecology of two major reef-building corals in the eastern Pacific [Pocillopora damicornis (Linnaeus) andPocillopora elegans Dana] was investigated between 1984 and 1990 in Costa Rica, Panama (Gulf of Chiriqui and Gulf of Panama), and the Galapagos Islands (Ecuador) following the 1982–83 El Niño disturbance. Mature spermatocytes and oocytes were found in both species and were usually present in the same polyp in nearly equal ratios. Numerous zooxanthellae were observed in mature, unfertilized oocytes. Although spawning in field populations was not observed, it is likely that both pocilloporids are simultaneous hermaphroditic spawners, as evidenced by the disappearance of mature gametes after full moon. This is in contrast with most known pocilloporid corals that brood and release planula larvae. Corals were reproductively most active in the thermally stable environments of Costa Rica and the Gulf of Chiriqui (Panama) where 32 to 90% of all colonies contained gametes. In the moderately varying thermal conditions in the Galapagos Islands, 16 to 40% of colonies contained gametes, and in the pronounced seasonal upwelling environment of the Pearl Islands (Panama) only 6 to 18% of colonies contained gametes. Year-round reproduction occurred in Costa Rica and the Gulf of Chiriqui, whereas reproduction was confined to warm periods in the seasonally varying environments of the Galapagos Islands and the Gulf of Panama. Pocilloporid corals in Costa Rica and the Gulf of Chiriqui demonstrated lunar spawning activity, with mature gametes present a few days before and after full moon. Some limited spawning may have occurred also at new moon. While frequent gamete maturation has been demonstrated in this study, the relatively low rates of larval recruitment occurring on eastern Pacific coral reefs disturbed by the 1982–83 El Niño suggest that the recovery of important frame-building corals could be greatly prolonged. 相似文献
13.
To understand how regeneration in corals may be affected by intrinsic and extrinsic factors, the process of repair of experimentally
induced tissue lesions was investigated in the solitary scleractinian coral Fungia granulosa. Three lesion sizes were inflicted in situ on large, sexually mature individuals (>5.5 cm diameter) and in small sexually
immature (<5.0 cm) individuals. Repair was monitored using photography and computerized image analysis. This procedure was
carried out in fall (September to November; post-reproductive months), and repeated with a new set of corals in spring (March
to May; gametogenic months). Reproductive effort was investigated histologically 1 to 2 months following lesion infliction.
In field experiments, there was a significant difference in percent of tissue coverage 8 weeks after lesion infliction between
spring and fall for all lesion sizes in large corals. During the fall, all lesion sizes in large corals were repaired within
8 weeks. Large lesions in small corals did not undergo repair regardless of season. During the spring, none of the corals
underwent complete repair regardless of coral size, and many of the small corals died. In laboratory experiments, 83.3% of
the corals kept at 25 °C and 16.7% of those kept at 21 °C underwent repair during the fall. None of the corals maintained
at 21 °C and only 16.7% of those corals maintained at 25 °C underwent complete repair during spring. Though both fecundity
and tissue regeneration were significantly reduced, gametogenesis continued in corals that had previously undergone experimental
injury. These results indicate that in fungiid corals, regeneration is affected by intrinsic factors such as size and reproductive
state as well as by environmental factors such as ambient water temperatures. Moreover, it is possible that, following injury,
energetic resources are diverted from repair towards the maintenance of reproductive effort.
Received: 21 March 2000 / Accepted: 28 July 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.
There are few data on the reproductive biology of coral species living in temperate zones, particularly in the Mediterranean
Sea. Leptopsammia pruvoti is a solitary coral that is commonly found in sea caves and under overhangs throughout the Mediterranean basin and along
European coasts from Portugal to southern England. In this paper, we describe its annual reproductive cycle in the eastern
Ligurian Sea near the city of Leghorn (Tuscany, Italy). Polyps were sexually mature at 3 mm in length (maximum diameter of
the oral disc), were dioecious with a sex ratio of 1:1, and brooded their larvae. The maturation of spermaries took 12 months
and oocytes 24 months. The rate of gonad development increased significantly from November to January, fertilization occurred
from January to April and planulation during May and June. Seasonal variations in water temperature and photoperiod may have
played an important role in regulating reproductive events. The amount of energy devoted to male gametogenesis (quantified
by gonad index) was significantly higher in the sex separated species L. pruvoti than in the hermaphroditic dendrophylliid Balanophyllia europaea, whose reproduction has been studied in a previous work. We hypothesize that this difference is due to the contrasting sexuality
or fertilization biology of these two species (cross-fertilization in the sex separated L. pruvoti versus possibly self-fertilization in the hermaphroditic B. europaea). Greater male sexual allocation in reproductive strategies characterized by dioecism or cross-fertilization when compared
to those characterized by hermaphroditism or self-fertilization is common in plant mating systems. In relation to other solitary
dendrophylliids, L. pruvoti presents an ‘r’-reproductive strategy. 相似文献
16.
The azooxanthellate coral Acabaria biserialis Kükenthal, 1908 (Octocorallia: Alcyonacea) is highly abundant on the vertical underwater structures of the oil jetties at
Eilat (Red Sea), but it is rare on the adjacent natural reefs. To understand its success on such artificial substrata we examined
various aspects of its life history and population dynamics. A. biserialis is a gonochoric brooder. The percentage of colonies on the artificial substrata bearing gonads ranged from none (September
1994 and 1995) to 100% (January 1994, 1995 and April 1994). Mature oocytes and sperm sacs reached rather small maximum diameters
of 240 and 160 μm, respectively, probably dictated by the small gastrovascular cavities. A continuous release of planulae
was observed in the laboratory from March to July 1995. Planulation occurred during various lunar phases, and both by day
and night. Recruitment of A. biserialis on PVC plates attached to the jetties coincided with the breeding period inferred from the laboratory findings. Recruits
reached a maximum height of 3 cm within 3 months, thus exhibiting a remarkably rapid growth rate compared with other gorgonians.
This high colony growth rate may compensate for the lack of clonal propagation in the studied A. biserialis population. The complex substrata of the jetties provide the conditions required for successful colonization, which include
upside-down orientation, an adequate light regime and exposure to flow. The findings of our study may provide a useful contribution
to the design of artificial reefs aimed at attracting rapid colonization by A. biserialis colonies.
Received: 30 December 1998 / Accepted: 19 August 1999 相似文献
17.
Reproduction and recruitment of scleractinian corals in a high-latitude coral community, Amakusa, southwestern Japan 总被引:1,自引:0,他引:1
Reproduction and recruitment in high-latitude coral populations in Japan have been little studied. A comprehensive study of the reproduction and early life history was conducted on nine common scleractinian coral species in Amakusa, southwestern Japan (32°N) from 2001 to 2003 including; (1) fecundity (the proportion of colonies with mature eggs), (2) timing and synchrony of spawning, (3) initial larval settlement pattern, (4) recruitment, (5) post-settlement mortality. The fecundity was high (76.7–100%) in six of seven species examined in 2002 and 2003. Annual spawning of the seven species occurred from mid July to August in 2001–2003, when seawater temperature was at the annual maximum. Spawning was highly synchronised among conspecific colonies and species in 2002 and 2003, with five species spawning five to nine nights after the full moon and another two spawning around the new moon. Temporal patterns of larval settlement of three spawning species during the first 10 days after spawning were similar to those of other spawning species from low latitudes. The number of scleractinian recruits on settlement plates, deployed from July to October (the major recruitment period at the study site), was low (2 recruits/m2) for the three consecutive years. Post-settlement mortality of 1–1.5 month old spat of five species ranged between 88 and 100% over 3–10 months in the field, similar to the values reported for both high and low latitude species (>94–99%). Among the key stages examined, the low recruitment rate may be the most important step in limiting successful reproduction and recruitment of these high-latitude scleractinian populations. The low recruitment rate may be attributable to (1) the reduced influx of larval supply from other coral populations, which are smaller and more isolated at high-latitudes and (2) the longer precompetent larval phase of broadcast-spawning corals which results in an increased chance of larvae being dispersed away from parent populations. 相似文献
18.
Water flow and prey capture by three scleractinian corals, Madracis mirabilis, Montastrea cavernosa and Porites porites, in a field enclosure 总被引:8,自引:0,他引:8
Scleractinian corals experience a wide range of flow regimes which, coupled with colony morphology, can affect the ability
of corals to capture zooplankton and other particulate materials. We used a field enclosure oriented parallel to prevailing
oscillatory flow on the forereef at Discovery Bay, Jamaica, to investigate rates of zooplankton capture by corals of varying
morphology and polyp size under realistic flow speeds. Experiments were carried out from 1989 to 1992. Particles (Artemia salina cysts) and naturally occurring zooplankton attracted into the enclosures were used as prey for the corals Madracis mirabilis (Duchassaing and Michelotti) (narrow branches, small polyps), Montastrea cavernosa (Linnaeus) (mounding, large polyps), and Porites porites (Pallas) (wide branches, small polyps). This design allowed corals to be used without removing them or their prey from the
reef environment, and avoided contact of zooplankton with net surfaces. Flow speed had significant effects on capture rate
for cysts (M. mirabilis), total zooplankton (M. mirabilis, M. cavernosa), and non-copepod zooplankton (M. mirabilis). Zooplankton prey capture increased with prey concentration for M. mirabilis and M. cavernosa, over a broad range of concentrations, indicating that saturation of the feeding response had not occurred until prey density
was over 104 items m−3, a concentration at least an order of magnitude greater than the normal range of reef zooplankton concentrations. Location
of cyst capture on coral surfaces was not uniform; for M. cavernosa, sides and tops of mounds captured most particles, and for P. porites, capture was greatest near branch tops, but was close to uniform for M. mirabilis branches in all flow conditions. The present study confirms laboratory flume results, and field results for other species,
suggesting that many coral species experience particle flux and encounter rate limitations at low flow speeds, decreasing
potential zooplankton capture rates.
Received: 17 September 1996 / Accepted: 22 November 1997 相似文献
19.
In this study eight different species of barnacles were found within nine species of sponges from the Red Sea. This brings
to 11 the number of sponge-symbiotic barnacles reported from the Red Sea, two of these are new Acasta species (not described herein) and one (A. tzetlini Kolbasov) is a new record for this sea. This number is much higher than that of symbiotic barnacles found within sponges
from either the N. Atlantic (2) or the Mediterranean (4). Two possible explanations for this are the presence of numerous
predators in coral reefs and scarcity of available substrate for settlement. These factors can lead to high incidence of symbiotic
relationships. Of the nine sponge species, only one (Suberites cf. clavatus) had previously been known to contain barnacles. Even at the family level, this is the first record of symbiotic barnacles
in two out of the seven sponge families (Latrunculiidae, Theonellidae). Our present findings strengthen the apparent rule
that the wider the openings in a barnacle shell, the fewer the host taxa with which it will associate, usually from one or
two closely related families, and the more frequent it will associate with elastic sponges. Most Neoacasta laevigata found on Carteriospongia foliascens were located on the same side as the sponge's ostia, i.e. facing the incoming water. This adaptation allows the barnacles
to catch more suspended particles from the water, provides them with more oxygen and prevents their exposure to discharged
sponge waste. The highest density of barnacles observed on one face of a “leaf ” (with ostia) was 0.389 barnacles cm−2 (one barnacle per 2.57 cm2) and on average 0.181 ± 0.68, while the average on the other side was only 0.068 ± 0.52 barnacles cm−2. As indicated by the Morisita index, these barnacles most frequently (58%, n = 12) had a clumped spatial distribution (while the rest were randomly distributed), as is to be expected from such sessile
organisms with internal fertilization via copulation. The presence of N. laevigata induced the growth of secondary perpendicular projections of its host C. foliascens. Of the N. laevigata examined, 17% brooded 324 ± 41 embryos each, of 286 ± 17 μm total length; only 5.7% (n = 123) were found to be dead. Size distribution analysis of skeletal elements from dead barnacles showed them to be significantly
larger than the skeletal elements of the population of live barnacles ( p < 0.05).
Received: 26 June 1998 / Accepted: 1 December 1998 相似文献
20.
Recruitment rates of stony corals to artificial substrates were monitored for 2 years at 20 sites along the coast of Eilat, northern Red Sea, to compare with those recorded at other coral reef locations and to assess variation in recruitment at several spatial scales. Coral recruitment was low compared to that observed on the Great Barrier Reef in Australia, but was similar to levels reported from other high-latitude reef locations. Pocilloporids were the most abundant coral recruits in all seasons. Recruitment was twofold higher during the first year than during the second year of study. There was considerable spatial variability, with the largest proportion of variance, apart from the error term, attributable to differences between sites, at a scale of 102 m. Spearmans ranked correlation showed consistency in spatial patterns of recruitment of pocilloporid corals between years, but not of acroporid corals. During spring, when only the brooding pocilloporid coral Stylophora pistillata reproduces at this locality, most coral recruitment occurred at central and southern sites adjacent to well-developed coral reefs. During summer, recruitment patterns varied significantly between years, with wide variation in the recruitment of broadcasting acroporid corals at northern sites located distant from coral reefs. Settlement was low at all sites during autumn and winter. This work is the first detailed analysis of coral recruitment patterns in the Red Sea, and contributes to the understanding of the spatial and temporal scales of variation in this important reef process.Communicated by O. Kinne, Oldendorf/Luhe 相似文献