Early Life History of Deep-Water Gorgonian Corals May Limit Their Abundance

Deep-water gorgonian corals are long-lived organisms found worldwide off continental margins and seamounts, usually occurring at depths of ∼200–1,000 m. Most corals undergo sexual reproduction by releasing a planktonic larval stage that disperses; however, recruitment rates and the environmental and biological factors influencing recruitment in deep-sea species are poorly known. Here, we present results from a 4-year field experiment conducted in the Gulf of Maine (northwest Atlantic) at depths >650 m that document recruitment for 2 species of deep-water gorgonian corals, Primnoa resedaeformis and Paragorgia arborea. The abundance of P. resedaeformis recruits was high, and influenced by the structural complexity of the recipient habitat, but very few recruits of P. arborea were found. We suggest that divergent reproductive modes (P. resedaeformis as a broadcast spawner and P. arborea as a brooder) may explain this pattern. Despite the high recruitment of P. resedaeformis, severe mortality early on in the benthic stage of this species may limit the abundance of adult colonies. Most recruits of this species (∼80%) were at the primary polyp stage, and less than 1% of recruits were at stage of 4 polyps or more. We propose that biological disturbance, possibly by the presence of suspension-feeding brittle stars, and limited food supply in the deep sea may cause this mortality. Our findings reinforce the vulnerability of these corals to anthropogenic disturbances, such as trawling with mobile gear, and the importance of incorporating knowledge on processes during the early life history stages in conservation decisions.     

A Novel Method for Coral Explant Culture and Micropropagation

We describe here a method for the micropropagation of coral that creates progeny from tissue explants derived from a single polyp or colonial corals. Coral tissue explants of various sizes (0.5?C2.5?mm in diameter) were manually microdissected from the solitary coral Fungia granulosa. Explants could be maintained in an undeveloped state or induced to develop into polyps by manipulating environmental parameters such as light and temperature regimes, as well as substrate type. Fully developed polyps were able to be maintained for a long-term in a closed sea water system. Further, we demonstrate that mature explants are also amenable to this technique with the micropropagation of second-generation explants and their development into mature polyps. We thereby experimentally have established coral clonal lines that maintain their ability to differentiate without the need for chemical induction or genetic manipulation. The versatility of this method is also demonstrated through its application to two other coral species, the colonial corals Oculina patigonica and Favia favus.     

Signaling pathways of heat- and hypersalinity-induced polyp bailout in Pocillopora acuta

Polyp bailout is a drastic response to acute stress where coral coloniality breaks down and polyps detach. We induced polyp bailout in Pocillopora acuta with heat stress and tested for differential gene expression using RNAseq and a qPCR assay. Furthermore, we induced polyp bailout with hypersalinity and compared the results to identify stressor-independent signals and pathways active during polyp bailout. Both stressors led to the onset of polyp bailout and the detachment of vital polyps. We observed activation of microbe-associated molecular pattern receptors and downstream signaling pathways of the innate immune system. Further, we detected growth factors and genes active during Wnt-signaling potentially contributing to wound healing, regeneration, and proliferation. Upregulation of several genes encoding for matrix metalloproteinases and the fibroblast growth factor signaling pathway are the most likely involved in the remodeling of the extracellular matrix, as well as in the detachment of polyps from the calcareous skeleton during polyp bailout. Expression of genes of interest in our qPCR assay of vital polyps from our heat-stress experiment, showed a trend for a normalization of gene expression after polyp bailout. Our results provide new insights into the signaling cascades leading to the observed physiological responses during polyp bailout. Comparison between the two stressors showed that certain signaling pathways are independent of the stressor and suggested that polyp bailout is a general response of corals to acute stress. Furthermore, immune system responses during polyp bailout indicate that microbe-associated partners of corals may lead to the polyp bailout response.

     

Sexual systems in scleractinian corals: an unusual pattern in the reef-building species Diploastrea heliopora

The sexual system in corals refers to the spatial and temporal pattern of sexual function within an individual coral polyp, colony or population. Although information on sexual systems now exists for over 400 scleractinian species, data are still lacking for some important reef-building taxa. The vast majority of scleractinians are either simultaneous hermaphrodites or gonochoric with other sexual systems rarely occurring. Diploastrea heliopora is one of the most ubiquitous and easily recognised reef-building species in the Indo-West Pacific; however, surprisingly little is known about its reproductive biology. The aim of the present study was to examine the reproductive biology of D. heliopora colonies on chronically impacted, equatorial reefs south of Singapore. Here we show that in Singapore, D. heliopora is a broadcast spawner with predominantly gonochoric polyps. Colonies, however, contained male, female and a low proportion of cosexual polyps during the 14-month sampling period. The most plausible explanation for this is that polyps switch sexes with oogenic and spermatogenic cycles occasionally overlapping. This leads to colony level alternation of sex function within and between breeding seasons. While this sexual system is atypical for scleractinians, it supports molecular evidence that D. heliopora is phylogenetically distinct from species formerly in the family Faviidae.     

Within-colony feeding selectivity by a corallivorous reef fish: foraging to maximize reward?

Foraging theory predicts that individuals should choose a prey that maximizes energy rewards relative to the energy expended to access, capture, and consume the prey. However, the relative roles of differences in the nutritive value of foods and costs associated with differences in prey accessibility are not always clear. Coral‐feeding fishes are known to be highly selective feeders on particular coral genera or species and even different parts of individual coral colonies. The absence of strong correlations between the nutritional value of corals and prey preferences suggests other factors such as polyp accessibility may be important. Here, we investigated within‐colony feeding selectivity by the corallivorous filefish, Oxymonacanthus longirostris, and if prey accessibility determines foraging patterns. After confirming that this fish primarily feeds on coral polyps, we examined whether fish show a preference for different parts of a common branching coral, Acropora nobilis, both in the field and in the laboratory experiments with simulated corals. We then experimentally tested whether nonuniform patterns of feeding on preferred coral species reflect structural differences between polyps. We found that O. longirostris exhibits nonuniform patterns of foraging in the field, selectively feeding midway along branches. On simulated corals, fish replicated this pattern when food accessibility was equal along the branch. However, when food access varied, fish consistently modified their foraging behavior, preferring to feed where food was most accessible. When foraging patterns were compared with coral morphology, fish preferred larger polyps and less skeletal protection. Our results highlight that patterns of interspecific and intraspecific selectivity can reflect coral morphology, with fish preferring corals or parts of coral colonies with structural characteristics that increase prey accessibility.     

A new laboratory method for monitoring deep-water coral polyp behaviour

Deep-water corals are found along the oceanic margins world-wide and in the north east Atlantic the most abundant species is Lophelia pertusa (L.). There is now growing evidence that deep-water reefs formed by such species are coming under increasing pressures from resource exploitation, principally deep-sea trawling and hydrocarbon exploration. Here a novel and unobtrusive method of recording deep-water coral behaviour in the laboratory is described using time-lapse video to record silhouettes of the polyps under infrared illumination. The polyps of L. pertusa behaved asynchronously and did not show any clear diurnal patterns over a three-day observation period. Conceptually, sessile benthic suspension feeders appear to be vulnerable to smothering by sediments disturbed by bottom trawls or sub-seabed drilling. This method allows deep-water coral polyp behaviour to be continuously monitored in the laboratory and, therefore, the responses of coral polyps to environmental perturbations such as sedimentation can be recorded. Further work is necessary to resolve the sensitivity of deep-water corals to short-term environmental change and the combined approach of in situ monitoring and subsequent laboratory experimentation has great potential to address these issues.     

An experimental analysis of the effects of light and zooplankton on coral zonation

Summary In Panamá, vertical zonation of coral species is well marked; branching corals (Pocillopora spp.) predominate in shallow (1–6 m) water while massive forms (Pavona spp.) occupy the deeper (6–10 m) areas of the reef. To test the hypothesis that this zonation represents differential resource utilization (i.e., niche partitioning of food resources), one year manipulative field experiments were conducted at two depths (1 m and 7 m below Mean Lower Sea Level) assessing the relative contribution of light and zooplankton to the nutrition of three Pacific corals: Pocillopora damicornis, Pavona clavus and Pavona gigantea. Also tested were the related hypotheses that (i) energy for the maintenance and growth of corals comes mainly from light, independent of zooplankton supply and (ii) Porter's model, in which coral morphology is a predictor of the phototrophic-heterotrophic capabilities of a particular species. That is, corals with a branching morphology and a small polyp diameter (and short tentacle length) should be primarily phototrophic while those species with larger polyps and/or a massive form should show a greater degree of heterotrophy.The comparison of caged versus control corals indicated that the branching coral, Pocillopora damicornis (polyp diameter — 1 mm) grew independent of zooplankton supply (>95) but was markedly affected by shading. Pavona clavus (massive form with intermediate size polyps — 2 mm) was also negatively affected by shading but this effect was minimized when zooplankton was present. Surprisingly, under ambient light conditions, the growth of this specics was independent of zooplankton (>95); perhaps indicating a facultative reliance on zooplankton especially in shallow water. The third species, Pavona gigan-tea (massive form with largest polyps — 3 mm) was highly dependent on both light and zooplankton and was unable to compensate for the effects of shading by zooplankton feeding. This high dependence on light was unexpected since large polyps, according to Porter's model, would predict a more heterotrophic existence.Under all treatments, in both shallow and deep water, Pocillopora was found to grow more rapidly than either massive species. Thus, this study indicates that zonation on eastern Pacific reefs cannot be explained by depth-related differences in nutritional requirements among the species present. These results do provide the first long-term, experimental field evidence that corals are largely phototrophic organisms. The validity of Porter's model attempting to correlate phototrophic-heterotrophic abilities to morphological characteristics is, at least, partially verified: species with larger tentacles do appear to utilize zooplankton to a greater extent than those species with smaller tentacles. However, the significance of corallum morphology in predicting the mode of nutrient acquisition is unclear. Rather, behavioral patterns (tentacle expansion-contraction cycles) and location on the reef may be more important factors to consider.     

Responses of solitary and colonial coronate polyps (Cnidaria, Scyphozoa, Coronatae) to sedimentation and burial

Coronate polyps retract their soft bodies into a protective peridermal tube after mechanical irritation. Sediment may enter the tube of contracted polyps, however, and block the opening [Jarms, G., 1990. Neubeschreibung dreier Arten der Gattung Nausithoe (Coronatae, Scyphozoa) sowie Wiederbeschreibung der Art Nausithoe marginata Kölliker, 1853. Mitt. Hamb. Zool. Mus. Inst. 87, 7-39; Silveira, F.L. da, Jarms, G., Morandini, A.C., 2003. Experiments in nature and laboratory observations with Nausithoe aurea (Scyphozoa: Coronatae) support the concept of perennation by tissue saving and confirm dormancy. Biota Neotropica 2 (2), 1-25]. In the present study, the ability of different coronate species [Nausithoe aurea Silveira and Morandini, 1997, Nausithoe planulophora (Werner, 1971), Thecoscyphus zibrowii Werner, 1984, Linuche unguiculata (Swarts, 1788)] to expel sediment particles from the tube was investigated. In laboratory experiments, sand grains and mussel shell fragments were inserted into the tubes and the responses of polyps were observed. Particles were ingested as polyps extended themselves, and after extension, they were defecated. Ingestion was effected by an aborally directed flagellar beat of the flagellated gastrodermal epithelia that was reversed for defecation. Particles only slightly smaller than the tube opening could be expelled, and extension of the polyp was possible even if grains blocked 2/3 of the tube. However, if particles became stuck in the tube, ingestion was impossible and polyp extension failed. Comparisons among the tested species showed that expulsion success depended on tube shape and polyp morphology. In N. aurea and N. planulophora, less than 5% of tubes were permanently blocked. The cave-dwelling species T. zibrowii was not able to ingest particles due to its particular morphology, and in 25% of experiments with shell fragments tubes were permanently blocked. Thin, elongate tubes of the colonial polyps L. unguiculata were also often permanently blocked by shell fragments (50%), but new polyps were developed from the scyphorhiza to ensure survival of the colony. Solitary polyps were able to survive more than 5 months retracted beneath any blocking particles. After tubes were cut off beneath such particles normal polyps developed. From our observations, we suggest that coronate polyps can exist in habitats with moderate sedimentation, and that they can survive being temporarily buried.     

Telomerase activity is not related to life history stage in the jellyfish Cassiopea sp.

The polyp (scyphistoma) of the jellyfish Cassiopea sp. can be maintained in culture for a long time, as polyps repeatedly reproduce asexually via formation of vegetative buds or propagules. The medusa, which is the sexually reproducing stage, typically has a relatively short life span. As a first step to understand the difference in life spans of the polyp and medusa stages of Cassiopea sp., we measured telomerase activity in different life cycle stages. We found telomerase activity in tissues of aposymbiotic polyps and propagules and symbiotic ephyrae (newly budded medusae) and adult medusae. No significant difference in telomerase activity was found between polyps and the bell region of the medusae. The cloned elongation products of the stretch PCR contained the TTAGGG repeats suggesting that the jellyfish has the ‘vertebrate’ telomere motif (TTAGGG)_n. This is the first study to show that somatic tissues of both polyp and medusa stages of a cnidarian had telomerase activity. Telomerase activity in somatic tissues may be related to the presence of multipotent interstitial cells and high regenerative capacity of cnidarians.     

Differences in the activity rhythms of juvenile gobiid fish,Chasmichthys gulosus,from different tidal localities

Activity patterns of intertidal gobiid fish,Chasmichthys gulosus, collected from different tidal localities, were recorded in a constant environment. Gobies collected from a rocky shore with a large tidal range and a regular tidal regime displayed a ca. 12 hour rhythm in their activity pattern. Gobies from a rocky shore with a small tidal range and an irregular tidal regime, however, did not clearly display any such rhythm. The ecological implications of such activity rhythms are discussed from the viewpoints of feeding and avoidance of predators.     

Calcification process dynamics in coral primary polyps as observed using a calcein incubation method

Calcification processes are largely unknown in scleractinian corals. In this study, live confocal imaging was used to elucidate the spatiotemporal dynamics of the calcification process in aposymbiotic primary polyps of the coral species Acropora digitifera. The fluorophore calcein was used as a calcium deposition marker and a visible indicator of extracellular fluid distribution at the tissue-skeleton interface (subcalicoblastic medium, SCM) in primary polyp tissues. Under continuous incubation in calcein-containing seawater, initial crystallization and skeletal growth were visualized among the calicoblastic cells in live primary polyp tissues. Additionally, the distribution of calcein-stained SCM and contraction movements of the pockets of SCM were captured at intervals of a few minutes. Our experimental system provided several new insights into coral calcification, particularly as a first step in monitoring the relationship between cellular dynamics and calcification in vivo. Our study suggests that coral calcification initiates at intercellular spaces, a finding that may contribute to the general understanding of coral calcification processes.     

High level of tetracosapolyenoic fatty acids in the cold-water mollusk <Emphasis Type="Italic">Tochuina</Emphasis><Emphasis Type="Italic">tetraquetra</Emphasis> is a result of the nudibranch feeding on soft corals

Fatty acid (FA) markers are used to trace predator–prey relationships in the marine environment. Soft corals contain tetracosapolyenoic acids (TPA), namely 24:5n-6 and 24:6n-3, which are considered as octocoral FA markers. The nudibranch mollusks are known to feed on soft corals. To check whether TPA are transferred from soft corals to nudibranch mollusks during their nutrition, we determined and compared FA compositions of total lipids of Tochuina tetraquetra and soft corals (Acanella sp., Anthomastus rylovi, Gersemia fruticosa, and Paragorgia arborea) collected together near the Kuril Islands (the depths of 80–550 m). FA compositions of T. tetraquetra, Acanella sp. and A. rylovi were described for the first time. In Acanella sp., G. fruticosa, A. rylovi, and P. arborea, the average contents of TPA were 6.5, 13.4, 5.9, and 12.0 % of total FAs, whereas the 24:5n-6/24:6n-3 ratio was 1.0, 1.4, 5.4, and 2.6, respectively. The high level of TPA (21.7 %) found in T. tetraquetra indicates that 24:5n-6 and 24:6n-3 are transferred from soft corals to the mollusks during their feeding and accumulated in mollusk tissues. The most possible feed source of the mollusk is suggested to be G. fruticosa and/or Acanella sp., because the 24:5n-6/24:6n-3 ratios in T. tetraquetra and these soft corals were similar. Thus, the TPA could be used as FA markers to estimate a proportion of soft corals in feeding of cold-water nudibranch mollusks.     

Induction of mixed-function oxygenase system and antioxidant enzymes in the coral Montastraea faveolata on acute exposure to benzo(a)pyrene

Components of the cytochrome P(450) monooxygenase system (MFO) and antioxidant enzymes were investigated in the coral Montastraea faveolata exposed to the organic contaminant benzo(a)pyrene (B(a)P). For bioassays the corals were exposed to increasing concentrations of B(a)P (0.01 and 0.1 ppm) for 24 and 72 h, with water renewal every 24 h. Enzymatic activity of catalase (CAT), superoxide dismutase (SOD) and glutathione S-transferase (GST) were measured in host (polyp) and hosted (zooxanthellae) cells. NADPH cytochrome c reductase activity and contents of cytochrome P(450) and P(420) were only measured in the polyp. Antioxidant enzymes CAT and SOD in polyps and zooxanthellae and GST in polyps increased significantly at the highest concentration and maximum time of exposure. Cytochrome P(420) was found in all colonies, and the cytochrome P(450) content was greatest in the colonies from the highest concentrations of contaminant. NADPH cytochrome c reductase activity and the concentration of pigments did not vary between treatments. This is the first report of the induction of both detoxifying mechanisms, the MFO system and antioxidant enzymes on acute exposure to an organic contaminant in the reef-constructing coral species M. faveolata.     

Effects of colony size and polyp position on polyp fecundity in the scleractinian coral genus Acropora

This study examined the effects of colony size and polyp position on six variables of polyp fecundity [egg number, egg size, total egg volume, total testis volume, total gonad volume, and gonad ratio (egg volume/testis volume)] in three tabular Acropora corals (Scleractinia), A. hyacinthus, A. japonica, and A. solitaryensis. Samples were collected from various colony sizes (n = 21–30 colonies species^?1), just before the predicted spawning at Kochi, Japan, in 2009. Five replicate polyps were sampled at three positions (center, middle, and outer) from the center to the marginal area in each tabular colony. Results indicated effects of colony size and polyp position on both male and female gonads polyp^?1. A positive effect of colony size was observed on variables of female gonads polyp^?1 (egg number, total egg volume) in A. hyacinthus only, while the positive effect on the variable of male gonads polyp^?1 (total testis volume) was common in all Acropora species, with total testis volume polyp^?1 increasing 2–4-fold from the small (200–400 cm²) to the large size class (5,000–9,000 cm²). Among the polyp positions, lower values were observed mostly in center polyps in A. hyacinthus, while lower values were observed only in outer polyps in the other Acropora species. The distinct patterns between A. hyacinthus and the other two Acropora species suggest different reproductive strategies at the species level. Further studies are needed to confirm the prevalence of these effects in scleractinian corals, which will broaden our understanding of reproductive life history strategies and improve the estimation of reproductive performance.     

Rhythmic swimming activity in Anguilla anguilla glass eels: Synchronisation to water current reversal under laboratory conditions

Synchronisation of swimming activity to water current reversal every 6.2 h was tested in the European glass eel (Anguilla anguilla L.). When presented with a change in water current direction, glass eels exhibited rhythmic patterns of activity with a period close to the tidal one. Glass eels began to swim with the current and then alternated between positive and negative rheotaxis after each change in the water current direction. Results are discussed in relation to the flood tidal transport theory. Following synchronisation to current reversal, glass eels subjected to constant conditions displayed a weak rhythmic activity suggesting that locomotor behaviour might, in the wild, synchronise to several environmental cues related to the tide. Results obtained with different densities also suggest that social cues might improve the synchronisation.     

Oxygen consumption in Mediterranean octocorals under different temperatures

Ecosystem resilience to climate anomalies is related to the physiological plasticity of organisms. To characterize the physiological response of some common Mediterranean gorgonians to fluctuations in temperature, four species (Paramuricea clavata, Eunicella singularis, Eunicella cavolinii and Corallium rubrum) were maintained in aquaria, in which the temperature was increased every ten days with increments of 2-3 °C, starting at 14 °C, ending at 25 °C. Oxygen consumption, number of open/closed polyps and percentage of necrotic tissue were monitored. All species showed similar activity patterns with increasing temperature. P. clavata and E. singularis showed the highest respiration rate at 18 °C, E. cavolinii and C. rubrum at 20 °C. Above these temperatures, both oxygen consumption and polyp reactivity decreased in all species. The present data confirm a reduction of the metabolic activity in Mediterranean gorgonians during periods of high temperature. At temperatures above 18 °C, the percentage of open polyps (considered as a parameter to evaluate polyps reactivity) decreased, thus mirroring the trend of oxygen consumption. The average values of Q₁₀ indicated that gorgonians have a definite temperature limit over which the metabolism (oxygen consumption) stop to follow the temperature increase. After three days at 25 °C, metabolic activity in E. cavolinii, C. rubrum and P. clavata further decreased and the first signs of necrosis were observed. At this temperature, activity remained unchanged in E. singularis. This species seems to more resistant to thermal stress. The symbiotic zooxanthellae present in this species are likely to provide an alternative source of energy when polyps reduce their feeding activity.     

Factors Influencing the Recurrence Potential of Benign Endometrial Polyps after Hysteroscopic Polypectomy

Background

An endometrial polyp is a frequently encountered gynecologic disease with abnormal uterine bleeding and infertility being the two common presenting problems, and hysteroscopic polypectomy is an effective method to remove them. The postoperative polyp recurrence might result in reappearance of abnormal uterine bleeding or infertility, whereas factors influencing the postoperative recurrence potential have limited data.

Methods

This case-series report included 168 premenopausal women who suffered from endometrial polyps and underwent hysteroscopic polypectomy. All of them were awaiting a future pregnancy. Office hysteroscopy was done before and after hysteroscopic polypectomy, in which preoperative hysteroscopy examined the number, type, and location of endometrial polyps, and postoperative hysteroscopy checked the polyp recurrence. Surgical indications, either infertility or the presentation of abnormal uterine bleeding, and follow-up duration were recorded.

Results

Seventy-three out of 168 (43%) women had polyp recurrence after hysteroscopic polypectomy. Multivariate logistic regression analysis revealed that more endometrial polyps (P = 0.015) and longer duration of follow-up (P = 0.004) were significantly associated with an increased risk of postoperative polyp recurrence. The type of endometrial polyps was not correlated with polyp recurrence potential, whereas pedunculated type endometrial polyps were closely related to the presentation of abnormal uterine bleeding (P = 0.001).

Conclusions

A higher number of endometrial polyps and longer follow-up duration are associated with a greater potential of polyp recurrence after hysteroscopic polypectomy.     

Physiological acclimation to elevated temperature in a reef-building coral from an upwelling environment

Recent work has found that pocilloporid corals from regions characterized by unstable temperatures, such as those exposed to periodic upwelling, display a remarkable degree of phenotypic plasticity. In order to understand whether important reef builders from these upwelling reefs remain physiologically uncompromised at temperatures they will experience in the coming decades as a result of global climate change, a long-term elevated temperature experiment was conducted with Pocillopora damicornis specimens collected from Houbihu, a small embayment within Nanwan Bay, southern Taiwan that is characterized by 8–9 °C temperature changes during upwelling events. Upon nine months of exposure to nearly 30 °C, all colony (mortality and surface area), polyp (Symbiodinium density and chlorophyll a content), tissue (total thickness), and molecular (gene expression and molecular composition)-level parameters were documented at similar levels between experimental corals and controls incubated at 26.5 °C, suggesting that this species can readily acclimate to elevated temperatures that cause significant degrees of stress, or even bleaching and mortality, in conspecifics of other regions of the Indo-Pacific. However, the gastrodermal tissue layer was relatively thicker in corals of the high temperature treatment sampled after nine months, possibly as an adaptive response to shade Symbiodinium from the higher photosynthetically active radiation levels that they were experiencing at that sampling time. Such shading may have prevented high light and high temperature-induced photoinhibition, and consequent bleaching, in these samples.     

Polyp oriented modelling of coral growth

The morphogenesis of colonial stony corals is the result of the collective behaviour of many coral polyps depositing coral skeleton on top of the old skeleton on which they live. Yet, models of coral growth often consider the polyps as a single continuous surface. In the present work, the polyps are modelled individually. Each polyp takes up resources, deposits skeleton, buds off new polyps and dies. In this polyp oriented model, spontaneous branching occurs. We argue that branching is caused by a so called “polyp fanning effect” by which polyps on a convex surface have a competitive advantage relative to polyps on a flat or concave surface. The fanning effect generates a more potent branching mechanism than the Laplacian growth mechanism that we have studied previously (J. Theor. Biol. 224 (2003) 153). We discuss the application of the polyp oriented model to the study of environmentally driven morphological plasticity in stony corals. In a few examples we show how the properties of the individual polyps influence the whole colony morphology. In our model, the spacing of polyps influences the thickness of coral branches and the overall compactness of the colony. Density variations in the coral skeleton may also be important for the whole colony morphology, which we address by studying two variants of the model. Finally, we discuss the importance of small scale resource translocation in the coral colony and its effects on the morphology of the colony.     

Larval development and survivorship in the corals Favia favus and Platygyra lamellina

Two Red Sea faviid species, Favia favus and Platygyra lamellina spawn eggs and sperm once a year, during the summer. External fertilization occurs 0.5 h after spawning, and mobile gastrulae appear 20 h later. Four stages in the early ontogenesis of these corals are described. The slow development (2–3 months) to the polyp stage in broadcasting species is attributed to the lack of zooxanthellae in their planulae and their appearance in the primary polyp only at a later stage. Survivorship of one-month-old primary polyps is ca 0.21% and 0.25% in F. favus and P. lamellina respectively, from the populations of 2–9-day-old planulae. Despite these low rates of survival, both species form dense populations in the Gulf of Eilat.