Motility of zooxanthellae isolated from the Red Sea soft coral Heteroxenia fuscescens (Cnidaria)

Unicellular dinoflagellate algae are among the best examples of organisms that exhibit biological clocks. This study examined the effect of light regime on rhythmicity of motility in the symbiotic dinoflagellate Symbiodinium sp., freshly isolated from the soft coral Heteroxenia fuscescens (Ehrenberg). Freshly isolated algal cells, placed under a 12-h L:12-h D cycle, exhibited motility with a diel rhythm. This motility occurred only during the period of illumination and lasted 8-9 h, with a peak at 2.5-4 h after lights on. Algal cells placed in an inverted light regime inverted their motility pattern. The response to the L/D regime was very precise, and even a 1-h shift backward or forward affected initiation of motility and time of its maximal peak. When placed in either constant light or dark, algal motility ceased until the L/D cycle was restored. These findings suggest that the rhythm is entrained by light cues and is not due to an endogenous circadian rhythm. Further, we provide evidence that the presence of juvenile hosts does not affect the algal motility pattern. These results offer the first evidence for the lack of impact by the host on rhythmicity of motility of free-living algal cells. The motility pattern found in freshly isolated algae may indicate the presence of light-induced diel rhythmicity in yet-to-be described free-living Symbiodinium.     

Host-finding behaviour and navigation capabilities of symbiotic zooxanthellae

Past studies have shown that the initiation of symbiosis between the Red-Sea soft coral Heteroxenia fuscescens and its symbiotic dinoflagellates occurs due to the chemical attraction of the motile algal cells to substances emanating from the coral polyps. However, the resulting swimming patterns of zooxanthellae have not been previously studied. This work examined algal swimming behaviour, host location and navigation capabilities under four conditions: (1) still water, (2) in still water with waterborne host attractants, (3) in flowing water, and (4) in flow with host attractants. Algae were capable of actively and effectively locating their host in still water as well as in flow. When in water containing host attractants, swimming became slower, motion patterns straighter and the direction of motion was mainly towards the host—even if this meant advancing upstream against flow velocities of up to 0.5 mm s⁻¹. Coral-algae encounter probability decreased the further downstream of the host algae were located, probably due to diffusion of the chemical signal. The results show how the chemoreceptive zooxanthellae modify their swimming pattern, direction, velocity, circuity and turning rate to accommodate efficient navigation in changing environmental conditions.     

Characterization of superoxide dismutases in anoxia- and hyperoxia-tolerant symbiotic cnidarians

Many cnidarians, such as sea anemones, contain photosynthetic symbiotic dinoflagellates called zooxanthellae. During a light/dark cycle, the intratentacular O(2) state changes in minutes from hypoxia to hyperoxia (3-fold normoxia). To understand the origin of the high tolerance to these unusual oxic conditions, we have characterized superoxide dismutases (SODs) from the three cellular compartments (ectoderm, endoderm and zooxanthellae) of the Mediterranean sea anemone Anemonia viridis. The lowest SOD activity was found in ectodermal cells while endodermal cells and zooxanthellae showed a higher SOD activity. Two, seven and six SOD activity bands were identified on native PAGE in ectoderm, endoderm and zooxanthellae, respectively. A CuZnSOD was identified in both ectodermal and endodermal tissues. MnSODs were detected in all compartments with two different subcellular localizations. One band displays a classical mitochondrial localization, the three others being extramitochondrial. FeSODs present in zooxanthellae also appeared in endodermal host tissue. The isoelectric points of all SODs were distributed between 4 and 5. For comparative study, a similar analysis was performed on the whole homogenate of a scleractinian coral Stylophora pistillata. These results are discussed in the context of tolerance to hyperoxia and to the transition from anoxia to hyperoxia.     

Characterization of a latent virus-like infection of symbiotic zooxanthellae

A latent virus-like agent, which we designated zooxanthella filamentous virus 1 (ZFV1), was isolated from Symbiodinium sp. strain CCMP 2465 and characterized. Transmission electron microscopy and analytical flow cytometry revealed the presence of a new group of distinctive filamentous virus-like particles after exposure of the zooxanthellae to UV light. Examination of thin sections of the zooxanthellae revealed the formation and proliferation of filamentous virus-like particles in the UV-induced cells. Assessment of Symbiodinium sp. cultures was used here as a model to show the effects of UV irradiance and induction of potential latent viruses. The unique host-virus system described here provides insight into the role of latent infections in zooxanthellae through environmentally regulated viral induction mechanisms.     

Molecular diversity of symbiotic algae (zooxanthellae) in scleractinian corals of Kenya

In this first sequence analysis of ‘zooxanthellae’ (symbiotic algae of the genus Symbiodinium) in scleractinian corals in Africa, seven Kenyan species sampled in 2001–2002 were analysed by RFLP and sequencing of a PCR-amplified fragment of the LSU rRNA gene. Zooxanthellae of phylotypes A, C and D, all described previously in corals from other regions of the world, were detected. All sequences of phylotype D were identical, while phylotype C was variable, with 14 distinct sequences, seven of which clustered in a previously unreported subgroup of phylotype C, among the 22 samples. These data on the diversity of zooxanthellae in Kenyan corals 3–4 years after the 1998 bleaching event are of potential value for longitudinal studies of temporal changes in zooxanthella diversity in Kenyan corals, especially in relation to future large-scale bleaching episodes.     

A symbiosome membrane is not required for the actions of two host signalling compounds regulating photosynthesis in symbiotic algae isolated from cnidarians

In many cnidarians, symbiotic algae live within host-derived symbiosomes. We determined whether a symbiosome membrane alters the response of isolated symbiotic algae to two signalling compounds that regulate algal carbon metabolism. Host release factor (HRF), which stimulates photosynthate release, and photosynthesis inhibiting factor (PIF), which inhibits photosynthetic carbon fixation, are found in homogenised tissue of the scleractinian coral Plesiastrea versipora. Compared with seawater controls, photosynthate release from isolated algae incubated in P. versipora homogenate for 2 h in the light was: 6 to 19-fold higher from its own algae (free of symbiosomes); 19 to 32-fold higher from Zoanthid robustus algae (within symbiosomes) and 3 to 24-fold higher from Z. robustus algae (free of symbiosomes); and from cultured algae (free of symbiosomes) was seven-fold higher from Montipora verrucosa and four-fold higher from Cassiopeia xamachana. Incubation of algae in P. versipora homogenate inhibited photosynthesis by: 33-49% in P. versipora algae; 29-47% in Z. robustus algae (regardless of whether or not the symbiosome was present); and 25% in M. verrucosa algae. In C. xamachana algae, photosynthesis increased. We conclude that the symbiosome is not essential for, yet does not block, the effects of HRF and PIF.     

The taxonomy and biology of further aeolidacean and arminacean nudibranch molluscs with symbiotic zooxanthellae

The occurrence of symbiotic zooxanthellae in further aeolid and arminacean nudibranch molluscs is described for the first time. The aeolid Aeolidiopsis ransoni Pruvot-Fol is redescribed, and a new species of Aeolidiopsis , also feeding on the colonial zoantharian Palythoa , is described. Both have symbiotic zooxanthellae. The taxonomy of the family Aeolidiidae is discussed and the genus Berghia Trinchese, 1877 is considered a synonym of Spurilla Bergh, 1864. Spurilla major (Eliot, 1903) and a new species of Spurilla are reported to have zooxanthellae while another new species of Spurilla is without zooxanthellae. The glaucid aeolid Pteraeolidia ianthina (Angas) is shown to have symbiotic zooxanthellae, as is the arminacean Doridomorpha gardineri Eliot, which is reported to feed on the alcyonarian blue coral, Heliopora. In all cases, the morphological adaptations developed for this symbiosis are described. Further notes on the Porites-fetding arminacean Pinufius rebus Marcus & Marcus and the aeolid Phestilla lugubris (Bergh) are included and a facultative symbiosis with zooxanthellae is suggested for the latter. The tion of symbiosis with zooxanthellae within nudibranchs is discussed and it is suggested that the relationship has evolved independently on several occasions.     

Stability and instability of marine ecosystems,illustrated by examples from the Red Sea

With all the limitations of novelty, ecology today is able to discern certain practices that may be destructive to the existing ecosystems, and to predict what the damages in the systems will be if preventive measures are not taken. The aim of this paper is to present some ideas about the importance of predictable evolution of all the compounds of ecosystems leading toward the development of climax communities, with high homeostatic power. Recent perturbations, caused mostly by human activity, have disturbed the predictability of events, and as a result also the stability of ecosystem development. Such disturbances produce situations de novo in ecosystems, cause reselection of the biological partners, and eliminate the more sensitive ones. These ideas are illustrated in several investigations performed in the coral reef region of the Gulf of Aqaba, Red Sea. The results of these studies showed that the perturbations caused by man's activity increase the instability of coral reef ecosystems. This is illustrated by a decrease in the affinity of samples taken at the same spot and a decrease in the evenness of distribution. These changes produce new forms of ecosystems, unpredictable as to their final stages of development.This investigation was supported by the U.S.-Israel Binational Science Foundation Grant No. 356.     

Carbohydrate composition of mucus from scleractinian corals from the central Red Sea

Coral Reefs - Coral mucus is continuously released by most corals and acts as an important protective barrier and as a substrate for host-associated microbial communities due to its complex...     

The breakdown of symbiotic zooxanthellae in the sea anemone Phyllactis (=Oulactis) flosculifera (Actiniaria)

The sea anemone Phyllactis (=Oulactis) flosculifera Lesueur (Actiniaria) has developed specialized adaptations of a structural, behavioural and chemical nature, which allow the farming of its symbiotic zooxanthellae as well as their breakdown and use as a source of nutrition. The presence of an extension of the upper column, the ruff, increases the exposed surface area, and the pattern of expansion and contraction of ruff and tentacles allows the high standing crop of algal symbionts they contain maximum exposure to illumination. A protein extract from the combined ruff, oral disc and tentacles has a destructive effect in vitro on the zooxanthellae of Phyllactis (52%), Aiptasia (37·5%) and Zoanthus (16%). Intracellular degeneration of zooxanthellae is greatest in the phagocytic cells of the trefoil forming the free end of the upper mesentery, but also occurs in other parts of the mesentery. The algal pellet extruded by Phyllactis consists mostly of debris, testifying to the anemone's ability to break down its zooxanthellae. Aiptasia tagetes Duch. & Mich, shows only a simple phototactic response, has no algal-damaging agent and very few degenerate zooxanthellae in its mesenteries, but it extrudes large numbers of its symbionts in all stages of the life history.     

Non-native fishes in the Mediterranean from the Red Sea,by way of the Suez Canal

The opening of the Suez Canal in 1869 caused a migration generally from the Red Sea to the Mediterranean, rarely the opposite direction, and 63 lessepsian fish species penetrated into the Mediterranean by way of this canal. These species usually spread northward and most of them can establish wide populations in this area, but some of them can not be successful with respect to establishment. Thus, it is clearly seen that there are a lot of factors influencing the success of species with respect to migration, spreading and establishment. So, the lessepsian migration has been formed by the effects of these factors. Lessepsian species also have the ability to adapt to the ecological conditions of their new environment. Therefore, the influential factors, their effectiveness and the observed changes in lessepsian species due to the effects of these factors have been discussed by considering fishes in this paper.     

Some algae from the Red Sea Hills in north-eastern Sudan

The algae contained in some plankton samples from several localities on four wadi in N.E. Sudan were examined. The observed algae amount to 260 taxa, of which the diatoms, representing 50% of the algal flora, are the most numerous. Other large groups are the blue-green algae (17%) and the green algae (24%) among which the desmids (6%) are rather unimportant.     

Novel polyhydroxysterols from the Red Sea marine sponge Lamellodysidea herbacea

Chemical investigation of the dichloromethane extract of the Red Sea marine sponge Lamellodysidea herbacea led to the isolation of four novel polyhydroxysteroids: cholesta-8-en-3beta,5alpha,6alpha,25-tetrol (1), cholesta-8(14)-en-3beta,5alpha,6alpha,25-tetrol (2), cholesta-8,24-dien-3beta,5alpha,6alpha-triol (3), and cholesta-8(14),24-dien-3beta,5alpha,6alpha-triol (4). Their structures were identified through 1D and 2D NMR studies. Relative stereochemistries were established by analysis of chemical shifts, coupling constants, and NOESY correlations. Compounds 3-4 showed antifungal activity against Candida tropicalis, with an inhibition diameter of 13 and 11 mm at 10 microg/disc, respectively.     

Expulsion of proteins from water-in-oil microemulsions by treatment with cosurfactant

A quick and simple method has been developed for the recovery of proteins from water-in-oil microemulsions (w/o-MEs), which is needed to further the use of liquid-liquid extraction in bioseparations. By adding a small portion (0.1 v/v or less) of cosurfactant (e.g., 1-alkanol) to w/o-ME solution, proteins were readily expelled, sometimes as solids, while most or all of the surfactant (Aerosol OT) remained in solution. The release of proteins increased with the further addition of cosurfactant and was greater when the molar ratio of protein to w/o-ME or fractional occupancy (f) was high. However, protein expulsion was also significant when f was small. The addition of cosurfactant released ribonuclease, lysozyme, alpha-chymotrypsin, pepsin, bovine serum albumin (BSA), and catalase from w/o-ME solution, but the expulsion was greater for BSA relative to chymotrypsin and lysozyme. Protein expulsion also increased with cosurfactant chain length for the homologous series of 1-alkanols starting at 1-butanol; however, water was also coexpelled in significant amounts. An exception to the latter rule was 1-butanol, which readily promoted the release of protein, but not encapsulated water. The addition of 1-butanol to a w/o-ME solution containing alpha-chymotrypsin and BSA selectively released the former protein, with chymotryptic activity occurring in the recovered protein. Possible mechanisms for the cosurfactant-mediated release of protein are discussed. Copyright 1998 John Wiley & Sons, Inc.     

Suppression of termite feeding and symbiotic protozoans by the dye, Sudan Red 7 B

Laboratory groups of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), were fed for 14 days on wood shavings soaked in acetone solutions of 0%, 0.5% or 1% concentrations of the dye, Sudan Red 7B or on shavings not soaked in acetone (0% non-acetone, NA). Termites feeding on dyed wood became visibly stained red. Groups of dyed or non-dyed termites were then placed in containers and allowed to feed on non-dyed wood for 21 days. Dyed termites had lower numbers of symbiotic protozoans, lower feeding rates, and lower survivorship than did non-dyed termites. Survivorship was significantly lower in the 1% concentration than in the 0.5% concentration. Covariate analyses suggested that Sudan Red acts both directly and indirectly (via suppression of gut fauna) to reduce vigor in termites. Because there is variable survival response to this dye by different populations of C. formosanus, we recommend preliminary tests of dye toxicity before using it extensively in experiments.

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Résumé Le colorant rouge Soudan 7B (BASF, Wyandotte Corp.) soluble dans l'huile, est un marqueur efficace des termites pour les études dans la nature. Quand les termites consomment des matériaux marqués par ce colorant, ils deviennent nettement colorés en rouge. Bien que certains travaux indiquent que le rouge Soudan n'augmente pas considérablement la mortalité, il n'y a aucune donnée concernant l'effet du colorant sur l'alimentation des termites.Un groupe de Coptotermes formosanus récolté au lac Charles en Louisiane, a été alimenté pendant 14 jours sur copeaux de Pinus sp. colorés avec des solutions 0, 0.5% et 1% (en poids) de rouge Soudan 7B dans l'acétone, ou sur copeaux non colorés et sans acétone (NA). Les groupes de termites colorés ou non sont alors placés dans des récipients pour s'alimenter sur bois non coloré pendant 21 jours. Des différences significatives ont été observées (t. 1): les termites colorés avaient moins de protozoaires symbiontes, consommaient moins de bois et vivaient moins long-temps que les termites sans colorant (t. 2). La survie a été plus faible avec la concentration 1% qu'avec 0.5%. Le nombre de protozoaires était plus faible avec une solution acétonique sans rouge Soudan qu'avec du bois sans acétone, ce qui suggère que l'effet négatif du rouge Soudan sur les protozoaires a pu être augmenté par l'extraction d'une substance favorisant les protozoaires contenue dans les copeaux de pin.La chute de la prise de nourriture a été accompagnée d'une chute parallèle de l'effectif de protozoaires. En réexaminant les résultats de Lai et al. (1983), nous constatons qu'eux aussi avaient observé une réduction de l'effectif de protozoaires de C. formosanus sous l'effet du rouge Soudan. Dans notre étude, nous trouvons que 49,6% de l'effet réducteur du colorant sur la nutrition est expliqué par l'effet simultané sur les protozoaires. Nos résultats sur la survie confirment dans l'ensemble ceux de Su et al. (1983 a) sur C. formosanus de Louisiane. Cependant, C. formosanus de Hawaï (Lai et al., 1983) et de Floride (Su et al., 1988) avaient des taux de survie bien plus élevés. C. formosanus présente nettement des réactions variables au rouge Soudan. Dans notre travail, 64,1% de l'effet du colorant sur la survie a été expliqué par des modifications chez les protozoaires. Ainsi, il semble que le rouge Soudan agisse directement sur l'alimentation et la survie de C. formosanus, et indirectement par la suppression de sa faune intestinale.Bien que nos résultats montrent les effets délétères du rouge Soudan 7B sur C. formosanus, il reste le meilleur colorant pour les termitologistes. par suite de la variabilité de son effet sur la survie, nous conseillons des tests de toxicité avant son utilisation intensive dans des expériences.

     

Increased 5-Hydroxytryptamine and Norepinephrine Release from Rat Brain Slices by the Red Sea Flatfish

The effect of the Red Sea flatfish toxin pardaxin was examined on K+-evoked and on basal release of either [3H]norepinephrine or [3H]5-hydroxytryptamine from preloaded rat cortical slices. The K+-induced release of the neurotransmitters was stimulated in a dose-related manner at concentrations ranging from 0.5 to 4 micrograms/ml. Basal release of the two transmitters was elevated to a lesser extent. Although the stimulation of evoked release was approximately equivalent for the two neurotransmitters, the response to 5-hydroxytryptamine was reversible whereas that of norepinephrine was not washed by 20 min of superfusion. The mechanisms involved in producing these actions of pardaxin are not known; however, they may be mediated by changes in electrolyte fluxes across the neuronal membranes.     

New purine alkaloids from the Red Sea marine tunicate Symplegma rubra

Investigation of the Red Sea marine tunicate Symplegma rubra Monniot, 1972 gave three new purine alkaloids namely 6-methoxy-7,9-dimethyl-8-oxoguanine (1), 6-methoxy-9-methyl-8-oxoguanine (2), and 2-methoxy-7-methyl-8-oxoadenine (4) together with seven known compounds: 6-methoxy-7-methyl-8-oxoguanine (3), 9-methyl-8-oxoadenine (5), 7-methyl-8-oxoadenine (6), 8-oxoadenine (7), 3-methylxanthine (8), inosine (9), and homarine (pyridinium-2-carboxylic acid-1-methyl) (10). Compound 6 was reported here for the first time from a natural source. The structure determination of the compounds was accomplished by extensive interpretation of their spectroscopic data including 1D (¹H and ¹³C) and 2D (¹H–¹H COSY, HSQC, and HMBC) NMR and high-resolution mass spectral data. The isolated compounds were evaluated for their protein kinase inhibitory activity against different kinases (CDK5, CK1, DyrK1A, and GSK3) at 10 μg/mL. The compounds showed moderate activity against these kinases.