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  • 1
    Electronic Resource
    Electronic Resource
    The effects of elevated temperature on the photosynthetic efficiency of zooxanthellae in hospite from four different species of reef coral: a novel approach (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bleaching of reef corals is a phenomenon linked to temperature stress which involves loss of the symbiotic algae of the coral, which are known as zooxanthellae, and/or loss of algal pigments. The photosynthetic efficiency of zooxanthellae within the corals Montastrea annularis, Agaricia lamarki, Agaricia agaricites and Siderastrea radians was examined by pulse-amplitude modulation fluorometry (PAM) during exposure to elevated temperatures (30–36°C). Zooxanthellae within M. annularis and A. lamarki were found to be more sensitive to elevated temperature, virtually complete disruption of photosynthesis being noted during exposure to temperatures of 32 and 34°C. The photosynthetic efficiency of zooxanthellae within S. radians and A. agaricites decreased to a lesser extent. Differences in the loss of algal cells on an aerial basis and in the cellular chlorophyll concentration were also found between these species. By combining the non-invasive PAM technique with whole-cell fluorescence of freshly isolated zooxanthellae, we have identified fundamental differences in the physiology of the symbionts within different species of coral. Zooxanthellae within M. annularis appear to be more susceptible to heat-induced damage at or near the reaction centre of Photosystem II, while zooxanthellae living in S. radians remain capable of dissipating excess excitation energy through non-photochemical pathways, thereby protecting the photosystem from damage during heat exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00251.x
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  • 2
    Electronic Resource
    Electronic Resource
    The role of chemosensory behavior of Symbiodinium microadriaticum, intermediate hosts, and host behavior in the infection of coelenterates and molluscs with zooxanthellae (1984)
    Springer
    Marine biology 81 (1984), S. 9-17 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Symbiotic dinoflagellates, Symbiodinium microadriaticum (=zooxanthellae), may gain access to aposymbiotic hosts (i.e., those lacking zooxanthellae) by chemosensory attraction of the motile algae by the potential host or via an “intermediate” host. Laboratory experiments showed that motile zooxanthellae were attracted to intact aposymbiotic host animals, but not to starved symbiotic hosts. Fed symbiotic hosts and brine shrimp (Artemia sp.) nauplii also attracted motile zooxanthellae. The attraction of these zooxanthellae was directly correlated with nitrogen levels in the seawater surrounding the hosts; thus ammonia and possibly nitrate could be atractants. Brine shrimp nauplii, acting as “intermediate” hosts actively ingested both motile and non-motile zooxanthellae. the ingested zooxanthellae tended to remain morphologically unaltered during and after passage through the gut of the brine shrimp. Capture and ingestion of brine shrimp containing zooxanthellae by aposymbiotic scyphistomae of the jellyfish Cassiopeia xamachana led to infection of the scyphistomae with zooxanthellae. Zooxanthellae isolated from 17 different species of coelenterates and molluscs could be transferred via brine shrimp to the endodermal cells of the scyphistomae. However only 10 of these isolates persisted to establish a permanent association with C. xamachana. Scyphistomae in suspensions of motile zooxanthellae responded by a classical coelenterate feeding response, which may facilitate ingestion of the potential symbionts and establishment of a symbiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397620
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  • 3
    Electronic Resource
    Electronic Resource
    Diurnal changes in photochemical efficiency and xanthophyll concentrations in shallow water reef corals : evidence for photoinhibition and photoprotection (1999)
    Springer
    Coral reefs 18 (1999), S. 99-105 
    Details
    ISSN: 1432-0975
    Keywords: Key words Xanthophylls ; Photoinhibition ; Corals ; Photoprotection ; Bleaching Symbiotic dinoflagellates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  Diurnal patterns of photoinhibition have been identified in seven species of shallow water reef corals from the Andaman Sea, off the west coast of Thailand, using pulse amplitude fluorometry. Photochemical efficiency (Fv/Fm) and quantum yield (ΔF/Fm∑) of symbiotic dinoflagellates within the corals declined after dawn to reach a minimum between midday and early afternoon, recovering to former dawn levels by early evening. Parallel studies on the xanthophylls diadinoxanthin (Dn) and diatoxanthin (Dt), and their inter-conversion, also revealed a strong diurnal pattern as well as inverse correlations between the xanthophyll ratio Dt/(Dn+Dt) and Fv/Fm and ΔF/Fm′. These findings suggest a photoprotective function for these pigments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003380050163
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  • 4
    Electronic Resource
    Electronic Resource
    Nitrogen flux in giant clams: size-dependency and relationship to zooxanthellae density and clam biomass in the uptake of dissolved inorganic nitrogen (1993)
    Springer
    Marine biology 117 (1993), S. 381-386 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tridacnid clams live on coral reefs in the Indo-Pacific, in waters containing low concentrations of inorganic nitrogen. This study examined nitrogen flux in the giant clam Tridacna gigas. Adults and juveniles of this species typically occur with symbiotic dinoflagellates of the genus Symbiodinium sp., often referred to as zooxanthellae, which live in their tissues. Intact clams took up or released dissolved inorganic nitrogen (DIN), with the direction and magnitude of the fluxes dependent on clam size. Non-symbiotic larvae and newly-settled juveniles with few zooxanthellae released ammonium. Larger juveniles and adults depleted ammonium or nitrate from seawater, when offered separately. Rates of uptake of DIN, standardized to either clam wet weight or number of zooxanthellae, were highest in small clams (1 to 5 cm in length), and decreased with increasing clam size (〉5 cm). Clams maintained in seawater containing high concentrations of ammonium (ca. 20 μM) for ≥ 1 wk generally released ammonium in the dark and exhibited net uptake in the light. Freshly isolated zooxanthellae (FIZ) from small clams had higher uptake rates than FIZ from larger clams, implying that the latter may be more nitrogen-sufficient than the former. The gradient of nitrogen sufficiency in giant clams is related to zooxanthellae density, with peaks of both algal density and rates of uptake of DIN occurring in small sizes of clams, whose growth also appears to be limited by nitrogen availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349313
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  • 5
    Electronic Resource
    Electronic Resource
    Host glutamine synthetase activities in the giant clam—zooxanthellae symbiosis: effects of clam size, elevated ammonia and continuous darkness (1994)
    Springer
    Marine biology 118 (1994), S. 681-685 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Host tissues and zooxanthellae of the giant clam Tridacna gigas contained glutamine synthetase, with the highest transferase activities present in the gill, followed by the kidney, mantle, zooxanthellae, foot, heart and adductor muscle, in that order. Synthetase activities of glutamine synthetase in host tissues and zooxanthellae were in a similar order, but the differences were not so marked. Host tissues also contained hexokinase, glucose-6-phosphate dehydrogenase and malate dehydrogenase. Highest hexokinase activities were present in the heart, followed, in order, by the gill, mantle, adductor muscle and foot. Highest glucose-6-phosphate dehydrogenase activities were present in the gill, followed by the mantle, heart, adductor muscle and foot. All tissues assayed contained high malate dehydrogenase activities. There was no detectable glutamate dehydrogenase activity. Glutamine synthetase activity in gill and mantle tissue decreased by 1.6% with every 1 cm increase in clam size. Host glutamine synthetase activity decreased by 80% in gill tissue and by 45% in mantle tissue in clams which were maintained for 8 d in continuous darkness. Similar effects were found when clams were kept in light in the presence of elevated ammonia concentrations. It is suggested that both host and symbionts are nitrogen-deficient in small clams and that host glutamine synthetase plays a role in ammonia assimilation by the intact association.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00347516
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of a water-soluble fraction of a crude oil on the coral reef hydroid Myrionema hargitti: feeding, growth and algal symbionts (1984)
    Springer
    Marine biology 84 (1984), S. 143-154 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The water-soluble fraction (WSF) of crude oil affects two nutritional inputs, symbiotic algae and zooplankton capture, of the tropical hydroid Myrionema hargitti. Hydroids, collected from Discovery Bay, Jamaica, during December 1983 and January 1984, and treated for 1 h with 100% WSF (approximately 20 ppm) exhibited a reduced induction of tentacle contraction and decreased ability to capture brine shrimp nauplii. After a 24 h exposure, most tentacles had degenerated and polyps were rotund and distorted, with no responsiveness evident. In contrast, algal photosynthesis and translocation of photosynthetically-fixed carbon to the host were not significantly affected by short-term (〈3 h) exposures to WSF. However, the algae in 24 and 48 h-treated individuals showed reductions in both photosynthesis and carbon translocation rates. The contribution of translocated carbon from the symbiotic algae to the hydroids' respiration (CZAR) was about 81% at 24 h and 23% at 48 h, compared to control levels in freshly collected individuals of 118%. The net effect of oil treatment for 24h or more on M. hargitti colonies was a loss of polyps and a reduction of stolon length during the treatment period. Treatment in 100% WSF for 7 d led to bleaching and eventual death of the colonies. Hydroids exposed to 100% WSF for 48h or less developed new polyps and recovered both their photosynthetic capability and ability to catch food within 3d of transfer from WSF to seawater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392999
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  • 7
    Electronic Resource
    Electronic Resource
    Competence and delay of metamorphosis in the Pacific oysterCrassostrea gigas (1990)
    Springer
    Marine biology 106 (1990), S. 379-387 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The temporal relationship between the onset of behavioral and morphogenetic competence was determined inCrassostrea gigas (Thunberg) larvae by exposure to appropriate chemical inducers during development. Larvae exhibited settlement behavior in response to L-3,4-dihydroxyphenylalanine (L-DOPA) before becoming competent to metamorphose in response to epinephrine. For larvae past the onset of competence, the apparent stimulus-threshold decreased and they were increasingly likely to metamorphose subsequent to induced settlement behavior. In the absence of chemical stimulation, cultured oyster larvae were able to delay metamorphosisand maintain competence for at least 30 d. Competence was correlated with, but not dependent upon, larval size and eyespot development. A mechanistic model of oyster settlement and metamorphosis is proposed which incorporates these new data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344316
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  • 8
    Electronic Resource
    Electronic Resource
    Settlement behavior and metamorphosis of oyster larvae (Crassostrea gigas) in response to bacterial supernatants (1990)
    Springer
    Marine biology 106 (1990), S. 389-394 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Veliger larvae of the oysterCrassostrea gigas (Thunberg) responded to unknown dissolved chemical inducers found in supernatants of cultures of the bacteriaAlteromonas colwelliana andVibrio cholerae. The response, which was similar to that seen when larvae were exposed to the neurotransmitter precursor L-3,4-dihydroxyphenylalanine (L-DOPA), consisted of an initial settlement phase of swimming with the foot extended and crawling on the substrate. Subsequently larvae attached to the substrate and metamorphosed. The percentage of veligers metamorphosing following inducation of settlement behavior was higher in a group of older larvae, a response similar to that seen with L-DOPA, suggesting that competence to respond to bacterial supernatants is divided into two phases: behavioral competence followed by morphogenetic competence. Following size exclusion chromatography, the molecular weight of the peak containing the activity which induced settlement behavior was determined to be ≤ 300 daltons. Autoclaved Marine Broth, which induced low levels of settlement behavior also contained this low molecular weight active peak, suggesting that an oyster settlement inducer is also present in this medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344317
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of starvation, and light and dark on the energy metabolism of symbiotic and aposymbiotic sea anemones, Anthopleura elegantissima (1981)
    Springer
    Marine biology 61 (1981), S. 199-205 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rates of oxygen and carbon-dioxide exhange were measured in symbiotic and aposymbiotic specimens of the sea anemone Anthopleura elegantissima while fed and starved under light or dark conditions. Respiratory quotients indicated that fed anemones switched from a carbohydrate to a fat catabolism when starved, with the exception that symbiotic individuals starved in the light showed a pronounced carbohydrate catabolism for over 1 month. The source of the carbohydrate was probably photosynthate translocated by the dinoflagellate Symbiodinium (=Gymnodinium) microadriaticum (Freudenthal) living in the anemones' tissues. The starved symbiotic anemones maintained in the light had lipid levels not significantly different from fed controls and 44 to 61% higher than starved aposymbiotic anemones after 1 month. Thus, the quality and quantity of the metabolic flux from the symbionts to the sea anemone were sufficient to conserve the host's lipid reserves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386660
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  • 10
    Electronic Resource
    Electronic Resource
    Requirement of exogenous inducers for metamorphosis of axenic larvae and buds of Cassiopea andromeda (Cnidaria: Scyphozoa) (1987)
    Springer
    Marine biology 94 (1987), S. 415-422 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Planula larvae and asexually-produced buds of the rhizostome scyphozoan Cassiopea andromeda (collected throughout the year in Eilat, Israel) have the ability, under axenic conditions, to attach to a substrate and undergo morphogenetic development to form a polyp (=scyphistoma) in: (1) the presence of unidentified inducers found in the adult habitat and (2) the presence of cefined organic compounds. Axenic planulae and buds were unable to settle and complete metamorphosis in autoclaved artificial or natural seawater from the North Sea when maintained without food, but continued swimming while decreasing in size and protein content, eventually dying within three months. When maintained in autoclaved seawater from the Red Sea, between 25 and 46% of the planulae and 4 and 11% of the buds metamorphosed within 30 d. Axenic solutions of cholera toxin, thyroid stimulating hormone, and pancreatic casein hydrolysate peptides in artificial seawater induced morphogenic development of 20 to 100% of planulae and buds within 2 to 18 d. The natural inducer(s) in Red Sea seawater, though unidentified, may have characteristics similar to the large proteins and small peptide inducers used in this study. Planulae and buds older than 20 d metamorphosed sooner and responded to lower concentrations of pancreatic casein hydrolysate peptides than younger individuals. This may be a physiological mechanism for enhancing metamorphosis and survival in nature. The data show that settlement and metamorphosis can be induced by solutions of cholera toxin and thyroid stimulating hormone, suggesting that, as in mammalian systems, the mechanism of action of these chemicals may involve cyclic adenosine monophosphate (cAMP) as an intermediate messenger. However, dibutyric cAMP, which is capable of passing through membranes and functioning normally inside the cell, did not induce metamorphosis of buds, and the levels of intracellular cAMP in buds and larvae typically increased slowly during induction of metamorphosis, unlike the high and rapid increases associated with cAMP-mediated biochemical events in mammalian cells. These results suggest that the observed cAMP changes seen were associated with metamorphic development, but not with the triggering mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428248
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