Hideyuki Yamashiro

Composition of lipids, fatty acids and sterols in Okinawan corals

A survey of lipid composition was made for 15 cnidarians from Okinawa, Japan. Eleven zooxanthellate scleractinian corals, an azooxanthellate scleractinian coral Tubastrea sp., a soft coral Lobophytum crassum, a hydroid coral Millepora murrayi and a sea anemone Boloceroides sp. were examined to elucidate the total lipid content, fatty acid composition for each lipid class and sterol composition. All specimens contained monoalkyldiacylglycerol which migrated between the triacylglycerols and esters on thin layer chromatography (TLC). Analysis by high performance thin layer chromatography (HPTLC) and Gas chromatography-mass spectrometry (GC-MS) revealed that these cnidarians were rich in wax ester and triacylglycerol, and that palmitic acid (16:0) was the most abundant fatty acid component of these lipid classes, followed by stearic (18:0) and oleic (18:1, n-9) acid in order of concentration. Of 11 sterols separated, four sterols were identified. It is suggested that sterol composition may be more useful for the biochemical classification of these cnidarians than fatty acid composition.

Seasonal changes in the content and composition of lipids in the coral Goniastrea aspera

Reef-building corals contain large amounts of storage lipids, which range from 9 to 47% of the dry weight of their tissues (Harland et al. 1993; Yamashiro et al. 1999). These lipids are mainly derived from carbon photosynthetically fixed by symbiotic zooxanthellae (Kelogg and Patton 1983; Harland et al. 1993). Lipid levels in coral tissue appeared to vary with the energy balance between input from zooxanthellae and output as respiration, cell renewal, and release of reproductive materials (Battey and Patton 1984; Rinkevich 1989; Arai et al. 1993; Ward 1995). Lipid levels in corals may show seasonal changes because production of photosynthates varies with light intensity and water temperature (Harland et al. 1992; Al-Moghrabi et al. 1995); however, this has yet to be demonstrated. This study examined the lipid content and composition of the reef-building coral Goniastrea aspera throughout a year. Materials and methods

Experimental study of growth and asexual reproduction in Diaseris distorta (Michelin, 1843), a free-living fungiid coral

A solitary, free-living fungiid coral, Diaseris distorta, was reared in an aquarium and X-radiographed monthly for one year to study growth and asexual reproduction. The corals were treated three ways: 1) hand-split along radially oriented slits, 2) cut into pieces with scissors, and 3) reared without manipulation. The number of corals increased with time by radial fragmentation, a result of natural autotomy. Fragments, both control and hand-split, generated equal numbers of daughter segments. Corals that were cut produced more regenerated segments than control or hand-split corals because the cut corals provided a greater periphery from which daughter segments could regenerate. Growth rate was size-dependent. After fragmentation, the founder segment ceased horizontal growth until the new, regenerating segments gained nearly the same size as the founder segment.

Coral tumors store reduced level of lipids

The reef building coral Montipora informis (Scleractinia, Acroporidae) found on the colony surface of the fringing reef of Sesoko Island, Okinawa, Japan frequently carries hemispherical protuberances (tumors). We compared the total lipid content and the compositions of lipid and fatty acid between normal and tumorous tissues. The lipid content of tumor was 10.6% of the dry tissue weight, and was much lower than that for normal tissues (32.2%). The decrease in the total lipid content of tumorous tissue accompanied a reduced proportion of wax and triacylglycerol (TG). The major fatty acid component was 16:0 (palmitic) acid, and comprised comparable proportion of polar lipids and free fatty acid from both tumorous and normal tissues. An increasing tendency of polyunsaturated fatty acid (PUFA; C>20) was noted in the free fatty acid and polar lipid fractions from tumorous tissues compared with the normal tissue. Thus, the present study first demonstrated the reduced lipid storage level in the tumorous coral, and discussed the rationale for these observations.

Effect of bleaching on lipid content and composition of Okinawan corals

Lipid contents and compositions of the bleached Okinawan corals were analyzed for the first time. Bleached corals collected at Sesoko Okinawa, Japan (26°38′N, 127°52′E), after the 1998 bleaching event showed decreased lipid content with a concomitant decline of wax in the lipid composition. The reductionin the lipid content of corals showed diversity depending on their colony morphology. On the whole, corals of massive morphology were relatively rich in lipid even after the bleaching event, and hence lesser reduction in the lipid content compared with the cases for those of branching morphology. Furthermore, there was a positive correlation between lipid content and zooxanthellae density in the bleached corals, suggesting again the importance of symbiont for the supply of lipid to the host cells, and hence for the survival of the bleaching event.

The effects of HEBP, an inhibitor of mineral deposition, upon photosynthesis and calcification in the scleractinian coral, Stylophora pistillata

Abstract In reef-building corals, photosynthesis by endosymbiotic algae enhances calcification; this rate of calcification is reduced by shading and by inhibitors of photosynthesis. Calcification can also be reduced by compounds which prevent mineral deposition rather than affecting the metabolic processes. The effects of such compounds upon the photosynthesis of endosymbiotic algae has not yet been tested. In the present study, photosynthesis and calcification in branches of Stylophora pistillata were measured in the presence of 1-hydroxyethylidene-1, 1-bisphosphonic acid (HEBP), a specific inhibitor of mineral deposition. HEBP strongly inhibited calcification of the coral with 36% inhibition at 0.01 mM, 90% at 0.1 mM and 99% at more than 0.5 mM. However, the level of photosynthetically fixed organic carbon was almost constant in concentrations of HEBP up to 2 mM. Rate of photosynthesis was not affected when calcification was inhibited using 0.5 mM HEBP. It is suggested that coral calcification does not enhance algal photosynthesis.

Phototaxis in Fungiidae corals (Scleractinia)

Corals within the scleractinian family Fungiidae were observed to move toward light (positive phototaxis). Negative phototactic movement was not observed in any of the specimens tested. On sandy substratum, Diaseris distorta moved faster (max. speed of 3 cm h-1) than other species. Although D. distorta has symbiotic algae, phototactic movement also was observed both in bleached corals and in those treated with a specific inhibitor (dichlorophenyl dimethyl urea) of photosynthesis. D. distorta was phototactic even on a glass plate, and climbed up a steep slope (up to 30°). Based on experiments with Fungia fungites and D. distorta, soft tissues at the peripheral region of the dise seem to be responsible for movement via peristalsis. It is suggested that positive phototaxis in symbiontbearing fungiid corals is an important trait for selection of favorable habitats.

Morphological studies of the soft tissues involved in skeletal dissolution in the coralFungia fungites

Light and transmission electron microscopy were used to study mechanisms involved in the separation of the disc from the stalk in juvenileFungia fungites (Scleractinia, Fungiidae). Separation occurs because the skeleton is weakened by dissolution across a distinct plane at the junction of the stalk and disc. The tissue layer adjacent to the skeleton in the stalk was composed of typical, squamose, calicoblastic cells. In contrast, calicoblastic cells in the region of skeletal dissolution were tall and columnar. They contained many microvilli, abundant mitochondria and several different types of vesicles. It is assumed that these calicoblastic cells are actively involved in skeletal dissolution.

Development of Underwater Monitoring Wireless Sensor Network to Support Coral Reef Observation

We have been developing a wireless sensor network system to support coral ecological system survey activities. This paper studies the required functions of a wireless sensor node for gathering information on underwater environmental conditions. For this purpose, a prototype sensor node is developed to clarify necessary functions through a practical experiment. In this paper, the hardware configuration of a latest prototype of wireless sensor node is described. The design of this prototype was based on our previous experiments and the comments of coral reef researchers. We conducted practical field experiments to observe the coral reefs along the Okinawa coast in Japan by using the prototype. Moreover, a browsing system of gathered information by the sensor network is described. Finally, we discuss the experimental results and the required functions of the sensor node for the future research.

Underwater Image Gathering by Utilizing Stationary and Movable Sensor Nodes: Towards Observation of Symbiosis System in the Coral Reef of Okinawa

This paper describes the underwater data collection utilizing stationary sensor node and movable sensor node. We consider applying the system to investigate the conditions of marine ecosystem around the coral reef at Okinawa, Japan. The framework and fundamental design of our proposed underwater information gathering system under development are introduced. It is also reported the development of the prototypes of the sensory node and movable sensor node. Basic examinations utilizing such prototype at underwater environment are also described. This paper also describes experimental results of image gathering from via wireless local area network communication. Our future trials based on the current developmental situation are also discussed.