Marine dinoflagellateshave proved to be a subject of considerable attention as a new valuable source of bioactive compounds.1} During our studies on bioactive substances from Okinawanmarine organisms,^we have isolated five cytotoxic macrolides, named amphidinolides A~E, from the laboratorycultured dinoflagellate Amphidinium sp.3>4) Recently, we further investigated a dinoflagellate of the genus Amphidinium which was associated with the Okinawanflatworm Amphiscolops magniviridis and a different species from those reported previously. x ' 3) Here we wish to describe the isolation and structure elucidation of a new cytotoxic 25-membered macrocyclic lactone, named amphidinolide. F (1).The host invertebrate A. magniviridis was collected at Zanpa, Okinawa, and the associated dinoflagellate Amphidinium sp. was isolated and mass cultured unialgally at 25°C for 2 weeks in a sea water medium enriched with 1% ES supplement.5) The cultured alga was harvested by centrifugation to yield 740g of cells (wet weight) from 960 liters of culture. The harvested alga was extracted with and the extract was partitioned between toluene and 1m aq NaCl. The toluene-soluble fraction was subjected to a silica gel column eluted with 5-30% MeOHin CHC13 followed by reversed-phase medium and HPLC's (Develosil LOP-ODS 24S and Develosil ODS-5)with 75% acetonitrile to give a macrolide mixture.
The retina of the distal and proximal lens-bearing complex ocelli are composed of pigmented sensory cells and long pigmented cells. A ciliary sheath from each sensory cell, together with the processes of long pigmented cells, extends through the vitreous layer as far as the capsule that envelops the lens. Each ciliary sheath has several ballon-like swellings and the ciliary microtubules, arranged in the 9+2 pattern in the proximal part, are markedly disorganized distally in the swollen parts, out of which extends most of the microvilli in the vitreous layer. It is suggested that some of the microvilli may originate in vesicles that are constricted off from the surface of the pigmented sensory cells. Closely packed microvilli run in parallel in short bundles. In addition to characteristic junctions between sensory cells, junctions that are presumably synaptic and, of a new type in coelenterates, are observed between sensory cells and nerve endings.
The symbiotic condition of Convoluta roscoffensis has been resynthesized in vitro by feeding new-born colourless larvae with various clones of Platymonas convolutae Parke & Manton available in culture. Greening has also been brought about by feeding larvae with other species distinguishable from the natural symbiont by pyrenoid characters, but subsequent growth of the greened larvae was less and the length of time required for greening greater. The minimum presentation time effective in initiating greening with alien symbionts in 100% of tested larvae was also greater. Cell multiplication of successful symbionts is mitotic, division stages being demonstrated in sections of worms with different types of symbiont. When cultures of potential symbionts were made available competitively in pairs, greening normally involved only one member of a pair, success being apparently determined by the order of relative efficiency demonstrated in the single-culture infections. A chimaeral condition, with two different symbionts present together, was produced and is demonstrated—but only as a temporary phase in an experiment designed to give an alien symbiont a very long start before admitting the real one. In this experiment effective greening with Prasinocladus marinas did not impede prompt entry of Platymonas convolutae when it was supplied, and this was followed by rapid and complete elimination of the alien symbiont. An interpretation of these various findings is discussed in a preliminary way.
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