An Ultrastructural Study of Bodo saliens Recovered from Marine Sediments at 4,900 m
William H. GAZE*a, Chiaki KATOa, David McL. ROBERTSb, and Koki HORIKOSHIa
a The DEEPSTAR group, Japan Marine Science and Technology Center, 2-15 Natsushima- cho, Yokosuka 237, Japan
b Dept. Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, Great Britain
Flagellates have been reported from depths of up to 4,600 m (Patterson et al., 1993) from the mid North Atlantic, with Ancyromonas sigmoides and Bodo curvifilis recovered from the greatest depths sampled. A barophilic Bodo sp. (Turley, Lochte & Patterson, 1988) isolated from 4,500 m, which Patterson et al., (1993) suggests may be B. curvifitis was shown to be unable to grow at atmospheric pressure. Conversely, as discussed by Patterson et al. (1993) recovery of protists in cultures at atmospheric pressure, does not tell us if they were active at the depths from which they were sampled.
Core samples were taken using the manned submersible‘Shinkai 6500' from the Palau Trench (10-11/96) in the West Pacific. Samples were stored at 2-4℃ for the duration of the cruise. Cultures were made using 0.45 μm filtered sea water collected at 4,500 m enriched with a wheat grain, from samples collected at 1,455 - 6,500 m and maintained at atmospheric pressure and 2℃. One sample collected from 4,906 m developed a population of flagellates resembling Bodo saliens Larsen and Patterson 1990, illustrating typical rapid darting movement with the long recurrent flagellum touching the substrate. Preliminary pressure experiments suggest that this organism is incapable of growth at the depth sampled. Cysts were commonly observed in cultures at atmospheric pressure, with dense clumps and intermediate stages during encystation observed. Whilst freshwater and soil bodonids are known to produce cysts most descriptions of marine bodonids including those sampled from depth give no mention of this process. It can not be ruled out that the species encountered in this study is a contaminant from surface waters, although in this study as mentioned by Patterson et al. (1993) the majority of deep-sea samples did not yield any protists suggesting that contamination is unlikely. That this species tentatively identified as Bodo saliens has been observed to form cysts, gives plausibility to the idea that this organism was present at close to 5,000 m in the form of cysts sedimented from the water column.
