FIELD OBSERVATIONS OF FLABELLUM SPP. AND LABORATORY STUDY OF THE BEHAVIOR AND RESPIRATION OF FLABELLUM ALABASTRUM

摘要

Video observations of the seafloor show that cup corals, Flabellum spp. are common and locally abundant on the continental slope off Nova Scotia. Flabellum al-abstrum Moseley, 1876 was the most common with an average abundance, when present of 1.1 individual per square meter. Flabellum macandrewi Gray, 1849 was often encountered in clusters of up to seven individuals close enough for tentacles to interact. Occurrence of live fragments in the field may indicate fisheries impact or that fragmentation represents an asexual reproduction mode. Live specimens of F. alabastrum were collected with a remotely operated vehicle and videograb, and studied in laboratory for 21 mo. The corals were kept in a tank and aquarium with stable temperature and salinity. Observations were made on patterns of polyp expansion/contraction, movement, feeding behavior, and survival and regeneration of coral fragments. Large (0.1-1.5 cm) pieces of dead krill (Euphausiacea) were handled with a relatively rapid withdrawal of the tentacles, whereas smaller (< 1 mm) particles were transferred to the mouth by "licking" upper and lower sets of tentacles separately at a slower pace. The coral has the ability to rapidly expand the polyp volume more than ten times its normal size. This behavior may be related to food uptake, excretion/exchange of metabolites, and respiration, but may also represent a way to facilitate movement along the bottom by means of increased buoyancy and drag. Expanded individuals were also observed in the field. In aquarium, F. alabastrum was observed moving slowly (up to 3.2 cm mo~(-1)), leaving tracks in the sediment, but the mechanism for this is not understood. Respiration of F. alabastrum was measured on selected individuals as oxygen consumption in closed chambers, and rates varied between 1.61-3.2 O_2μl g~(-1)WWh~(-1) for individual corals. The turnover time was estimated to 5.5 yrs with a production of 0.09 g C m~(-2) yr~(-1) in areas with an average abundance of the coral.