Role of Symbiotic Algae in Hatching of Gemmules of the Freshwater Sponge, Rndiospongilla cerebellata : Developmental Biology

概要

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The role of symbiotic algae in the gemmule hatching of the freshwater green sponge, Radiospongilla cerebellata, was investigated. Under optimal conditions, gemmules of this sponge hatched almost 100% in 10 days. Dormant gemmules of the sponge colonized chlorellae in the thesocytes. These symbiotic algae were in two states: those with a high chlorophyll content (active algae) and those with little or no chlorophyll content (inactive algae). As incubation time proceeded, the ratio of thesocytes which contained active algae and the number of the active algae in a single thesocyte increased. Uner darkness, gemmules of this sponge were unable to hatch. The minimum light intensity required to effect 100% hatching was 160 lx in a 12L-12D photoperiod, and the minimum potoperiod at 1300 lx was 30min per day. A photosynthetic inhibitor, Diuron, suppressed the gemmule hatching, and concurrently suppressed the increase of thesocytes contained the acitive algae. These results suggested that the hatching of the gemmule of this sponge is promoted by photosynthetic activity in the symbiotic algae colonized in the thesocytes. This may be an example of plant/animal obligatory endosymbiosis, in which the symbiotic algae in gemmular cells are essential for the sponge to survive through the unfavorable winter season.
社団法人日本動物学会の論文
1990-08-15