Parachlorella kessleri strain KNK-A001 is a green microalga that is taxonomically related to P. k... more Parachlorella kessleri strain KNK-A001 is a green microalga that is taxonomically related to P. kessleri. This alga tentatively named as “KNK-A001” has extremely abundant chloroplasts occupying a large area of the cytosol and a thick extracellular matrix instead of a robust cell-wall as its unique characteristics. In this study, we investigated the usefulness of dry powdered KNK-A001 as a feed for spats of the Pacific oyster Crassostrea gigas and the zooplankton rotifer Brachionus plicatilis. When dry powdered KNK-A001 was used as the sole diet, the Pacific oyster spats exhibited reasonable growth which was nearly equivalent to growth when fed on live diatom Chaetoceros gracilis, whereas growth of spats fed on dry powdered chlorella Chlorella vulgaris was obviously lower than those fed on KNK-A001 and diatom. Since many undigested cells were observed in the excretory substances of chlorella fed spats, ineffectiveness of chlorella as a feed for the Pacific oyster spats may be partly due to the indigestible rigid cell-wall. In addition, increase in the number of live rotifer fed on dry powdered KNK-A001 was observed, although the growth rate was lower than the group fed on live Nannochloropsis oculata. These results suggest that dry powdered KNK-A001 has good food value as feed at least for the Pacific oyster spat and rotifer.
Oyster larvae initially have an eyespot on settlement stage (pediveligers). This study investigat... more Oyster larvae initially have an eyespot on settlement stage (pediveligers). This study investigated the eyespot with light wavelength-dependent absorbance, and its functional details for settlement in the Pacific oyster Magallana gigas larvae. Eyespot efficiently absorbed 500–650 nm of light wavelength. Based on the eyespot absorbance, pediveligers were subjected to different light conditions with light-emitting diodes (LEDs): near ultraviolet (NUV), blue, white, green, red, and near infrared (NIR), set at 3 intensities (5, 15, 25 W/m2, except for NIR, which was at 25, 50, 100 lux). LEDs modulated at each intensity were continuously irradiated for 2 days, and the number of settled larvae on a substrate of shell chips was counted daily. NUV at 15, 25 W/m2, and white and green light at 5, 15 W/m2 disrupted larval settlement, whereas red at 25 W/m2 and NIR at 100 lux showed strong settlement-inducing activities. Red and NIR were further tested with ceramic paper substrates; inert substrates. These lights maintained their performance, with settlement rates higher than controls in darkness. Our findings contribute to the further understanding of the function of eyespot in the settlement of oyster larvae, and to establish criteria to evaluate light pollution levels for protecting benthic ecosystem.
Straight-hinge veliger and pediveliger larvae of the mussel Mytilus galloprovincialis were refrig... more Straight-hinge veliger and pediveliger larvae of the mussel Mytilus galloprovincialis were refrigerated for varying periods for use in bioassays. Straight-hinge veliger larvae grew to the umbo-veliger stage after 2 months in the refrigerator, but no pediveligers were observed during the 3-month refrigeration period. The average survival rate of larvae in the refrigerator was 79% after 1 month, but gradually decreased with the refrigeration period, and was as low as 22% after 3 months. All refrigerated larvae grew to the pediveliger stage in the incubator at 17 degrees C at the same rate as that of the control larvae that were not refrigerated. Settlement and metamorphosis of pediveligers from both refrigerated and control groups were facilitated by microbial film and epinephrine and inhibited by phentolamine. Thus, refrigeration can be used as an effective method of storing larvae of M. galloprovincialis for use in assays to assess candidate settlement inducers and antifouling substances.
... Jin-Long Yang · Cyril Glenn Satuito · Wei-Yang Bao · Hitoshi Kitamura ... conducted by numero... more ... Jin-Long Yang · Cyril Glenn Satuito · Wei-Yang Bao · Hitoshi Kitamura ... conducted by numerous researchers showed mussel settlement to be commonly associated with macroalgae, in particular filamentous macroalgae (eg, Bayne 1964; Davis and Moreno 1995; Dobretsov 1999 ...
Parachlorella kessleri strain KNK-A001 is a green microalga that is taxonomically related to P. k... more Parachlorella kessleri strain KNK-A001 is a green microalga that is taxonomically related to P. kessleri. This alga tentatively named as “KNK-A001” has extremely abundant chloroplasts occupying a large area of the cytosol and a thick extracellular matrix instead of a robust cell-wall as its unique characteristics. In this study, we investigated the usefulness of dry powdered KNK-A001 as a feed for spats of the Pacific oyster Crassostrea gigas and the zooplankton rotifer Brachionus plicatilis. When dry powdered KNK-A001 was used as the sole diet, the Pacific oyster spats exhibited reasonable growth which was nearly equivalent to growth when fed on live diatom Chaetoceros gracilis, whereas growth of spats fed on dry powdered chlorella Chlorella vulgaris was obviously lower than those fed on KNK-A001 and diatom. Since many undigested cells were observed in the excretory substances of chlorella fed spats, ineffectiveness of chlorella as a feed for the Pacific oyster spats may be partly due to the indigestible rigid cell-wall. In addition, increase in the number of live rotifer fed on dry powdered KNK-A001 was observed, although the growth rate was lower than the group fed on live Nannochloropsis oculata. These results suggest that dry powdered KNK-A001 has good food value as feed at least for the Pacific oyster spat and rotifer.
Oyster larvae initially have an eyespot on settlement stage (pediveligers). This study investigat... more Oyster larvae initially have an eyespot on settlement stage (pediveligers). This study investigated the eyespot with light wavelength-dependent absorbance, and its functional details for settlement in the Pacific oyster Magallana gigas larvae. Eyespot efficiently absorbed 500–650 nm of light wavelength. Based on the eyespot absorbance, pediveligers were subjected to different light conditions with light-emitting diodes (LEDs): near ultraviolet (NUV), blue, white, green, red, and near infrared (NIR), set at 3 intensities (5, 15, 25 W/m2, except for NIR, which was at 25, 50, 100 lux). LEDs modulated at each intensity were continuously irradiated for 2 days, and the number of settled larvae on a substrate of shell chips was counted daily. NUV at 15, 25 W/m2, and white and green light at 5, 15 W/m2 disrupted larval settlement, whereas red at 25 W/m2 and NIR at 100 lux showed strong settlement-inducing activities. Red and NIR were further tested with ceramic paper substrates; inert substrates. These lights maintained their performance, with settlement rates higher than controls in darkness. Our findings contribute to the further understanding of the function of eyespot in the settlement of oyster larvae, and to establish criteria to evaluate light pollution levels for protecting benthic ecosystem.
Straight-hinge veliger and pediveliger larvae of the mussel Mytilus galloprovincialis were refrig... more Straight-hinge veliger and pediveliger larvae of the mussel Mytilus galloprovincialis were refrigerated for varying periods for use in bioassays. Straight-hinge veliger larvae grew to the umbo-veliger stage after 2 months in the refrigerator, but no pediveligers were observed during the 3-month refrigeration period. The average survival rate of larvae in the refrigerator was 79% after 1 month, but gradually decreased with the refrigeration period, and was as low as 22% after 3 months. All refrigerated larvae grew to the pediveliger stage in the incubator at 17 degrees C at the same rate as that of the control larvae that were not refrigerated. Settlement and metamorphosis of pediveligers from both refrigerated and control groups were facilitated by microbial film and epinephrine and inhibited by phentolamine. Thus, refrigeration can be used as an effective method of storing larvae of M. galloprovincialis for use in assays to assess candidate settlement inducers and antifouling substances.
... Jin-Long Yang · Cyril Glenn Satuito · Wei-Yang Bao · Hitoshi Kitamura ... conducted by numero... more ... Jin-Long Yang · Cyril Glenn Satuito · Wei-Yang Bao · Hitoshi Kitamura ... conducted by numerous researchers showed mussel settlement to be commonly associated with macroalgae, in particular filamentous macroalgae (eg, Bayne 1964; Davis and Moreno 1995; Dobretsov 1999 ...
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