Litopenaeus vannamei, a euryhaline species, can be cultured at a wide range of salinities. The emergence of freshwater pond-culture ofL. vannamei is an important prelude to the continued development of shrimp culture ...Litopenaeus vannamei, a euryhaline species, can be cultured at a wide range of salinities. The emergence of freshwater pond-culture ofL. vannamei is an important prelude to the continued development of shrimp culture in China. In this study, we com- pared the respiratory metabolism of juvenile L. vannamei cultured in freshwater and saltwater by measuring their oxygen consump-tion rate （OCR）, ammonium-type nitrogen excretion rate （AER） and pyruvate kinase （PK） and lactate dehydrogenase （LDH） activi-ties at different molting stages in order to physiecologically characterize juvenile L. vannamei under freshwater conditions. The re- suits showed that OCR was significantly higher in saltwater than in freshwater at all stages of molting cycle. However, variation of OCR among molting stages in saltwater was similar with that in freshwater, and the highest OCR was observed at post-molting stage. At all stages of molting cycle, AER was significantly higher in freshwater than in saltwater, and the highest was observed at post-molting stage. The activity of PK was significantly higher in saltwater than in freshwater. Conversely, the activity of LDH was higher in freshwater than in saltwater in general. Significant variation of PK and LDH activities in molting cycle was observed in saltwater and freshwater. The results indicated that aerobic metabolism of juvenile L. vannamei was more active in saltwater than in freshwater; while its protein metabolism was more active in freshwater than in saltwater.展开更多
Developmental changes in hemolymph ecdysteroid level, ecdysteroid synthesis by prothoracic glands （PGs） in vitro, prothoracicotropic hormone （PTTH） activity in brain extracts, and PTTH activity in the hemolymph we...Developmental changes in hemolymph ecdysteroid level, ecdysteroid synthesis by prothoracic glands （PGs） in vitro, prothoracicotropic hormone （PTTH） activity in brain extracts, and PTTH activity in the hemolymph were measured during the fifth larval instar of the Eri silkworm, Samia cynthia ricini. The changing patterns of hemolymph ecdysteroid level and ecdysteroid synthesis by laGs in vitro are similar to each other, with maximums on day 9. However, on this day, hemolymph ecdysteroid level was substantially higher than ecdysteroid synthesis by PGs in vitro suggesting a high PTTH activity in the hemolymph on day 9. Moreover, the changing pattern of PTTH activity in brain extracts is also similar to that of PTTH activity in the hemolymph, both peaking on day 9. However, on this day, activity in brain extracts was much smaller than PTTH activity in the hemolymph implying that most PTTH synthesized by the brain is secreted to the hemolymph and the brain stores a very little amount of PTTH. This study provides unique insights onto the hormonal regulation of ecdysteroid synthesis in the Eri silkworm and is useful for our future studies on signal transduction of insect neurolaelatides.展开更多
基金supported by National Program on Key Basic Research Project (Grant No.2009CB118706)
文摘Litopenaeus vannamei, a euryhaline species, can be cultured at a wide range of salinities. The emergence of freshwater pond-culture ofL. vannamei is an important prelude to the continued development of shrimp culture in China. In this study, we com- pared the respiratory metabolism of juvenile L. vannamei cultured in freshwater and saltwater by measuring their oxygen consump-tion rate （OCR）, ammonium-type nitrogen excretion rate （AER） and pyruvate kinase （PK） and lactate dehydrogenase （LDH） activi-ties at different molting stages in order to physiecologically characterize juvenile L. vannamei under freshwater conditions. The re- suits showed that OCR was significantly higher in saltwater than in freshwater at all stages of molting cycle. However, variation of OCR among molting stages in saltwater was similar with that in freshwater, and the highest OCR was observed at post-molting stage. At all stages of molting cycle, AER was significantly higher in freshwater than in saltwater, and the highest was observed at post-molting stage. The activity of PK was significantly higher in saltwater than in freshwater. Conversely, the activity of LDH was higher in freshwater than in saltwater in general. Significant variation of PK and LDH activities in molting cycle was observed in saltwater and freshwater. The results indicated that aerobic metabolism of juvenile L. vannamei was more active in saltwater than in freshwater; while its protein metabolism was more active in freshwater than in saltwater.
文摘Developmental changes in hemolymph ecdysteroid level, ecdysteroid synthesis by prothoracic glands （PGs） in vitro, prothoracicotropic hormone （PTTH） activity in brain extracts, and PTTH activity in the hemolymph were measured during the fifth larval instar of the Eri silkworm, Samia cynthia ricini. The changing patterns of hemolymph ecdysteroid level and ecdysteroid synthesis by laGs in vitro are similar to each other, with maximums on day 9. However, on this day, hemolymph ecdysteroid level was substantially higher than ecdysteroid synthesis by PGs in vitro suggesting a high PTTH activity in the hemolymph on day 9. Moreover, the changing pattern of PTTH activity in brain extracts is also similar to that of PTTH activity in the hemolymph, both peaking on day 9. However, on this day, activity in brain extracts was much smaller than PTTH activity in the hemolymph implying that most PTTH synthesized by the brain is secreted to the hemolymph and the brain stores a very little amount of PTTH. This study provides unique insights onto the hormonal regulation of ecdysteroid synthesis in the Eri silkworm and is useful for our future studies on signal transduction of insect neurolaelatides.
