光周期对罗氏沼虾幼体生长及能量收支的影响

INFLUENCE OF PHOTOPERIODS ON GROWTH AND ENERGY BUDGET OF MACROBRACHIUM ROSENBERGII LARVAE

于1995年2－5月，在L：D为4：20，8：16，12：12和24：0四种光周期条件下，用卤虫无节幼体作饵料培养罗氏沼虾幼体，测定其生长和能量收支。结果表明，随着光照时间（对的延长，幼体生长率（g）增大，两者关系为：g＝6．5245＋3．6045lnT,但光周期对幼体C，N含量和C：N值没有显著的影响；与最短的光照条件相比，长光照条件下摄食能分配于生长的比例增加9．5％，损失于排粪排泄的比例减少7．7％。实验证明，长光照特别是连续光照能提高幼体的生长率和能量效率，可为幼体大量培育时提高生产效益的有效措施。

Experiments were carried out in the labothery to examine the effects of photoperiodson the growth and energy budget of the larvae of Macrobrachium rosenbergii (De mp fromFebrura to Ma, 1995. Four experimental groups were estimated undr four L;D photperiods. 4: 20,8; 16, 12; 12 and 24;0 . For each group, the first zoael larvas were reared in drie glass containers,each containing 800 individuals in 10L of filtered seawater, and fed on Artemia nauplii at a densityof 5 ind / ml until the larvae reached a postlarval stage. Water temperatUre was maintrined at 28 ±1℃, salinity at 15, light intensity at 1 500 lx throughout the experimental period. The larval growthrate was calculated by increasing in bod dry weight and rearing duration. Energy for growth (G)and energy intak (F) were calculated from the measured data on tw weight and carbon content oflarvae and the amount of food consumd. Energy for metaboic costs (R) was calculated from themeasured data on respiration rates. Energy of the exuvia (Ev) was calculated from the exuvia dryweight and the energy for rejection (E egestion plus excretion was calculated from the energybodget Differences among experimental data in each group were compared by analysis of vallance.The results are described below.The specific growth rate (g) increased with increasing light period (T), with a relationshipbetween those tWo pmters of g = 6.524 5 + 3.604 5 lnT Undr all the four photoperiods, larvalgrowth can be expressed by a formula DW= aedt, in which DW represents the body dry weight ofthe larvas, t the number of days for the lareas rearing, and the index b indicates the speed ofgrowth. There were no sighificant differences in carbon and nitrogen contents of larvae reared fordifferent photoperiods. No matter how the body weight of larvae, their respiration the (r') alwaysremarkably increased after feeding, but decreased with an increase in the body weight both beforeand after feeding. The pmters of r′ and DW showed a remarkabe negative relationship i.e. log r′= 0.601 7 - 0.169 2 log DW before feeding and log r′ = 0.711 1-0. 164 9 log DW after feeding. Thedry weight of exuvia (EDW) occupied about 2.3%-2.6% of lareal body tw weight with aregressive relationship of EDW= - 0.425 2 + 0.026 8DW The allocation of food energy showed noremarkale differences among the fore groups of the larvas reared under L; D = 8; 16,12;12 and 24;0photoperiods, but had an increase of 9.5% allocated to growth and a decrease of 7.7% lost torejechon in these groups if compared to those reared under the L;D = 4;20 photoperiod. The energybudget for total development of lareae were 100F = 20.73G + 40.14R+ 1.53Ev + 37.60E for the L;D= 4;20 group and 100F = 30.18G + 38.13R+ 1.80Ev + 29.88E for the average of the rest of thegroups.Results of the present study indicare tha long period of daytime, especially under a continuouslight exposure condition, may increase the growth rate, gross growth efficiency and assimilationefficiency of the lareae. Prolonging light exposure is considered to be an effective measure forincreasing the production in the mass larval culture.