Studies On Gonad And Larval Development Of Cephalothrix Spp

Focusing on Cephalothrix hongkongiensis，Cephalothrix cf. filiformis andCephalothrix simula, this thesis mainly studies the embryonic and larval developmentof Cephalothrix, and the effect of temperature, photoperiod, decapitation andmelatonin on gonad development of these nemerteans. The results were summarizedas follows:1. The effect of temperature and photoperiod on maturation of CephalothrixhongkongiensisEffects of temperature and photoperiod on body weight, sex ratio, spawningtime and gonad development of Cephalothrix hongkongiensis were experimentallystudied. Worms in4oC and6oC treatments showed no predation, growth and allworms died within109days, and no gonad development and spawning were observed.For worms at8oC and12oC, growth could be seen almost throughout the wholeexperiment period (360days) and gonads appeared from90to360day but nospawning events were observed throughout the experiment period. The body weightof worms in16oC,24oC and28oC treatments increase during the first stage ofexperiment, but, due to spawning, turned to decrease after150,90and30days,respectively. Furthermore, the first spawning time and duration were also differentamong the16oC,24oC and28oC treatments. Photoperiod did not have significantimpact on sex ratio, spawning and maturation, but did have an impact on body weight.2. The effect of temperature and photoperiod on maturation of Cephalothrix cf.filiformis Effects of temperature on sex ratio, gonad development and spawningCephalothrix cf. filiformis were observedunder different temperatures (0oC,6oC,12oC,18oC and24oC). Results showed that the worms under6,12and18oC gainedsinificanly higher body weight than those under0oC and24oC. Gonads of wormsunder6oC and12oC developed faster than which under0oC,18oC and24oC; Expect12oC amd18oC groups, no spawning events were observed throughout theexperiment period. It seems that the sex ratio (male/female) decrease with theelevation of temperature. Present results show that temperature is a important factorinfluencing maturation of Cephalothrix cf. filiformis.3. The effect of decapitation and melatonin on gonad development ofCephalothrix hongkongiensis and immunocytochemical localization of HIOMTEffects of decapitation and exogenous melatonin on gonad development ofCephalothrix hongkongiensis were studied and HIOMT were determined by Westernblot and immunocytochemical methods. Results showed that the operationsignificantly affected the gonad development speed (P<0.01). Gonads of decapitatedworms totally matured40days after operation, but intact worms did not show anygonad during the XX-day experiment, suggesting that a hormone (GIH) originatinglocated in the worm’s head may play an important role in the control of sexualmaturation. The melatonin significantly inhaibit maturation of C. hongkongiensis, theeffect could be enhanced by elevating the melatonin concentration. The gonads ofworms in75mg/L melatonin degenerated completely at day40. HIOMT wereexamined by Western-bolt and showed a clear band of38kDa in molecular mass. Afew cells in the cerebral ganglia were found to have positive reaction with HIOMTimmunoglobulins.4. Study on the embryonic and larval development of CephalothrixhongkongiensisThe embryonic and larval development of Cephalothrix hongkongiensis arestudied by observing living embryos/larvae, histological sections and fluorescent staining material. Under22°C condition, the timetable for early development is asfollows: first polar body,30min,;, second polar body,40min; first cleavage,60min;4-cells stage,80min;8-cells stage,110min;16-cells stage,140min;32-cells stage,170min; blastula stage,15h; gastrula stage (by invaginationmethod),20h; formation of apical tuft,30-h; The larva swims in a straight linealong the long axis of the body; nerve rudiments invagination,,44-h;formation ofcaudal tuft,45h; formation of lateral tufts,80h; formation of ocelli,90h..Cytoskeleton system of larva possesses a ring structure surrounding the blastoporeand two other ring structures perpendicular to the longitudinal body axis, the formerappeared earlier than the latter two. The oxygen consumption rate of embryos andlarvae increased with time..5. Study on the embryonic and larval development of Cephalothrix simulaThe embryonic and larval development of Cephalothrix simula was studied byobserving living embryos/larvae and histological sectionsl. The effect of temperatureon survical of embryos/larvae was determined andthe oxygen consumption rate ofembryos/larvae was also studied. The timetable of the early development (under20°C)is as follows:: formation of the first polar body,40min; first cleavage,80min;blastula stag,18he; gastrula stage,26h; formation of apical tuft,45-h;formationof caudal tuft,53h; formation of lateral tufts and ocelli,85h. Temperature showeda significant influence on survival of larvae (P<0.05). The oxygen consumption rateof embryos and larvae increased with time.