Studies On Respiratory Metabolism And The Histology Of Immune And Olfactory Organs In Mugil Cephalus

Grey mullet (Mugil cephalus) is a high quality, well received, artificialcultured brackish water fish because of its economic value especially inthe matter of improving culture benefit in polyculture. In the presentstudy, the characteristic of juvenile respiratory metabolism, the structureand function of immune and olfactory organ in the adult fish wereinvestigated in order to establish the theoretical basis and thereforefacilitate the healthy aquaculture of mullet. The detailed results were asfollows:1. Oxygen consumption, ammonia excretion and suffocation point inMugil cephalus juvenileWater flow experiment was performed to estimate the oxygenconsumption rate and ammonia excretion rate responding to differentweight, light, stocking density, water velocity and diurnal variation inMugil cephalus juvenile. Impact of body weight on juvenile suffocationpoint and suffocation time were observed at the same time. Resultindicated that there was a positive correlation between body weight andoxygen consumption rate. Power equation is Y=0.4759X0.1878 （R2=0.9454）. Light had significant effect on the oxygen consumptionrate but had no significant effect on ammonia excretion rate. Stockingdensity had significant influence on the oxygen consumption rate (P<0.05)as well as the ammonia excretion rate (P<0.001). As to the diurnalvariation, juvelie respiratory metabolism was active during the time from11a.m to11p.m. Influence of water velocity was significant on bothoxygen consumption rate and ammonia excretion rate (P<0.001). Weighthad a great effect on suffocation point and suffocation time. Extremelysignificant difference was observed (P<0.001).2. Influenc of temperature，salinity and pH on oxygen consumption rate,ammonia excretion rate and suffocation point in Mugil cephalus juvenileThe effects of temperature, salinity and pH on oxygen consumptionand ammonia excretion of Mugil cephalus juvenile were determined bywater flow experimental methods. Water temperature had significanteffect on oxygen consumption rate and ammonia excretion rate (p<0.05).The oxygen consumption rate and ammonia excretion rate of Mugilcephalus juvenile increased with the highest value at24℃as watertemperature rose and then followed by a decrease. The salinity also hadsignificant effect on the oxygen consumption rate and ammonia excretionrate (P<0.001). When the salinity was within the range5-30，the oxygenconsumption rate increased from the first followed by a decrease，thenincreased again as the salinity rose. However the ammonia excretion rate increased first, then decreased. The oxygen consumption excretionincreased first，then decreased with pH increasing. pH also had significanteffect on the oxygen consumption rate (P<0.01) as well as ammoniaexcretion rate (P<0.001). Water temperature and pH had significanteffects on suffocation point (P<0.001). The salinity also had significanteffect on suffocation point (P<0.05).3. Study on the morphology and structure of spleen and head-kidney inMugil cephalusThe morphology and structure of spleen and head-kidney in Mugilcephalus were studied by using light microscope. It was found that thesurface of the spleen was covered with a thin layer of fibroid connectivetissue capsule which extended inwards to divide the spleen into irregularlobules. The spleen, without obvious trabcula, was chiefly composed oflarge quantities of lymphocytes, granulocytes, blood cells andmelano-macrophage centers. Many arteries, veins and nerve bundles thatoften in parallel arrangement and ellipsoid were found in spleen. Thehead-kidney has two lobules，separated from the kidney. The head kidneyas a reticular lymphoid tissue, with no nephron and obvious trabcula, wascovered with a very thin layer of fibroid connective tissue capsule as well.There were red blood cell centers, leukocyte centers, melano-macrophagecenters in head-kidney. There were fewer arteries and veins inhead-kidney compared to spleen. The results showed that the spleen and head kidney tissue were the major hematopoietic organ and immuneorgan in this species.4. Morphological structure and function of olfactory organ in MugilcephalusOlfactory sac and olfactory lamellae cell of wild grey mullet (Mugilcephalus,35.5-40cm in length) are studied by technology of paraffinsection and transmission electron microscope. The results show that theolfactory organ of grey mullet has two flat ellipsoidal olfactory sacs in theboth side of the head. Each sac had an incurrent and an excurrent nostrilinterlinked with the outside world. In size, the olfactory sac was smallerthan the eye and the average ratio between them was0.8. The ratiobetween length and breadth of the olfactory sac was2.09. There were18-25lanceolated primary olfactory lamellas in the olfactory sac whichwere perpendicular to left and right sides of raphe at a orderly up-inclinedarrangement state. Olfactory lamella was really a composite that wascomposed of two layers of olfactory epithelium and a central core. Thecentral core was located at the central part of the olfactory lamella, whichwas composed of loose connective tissue and large amount of capillaries.The olfactory epithelium was divided into sensory area and non-sensoryarea. The inside of the olfactory lamella was the olfactory sensory area,which have developed cilia in a continuous distribution state. Thenon-sensory area had fewer cilia that located in the edge of olfactory lamella. By means of light microscope and transmission electronmicroscope, the results showed that the cells of olfactory epitheliumcan be broadly divided into five categories: basal cells, supporting cells,ciliated non-sensory cells, ciliated receptor cells and rod cells. Conclusionwas that the grey mullet was a fish that both good at sight and smell.