Valve Teratology Of Two Marine Diatoms Under The Artificial Culture:Forms And Potential Mechanism

Diatom cell wall is composed of a layer of silicon, formed by the epitheca and hypotheca, the species-specific shape and ornamentation of the silicon cell wall is an important basis of diatom taxonomy. The outline of the shape and pattern of the striation have typical rules, but if exposed to different kinds of stress during reproductive processes, the cell outline and striation pattern of diatoms may change in different ways, producing teratological forms. These modifications can be slight, leading to difficulties in establishing a threshold between normal and teratological cells. Most frequently, diatoms present abnormal valve outline, distorted raphe system or abnormal striation pattern. The reason that cause teratological forms are more, artificial conditions often lead to high percentage of teratological valves.This paper is a preliminary study on the deformed diatoms of Haslea ostrearia and Baciliaria paradoxa under artificial conditions as a part of a research project entitled Characteristics and ecological mechanism of marine diatom valve deformation, supported by the National Natural Science Foundation of China (41076079).1. Morphological observation of deformed diatoms of H. ostrearia and B.paradoxa was made with the samples from artificial conditions. We summarized the abnormal forms of H. ostrearia into four types:Type1:abnormal outline of valve and normal striation pattern; Type2:regular valve shape with abnormal striae orientation; Type3: raphe modifications. Type4:mixed deformation. Type2is the most frequent type, about63%.The most frequently teratological form of B.paradoxa is abnormal outline, sometimes abnormal raphe system, keel puncta, striation pattern happens.2. Morphological description of teratelogicol form of each taxon was made with LM and EM photographs and illustrated pictures. Compared the difference between normal forms and teratological forms and made statistical analysis of length,width, striae density. The two species all show extreme size (length) reduction,but striae density almost has no change.This study made important supplement to morphological taxonomy. Except for the morphology change, artificial conditions also causes the decrease of marennine production by H. ostrearia and changes constitution of colony of B.paradoxa changing。 3.Monoclonal cultured the single deformed cell of H.ostrearia, gained pure deformed cell,the longest time of survive could be more than60days, proved that the abnormal outline of the frustule, can be genetically transferred during vegetative reproduction, and found the activity of distortion cells is weak, the speed of cell division is low, and declines quickly.4. Indoor culture experiment was desigened to study the influence of container, temperature, illumination and ventilatory capacity conditions on B.paradoxa and their potential relationship with teratological forms of B.paradoxa. The study shows that compared with flask cultivation, the plate cultivation has higher growth rate,lower maximum cell density,average deformation rate reduce four percents; range from18degree to21degree, increase the temperature can reduce deformation rate, however once above25degree,the deformation rate rises;the illumination and ventilatory capacity has a negetative correlation with the deformation rate of B.paradoxa, ventilatory capacity can lead to the decrease of deformation rate for ten percents.