Date of Award


Degree Type


Degree Name

Master of Science in Oceanography


Biological Oceanography



First Advisor

Paul Hargraves


A comparison was made of the lengths of the restriction fragments produced when total DNA from eight clones of three species of diatoms, Thalassiosira rotula (Meunier), T. gravida (Cleve) and T. nordenskioeldii (Cleve), was digested with twelve restriction endonucleases and probed with two heterologous chloroplast DNA probes from C. reinhardtii. DNA from the T. rotula clones would not hybridize with the C. reinhardtii probes under high stringency conditions but the T. grayjda and T. nordenskioeldii DNA hybridized strongly to these same probes. The most likely reason for lack of hybridization with T. rotu la DNA is its contamination with high amounts of polysaccharide material. There was a high degree of molecular similarity in the DNAs within a species for T. nordenskioeldii and T. gravida (100 % and 91%, respectively), but much less between species (32%) implying a genetic congruence with the morphological species concept in diatom systematics. Genetic similarity between and within species is based on the probe detection of 44 restriction fragments, or 264 DNA bases which comprise 0.18% of the entire chloroplast genome, estimated at 147 kilobase pairs.