Date of Award

Summer 1986

Document Type


Degree Name

Master of Science (MS)


Ocean & Earth Sciences



Committee Director

John R. McConaugha

Committee Member

William M. Dunstan

Committee Member

Patricia A. Tester


Mandibular organs of the mud crab, Rhithropanopeus harrisii (Gould) were histologically located and followed throughout the larval cycle to determine their role in metamorphosis. Specimens from each day of the four larval stages and the megalopa stage were embedded in paraffin, sectioned at 8 μm, stained and observed under the microscope for the mandibular organs. The organs were located in the mandibular area of second, third and fourth stage larvae. The organs were probably present in the first stage zoeae and in the megalopa stage, although the

techniques of the study were not sensitive enough to observe them. The activity of the organs varied throughout the larval cycle. They were active during the early stages, much less active in the final larval stage, and inactive in the megalopa stage. These changes in activity suggest that the mandibular organs are secreting a juvenile hormone-like substance that controls metamorphosis.


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