RICHARDSON, J.F.*; ERNST, H.H.; SATTERLIE, R.A.: Pleural Ganglion Asymmetry in the Sexually Immature and Mature Pteropod Mollusc, Clione limacina

In immature specimens of the pteropod mollusk Clione limacina, the right pleural ganglion is slightly larger than the left. The average diameter of the former is 180um, while that of the latter is 160um. The right-to-left diameter ratio is 1.13. In mature animals, average diameters are 300um for the right ganglion and 200um for the left, for a right-to-left diameter ratio of 1.50. A left-to-left ganglion comparison of mature vs. immature animals yields a diameter ratio of 1.25, while a right-to-right ganglion comparison gives a ratio of 1.67. Thus, the right pleural ganglion grows out of proportion to the left with development of sexual maturity. Cell counts were conducted to determine if the increase in size was due to an increase of cell number, an increase in cell size, or both. Initial cell counts utilizing the fluorescent nuclear dye, Hoechst 33342, indicate a significant increase in cell number in the right pleural ganglion when comparing immature to mature animals. The sexual maturity-onset changes in the pleural ganglia parallel significant development of both male and female reproductive structures.