Nuclear counts in the brain lobes of octopus vulgaris as a function of body size

Abstract

A quick method is described for determining the number of cells in the brain of Octopus vulgaris. The method is based on nuclear counts of fresh homogenates. The total number of brain cell nuclei increases with age from approx. 4 · 10 7 at 10–20 g body weight to approx. 17 · 10 7 at about 1 kg. Within this body-size range the overall increase in the vertical and optic lobes is 5- and 6-fold and in subordinate brain centres 3- and 4-fold. Almost no further increase was found above 1 kg. The average DNA content per nucleus is higher than expected from diploid cells and increases with age in all the main divisions of the brain except the vertical lobe which has a diploid content throughout life (10.4 pg). The overall number of nuclei per mg wet tissue declines between early and late ontogeny. The decline is chiefly in the suboesophageal lobes; in the vertical lobes there is no change in nuclear concentration.