The density and dimensions of exchange vessels in Octopus pallidus

Abstract

The microvasculature of the brachial muscle and neuropil tissues of Octopus pallidus was investigated quantitatively with the aid of electron microscopy. Morphometrically the microvascular beds of the two tissue types proved very similar. The average lumenal diameter of the exchange vessels was approximately 8·0 μm, and the average minimum vessel wall (or pericyte) thickness and associated basement membrane thickness were about 0·1 and 0·08 μm, respectively. Forty‐four or 45 vessels were encountered per mm2. The results were incorporated into the Krogh‐Erlang equation. The analysis indicated that the Octopus tissues studied are likely to quickly suffer oxygen deprivation once the metabolic rate moves above the resting level. The results are compared with the vertebrate system where vessels are essentially similar in lumenal diameter and wall thickness, but where the microvascular density is an order of magnitude, or more, higher.