Vascular and microvascular anatomy of the gill of the southern rock lobster, Jasus novaehollandiae Holthius

Abstract

The vascular architecture of the gill of J. novaehollandiae was studied by light microscopy, scanning electron microscopy and vascular casting. Before fixation or infusion of the vascular casting medium, haemolymph was flushed from the lobster using 3.5% saline infused into the dorsal aorta. J. novaehollandiae has a complex gill circulation, with three types of gill filament present. The fewer, but larger, inner filaments have a longitudinal septum, from 3 to 8 pm thick, dividing them into afferent and efferent channels. By contrast, the septum in the outer filaments is 11-22µm thick. Middle filaments, found between the inner and outer ones, have two septa dividing them into three channels. The gill axis has four major vessels: an afferent vessel supplying the outer and middle filaments, two lateral canals draining the outer filaments, connecting to the middle filaments and supplying the inner filaments on each side of the gill, and an efferent vessel draining the middle and inner filaments. Thus, most of the haemolymph passes through both outer and inner filaments on its route through the gill. Movement of haemolymph from one channel to another within each filament is via a number of lateral lacunae around the sides of the filament. It is postulated that the relatively thick septum of the outer filament acts as a barner to counter-current loss of oxygen from the efferent to the afferent channels of the filament, whereas the thinner septum of the inner filament may not function in this capacity.