Changes in chloride cell distribution during early larval stages of Clupea harengus



A non-uniform distribution of cutaneous chloride cells was found in the early, pre-feeding larval stages of herring Clupea harengus. Chloride cells on the head, yolk-sac and trunk regions were unevenly distributed, whereas more densely packed chloride cells were observed in the pericardial and prebranchial regions. The pattern of chloride cell distribution changed during development and two distinct changes are described. The density of choride cells on the ventral trunk increased substantially during the period of yolk absorption, presumably due to contraction of the yolk sac and selective retention of yolk-sac chloride cells. Also during this period the cells on the lateral body wall increased in number and became distributed in segmental bands overlying the myosepta. Most chloride cells were found in association with the haemocoel or primordial blood vessels. Superficial segmental blood vessels were not found in the early larva, but the segmental bands of chloride cells overlay nerve tracts in the myosepta which were tentatively identified as the focal innervation of myotomes. It is concluded that both the circulatory system and the peripheral nervous system may play a role in determining chloride cell distribution in early larvae.