THE APPEARANCE OF RODS IN THE EYES OF HERRING AND INCREASED DI-DOCOSAHEXAENOYL MOLECULAR-SPECIES OF PHOSPHOLIPIDS

The retina of larval herring (Clupea harengus L.) contains only cones, with rods recruited progressively from about eight weeks onwards. The molecular species composition of phospholipids from the eyes of herri ng of different ages was determined to find whether the appearance of di-docosahexaenoyl molecular species (di22:6n-3) of phospholipids, whi ch are characteristic of rod outer segment membranes in higher vertebr ates, coincided with the appearance of rods. In the eyes of larval her ring (cone-only retina) di22:6n-3 molecular species comprised 25.9% of phosphatidylethanolamine (PE), 22.9% of phosphatidylserine (PS) and 4 .2% of phosphatidylcholine (PC). In the eyes of adult herring (rod:con e ratio of about 20:1) the proportion of di22:6n-3 molecular species h ad increased to 49.5%, 39.0% and 16.8% in PE, PS and PC, respectively. Juvenile herring had intermediate values of di22:6n-3 phospholipids. The results confirm the hypothesis that the amounts of di22:6n-3 molec ular species of phospholipids in retina increase during development as rods appear, and also show that cones contain smaller amounts of thes e unique lipids. Three other molecular species containing docosahexaen oic acid, 16:0/22:6n-3,18:1/22:6n-3 and 18:0/22:6n-3 were also major c omponents of eye phospholipids, emphasizing the important role of 22:6 n-3 in vision.