Retinal fine structure in the European eel Anguilla anguilla. V. Pigment epithelium of the sexually immature silver eel stage.
The fine structure of the retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaris has been investigated in the sexually immature silver eel and compared with previous observations made at the glass and yellow eel stages of the lengthy life cycle of the European eel. As in the previous stages the retinal pigment epithelium of the sexually immature silver eel consists of a single layer of cuboidal to squamous cells joined laterally by apically located cell junctions. The basal (scleral) and lateral borders of these cells are relatively smooth while apical (vitreal) processes enclosing photoreceptor outer segments are plentiful. Internally the epithelial cells display a vesicular pleomorphic nucleus, abundant mitochondria and melanosomes as well as myeloid bodies, phagosomes and polysomes. Smooth endoplasmic reticulum (SER) is abundant while rough endoplasmic reticulum (RER) is uncommon. Lipid droplets are also scarce. Wandering phagocytes are a regular feature amongst the retinal epithelial cells. Bruch's membrane is trilaminate and remains thin as in the previous stages investigated. The choriocapillaris is a single discontinuous layer of capillaries showing fenestrations on the side facing Bruch's membrane. A stratum argenteum remains in the choroid but separated from the retinal epithelium by pigment cells of the choroid.
Braekevelt
C R
CR
Department of Anatomy, University of Manitoba, Winnipeg, Canada.
D000811:Anguilla / Q000033:anatomy & histology* / Q000254:growth & development; D000818:Animals; D002196:Capillaries; D008297:Male; D008854:Microscopy, Electron; D010857:Pigment Epithelium of Eye / Q000648:ultrastructure*; D012160:Retina / Q000648:ultrastructure*; D012171:Retinal Vessels / Q000648:ultrastructure