Abstract
Sediment samples were collected at low tide from various localities of Jubail Marine Wildlife Sanctuary in the Arabian Gulf during 1996-1997 for the study of the marine interstitial ciliate fauna of the Sanctuary. Nineteen species belonging to the order Heterotrichida were identified, eleven of these represent new records for the fauna of the Arabian Gulf and Saudi Arabia: Blepharisma seculum, B. hyalinum, Gruberia beninensis, Pseudeblepharisma tenue, Spirostomum teres, Metopus contortus, Condylostoma acuta, C. longicaudata, C, tardum, Linostoma vorticella, and Stenter niger. The distribution and main taxonomic characters of each species were compared to those in similar habitats worldwide.