The zonation of 36 species of rocky shore invertebrates at Mkomani and Nyali cliffs, Mombasa is described. Studies of their positioning on the cliffs compared to those of other parts of the western Indian Ocean showed that species which abundantly appeared 1) in the littoral fringe were Littorina kraussi, L. scabra, Nodolittorina natalensis, Nerita plicata and N. undata; 2) in the upper eulittoral zone were Isognomon dentifer, Acmaea profunda, Crassostrea cucullata, Nerita textilis, Acanthopleura spinigera, Thais savignyi, Purpura rudolphi and Morula anexeres, while 3) in the lower eulittoral zone were Echinometra mathaei, Drupa ricina, D. morum, Nerita albicilla, Tetraclita squamosal and Morula granulate. The herbivorous neritids exhibited a more orderly interspecific zonation than the carnivorous thaisids which appeared erratic. The possible influence of topography on zonation in this tropical situation is discussed. |
