Morphology and ontogenesis of Novistrombidium apsheronicum nov comb. and Strombidium arenicola (Protozoa, Ciliophora):: a comparative light microscopical and SEM study

Strombidium arenicola Dragesco, 1960 and Novistrombidium apsheronicum (Alekperov and Asadullayeva, 1997) nov. comb. are redescribed from marine waters of the Mediterranean Sea and Saudi Arabia, respectively, using live observation, protargol impregnation, and scanning electron microscopy. For the first time, the ontogenesis of a strombidiid, i.e. S. arenicola, is not only described using protargol-impregnated material but also documented by scanning electron micrographs. Strombidium arenicola and N. apsheronicum have an enantiotropic division mode and the somatic ciliature originates by simple division after intrakinetal proliferation of kinetids. The location of the oral primordium is, however, different in S. arenicola and N. apsheronicum, i.e. below vs. above the left portion of the girdle kinety. Since the ontogenesis of Strombidium recapitulates the dextrally spiralled girdle kinety of Novistrombidium, the latter is regarded as ancestral. The diagnosis of the genus Novistrombidium is made more precise by including the location of the oral primordium.