STOMATOGENESIS AND MORPHOLOGICAL REDESCRIPTION OF PSEUDOCOHNILEMBUS PERSALINUS (CILIOPHORA: SCUTICOCILIATIDA)

Pseudocohnilembus species are ubiquitous in various habitats worldwide and play a great role on the circulation of ecological systems, therefore there are many reports concerning their morphology and diversity. However, these species remain insufficiently described owing to lack of detailed description of morphology in vivo, infraciliature. Divisional morphogenesis can provide evidences to support conceptual schemes of phylogenetic interrelationships among Scuticociliates, but the detailed morphogenesis information of these species remains unknown. The morphology and morphogenesis of Pseudocohnilembus persalinus, isolated from coast waters off Qingdao, were investigated by using protargol impregnation method in this paper. The new information of morphology and morphogenesis of this species was supplied, and a steady mode of morphogenesis in genus Pseudocohnilembus was established. Ciliates were collected in July, 2010, from coast off Qingdao (Tsingtao, 36° 08′ N; 120° 43′ E), China. The salinity was 20‰ and the pH was 7.5. After isolation, specimens were maintained as pure or raw cultures in Petri dishes in the laboratory for days to weeks with rice grains as food source for bacteria. Living observations were made under a microscope equipped with phase-contrast apparatus. Protargol impregnation method was used to reveal the infraciliature in different morphogenetic stages. Measurements were carried out under oil immersion (1250 ×). Drawings were performed with the help of camera lucida. The result showed that the Qingdao population of this species possessed typical characteristics of the genus Pseudocohnilembus: the buccal apparatus consisted of 3 highly specialized membranelles; membranelle 1 comprised single row of kinetosomes, was parallel to membranelle 2, and lied anterior to the paroral membrane; membranelle 2 was longer than membranelle 1 and also comprised of one row of kinetosomes; membranelle 3 was located near the middle of the paroral membrane and comprised 3 rows of kinetosomes. In terms of live morphology and infraciliature, the Qingdao population corresponded well with previous ones. Its stomatogenesis proceeded generally in the similar way as in other congeners, and indicated evidently that the descriptions about P. persalinus by Evans & Corliss (1964) and Pomp & Wilbert (1988) were incomplete and incorrect: the membranelle 2 was derived from, as revealed in our present work, completely from the paroral membrane while not from the old scutica. As a conclusion, the stomatogenesis could be summarized as follows: firstly, the parental scutica proliferates and became the primordial field, which finally formed membranelle 3 of the opisthe. The secondary proliferated field, which derived from the zigzag configuration of parental paroral membrane, also developed in two parts, with the anterior part becoming the paroral membrane as well as scutica of the opisthe and the posterior part developing into membranelles 1 and 2 of the opisthe. The remnants of the parental paroral membrane gave rise to the paroral membrane and scutica of the proter.