Ref ID : 4991
Wonho Yih, Hyung Seop Kim, Hae Jin Jeong, Geumog Myung, and Young Geel Kim; Ingestion of cryptophyte cells by the marine photosynthetic ciliate Mesodinium rubrum. Aquatic Microbial Ecology 36:165-170, 2004
Reprint : In File
Notes : We investigated the mechanism of capturing and ingesting cryptophyte cells by a laboratory strain of the marine photosynthetic ciliate Mesodinium rubrum Lohmann 1908 (= Myrionecta rubra Jankowski 1976), a cosmopolitan red tide species. When offered cryptophytes as food, M. rubrum, originally grown photosynthetically for 2 wk, used its bifurcated oral tentacles to instantly size prey cells when encountered. Immediately after capturing a prey cell, M. rubrum swam in a zigzag pattern (30 to 60 um long linear paths) for > 4s, without showing the large jumps (with ca. 2000 um long linear paths) that were usually observed when the predator was not feeding. M. rubrum with a cryptophyte attached to its tentacles became motionless while the prey cell was moved to the oral surface of the predator, a process that took < 10s. Engulfment of a captured prey cell by M. rubrum occurred through a cytostome-like structure and took ca. 15s. Once engulfed, the prey was slowly delivered to the posterior end of the ciliate over a period of ca. 63s. The whole feeding process lasted approximately 92s. With increasing mean prey concentration, specific growth rates of M. rubrum feeding on the cryptophyte increased, with saturation at a mean prey concentration of 44 cell ml-1. The maximum specific growth rate (mixotrophic growth) of M. rubrum feeding on the cryptophyte was 0.521 d-1, under continuous illumination of 60 uE m-2 s-1, while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.357 d-1. The ingestion rate of M. rubrum feeding on cryptophytes increased continuously with increasing prey concentration. The maximum ingestion rate was 8.9 cryptophytes ciliate-1 d-1. M. rubrum may sometimes exert considerable impact on prey populations.