Ref ID : 7587
Michele Laval-Peuto; Construction of the Lorica in Ciliata Tintinnina. In vivo Study of Favella ehrenbergii: Variability of the Phenotypes during the Cycle, Biology, Statistics, Biometry. Protistologica XVII(2):249-272, 1981
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Lorica-building in Favella ehrenbergii (Ciliata, Tintinnina) was studied in three ways: (1) biological observations in vivo, using both individual and "en masse" cultures, (2) statistical and biometrical analyses of the loricae in a fixed planktonic populations, (3) experiments in culture on the influence of the medium upon lorica-building. The goal was to establish the daily cycle of this species, to demonstrate the variability of the phenotypes of loricae during that cycle and to determine its origin. A new complete lorica may be constructed by this tintinnine, not only immediately following the division, but also during the trophic life: the loricae of the proter (2 principal phenotypes, favella and decipiens forms) and the replacement lorica (coxliella form) are discontinuous phenotypes considered until now as different species and even different genera from different families. They appear in definite conditions. The building-behavior is the same in the proter and in the trophont: only the somatic ciliature is responsible for the helical deposit of the lorica material, always from rear to front, and the helix may be hidden or very obvious. The available quantity of lorica material, its fluidity or viscosity, induces the duration of the construction (10 min or 4 hr) and the structure of the wall in the principal phenotypes (continuous, sutured-spiraled, overlapped-spiraled), without any noticeable influence of the temperature on their appearance, after the experiments. Before its solidification, which is fast, the lorica material is very fragile: that gives rise to numerous variations and anomalies, always related to the shape of the aboral end (particularly the aboral horn) and to the length of the lorica. There are no repairs, but some additions are possible in the anterior part (supernumerary collars), during the trophic life. The proportions of the different phenotypes, the morphological and dimensional characteristics of their variations, have then been analyzed on a planktonic population in a stage of growth (fixed sample): that allowed to verify the in culture biological observations and to situate them. The length of the different elements of the loricae (collar, bowl, aboral horn) and 3 diameters have been measured and compared (diagrams of correlation, histograms of frequency): all these elements are very variable, except the oral diameter and principally the internal diameter; the ratio of the oral diameter to the overall length, recommended in the systematics, is also variable and then without any value. The methods employed and the results are discussed (particularly, the origin of the variability of the loricae, the role of the constructions of the trophic life, the periods of elaboration of the lorica material), with regard to the few studies in vivo and numerous theories propound for lorica-building, which mostly ought to be rejected. It appears that at least a large group of Tintinnina must build their lorica like F. ehrenbergii. As the lorica is traditionally used in systematics since Kofoid & Campbell (1929), the understanding of the biology of its construction allows one to define the limits, much more restricted, and the precise conditions under which the lorica remains a reliable means of the definition of the species of tintinnines.