Morphogenetic Transitions and Cytoskeletal Elements of the Stalked Zooid and the Telotroch Stages in the Peritrich Ciliate Vorticella convallaria

Abstract

ABSTRACT. A method is described for obtaining large numbers of telotrochs from mass cultures of Vorticella convallaria. These free‐swimming cells contract slightly along the aboral‐oral plane when extracted with Triton X‐100, and thus appear more similar in shape to zooids than unextracted telotrochs. Cytoskeletal structures associated with feeding, such as the infudibulum and the cytopharynx, are visible in cytoskeletal preparations of these non‐feeding telotrochs and thus appear not to be disassembled during telotroch formation. The telotroch to stalked‐zooid transition proceeds rapidly through a set series of morphogenetic stages. After telotroch attachment, the aboral cilia cease beating and are resorbed. Within 7 min the cell is inverted bell‐shaped and the zooid begins feeding. Stalk elongation begins about 15–20 min after attachment, lengthening at the rate of 0.5 μ/min for the first hour and more slowly (0.1 μm/min) after that. Interestingly, these developmental stages are essentially the same as those described for the telotroch to zooid transition in the colonial peritrich Zoothamnium. This evolutionary conservation suggests that the precise sequence and timing of these events are critical for their successful completion. Furthermore, the facts that the telotroch to zooid transition occurs very rapidly, that the feeding structures are maintained throughout the transformation, and that basic cytoskeletal architecture is relatively unchanged is consistent with the hypothesis that the transformation occurs through controlled cytoskeletal rearrangements rather than by changes in gene expression.

Telotroch formation, survival, and attachment in the epibiotic peritrich Zoothamnium intermedium (Ciliophora, Oligohymenophorea)

“…Evacuation of dead hosts, however, took several hours, with free‐swimming telotrochs appearing 2–7 h after copepods were killed. By contrast, shifting the free‐living peritrich Vorticella convallaria from Cerophyl growth medium to an inorganic medium stimulated rapid formation of telotrochs, with maximum densities being reached within 2 h (Vacchiano et al 1992). The discrepancy in time required for production of dispersal stages in these two species may reflect a difference in the duration of morphogenetic events leading to telotrochs, or may indicate a lag in the ability of members of Z. intermedium to detect the death of its host.…”

“…While precautions were taken to avoid injuring colonies of Z. intermedium when killing host organisms, we cannot rule out the possibility that some cells were damaged. Because injury of zooids may promote telotroch formation in peritrichs (Vacchiano et al 1992), it is possible that the method we used to kill infested copepods contributed to telotroch formation. Thus, the factors that trigger telotroch formation in Z. intermedium remain elusive, but likely include a combination of physical and chemical stimuli.…”

Triassic leech cocoon from Antarctica contains fossil bell animal

“…They are hemisessile filter feeders anchored by their retractable stalks to plant matter, metazoan shells, and other substrates. Under unfavorable conditions, the zooid can detach from the stalk and become a free-swimming swarmer (telotroch) to relocate itself; once the swarmer has settled on a suitable new substrate, a new stalk is produced within a few hours (27). It appears that the Triassic Vorticella-like organism from Antarctica must have anchored itself to a freshly deposited clitellate cocoon, and then became trapped in the solidifying cocoon wall.…”

Changes in epibiotic burden during the intermolt of Daphnia determined by hypodermal retraction stages

“…Green (1974) showed that the peritrich, Epistylis helenae, could anticipate the molt of D. pulex. If Vorticella has the same ability to detect molt and detach, then free-living cells (telotrochs ; Vacchiano, et al, 1992) should be available for immediate recolonization when the molt is complete . If C. calvum cannot anticipate the Daphnia molt, then re-colonization may be delayed by the time necessary for the attached cells to regenerate their motile flagella, detach from the castskin, and locate a new substrate organism (see Ward & Willey, 1981) .…”