Bading, Katharina (2015) Healing & regeneration assessments on the ctenophore Mnemiopsis leidyi in its larval life cycle stage with observations on larval reproduction. (Master thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 86 pp.

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Abstract

The overall research focus was to investigate healing & regeneration (H&R) potential in different life cycle phases of M.leidyi under the influence of ecological factors. This thesis focuses on H&R in the larval life cycle stage of M.leidyi. The main objectives were to investigate the role of internal and external energy supply during H&R processes and to test variable food supply (including complete food deprivation) and abiotic factors with focus on temperature. The main ecological treatment was injury simulation via cutting in order to trigger H&R processes in larval animal halves and the ecological factors food and temperature. An important methodical requirement for the overall research objective was to develop a morphological assessment tool in order to quantify the influence of ecological factors on the course of H&R processes and to make it applicable for statistical methods, like linear regressions analysis. The main findings can be summarized as followed: Regenerating outer tissues structures are quickly reconnected to the endodermal supply system once they reached a fully developed but still miniature-size state indicating that the tissues need to be connected to the endodermal canal system in order to receive sufficient energy supply in order to grow and reach their full tissue size. Under post-cutting food deprivation, larval energy reserves do not suffice to regenerate missing tissue structures completely to their initial size which results in fully regenerated but asymmetric-looking larvae. Endodermal tissue structures serve as main energy reserves and often thin out during regeneration. Smaller larvae were shown to regenerate significantly faster than larger ones. Preliminary results on regeneration under temperature have shown significant faster regeneration speed at higher temperature but also a trend of increased bacterial infection. Under constant high (100μgCL-1) or low (10μgCL-1) food treatments (prior and after cutting) a significantly higher number of ‘stable’ half animals form, which indicates that an underlying decision-making mechanism based on “sensing” internal energy supply for regeneration. Under high food supply, the regeneration success was significantly higher leading to complete regeneration of normal looking larvae within 8 days. At high prey, prey ingestion was observed after 6 days in fully regenerated as well as stable half animals. The survival chances for half and regenerated animals were similar. Observations on larval reproduction were collected as side results during two lab-based pilot studies. It was observed that larval reproduction and regeneration can occur parallel after injuries. Under post-cutting starvation, larval reproduction lastest for 3 days. Overall, this shows that the larval stage of Mnemiopsis can readily employ healing and regeneration under different ecological food and temperature levels. In future studies, it would be important to systematically investigate ecological requirements and triggers for larval reproduction in order to evaluate its role for population dynamics of M.leidyi.

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