Sea Star, Luidia clathrata, Responses to Physical and Thermal Stress

Kusum Parajuli, Purdue University

Abstract

Human actions and the resultant global warming are leading to considerable environmental changes that are negatively impacting marine ecosystems and their biodiversity. Luidia clathrata, a starfish species, is essential to the marine ecosystem, and understanding its sensitivity to stressors can help predict its future adaptations and role in the reef ecosystem. The study involved subjecting L. clathrata to thermal stress by incrementally raising the temperature by 1°C each day for a period of seven days. Physiological responses were evaluated on two separate occasions: day 1, which corresponded to the acute stress response, and day 7, which corresponded to the chronic stress response. The results showed a minor increase in phagocytic activity during acute thermal stress, but a significant decrease during chronic exposure. Although there was a slight decrease in total coelomic plasma protein during acute thermal stress, it significantly increased during post-chronic exposure. The amputated starfish avoided using the injured arm when righting themselves, indicating the development of neurosensory potential. Total cell count increased slightly in all stressed groups during acute stress but decreased after prolonged exposure to stressors. The mortality rate of the temperature-stressed groups was 33%, indicating that prolonged exposure to temperatures exceeding expected future temperatures could be harmful to L. clathrata. To support the hypothesis at the molecular level, RNA/DNA ratios and Heat shock protein gene 90, a molecular marker for cellular stress, were studied. Although no significant differences were observed in transcriptomic level, the temperature-stressed group showed slightly upregulated hsp90 gene expression. The findings indicate that L. clathrataresponds to stress similarly to vertebrates, highlighting the potential impact of climate change on marine ecosystems. This study provides a baseline for comprehending the stress response of starfish, and further research is recommended with a larger sample size and over a more extended period. It is interesting to note that the gonad and body wall extracts of starfish exhibit significant inhibitory activity against various tested pathogens. The findings suggest that starfish extracts may have potential medicinal uses as antimicrobial agents. However further research is needed to understand the mechanisms of action behind these inhibitory activities and to identify the specific compounds responsible for them.

Degree

M.Sc.

Advisors

Mustafa, Purdue University.

Subject Area

Immunology|Climate Change|Physiology|Biological oceanography|Endocrinology|Wildlife Conservation

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