Seasonal changes influence nutritional state of the jellyfish (Clytia gregaria) off the northwest coast
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Date
2020
Authors
Li, Ya
Marco, Corrales-Uglade
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Cnidarian jellyfish are ubiquitous predators of pelagic communities, however, very little is known about their phenology and how food availability affects their reproductive cycles. However, research shows that starved jellyfish tend to decrease somatic growth and allocate more resources to gonad development. Thus, a ratio of body size to gonad size might work as a proxy to the nutritional state of jellyfish. We hypothesize that when food is scarce, C. gregaria will have larger gonads relative to their body size. The jellyfish observed were collected both in a period of low primary productivity where food was scarce (winter) and a period of high primary productivity (summer) along two longitudinal transects in the North California Current System. ImageJ was used to analyze photos taken of the preserved specimens to obtain bell diameter and gonad area to then create a gonadal index (gonad area/bell area). The data shows a slightly higher gonad area to bell area ratio in the winter C. gregaria than those from summer indicating an increased effort towards reproduction when resources are depleted. Due to the preservation method causing a loss in biomass of the collected specimens, it makes it difficult to relate morphological measurements on preserved specimens to the morphology of live organisms. In the future, we will make a correction factor to convert between the measurements of live and preserved organisms. Understanding the links between oceanographic conditions and population dynamics of gelatinous predators will allow us to better predict their effects on zooplankton community dynamics.
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Keywords
Jellyfish, Gonadal Index, Prey Abundance, Nutritional State, Somatic Growth