Seasonal alternation of the ontogenetic development of the moon jellyfish Aurelia coerulea in Maizuru Bay, Japan.

Kentaro S Suzuki,Reiji Masuda,Hideki Sawada,Kana Sato,Keita W Suzuki,Yutaro Oe,Tasuku Sato,Emi Kumakura,Yasuyuki Nogata,Erik V Thuesen

doi:10.1371/journal.pone.0225513

Abstract

Outbreaks of moon jellyfish Aurelia spp. are frequently reported from many parts of the world’s coastal areas. Aurelia spp. canonically show a metagenetic life cycle in which planulae transform into sessile polyps, which can drastically increase in number through asexual reproduction. Therefore, their asexual reproduction has been recognized as one of the major causes of the outbreaks. Aurelia spp. also show direct development that lacks asexual reproduction during the polyp stage, which prevents us from understanding the mechanisms of its outbreaks. To clarify the seasonality of the metagenetic and direct-development life cycles of Aurelia sp. in Maizuru Bay, Japan, we conducted field observations and laboratory experiments throughout the year. Additionally, the two life cycle types were genetically analyzed to confirm that they belong to the single species Aurelia coerulea, which dominates in coastal waters in Japan. From July until October, Aurelia coerulea produced smaller eggs and planulae all of which developed into polyps. However, from December until May, larger eggs and planulae were produced and 90% of the planulae developed into planktonic ephyrae bypassing the sessile polyp stage. Our results demonstrated that a single species, A. coerulea, seasonally shifts between their two life cycle types at a water temperature threshold of 20°C in Maizuru Bay. The higher energy storage of larger planulae was suggested to enable the planulae to develop into ephyrae without external energy input through feeding during the polyp stage. The adaptive significances of the two life cycle types were also discussed.

Highlights

Outbreaks of scyphozoan jellyfish have been frequently reported from many parts of the world’s coastal areas [1,2,3]
Seasonal alternation of the ontogenetic development of moon jellyfish Aurelia coerulea did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript
To discuss the adaptive significances of the two life cycle types of A. coerulea in Maizuru Bay, we focus on the temporal overlapping of ephyra liberation, the seasonal separation of spawning and difference in the duration of the sessile stages between the two life cycle types

Summary

Introduction

Outbreaks of scyphozoan jellyfish have been frequently reported from many parts of the world’s coastal areas [1,2,3]. Moon jellyfish Aurelia spp. are most common in temperate coastal waters, and outbreaks of Aurelia spp. can have severe effects on coastal ecosystems and human enterprises, such as fisheries and coastal power plant operations. Seasonal alternation of the ontogenetic development of moon jellyfish Aurelia coerulea did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. There are no patents, products in development, or marketed products to declare. This does not alter our adherence to PLOS ONE policies in sharing data and materials. Mechanisms that cause the outbreaks of Aurelia spp. are of ecological and socio-economic interest

Methods

Results

Discussion

Conclusion