Carbon distribution strategy of Aurelia coerulea polyps in the strobilation process in relation to temperature and food supply

Mass occurrences of moon jellyfish have been observed in coastal waters. Strobilation directly determines the initial population size of adult jellyfish, but energy distribution during the strobilation process is not well understood. In this study, strobilation was induced in polyp of Aurelia coerulea by elevating temperature. The different stages in the strobilation process, including polyp budding, strobilation and body growth, were investigated at six temperature levels(8, 10, 13, 15, 17 and 19°C) and five food supply levels(0, 30, 60, 100 and 150 μg C/L). The results showed that the duration of strobilation preparation stage(SP) remarkably decreased with increasing temperature. Food level positively af fected the production of buds and ephyrae and the body growth of parent polyps. Of the six temperatures tested, 13°C was optimal for strobilation. At 13°C, strobilation activity was enhanced, and this treatment resulted in the greatest energy distribution, highest ephyrae production and longest duration of strobilation stage(SS). Polyps tended to allocate 6.58%–20.49% carbon to buds with sufficient food supply regardless of temperature. The body growth of parent polyps was highest at lower temperatures and higher food levels. This study is the first to provide information on carbon-based energy distribution strategy in the polyp strobilation process. We concluded that budding reproduction is a lower-risk strategy for A. coerulea polyps to increase populations. Even during strobilation season, polyps prioritize budding, but at the optimal strobilation temperature, polyps utilize a portion of the energy stored for budding to release ephyrae. The body carbon content of parent polyps may be considered as strategic energy reserves, which could help to support budding activities and strobilation during harsh conditions.

Inductive eff ect of bioactive substances on strobilation of jellyfi sh Aurelia coerulea

The moon jellyfi sh Aurelia spp.is a worldwide distributed scyphozoan species that seasonally blooms in coastal waters.Although the strobilation is directly responsible for the scale of jellyfi sh bloom,the underlying mechanisms remain largely unknown.We exposed Aurelia coerulea polyps to 18 bioactive substances to test their ability to induce strobilation at the natural typically non-strobilation temperature of 21°C.Results revealed that A.coerulea polyps responded in four types.Type I—no change for estradiol,folic acid,iodine,retinoic acid,serotonin hydrochloride,and vitamin A.We suggested that 5-aza-2-deoxycytidine and N-acetyl-L-glutamic acid could not induce strobilation,since the percent of strobilated polyps in these two substances treatments was 3.3%and 1%,respectively.Type II—polyp body elongation for 3,5-diiodo-Ltyrosine,indole-3-acetic acid,L-dopamine,and noradrenaline treatments.Type III—transverse constrictions for L-thyroxine,progesterone,and melatonin treatments.Finally,Type IV—complete strobilation for 5-methoxy-2-methylindole,acetylcholine chloride,and indomethacin treatments,where the pre-strobilation periods were 2,4,and 2 days,and the mean numbers of ephyrae released per strobila were 4.7,5.7,and 5.7,respectively.The results reveal that indole derivatives,which contained methoxy or methyl pharmacophore,were the common strobilation inducer in the genus Aurelia.Iodinated organic compounds,catecholamine,acetylcholine chloride,and retinoic acid are species-specifi c strobilation inducer.Therefore,A.coerulea strobilation is regulated by neuronal and endocrine processes.Our fi ndings provide clues in understanding the mechanism of strobilation and contribute to developing specifi c strobilation antagonists in controlling moon jellyfi sh blooms.

Metabolomics provide insights into the endogenous mechanism of strobilation in the scyphozoan jellyfi sh Rhopilema esculentum

Strobilation is a well-organized metamorphosis process in scyphozoan jellyfi sh,through which the benthic polyp develops into the pelagic medusa.So far,knowledge on the molecular mechanisms behind the drastic morphological and physiological changes remains limited.In the present study,the metabolic profi les in polyp and strobila stages of jellyfi sh Rhopilema esculentum were examined using ultra-performance liquid chromatography coupled to a mass spectrometer.A total of 3071 metabolites with putative annotation were detected,of which 167 were identifi ed as diff erential metabolites between the polyp and strobila.Among the metabolites,31 signifi cantly decreased and 136 signifi cantly increased in abundance in the strobila.Thyroxin,one of the previously proposed strobilation inducer of Aurelia,was not detected in this study.The indole-containing compounds are known for triggering strobilation in Discomedusae.Two indole derivatives and an indole-isomer containing metabolite were detected among the most signifi cantly increased metabolites,which may be potential endogenous molecules for strobilation initiation.The membrane-associated phospholipids and the infl ammation and oxidative stress-related eicosanoids were found to have signifi cant changes.Although the functions of these metabolites in strobilation are not yet completely known,they provide some clues to the induction of the process of strobilation and metabolic responses that take place during strobilation.

Male spike strobiles with Gnetum affinity from the Early Cretaceous in western Liaoning,Northeast China

A fossil with Gnetum affinity was found in the Jianshangou Member （Barremian Age） of the Yixian Formation （Lower Cretaceous Epoch） of the Jehol Group in western Liaoning, northeastern China. The single fossil specimen is represented by both elongate-cylindrical male spike strobiles which borne within a nodal bract of cauliflorous branch. The spike strobiles have apparent nodes, invisible internodes, and numerous verticillate involucral collars. The microsporangiate units within involucral collars are not seen. The male spike strobiles with verticillate involucral collars occur exclusively in Gnetum; hence, the fossil strobiles are attributed to a new taxon, Khitania columnispicata gen. ＆ sp. nov., being closely related to Gnetum. The general isotopic dating suggests an age of Barremian, ca. 125-122 million years （Myr） ago for the Jianshangou Member. The palaeoecological and palaeoclimatic inference based on the compositions of flora and fauna, and lithological characters of the fossil locality suggests that the fossil plants grew in a subtropical mesophytic forest and under a warmer climate. The remains of male spike strobiles are the first record of gnetalean macrofossil. It documents the evolution of the distinct gnetoid morphology and indicates a wider range of distribution of Gnetaceae in the Early Cretaceous than present day.