Abstract
This research explores the thermal and osmotic tolerance of the polyp stage of the Irukandji jellyfish Carukia barnesi, which provides new insights into potential polyp habitat suitability. The research also targets temperature, salinity, feeding frequency, and combinations thereof, as cues for synchronous medusae production. Primary findings revealed 100% survivorship in osmotic treatments between 19 and 46‰, with the highest proliferation at 26‰. As salinity levels of 26‰ do not occur within the waters of the Great Barrier Reef or Coral Sea, we conclude that the polyp stage of C. barnesi is probably found in estuarine environments, where these lower salinity conditions commonly occur, in comparison to the medusa stage, which is oceanic. Population stability was achieved at temperatures between 18 and 31°C, with an optimum temperature of 22.9°C. We surmise that C. barnesi polyps may be restricted to warmer estuarine areas where water temperatures do not drop below 18°C. Asexual reproduction was also positively correlated with feeding frequency. Temperature, salinity, feeding frequency, and combinations thereof did not induce medusae production, suggesting that this species may use a different cue, possibly photoperiod, to initiate medusae production.
Highlights
Tropical Australian cubozoans are highly seasonal, with the medusa stage usually arriving along the tropical coastlines during the monsoonal summer months [1,2,3,4,5,6,7]
Asexual reproduction was high at temperatures that commonly occur in the waters of the Great Barrier Reef, this was not the case with salinity, where the highest polyp proliferation was not encompassed by salinity levels that occur in the waters of the Great Barrier Reef
Carukia barnesi polyps had a high tolerance to osmotic treatments with 100% survivorship from treatments between 18 and 46‰ (Fig 1), which indicates that this species may inhabit areas with a high degree of osmotic variation
Summary
Tropical Australian cubozoans are highly seasonal, with the medusa stage usually arriving along the tropical coastlines during the monsoonal summer months [1,2,3,4,5,6,7]. This ‘stinger season’ in Australia is typically between November and May, which has been reported to begin earlier, and last longer, in warmer areas closer to the equator such as in the Gulf of Carpentaria [3,8,9]. Medusa production in cubozoans is variable and can be in the form of complete metamorphosis of the polyp into a PLOS ONE | DOI:10.1371/journal.pone.0159380 July 21, 2016
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