Genetic Detection and a Method to Study the Ecology of Deadly Cubozoan Jellyfish

Abstract

Cubozoan jellyfish pose a risk of envenomation to humans and a threat to many businesses, yet crucial gaps exist in determining threats to stakeholders and understanding their ecology. Environmental DNA (eDNA) provides a cost-effective method for detection that is less labour intensive and provides a higher probability of detection. The objective of this study was to develop, optimise and trial the use of eDNA to detect the Australian box jellyfish, Chironex fleckeri. This species was the focus of this study as it is known to have the strongest venom of any cubozoan; it is responsible for more than 200 recorded deaths in the Indo-Pacific region. Further, its ecology is poorly known. Herein, a specific and sensitive probe-based assay, multiplexed with an endogenous control assay, was developed, and successfully utilised to detect the deadly jellyfish species and differentiate them from closely related taxa. A rapid eDNA decay rate of greater than 99% within 27 h was found with no detectable influence from temperature. The robustness of the technique indicates that it will be of high utility for detection and to address knowledge gaps in the ecology of C. fleckeri; further, it has broad applicability to other types of zooplankton.

Use of eDNA to Determine Source Locations of Deadly Jellyfish (Cubozoa) in an Open Coastal System

“…An equipment control, prior to sample collection, was also undertaken for each replicate sample to ensure the sampling equipment was not contaminated. Specific details surrounding collection, handling, and storage of eDNA samples can be found in Morrissey et al [29]. Further, a conductivity, temperature, and depth device (CTD; Seabird SBE 19 Plus) was utilised at each sample site to examine the level of stratification, as this is known to have an influence upon eDNA within the water column [38,39].…”

“…The resulting eDNA, now purified, was then stored under −20 • C conditions until the quantification process. Specific details surrounding eDNA extractions and purifications can be found in Morrissey et al [29].…”

“…This is due to limitations of current detection/sampling techniques which hinder the ability of scientists to fill these critical knowledge gaps. Environmental DNA (eDNA), however, provides a new approach to investigate the ecology of these dangerous taxa [27][28][29][30][31].…”

“…A highly specific and sensitive eDNA detection assay has recently been developed for Chironex fleckeri [29]. This detection tool was successfully utilised as an ecological survey tool and successfully detected the elusive benthic polyp life history stage of the species [28].…”

“…From these findings, Brown [32] hypothesised that Horseshoe Bay was the source location of the species for the island and, therefore, most likely contained the polyp life history stage of the species. eDNA, as it can detect putative presence of nearby polyps, therefore allowed for the testing of components of this hypothesis [27,29]. Further, as C. fleckeri medusae have largely been observed along the north side of Magnetic Island, primarily within Horseshoe Bay, it is possible that the area may represent a local stock of the jellyfish.…”