Abundant box jellyfish, Chironex sp. (Cnidaria: Cubozoa: Chirodropidae), discovered at depths of over 50 m on western Australian coastal reefs.

John K Keesing,Joanna Strzelecki,Dongyan Liu,Marcus Stowar,Karen J Miller,Mary Wakeford,Lisa-Ann Gershwin

doi:10.1038/srep22290

Abstract

Box jellyfish cause human fatalities and have a life cycle and habit associated with shallow waters (<5 m) in mangrove creeks, coastal beaches, embayments. In north-western Australia, tow video and epibenthic sled surveys discovered large numbers (64 in a 1500 m tow or 0.05 m−2) of Chironex sp. very near to the benthos (<50 cm) at depths of 39–56 m. This is the first record of a population of box jellyfish closely associated with the benthos at such depths. Chironex were not widespread, occurring only in 2 of 33 tow videos and 3 of 41 epibenthic sleds spread over 2000 km2. All Chironex filmed or captured were on low to medium relief reefs with rich filter feeder communities. None were on soft sediment habitat despite these habitats comprising 49% of all sites. The importance of the reef habitat to Chironex remains unclear. Being associated with filter feeder communities might represent a hazard, and other studies have shown C. fleckeri avoid habitats which represent a risk of entanglement of their tentacles. Most of our observations were made during the period of lowest tidal current flow in the morning. This may represent a period favourable for active hunting for prey close to the seabed.

Highlights

Cubozoans or box jellyfish include members of the highly venomous genus Chironex and have been responsible for numerous fatalities in tropical and subtropical coastal regions of the world
There is reported to be a species of Chironex from the Kimberley region of Australia that remains undescribed[10]
Specimens from this study could not be confidently determined to be Chironex fleckeri and have been lodged with the Western Australian Museum, registration numbers, WAM Z68783 and WAM Z68784 (4 specimens)

Summary

Introduction

Cubozoans or box jellyfish include members of the highly venomous genus Chironex and have been responsible for numerous fatalities in tropical and subtropical coastal regions of the world. C. yamaguchii has been responsible for fatalities in Japan, and probably the Philippines[3,4] Despite their notoriety, many aspects of the behaviour and ecology of Chironex remain a mystery, and this is true for cubozoan jellyfish in general[5]. The opportunity to observe Chironex on deep coastal reefs arose during work for a large scale survey using an underwater towed video camera and epibenthic sled to characterise the sea bed habitats and biodiversity of Camden Sound, a remote, previously unsurveyed location in the Kimberley region of north-western Australia. During the survey of March 2015, one of the routine video stations discovered large numbers of box jellyfish close to the seabed in over 40 m of water. Rich filter feeder communities, and our objective is to document this phenomenon as a contribution to the scant information on box jellyfish habitat

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Conclusion