Teresa J. Carrette

Nematocyst ratio and prey in two Australian cubomedusans, Chironex fleckeri and Chiropsalmus sp.

This study examined differences in the nematocyst ratios between two species of Australian cubozoans. In Chiropsalmus sp., a species that feeds exclusively on shrimp, no changes in the ratio of the three groups of nematocyst present in the cnidome were detected with size of the individual animals. In Chironex fleckeri, the ratio of different types of nematocysts in the cnidome for small animals (less than 40 mm) was similar to that of Chiropsalmus sp. However, with an increase in body size in C. fleckeri, the nematocyst ratio changed, with mastigophores (nematocysts believed to hold the lethal venom component for prey) increasing in proportion. The change in cnidome ratio is correlated with a change in the prey of C. fleckeri with increased size. Small C. fleckeri appeared to feed exclusively on prawns, medium sized animals fed on fish and prawns and large animals fed predominantly on fish. An increase in the proportion of mastigophores (and presumably the lethal venom component) in the cnidome of C. fleckeri may also be responsible for why this species has caused numerous human fatalities, while the Australian Chiropsalmus sp. has not.

The use of pressure immobilization bandages in the first aid management of cubozoan envenomings

This study is aimed to evaluate whether the application of pressure results in additional release of venom from naturally discharged, vinegar soaked nematocysts of the box jellyfish Chironex fleckeri. The results show that large quantities of venom are expressed with the application of pressures similar to that applied by compression immobilization bandages. The volume of venom expressed by this pressure was similar to the quantity expressed upon initial natural discharge of the nematocysts. The current recommended practice of applying PIB to cubozoan stings might worsen the envenomation. As the existing data now show that PIB may be detrimental to victims envenomed by cubozoans, we suggest that the current practice of the use of PIB in cubozoan envenomings be discarded until there is direct experimental evidence to support its use.

Kinematic analysis of swimming in Australian box jellyfish, Chiropsalmus sp. and Chironex fleckeri (Cubozoa, Cnidaria: Chirodropidae)

Locomotion of the box jellyfish Chiropsalmus sp. (cf quadrigatus)1 (Haeckel) and Chironex fleckeri (Southcott) was analysed using digital video. Specimens of Chiropsalmus sp. and C. fleckeri were collected in 2001 and 2002, respectively, from coastal waters of Northern Queensland, Australia. Chiropsalmus sp. animals were videoed swimming in an aquarium, and C. fleckeri in a large outdoor tank. Locomotor sequences of nine Chiropsalmus sp. and seven C. fleckeri individuals were analysed using video techniques. A subset of animals had fluorescent dye injected into the sub-umbrellar cavity, to allow observation of water movements during ejection from the bell. Both species used an intermittent style of jet propulsion similar to that documented for some other species of cubozoan medusae. Computer analysis allowed examination of positions of bell parts over time intervals (0.04 s) by comparing coordinates of nodes marked on various bell parts using imaging software. Examination of node coordinates allowed a detailed qualitative description of gait, in addition to quantitative statistical analyses. General linear modelling showed that interspecific differences in locomotion were explicable in terms of body size. Larger animals of both species tended to swim faster, and with a lower pulse frequency, than smaller individuals. Smaller animals also tended to swim faster relative to their bell diameter.

Early life history of Alatina cf. moseri populations from Australia and Hawaii with implications for taxonomy (Cubozoa: Carybdeida, Alatinidae).

The early life stages of the cubomedusa Alatina cf. moseri from Osprey Reef (North Queensland, Australia) and Waikiki (Oahu, Hawaii) were studied using laboratory-based culturing conditions. Spawning populations from both regions were observed with reliable periodicity allowing polyp cultures from these locations to be collected and established under laboratory conditions. The polyps of this species were successfully reared from spawning adults. Polyps of Alatina cf. moseri were cultured at temperatures of 23–28°C, developed up to 19 tentacles and reached up to 1.70 mm in height. The balloon-shaped hypostomes possessed 4 well-defined lips. The polyps increased their numbers by means of formation of either sedentary polyp buds or creeping-polyp buds, which attached after 2–3 days. Metamorphosis occurred at temperatures of 25–28°C. Development of polyps and medusae were achieved for the first time within the genus Alatina and allowed comparisons of early life history between these and other species of the Carybdeida families. The metamorphosis and young medusa of this genus showed characters that differed distinctly from those noted for other Carybdeida species, but are very similar to the one described from Puerto Rico by Arneson and Cutress in 1976 for Alatina sp. (named by them Carybdea alata). Based on this evidence, the discrepancies in original specimen descriptions and the previous genetic comparisons, we support the suggestion that the two previously described species of Alatina from Australia and Hawaii (Alatina mordens and Alatina moseri) appear to represent artificial taxonomic units and may in fact be the same as the original Carybdea alata species named from Puerto Rico. Further taxonomic studies are desperately needed in order to clarify the various species and description discrepancies that exist within this newly proposed genus.

Cardiotoxic effects of venoms from Chironex fleckeri and Chiropsalmus sp. on an invertebrate model

Extracted venoms from two species of cubozoan, Chironex fleckeri (C. fleckeri)and Chiropsalmus sp., were injected into the freshwater crayfish Cherax quadricarinatus (C. quadricarinatus). By means of a Vascular Doppler, the cardiac parameters heart rate and contraction amplitude were recorded, with the theoretical total heart output calculated from these two recordings. Cherax quadricarinatus reflects prey items utilized by these two species in the wild and so comparisons of venom action on this animal have greater ecological relevance than those of previous mammalian models used. While the results of this study reflect previous research showing that the overall potency of C. fleckeri venom is greater than that of Chiropsalmus sp. venom, the action of the venoms on the heart muscle is found to be different. Chironex fleckeri,which has the most potent venom out of these two species, is actually less effective in reducing cardiac activity than Chiropsalmus sp., which may be a direct reflection of the variation in primary prey utilized by each species.