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.

Vascular dopplers: a new way of recording cardiac parameters in envenomed organisms.

Measuring cardiac activity in experimental animals for research purposes has great relevance and obvious implications for investigating venom actions and toxicity. Previous techniques have been confined to vertebrate models as traditional heart recording apparatuses require a closed vascular system to be effective. A new technique utilizing a Vascular Doppler placed external to the cardiac muscle was trialled in order to record previously undocumented invertebrate heart activity of envenomed animals. Combined with Avisoft sound collection software, this technique was found to be successful in recording cardiac parameters such as heart rate and extent of contraction in an invertebrate model. This method is advantageous as it is not only inexpensive and easily portable but allows for specific venom actions to be investigated in a wider variety of previously unreportable, but ecologically significant animals.

A rapid and repeatable method for venom extraction from cubozoan nematocysts.

Various comparative studies into the biological activity and relative toxicity of cubozoan venoms have been investigated, in particular the venom from the potentially lethal cubozoan Chironex fleckeri. Efficient and reliable extraction of venom from nematocysts is essential before any research into venom toxicity can be conducted and previous cited methods of extraction have varied greatly, each with their own associated problems. A new standardised technique for the recovery of venom from nematocysts of cubozoans is investigated to decrease the variation displayed between authors due to differing extraction techniques. The use of a mini bead mill beater, as investigated in this trial, allows for the rapid extraction of venom from nematocysts and is devoid of the previously isolated problems experienced with other methods of venom isolation, such as excessive heat build up.

Severe cardiac failure associated with presumed jellyfish sting. Irukandji syndrome?

We present a retrospective review of twelve cases of Irukandji syndrome associated with pulmonary oedema. This is a life-threatening envenoming due to a presumed jellyfish sting throughout Northern Australia, although only one case occurred outside North Queensland. Patients presented with significant and ongoing pain, tachycardia and hypertension. Half the patients became hypotensive requiring inotropic support. Cardiac echocardiography revealed significant cardiac dysfunction. Six patients required ventilatory support. There was no death reported due to pulmonary oedema, but one patient died of intracerebral haemorrhage. We believe patients may develop a toxin associated cardiomyopathy, and jellyfish other than Carukia barnesi may be responsible. As there is confusion with nomenclature, Carukia barnesi should be known as the Barnes jellyfish, and the diagnosis of cardiotoxic marine envenoming is suggested for any patient who has been stung by a jellyfish, develops no or minimal skin markings, and develops cardiogenic pulmonary oedema associated with Irukandji syndrome.

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.

Pressure immobilisation bandages in first-aid treatment of jellyfish envenomation: current recommendations reconsidered.

OBJECTIVE: To evaluate whether applying pressure equivalent to that of pressure immobilisation bandages (PIB) causes release of additional venom from discharged jellyfish nematocysts. DESIGN: In-vitro experiment--the venom beads released from electrically activated Chiropsalmus sp. nematocysts were viewed under direct microscopy before and after applying 40 mmHg pressure (replicating the pressure of PIB); and saline washings of discharged nematocysts before and after applying pressure were tested for toxicity (time to ventricular standstill after injecting into live prawns). RESULTS: Applying 40 mmHg pressure caused the venom beads to visibly increase in size, consistent with pressure expressing further venom from the discharged nematocysts. First washings of the nematocyst shafts before compression produced ventricular standstill in prawns within 60 seconds (n=3); second washings did not produce standstill during 540 seconds of observation (n=3); and washings after applying 40 mmHg pressure showed a return of toxicity, with ventricular standstill in all prawns within 180 seconds (n=3). CONCLUSION: Discharged nematocysts are by no means empty and harmless. Applying pressure results in further release of nematocyst venom. The currently recommended practice of applying PIB in the initial treatment of patients stung by a jellyfish may exacerbate the envenomation, and thus should not be recommended.