Notesthes robusta
Family Scorpaenidae
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Family
Scorpaenidae
Joan O'Connor
Introduction
The Bullrout (Notesthes robusta) is a member of the family Scorpaenidae and is found in estuaries along the eastern seaboard of Australia (Cameron and Endean 1966). This species causes severe and debilitating pain through the secretion of venom from twin venom glands associated with spines in the dorsal, ventral and anal fins (Grant 1978). Envenomation takes place when the spines puncture flesh, when the fish is stepped on, or when anglers attempt to disengage it from nets or lines. The resultant pain is described as intense and recommended treatments include the application of heat, administration of local anesthetics and analgesics with some of the victims requiring complete sedation in hospital (Sutherland 1983). Current literature is mainly descriptive of the fish and the painful effects of envenomation. Little, if any biochemical assessment has been carried out, consequently venom constituents are poorly understood at this time.
The family Scorpaenidae includes some of the most dangerous fish known (Kizer et al. 1985) and they are described by (Edmonds 1989) as resembling the perch and likened by (Keegan and Macfarlane 1963) to the Sea Bass. They have a characteristically large armoured head with sharp venomous spines on the fins. The number of spines in the fin areas vary from 11-17 and these become erect when the fish is aroused or threatened (Edmonds 1984). These fish vary in both form and colouration taking on the predominant colours of their environment. This means Scorpaenidae in tropical waters display brilliant reds, blues and yellows, such as the Butterfly cod - and those fish who inhabit rivers and estuaries such as N. Robusta display drab dark colours (Frey 1994). Known species include : Stonefish, Fortesque, Lionfish, Firefish, and the Rock Cod.
(Keegan and Macfarlane 1963) classify the species on the basis of the morphology of the venom apparatus. They list three types:
• Pterois or Zebrafish• Scorpaena or Scorpion Fish
• Synanceja or Stonefish
Venom apparatus differs in the size and shape of the spines and the presence or absence of a venom excretory duct. Pterois have elongated slender spines, Scorpaena moderately long, thick spines, and Synanceja short, stout, very thick spines. Both Pterois and Scorpaena have venom glands, while Synanceja have well developed excretory ducts as well as large, highly developed venom glands (Wiener 1959). The literature indicates the venom apparatus of all varieties of Scorpaedinae is used defensively as it seems the expulsion of venom cannot be controlled by the fish (Endean 1961).
Habitat
While the family Scorpaenidae is distributed world wide and includes over 300 species of fish only about 40 varieties are found in Australian waters (Allen 1989). The Bullrout (Nothesthes robusta ) inhabits slow moving streams and tidal estuaries in coastal waters from approximately the Daintree River in Far North Queensland (Pollard and Parker 1996) to the Clyde River in NSW (Allen 1989). N. Robusta leads a sedentary life style on the bottom of slow moving weed infested rivers and streams (Grant 1978) . The fish is also known as the Kroki due to the grunting noise it sometimes emits when first pulled from the water (Marshall 1964). The noise closely resembles frogs croaking but the phenomena has only been personally experienced on one occasion even though a great many Bullrout have been pulled from the river.
Physical Description
The fish is elliptical in shape with a large mouth and a lower jaw longer than the upper (Merrick and Schmida 1984) It has a characteristically stocky appearance with an armoured head containing 7 bony spines in the area of the cheeks and opercula (Thomson 1977). Sharp venomous spines are present in the dorsal, anal and ventral regions. There are 15 dorsal spines with 9-10 soft rays, 3 anal spines with 5 rays and a pair of single ventral spines. All spines are sloped toward the caudal end of the fish. (Merrick and Schmida 1984) reports internal fertilisation and ovoviviparity have been noted in other Scorpaenidae, however the reproductive biology of N. robusta is not well discussed in the literature. No reproductive activity was observed in the specimens held in aquaria facilities for the study.
Colouration
Colour varies from yellow to brown with black marbled blotches. When stressed Nothesthes robusta becomes pale in appearance and is dark to light yellow. Juveniles present with a pale 2 cm circular band around the belly region behind the pectoral fins. This mottled variegated colour pattern allows the fish to remain inconspicuous among the reeds and stones (Halstead et al. 1990). The hazard the fish presents to users of the waterways is increased by their natural camouflage and a tendency to remain motionless when approached (Thomson 1974). Cameron and Endean (1966) indicate the fish possesses a potent venom and an effective apparatus for venom delivery. These properties make Nothesthes robusta 'one of the most dangerous of Australian fishes' (Cameron and Endean, 1966:120).
Diet
Consists of small fish, prawns and other crustaceans such as yabbies and polycheate worms. The fish captured for this project have been maintained on a diet of Gambuzia, green prawns, yabbies, beach worms and occasional tadpoles. The fish enjoy live food and dart out quickly to take prey. Live yabbies remained a favourite food while beach worms are only just tolerated. Earth worms were trailed with little success as were live crickets. The worms were not lively enough to capture the fishes attention. Appearance of the crickets caused some animation among the fish but they quickly expelled them from their mouths possibly due to the chemical make up of the cricket. In times when the supply of Gambuzia was low, dead green prawns were lowered into the tanks on fine cotton to simulate life like movements. The fish accepted these as prey and in time actively sought prawns by coming to the top of the tanks and 'begging' for food. Prawns and yabbies are swallowed whole and backwards and frequently the fish were observed to have prawn whiskers hanging from their mouths. The captive fish had good appetites and the larger fish could accommodate an 8 cm live yabby withno difficulty.
Venom Apparatus
The venom glands of N. robusta are associated with the dorsal, anal and ventral spines, all of which articulate with the skeleton (Cameron and Endean 1966). Each of the spines is enclosed in an integumentary sheath which encloses twin venom glands positioned at the tip of the spines. The glands are accommodated in grooves running along the sides of each spine. When pressure is applied to the erected spine, the tip punctures the integument and physical disruption of the sheathoccurs due to the weight of the victim. The venom glands are compressed expelling the venom along the antero-lateral grooves. No musculature is involved in the venom discharge process. Partial regeneration of the integument and venom gland content commences within a week and continues for a period of 13 weeks (Merrick and Schmida 1984). The intensity of the sting depends largely on the number of spines involved and the depth to which they penetrate the flesh of the victim.
Venom Effects
Pain is the most distressing feature of Bullrout envenomation with the sting variously described as '...spectacularly painful' (Patkin and Freeman 1969)and 'immediate and intense' (Frey 1994). One of the earliest reports on the effects of the venom is by Cleland (1912) who indicates '...the pain is intense. It runs through the limb like fire. The injured part becomes red and inflamed.' (272). In 1915 Kesteven elaborated further and described the pain as '..out of all proportion to the very insignificant nature of the injury' (91) he goes on to say:
...it radiates in an altogether abnormal manner, compared with ordinary pricks or scratches, in many cases extending to the shoulder, or even up the side of the neck; the temperature varies greatly in most cases going up 2, 3 or more degrees within a very short time; lasting thus for a varying time and going down as rapidly, often below the normal, when severe collapse occurs, necessitating the free administration of stimulants to counteract heart failure which threatens (Kesteven 1914).
Accidental Injury
A personal appreciation of this description was gained after an accidental laboratory fish stick injury. This injury allowed first hand knowledge of the effects of envenomation and some insight into the potency of the venom. The injury caused an oblique 2 mm tear in the epidermal and dermal layers, 1 cm below the right thumb joint. Pain experienced was at first a sharp, pricking sensation which quickly deepened into a dull ache especially in the thumb joint. There was very little bleeding from the wound but bruising developed within one hour of injury. The injury progressed as a classical inflammatory response with swelling, redness and heat. The site became very tender and exuded fine beads of sweat which returned to the site within 2 minutes of being wiped away. Redness extended to the palm of the hand and around the skin between the thumb andthe first finger in blotchy patches. Swelling developed across the dorsal surface of the hand as the venom infiltrated the tissues. As each new area was affected dull aching pain was experienced in the joint of the affected area. Pain continued for three hours until gradually waning. The hand remained swollen and tender for two days post injury. While the actual physical damage caused to the hand was minimal (the fish spine punctured the skin to a depth of 1mm only) this wound produced a pain reaction out of proportion to the wound size. This outcome is consistent with the literature on the nature of Bullrout envenomation (Whitely, 1943). The venom is also described as heat labile yet application of hot packs did little to alleviate pain (Cameron and Endean 1966).
Treatment
Medical Intervention
Basic treatment protocols for marine stings includes alleviating the pain, neutralizing the venom and preventing secondary infection (Frey 1994). The treatment most often recommended for Bullrout sting is the use of heat to immobilise the venom and relieve pain. Immersion in water (45¡ C) for 30-90 minutes is seen to be effective because the venom is heat labile (Auerbach 1991). However as stated earlier this did not relieve the personal pain experienced after an accidental fish stick injury during the project. A survey distributed to North Coast hospitals from the Tweed to the Manning River areas provides an indication of current medical treatment of Bullrout sting. Heat and local anesthetics are most used treatments and a range of analgesics were administered from Pethidine to Panadol.
Before these analgesics were available oxidising chemicals such as potassium permanganate were used to offset the effects of the venom. Kesteven (1915) recommended the use of this compound for the relief of pain. Physicians would infiltrate and/or irrigate thewound with '...a few minims of 5% solution of potassium permanganate' (Wiener 1958) (220). Relief was seen to be 'dramatic' and 'almost instantaneous', with no adverse local effects. However in 1943 Hewitt began using hypodermic injections of Adrocain (Novocaine) 1% '...in amounts of one to three cubic centimeters, if possible along the punctured wound' (492). Later (Patkin and Freeman 1969) obtained better results by infiltrating the wound with 1 or 2% lignocaine and giving intravenous pethidine if the local anesthetic did not work.
Emetine Hydrochloride
An interesting treatments mentioned by several writers is the use of Emetine Hydrochloride for pain relief. This substance is a derivative of Ipecac a widely used emetic. The drug has been used inthe past for immediate and complete relief of pain with stings from various venomous fish such as Bullrout (Wiener 1958). The drug is seen to relieve pain because the compound has a low pH (4.2) which neutralizes the venom. It is also felt emetine reduces the hyaluronidase effects of Bullrout venom activity (Wiener 1984). Emetine infiltrated into the wound relieved pain within three minutes in some individuals (Wiener 1958). This drug is however no longer available in this country (Wiener 1984).
Some unusual remedies are discussed in the literature such as one used in the Dungog area of NSW is the application of tar from a tobacco pipe to the wound site (Patkin and Freeman 1969). Cleland (1915) reports a case study in which strong ammonia was applied to a sting, however the treatment did not seem to do much for the patient's pain which remained at high levels for 24 hours. One of the members of the Clarence River Fishermen's Cooperative believes pain from wounds on the hand can be reduced by heat immersion for 10 minutes then rotating the affected hand as rapidly as possible in a 360¡ arc for 10-15 minutes.
Traditional Native Cures
One of the earliest papers reviewed on the treatment of Bullrout envenomation is by (Cleland 1912) who discusses Indigenous Australian's dread of the Bullrout and writes '... the name Bull-rout may possibly be a corruption of some native word'. His observation regarding the Aboriginal's attitude to the fish is of interest in that Wiener (1958) notes some North Queensland tribes instruct their youth on the dangers of Stonefish during initiation ceremonies. Pearn and Covacevich (1988) also mention an initiation ceremony in which a beeswax model of a stonefish is used with dance and mime to impress the danger of stonefish envenomation on young people. It could therefore be postulated a similar approach would have been taken regarding the dangers of Bullrout.
References
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