Hydrophis cyanocinctus Natural history
THOMPSON M,
Hydrophis cyanocinctus
Sea Snakes, Family Hydrophiidae
Sea snakes are closely related to Elapids, but have usually been placed in a separate family - the Hydrophiidae. Recent studies, however, suggest there may have been two independant radiations of Elapids into the sea. One group of five species, the laticudines or sea kraits, are not as completely adapted to marine life as other sea snakes, and come ashore fairly regularly, both to rest and to lay their eggs. Their bodies are not as oar-like as those of other sea snakes, and they can crawl, albeit clumsily, across the sea shore. The main radiation of sea snakes appears to have originated from a group of terrestrial Austrialian elapids (the Demansia group). They do not appear to share a common marine or even aquatic ancestor with laticudines, and their marine adaptations probably arose independently. Approximately fifty species of true sea snakes are recognized. All are marine, except for a few species that inhabit freshwater lakes in the Philippine and Solomon Islands. Some species may reach 2.5 m in lengh, but the majority average between 1-2 m. All have a laterally compressed body, oar-like tail, and valve-like nostrils that are placed on the top of the snout. They are viviparous, giving birth to their young in surface waves. They feed mainly on fish, particularly eel, but some small-headed species eat fish eggs or shrimps and prawns. Most have highly toxic venoms, but are mainly docile and non-aggressive. In fact only a small percentage of people bitten by sea snakes ever show signs of poisoning.
The sea snakes comprise a group of some 50 species all of which have strongly flattened oarlike tails used as skulls. In addition most species have nostrils opening on the top of the head, a body that is flattened from side to side, and very small ventral scutes that may be difficult to distinguish from the adjoining scales. The scales of several kinds of sea snakes are juxtaposed rather than overlapping as in most land snakes. The only snakes likely to be confused with sea snakes are the elephant-trunk snakes (Acrochordus) and the river snakes (Enhydris and others); these have round or slightly flattened tails, but young elephant-trunk snakes have tails as paddle shaped as those of some sea snakes. However, all sea snakes have enlarged crown shields and the elephant-trunk snakes have only small juxtaposed scales. Eels are frequently confused with sea snakes; however, no sea snake has fins or gill openings, and none has a smooth skin without scales.
Sea snakes are reptiles essentially of south Asian and Australian coastal waters with a few species found well out into Oceania (Society and Gilbert Islands). One species, the pelagic sea snake (Pelamis), occurs far out into the open ocean ranging across the Pacific to the western coasts of Central and South America and south to New Zealand and the Cape of Good Hope. No sea snake may eventually find its way through the Panama Canal and become established in the Caribbean. The greatest numbers of both species and individuals are found in warm shallow waters without surf or strong currents. Mouths of rivers, bays, and mangrove swamps are especially favoured . Many species of sea snakes enter brackish or fresh water occasionally; two species are restricted to lakes.
The biology of sea snakes is poorly known. There is general opinion that they can remain submerged long periods- perhaps a few hours depending upon the temperature, degree of activity, and other factors. The depths to which they can dive are also unknown. An observer in the Philippines saw the snakes swim down out of sight in very clear water. Types of bottom dwelling fish found in stomachs indicate the snakes dive at least 20 to 30 feet to capture food. They are often seen at the surface in calm weather, and often species aggregate there vast numbers, but they may be related to breeding.
There are reports of both diurnal and nocturnal activity. In the Arabian Sea, some species range 10 to 20 miles off shore during the calm winter months but tend to seek coastal mangrove swamps during the monsoon storms. Their young are born in these swamps. Sea snakes feed largely upon fish. Eels are a favourite food of several species. At least a few species eat prawns and one species feeds on fish eggs.
Sea snakes are generally mild tempered reptiles, although both individual and species variation exists with respect to this trait. In open water they either seek to escape or remain almost indifferent to swimmers. Stranded on beaches, some species are almost totally helpless. Others crawl with varying degrees of facility. None can strike on land but most can turn to make an awkward snapping bite. Bites are usually seen when the snakes are slapped, kicked, or trodden upon in shallow water or when they are removed from nets, traps, or other fishing gear.
Some kinds of sea snakes are extensively used for human food in China, Japan, and parts of Polynesia.
While some sea snake species can be identified readily by the amateur, many are puzzling even to experienced herpetologists. Colour and pattern are extremely deceptive in this family. There are close similarities between remotely related species and marked differences between young and adults of the same species as well as a good deal of variation among adults of the same species.
Within their habitat range, sea snakes are ubiquitous and agile; the increasing activities of scuba divers are shedding light upon the wide depth ranges of these remarkable animals. However, they do not tolerate extremes in temperature well and are rarely found where the average sea temperature is less than 20°C. They avoid the higher temperatures of hot tropical waters by swimming by swimming submerged. As mentioned, sea snakes are found close to shore or around coral reefs (SUTHERLAND 1983; LIMPUS 1987), although the widely distributed yellow-bellied sea snake Pelamis platurus is pelagic (ocean-going). The majority of sea snakes are bottom feeders, but Pelamis platurus is a surface feeder.
APPEARANCE
Their general appearance is that of a land snake, but they lack ventral scales (needed for land locomotion) and have a paddle-like tail (flattened in the vertical plane) to aid in swimming (BARME 1968; ACOTT 1983; LIMPUS 1987) Recorded lengths have ranged from 30cm to 2m with the Hydrophis spp. tending to be the longer (BARME 1968). They are wonderfully graceful and agile swimmers.
They are often mistaken for eels, but lack the eel's fins and gills. They also have scales, and nostrils (which are closed by an operculum during submersion) (Plate 17.2).
They are air breathers equipped with a large right lung at least (considered the sole lung by BARME [1968]) and can stay submerged for up to two hours at the extreme (HEATWOLE 1975a). They are well suited to the marine environment, their adaptive physiology being complex and interesting (HEATWOLE and SEYMOUR 1975; ACOTT 1983). They are closely related to elapid snakes, and some authorities have postulated that the sea snakes have evolved from the Indo-Australian elapids or vice versa (SUTHERLAND 1983; LIMPUS 1987).
All sea snakes have venom glands, with the venom duct opening near the tip of the front fangs (SUTHERLAND 1983; LIMPUS 1987; HALSTEAD 1988).
ENVENOMATION
Sea snake bites have been reported as painless (BARME 1968; SUTHERLAND 1983; LIMPUS 19487; EDMONDS 1989), although in a small Australian series of eight sea snake bite victims of one of the authors (CA), all the victims complained of a painful bite (ACOTT 1983).
Most bites are single, although repeated separate strikes have been recorded As with other snake bites (and all other venomous creatures), sea snakes may bite but fail to inject venom or enough venom to cause any significant clinical effect (REID and LIM 1957; REID 1975a; BARME 1968; FERNANDO and GOONERATNE 1983; SUTHERLAND 19483; WHITE 1995). Thus clinical illness from envenoming is uncommon. Overall, about 80 per cent of bites will result in no envenoming or a trivial systemic disturbance (REID 1975a). As with envenomation generally, children are particularly at risk of serious effects, a fact borne out by both Malaysian and Australian documentations.
Sea snakes are curious, generally non-aggressive creatures. However, interference with them during mating, during an ascent to the surface to breathe, or rough handling, may provoke an attack (HEATWOLE 1978; LIMPUS 1987; ZIMMERMAN and HEATWOLE 1987).
Their venom yield tends to be smaller than that of comparable size terrestrial elapids. Fresh venom is usually a clear colourless liquid which dries to a white solid. The venom has neurotoxic and myotoxic (but no coagulopathic) properties, and only one of these two properties, may dominate the clinical presentation. The neurotoxin produces post-synaptic acetylcholine inhibition (causing paralysis) while the myotoxin causes muscle necrosis (MARSDEN and REID 1961; SUTHERLAND 1983; LIMPUS 1987). Reconstruction of damaged muscle commences one or two weeks after the bite. Myotoxins in sea snake venom appear to act similarly to the phospholipase A2 myotoxins found in some elapid and viper snake venoms (WHITE 1995). In pharmacological preparations, sea snake whole venom has little or no effect on heart or smooth muscle (LIMPUS 1987).
CLINICAL FEATURES OF ENVENOMATION
If no effective first aid measures have been employed then systematic signs of envenoming may occur between 30 minutes and 3.5 hours (REID 1961).
Generalised muscle aches and pains and non-specific weakness are usually the first symptoms. These may be associated with or preceded by signs and symptoms also associated with anxiety, e.g. nausea, vomiting, dizziness, dry throat, shallow breathing and rapid pulse. The painful muscles are usually those of the neck, face, trunk, arm or thigh. Often the muscle pain is described as stiffness which progresses to severe pain on movement. Jaw muscle pain leads to trismus (REID 1961; MARSDEN and REID 1961; SUTHERLAND 1983; ACOTT 1983). This movement pain produces a reluctance to move (the patient will remain motionless), which clinically may be mistaken for paralysis, suggesting neurotoxin involvement.
Myoglobinuria is proof positive of envenomation and may be evident three to six hours after envenoming if a myotoxin is active. Plasma creatine kinase (CPK) will be elevated (SUTHERLAND 1983), indicating muscle necrosis. Secondary renal damage may occur as a result of the myoglobinurua (ZIMMERMAN and HEATWOLE 1987), and hyperkalaemic deaths were reported by REID (1961, 1975; MARSDEN and REID 1961).
True paresis may be evident within minutes to some hours after the bite and is characterised by blurred vision, ptosis, drooling, inability to swallow, dysarthria, flaccid limb paralysis and respiratory distress (inability to cough, rapid breathing, inability to maintain an airway and finally apnoea as the diaphragm is paralysed) (ACOTT 1983).
Genus Hydrophis
Hydrophis cyanocinctus
Homoeopathic name and abbreviation: Hydrophis cyanocinctus; Hydroph. (Hydro-c)
Common names: Blue banded sea snake
Description:
Distribution: Pacific Islands, Australia, India and China
Range: Persian Gulf, Pakistan, India, Sri Lanka, Thailand, Malaysia, Indonesia, Vietnam, Philippines, China, Taiwan and Japan.
Venom:
Authority: Daudin, 1803.
Comments:
(O Leeser)
Colour dirty white, pale greenish, yellow or olive with blackish crossbands that may or may not encircle the body, are widest along the vertebral midline and are as wide as, or wider than, the interspaces between them. Head in adult olive, reddish, or dull yellow; in young blackish with the yellow horseshoe mark seen in some other species.
The adult length averages 4 1/2 to 5 1/2 feet with record specimens of about 6 1/2 feet.
Remarks: This snake frequents mangrove swamps but has been collected 12 to 20 miles offshore during winter. Although it has been seen to leave the water voluntarily, it crawls fairly well and can lift its head well free of the ground. It often bites if restrained.
Venom yields reported from this snake are approximately double those reported for the yellow sea snake, and the toxicity is somewhat higher. Data from Malaya indicate H. cyanocinctus causes more deaths than any sea snake species except the beaked sea snake.
Hydrophis cyanocinctus
Sea Snakes, Family Hydrophiidae
Sea snakes are closely related to Elapids, but have usually been placed in a separate family - the Hydrophiidae. Recent studies, however, suggest there may have been two independant radiations of Elapids into the sea. One group of five species, the laticudines or sea kraits, are not as completely adapted to marine life as other sea snakes, and come ashore fairly regularly, both to rest and to lay their eggs. Their bodies are not as oar-like as those of other sea snakes, and they can crawl, albeit clumsily, across the sea shore. The main radiation of sea snakes appears to have originated from a group of terrestrial Austrialian elapids (the Demansia group). They do not appear to share a common marine or even aquatic ancestor with laticudines, and their marine adaptations probably arose independently. Approximately fifty species of true sea snakes are recognized. All are marine, except for a few species that inhabit freshwater lakes in the Philippine and Solomon Islands. Some species may reach 2.5 m in lengh, but the majority average between 1-2 m. All have a laterally compressed body, oar-like tail, and valve-like nostrils that are placed on the top of the snout. They are viviparous, giving birth to their young in surface waves. They feed mainly on fish, particularly eel, but some small-headed species eat fish eggs or shrimps and prawns. Most have highly toxic venoms, but are mainly docile and non-aggressive. In fact only a small percentage of people bitten by sea snakes ever show signs of poisoning.
The sea snakes comprise a group of some 50 species all of which have strongly flattened oarlike tails used as skulls. In addition most species have nostrils opening on the top of the head, a body that is flattened from side to side, and very small ventral scutes that may be difficult to distinguish from the adjoining scales. The scales of several kinds of sea snakes are juxtaposed rather than overlapping as in most land snakes. The only snakes likely to be confused with sea snakes are the elephant-trunk snakes (Acrochordus) and the river snakes (Enhydris and others); these have round or slightly flattened tails, but young elephant-trunk snakes have tails as paddle shaped as those of some sea snakes. However, all sea snakes have enlarged crown shields and the elephant-trunk snakes have only small juxtaposed scales. Eels are frequently confused with sea snakes; however, no sea snake has fins or gill openings, and none has a smooth skin without scales.
Sea snakes are reptiles essentially of south Asian and Australian coastal waters with a few species found well out into Oceania (Society and Gilbert Islands). One species, the pelagic sea snake (Pelamis), occurs far out into the open ocean ranging across the Pacific to the western coasts of Central and South America and south to New Zealand and the Cape of Good Hope. No sea snake may eventually find its way through the Panama Canal and become established in the Caribbean. The greatest numbers of both species and individuals are found in warm shallow waters without surf or strong currents. Mouths of rivers, bays, and mangrove swamps are especially favoured . Many species of sea snakes enter brackish or fresh water occasionally; two species are restricted to lakes.
The biology of sea snakes is poorly known. There is general opinion that they can remain submerged long periods- perhaps a few hours depending upon the temperature, degree of activity, and other factors. The depths to which they can dive are also unknown. An observer in the Philippines saw the snakes swim down out of sight in very clear water. Types of bottom dwelling fish found in stomachs indicate the snakes dive at least 20 to 30 feet to capture food. They are often seen at the surface in calm weather, and often species aggregate there vast numbers, but they may be related to breeding.
There are reports of both diurnal and nocturnal activity. In the Arabian Sea, some species range 10 to 20 miles off shore during the calm winter months but tend to seek coastal mangrove swamps during the monsoon storms. Their young are born in these swamps. Sea snakes feed largely upon fish. Eels are a favourite food of several species. At least a few species eat prawns and one species feeds on fish eggs.
Sea snakes are generally mild tempered reptiles, although both individual and species variation exists with respect to this trait. In open water they either seek to escape or remain almost indifferent to swimmers. Stranded on beaches, some species are almost totally helpless. Others crawl with varying degrees of facility. None can strike on land but most can turn to make an awkward snapping bite. Bites are usually seen when the snakes are slapped, kicked, or trodden upon in shallow water or when they are removed from nets, traps, or other fishing gear.
Some kinds of sea snakes are extensively used for human food in China, Japan, and parts of Polynesia.
While some sea snake species can be identified readily by the amateur, many are puzzling even to experienced herpetologists. Colour and pattern are extremely deceptive in this family. There are close similarities between remotely related species and marked differences between young and adults of the same species as well as a good deal of variation among adults of the same species.
Within their habitat range, sea snakes are ubiquitous and agile; the increasing activities of scuba divers are shedding light upon the wide depth ranges of these remarkable animals. However, they do not tolerate extremes in temperature well and are rarely found where the average sea temperature is less than 20°C. They avoid the higher temperatures of hot tropical waters by swimming by swimming submerged. As mentioned, sea snakes are found close to shore or around coral reefs (SUTHERLAND 1983; LIMPUS 1987), although the widely distributed yellow-bellied sea snake Pelamis platurus is pelagic (ocean-going). The majority of sea snakes are bottom feeders, but Pelamis platurus is a surface feeder.
APPEARANCE
Their general appearance is that of a land snake, but they lack ventral scales (needed for land locomotion) and have a paddle-like tail (flattened in the vertical plane) to aid in swimming (BARME 1968; ACOTT 1983; LIMPUS 1987) Recorded lengths have ranged from 30cm to 2m with the Hydrophis spp. tending to be the longer (BARME 1968). They are wonderfully graceful and agile swimmers.
They are often mistaken for eels, but lack the eel's fins and gills. They also have scales, and nostrils (which are closed by an operculum during submersion) (Plate 17.2).
They are air breathers equipped with a large right lung at least (considered the sole lung by BARME [1968]) and can stay submerged for up to two hours at the extreme (HEATWOLE 1975a). They are well suited to the marine environment, their adaptive physiology being complex and interesting (HEATWOLE and SEYMOUR 1975; ACOTT 1983). They are closely related to elapid snakes, and some authorities have postulated that the sea snakes have evolved from the Indo-Australian elapids or vice versa (SUTHERLAND 1983; LIMPUS 1987).
All sea snakes have venom glands, with the venom duct opening near the tip of the front fangs (SUTHERLAND 1983; LIMPUS 1987; HALSTEAD 1988).
ENVENOMATION
Sea snake bites have been reported as painless (BARME 1968; SUTHERLAND 1983; LIMPUS 19487; EDMONDS 1989), although in a small Australian series of eight sea snake bite victims of one of the authors (CA), all the victims complained of a painful bite (ACOTT 1983).
Most bites are single, although repeated separate strikes have been recorded As with other snake bites (and all other venomous creatures), sea snakes may bite but fail to inject venom or enough venom to cause any significant clinical effect (REID and LIM 1957; REID 1975a; BARME 1968; FERNANDO and GOONERATNE 1983; SUTHERLAND 19483; WHITE 1995). Thus clinical illness from envenoming is uncommon. Overall, about 80 per cent of bites will result in no envenoming or a trivial systemic disturbance (REID 1975a). As with envenomation generally, children are particularly at risk of serious effects, a fact borne out by both Malaysian and Australian documentations.
Sea snakes are curious, generally non-aggressive creatures. However, interference with them during mating, during an ascent to the surface to breathe, or rough handling, may provoke an attack (HEATWOLE 1978; LIMPUS 1987; ZIMMERMAN and HEATWOLE 1987).
Their venom yield tends to be smaller than that of comparable size terrestrial elapids. Fresh venom is usually a clear colourless liquid which dries to a white solid. The venom has neurotoxic and myotoxic (but no coagulopathic) properties, and only one of these two properties, may dominate the clinical presentation. The neurotoxin produces post-synaptic acetylcholine inhibition (causing paralysis) while the myotoxin causes muscle necrosis (MARSDEN and REID 1961; SUTHERLAND 1983; LIMPUS 1987). Reconstruction of damaged muscle commences one or two weeks after the bite. Myotoxins in sea snake venom appear to act similarly to the phospholipase A2 myotoxins found in some elapid and viper snake venoms (WHITE 1995). In pharmacological preparations, sea snake whole venom has little or no effect on heart or smooth muscle (LIMPUS 1987).
CLINICAL FEATURES OF ENVENOMATION
If no effective first aid measures have been employed then systematic signs of envenoming may occur between 30 minutes and 3.5 hours (REID 1961).
Generalised muscle aches and pains and non-specific weakness are usually the first symptoms. These may be associated with or preceded by signs and symptoms also associated with anxiety, e.g. nausea, vomiting, dizziness, dry throat, shallow breathing and rapid pulse. The painful muscles are usually those of the neck, face, trunk, arm or thigh. Often the muscle pain is described as stiffness which progresses to severe pain on movement. Jaw muscle pain leads to trismus (REID 1961; MARSDEN and REID 1961; SUTHERLAND 1983; ACOTT 1983). This movement pain produces a reluctance to move (the patient will remain motionless), which clinically may be mistaken for paralysis, suggesting neurotoxin involvement.
Myoglobinuria is proof positive of envenomation and may be evident three to six hours after envenoming if a myotoxin is active. Plasma creatine kinase (CPK) will be elevated (SUTHERLAND 1983), indicating muscle necrosis. Secondary renal damage may occur as a result of the myoglobinurua (ZIMMERMAN and HEATWOLE 1987), and hyperkalaemic deaths were reported by REID (1961, 1975; MARSDEN and REID 1961).
True paresis may be evident within minutes to some hours after the bite and is characterised by blurred vision, ptosis, drooling, inability to swallow, dysarthria, flaccid limb paralysis and respiratory distress (inability to cough, rapid breathing, inability to maintain an airway and finally apnoea as the diaphragm is paralysed) (ACOTT 1983).
Genus Hydrophis
Hydrophis cyanocinctus
Homoeopathic name and abbreviation: Hydrophis cyanocinctus; Hydroph. (Hydro-c)
Common names: Blue banded sea snake
Description:
Distribution: Pacific Islands, Australia, India and China
Range: Persian Gulf, Pakistan, India, Sri Lanka, Thailand, Malaysia, Indonesia, Vietnam, Philippines, China, Taiwan and Japan.
Venom:
Authority: Daudin, 1803.
Comments:
(O Leeser)
Colour dirty white, pale greenish, yellow or olive with blackish crossbands that may or may not encircle the body, are widest along the vertebral midline and are as wide as, or wider than, the interspaces between them. Head in adult olive, reddish, or dull yellow; in young blackish with the yellow horseshoe mark seen in some other species.
The adult length averages 4 1/2 to 5 1/2 feet with record specimens of about 6 1/2 feet.
Remarks: This snake frequents mangrove swamps but has been collected 12 to 20 miles offshore during winter. Although it has been seen to leave the water voluntarily, it crawls fairly well and can lift its head well free of the ground. It often bites if restrained.
Venom yields reported from this snake are approximately double those reported for the yellow sea snake, and the toxicity is somewhat higher. Data from Malaya indicate H. cyanocinctus causes more deaths than any sea snake species except the beaked sea snake.
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