Notechis scutatus

Abstract: Female reproductive cycles were studied in seven species of Australian elapid snakes, and the results compared with published information on snake faunas of other continents. Of the species studied, five are live-bearing (Austrelaps superbus, Hemiaspis signata, Notechis scutatus, Pseudechis porphyriacus and Unechis gouldii) and two egg-laying (Pseudonaja nuchalis and P. textilis). The live-bearing species usually produce one clutch per year, a higher reproductive frequency than has been found in most previously studied venomous snakes. All live-bearing species show similar seasonal timing of ovulation and parturition. Gestation occupies about 14 weeks. The egg-laying species ovulate at about the same time as sympatric live-bearers, but oviposit shortly thereafter and may produce a second clutch of eggs in late summer. P. porphyriacus shows true 'viviparity', including placental transfer of nutrients (ash content of oocytes increases during gestation, energy content decreases only slightly). The live (wet) weight of the oocytes increases up to fourfold during gestation in live-bearing species, but dry weights change very little. Extra-uterine transfer of oocytes is common. Infertility is rare in A. superbus and P. porphyriacus, but frequent in N. scutatus. Clutch size is correlated with maternal body size in all species. The ratio of clutch weight to body weight decreased slightly with increasing maternal size in N. scutatus and P. porphyriacus. Published data on reptilian 'reproductive effort' are reviewed.

Abstract: SUMMARY 1. Some aspects of the response of mammalian skeletal muscle following the injection of purified toxins from the venom of the Australian tiger snake, Notechis scutatus scutatus, are described. 2. The toxins used were notexin, notechis II-5, notechis II-1 and a modified form of notexin (PBP-notexin). They were injected into the dorso-lateral aspect of one hind limb so that the soleus muscle would be exposed to the toxins. 3. Within 1 h after the injection of notexin, the soleus muscles were oedematous and by 3–6 h, polymorphonuclear leucocytes had entered the interstitial spaces. The invasion of necrotic muscle fibres was extensive by this time. Muscle spindles appeared relatively unaffected by the toxin. 4. The muscle regenerated via myoblasts at 2–3 days to myotubes at 3–5 days, immature muscle fibres at 7–14 days and fully differentiated muscle fibres by 21–28 days. Even after 6 months, however, the nuclei of many muscle fibres remained in a central position. 5. A second component of Australian tiger snake venom was also found to be myotoxic. It was slightly less potent than notexin, but caused qualitatively similar damage to that caused by notexin. It was identified as notechis II-5. A third fraction, notechis II-l, was found to be inactive. 6. Notexin could be neutralized by incubation with tiger snake antivenene; the simultaneous injection of antivenene with notexin did not afford complete protection against muscle damage.

Abstract: 1. The acute effects of a purified toxin from Australian Tiger snake (Notechis scutatus scutatus) venom have been investigated at the mammalian neuromuscular junction.2. The toxin was injected into the tail vein of mice. Death was due to respiratory paralysis.3. The resting membrane potential, and action potential of muscle fibres in muscles from in vivo intoxicated animals were normal.4. The frequency of miniature end plate potentials (m.e.p.p.s) from intoxicated nerve-muscle preparations was reduced, although m.e.p.p. amplitude was unaltered.5. Nerve stimulation resulted in end plate potentials (e.p.p.s) of quantal amplitude; only rarely was the e.p.p. large enough to give rise to an action potential.6. High (20 mM) K(+) did not increase m.e.p.p. frequency in intoxicated preparations.7. The toxin was largely ineffective in vitro.8. The similarities and differences between this toxin, beta-bungarotoxin and botulinum toxin are discussed.