On the affinities of the burrowing asps Atractaspis (Serpentes: Atractaspididae)

An analysis is presented of a sample of Atractaspididae ( sensu McDowell) plus Macrelaps, Aparallactus, Apostolepis, Elapomorphus, Homoroselaps and six genera of African elapids in respect of squamation, reproductive organs, skull, head muscles and vertebrae. Homoroselaps is linked with the African Elapidae and is returned to that family. Scattered special resemblances to atractaspids are interpreted as homoplasies. Some interrelationships of the African elapids are suggested. The South American Apostolepis and Elapomorphus represent a separate, possibly related, lineage at the same grade level as the African Atractaspididae. Macrelaps and Aparallactus are transferred to the Atractaspididae. Atractaspis emerges as a low grade but highly divergent member of the family. Macrelaps is the most primitive. The other taxonomic units are completely resolved with, however, the anomaly of reversal to the seemingly primitive states of six characters in four lineages (six genera). The Atractaspididae, Apostolepis and Elapomorphus are regarded as low grade members of the Caenophidia. It is suggested that early in the history of the caenophidian lineage a venom apparatus was acquired, prior to the major radiation of the group. Many descendent lineages show regression of the venom apparatus.     

Venom Toxins: Plausible Evolution from Digestive Enzymes

Some hydrolytic enzymes are common to the pancreas, the mammaliansalivary glands and the snake venom glands. Phospholipase A,which is found in elapid and viperid venoms and in the mammalianpancreas, shows 29 common amino acid residues out of 118–125positions. Presynaptic neurotoxins and other venom toxins areusually composed of 2–3 units or subumts,one of whichis a phospholipase. The Vipera palaestinae two-component toxinretains its lethality when the enzyme is replaced by heterologousvenom phospholipases, but not by the pig pancreatic enzyme.This toxin is neutralized by a factor found in the blood serumof snakes, which binds to the phospholipase and inhibits itsactivity. The blood serum of snakes also neutralizes hemorrhaginsand inhibits the protease activity of the venom. It is hypothesizedthat the developing venom glands first produced enzymes thatwere already secreted by the pancreas and against which inhibitorswere present in the blood. These inhibitors facilitated theevolution of enzyme-based toxins by neutralizing any damagingsubstances that might have escaped from the venom glands.     

The salivary glands of Aparallactinae (Golubridae) and the venom glands of Elaps (Elapidae) in relation to the taxonomic status of this genus

The venom glands of four specimens of Elaps lacteus were examined and found to be structurally similar to the glands of other Elapidae and consequently different from the variable glands of the colubrid Aparallactinae, Lycophidinae and Dispholidinae. The recently proposed removal of Elaps from the Elapidae and its inclusion in the Aparallactinae (McDowell, 1968) is discussed, and the conclusion is reached that Elaps should remain within the Elapidae.