Hatchlings remain in the burrow for about 130 d ( Holland and Jackson 2002), during which time they suckle from maternal “milk patches” ( Grant 1995). 1998) and comparable in development to a newborn marsupial ( Manger et al. The incubation period for eggs is thought to be only 6–10 d ( Grant 1995), so at hatching, the nestlings are only about 15 mm long ( Grant 1995 Manger et al. The gestation period of the platypus probably lasts between 15 and 21 d ( Holland and Jackson 2002).
The monotremes have features that place them definitively within the class Mammalia but are unique in laying eggs rather than giving birth to live young.
Convergent evolution has repeatedly selected genes coding for proteins containing specific structural motifs as templates for venom molecules. Here we show that several venom components have evolved separately in the platypus and reptiles. This led us to trace the evolutionary origins of other components of platypus and reptile venom. Intriguingly, some species of snakes and lizards also produce venoms containing similar molecules called crotamines and crotamine-like peptides. The OvDLP genes are located adjacent to the beta-defensins and share similar gene organization and peptide structures. We show that gene duplication and subsequent functional diversification of beta-defensins gave rise to these platypus OvDLPs. While searching the platypus genome for the sequences of antimicrobial defensin genes, we identified three Ornithorhynchus venom defensin-like peptide (OvDLP) genes, which produce the major components of platypus venom. The platypus genome sequence provides a unique opportunity to unravel the evolutionary history of many of these interesting features. Rather than delivering venom through a bite, as do snakes and shrews, male platypuses have venomous spurs on each hind leg. It is a most remarkable mammal, not only because it lays eggs but also because it is venomous. Similar spurs are found in many archaic mammal groups, indicating that this is an ancient characteristic for mammals as a whole, and not exclusive to the platypus or other monotremes.When the platypus ( Ornithorhynchus anatinus) was first discovered, it was thought to be a taxidermist’s hoax, as it has a blend of mammalian and reptilian features.
Since only males produce venom and production rises during the breeding season, it may be used as an offensive weapon to assert dominance during this period. The venom appears to have a different function from those produced by non-mammalian species its effects are not life-threatening to humans, but nevertheless powerful enough to seriously impair the victim. The female platypus, in common with echidnas, has rudimentary spur buds that do not develop (dropping off before the end of their first year) and lack functional crural glands. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to a calcaneus spur on each hind limb. Oedema rapidly develops around the wound and gradually spreads throughout the affected limb. Although powerful enough to kill smaller animals such as dogs, the venom is not lethal to humans, but the pain is so excruciating that the victim may be incapacitated. The function of defensins is to cause lysis in pathogenic bacteria and viruses, but in platypuses, they also are formed into venom for defense. The DLPs are produced by the immune system of the platypus. While both male and female platypuses are born with ankle spurs, only the spurs on the male's back ankles deliver venom, composed largely of defensin-like proteins (DLPs), three of which are unique to the platypus.
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