By Les Minter
The Cape Fold Mountains, with their amazing floral diversity and relict patches of indigenous forest are a pleasure to explore, and many do, but few are familiar with one of their most interesting inhabitants, the Velvet Worm, also known as Peripatus.
The word peripatus is derived from “peripatetic”, which is seldom used in everyday conversation, perhaps because it sounds like “very pathetic” when you say it, especially if you are wearing dentures: it means wandering, itinerant, roaming or nomadic, and that’s exactly what velvet worms do: wander around amongst the leaf litter on the forest floor at night, after rain, when it’s nice and wet, looking for food.
When you pick one up it usually lies motionless in your hand for a while, and
then rights itself and wanders off, unhurriedly and rather gracefully (for a worm), on its many pairs of little podgy legs.
Forests are quiet, cool places, like churches and cathedrals, and the perfect place to sit and introspect. While so occupied, you may want to indulge in a bit of observation too and try to find one of these creatures.
The best way is to carefully look under the bark of wet, decaying logs on the forest floor or break open small pieces of moist, rotting wood, trying not to create too much of a disturbance, and putting the bits back where you found them.
You will come across a host of creatures that live in this microhabitat, including beetles and their larvae, woodlice and their relatives, amphipods, (that leap about wildly when disturbed), millipedes, centipedes, occasionally, small, harmless black scorpions with thin tails, spiders and, if you are lucky, velvet worms!
The reward for all this effort, is to be looking at a creature that has come down to us from the Cambrian, surviving a series of major extinction events brought about by global warming, cooling, asteroid impact or large-scale larva flows, that eliminated major animal groups such as the trilobites, ammonites, and dinosaurs, leaving only fossils in their wake!
The Cambrian, in case you were wondering, is a Geological Period of earth history (485-538mya). The name was given to a succession of rock strata in Cambria (Wales) by Adam Sedgewick, a professor of geology at Cambridge.
The Cambrian was a time when Nature seemed to be experimenting with the newly evolved multicellular forms of life. In a relatively short period of geological time, referred to as the Cambrian Explosion, a wide variety of novel groups of animals appeared in the oceans.
Among these were elongated, worm-like animals with multiple pairs of short stubby legs (called lobopods) that ended in a pair of hooked claws. They bear a remarkable similarity to velvet worms and are thought to be ancestral to this group.
One of them, from the Burgess Shale in Canada, was so bizarre that it was named Hallucigenia “because it looked so dreamlike”! Closer to home, a fossil Lobopod was found, in 2009, in the Cedarberg Formation near Clanwilliam. It died about 444mya during the Ordovician Period.
Those of you that enjoy the comic character Asterix, might be interested to know that this geological period is named after a fierce tribe of Celts in Wales, the Ordovices, who were a thorn in the side of the Roman invaders, and the last to be defeated by them! The Cedarberg Formation also outcrops in several places in the Tradouw Pass, as a thin layer of white or yellow sandstone that weathers easily – look for it on the left as you pass the gate of Stonehaven.
About 230 species of velvet worms have been described, but recent studies indicate that there are many more cryptic species. Almost all the species occur in the southern hemisphere, where they seem to have diversified before the break-up of Gondwana. They come in an assortment of colours, including red, white and blue (no U.S. propaganda intended), have 13 – 34 pairs of legs and reach 20cm in length.
P. overbergiensis from Grootvadersbosch, Marloth and De Hoop Nature Reserves are only 14-32mm long and their colour ranges from black, grey, maroon or orange above, and creamy- white to orange below.
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They feed on other invertebrates in their habitat, locating them with their mobile antennae (their eyes are not designed to provide sharp, detailed images). Prey is immobilised by two streams of a very sticky secretion, ejected at high speed from glands on either side of the mouth – these open on nozzles that can be aimed directly at the prey.
They then use their sickle-shaped jaws and strong digestive enzymes to consume their food. It seems that Velvet Worms have thoroughly explored the possibilities of sexual reproduction: some lay eggs with beautifully sculpted shells, others are fully live-bearing and nourish their embryos internally with placenta-like structures attached to the wall of the mother’s uterus, while still others have eggs that are retained in the body until they hatch, upon which the young emerge from their
The method of fertilisation is equally varied. In South African species, males deposit packages of sperm, called spermatophores, on the female’s skin, and specialised cells (haemocytes) invade the point of contact, creating a hole through which the sperm enter and make their way to the female genital tract.
They may be stored there for long periods before being used to fertilise the eggs. One study showed that females are able to keep the sperm from different males apart and choose which sperm to use for fertilisation! In other species, males place their sperm directly into the genital tracts of the female. And of course there are always the exhibitionists, who wrap their sperm in ornate packages which they place on their heads, ready to be transferred to the opening of the female genital tract.
For more on the biology of Velvet Worms, see Velvet Worms by Blaxter and Sunnucks, in Current Biology Vol 21 No 7. Also, https://australian.museum>learn>animals>worms>velvet-worms
*Les Minter is a retired herpetologist and is therefore someone with friends in low places.