Friday, November 19, 2010

Splinters from the Cambrian explosion

One would love to be in a number of places but sadly this cannot be. Fortunately India is filled with people and hopefully there is someone near where I want to be, reading this, who can follow this up. The place I want to be in now is Rotung on the Dihang River, in Assam, not for birding although I would certainly look at the birds of the region, but to lift up and look under some stones and rotting logs in shaded humid places covered with a lot of leaf-litter. What I would be looking for is an animal from our deep evolutionary past - an animal that belongs to a phylum that is hardly even mentioned in college-level biology textbooks.

Meet Typhloperipatus williamsoni - the only representative of the Onychophora in the Indian region. Discovered in 1913 by Stanley Wells Kemp the Superintendent at the Indian Museum at  Calcutta when he went on the Abor expedition, hardly anything is known about this "velvet worm". The expedition really came about due to a local revolt in which the political officer of Sadiya, a Noel Williamson commemorated in the species name,  was killed. Strangely it seems that even political missions in those days had a zoologist on board!

Rotung in red ( )
The expedition found it under rocks along the Dihang river near Rotung. Fortunately one can locate the location today - and I can share the map because it is published by the US military and is therefore in public domain. The irony is that tax-payer funded work of the Indian government has to be purchased and even if you do, it is copyrighted and you are not even allowed to make a tracing of it ! And to add to all this sadness, little has been known about this species thanks to the wonderful way in which Indian establishments keep useful material away under lock and key - away from any interested researcher and available only to feed the far more needy Dermestidae and Thysanura. So imagine the joy when I finally get to access (thanks to the Biodiversity Heritage Library - an effort that has zero support from Indian museums and libraries) the scanned versions of the Records of the Indian Museum with the original description of Typhloperipatus. The genus name is from typhlo for blind and peripatus, an existing major genus of velvet worms was given since these worms were completely blind. The word Peripatus itself is derived from a path around a school, the one in which Aristotle taught and walked in a peripatetic way.
Peripatoides sp. (photograph by Bruno Vellutini)

The velvet-worms or Onychophorans are a mysterious group. They are found across the tropical zone and it is believed that their origins were in Gondwana. They were among the early land pioneers and we know that for certain, as they continue to require high humidity conditions to survive. Their unique body plan consists of a soft worm like body without an exoskeleton or clear segments and their legs are soft and tubular. There are no joints, the legs move by hydrostatic pressure - in effect they move somewhat like a caterpillar with tubular balloon legs that are inflated and deflated to achieve movement. The ends of these feet have tiny claws - from which the group is name is derived (Gr. onyches = claw) and the ancestry of the group and relationships is still much debated. Some have considered them as the leggy link between the annelids and the arthropods and their ancient divergence makes them difficult to study even using genetic material. They moult to grow and this has been used to place them in a suggested clade called the Ecdysozoa with the arthropods and other groups. Onychophora are mostly nocturnal, they have antennae with which they feel for prey - mostly small invertebrates - and when prey is detected, they squirt a sticky fluid, spiderman style, which arrests the victim. They then inject digestive juices into the prey and wait for the food to liquify and then suck it up along with their sticky slime. 
Close ups from the description of Typhloperipatus

Almost nothing is known about our Indian species, indeed nothing has perhaps ever been published after its discovery around 1913. Almost all members of the Peripatidae are on the endangered list - the Indian species however has evinced almost no interest - which is not surprising given that most conservation is money-dependent and small fleshy invertebrates lack the glamour needed to support flight and hotel bills. If ever the species can be found at Rotung or nearby regions in Assam, hopefully by interested locals (hope there are students, teachers and zoology enthusiasts reading) - the regions should be well worthy of some protection.

The Indian species is probably restricted north of the Brahmaputra - a major biogeographical barrier. Any relative discovered in south-western India would be even more spectacular, for it would probably show affinities to species from southern Africa.

Here is an extract from the original description:
The camp at Rotung where the majority of the specimens were found was situated at an elevation of 1320 ft. on a small plateau above  the Dihang River, one of the few approximately level pieces of ground seen in the Abor country. The site was at one time occupied by a village of Minyong Abors; but this was demolished in the latter half of 1911 and the villagers put up temporary dwellings half a mile further to the north at a considerably greater elevation.

The country in the vicinity of the camp was overgrown with dense scrub-jungle interspersed with stones and large trees, mostly jack-fruit. Here, as in so many parts, the ground had at one time been cleared for cultivation and scrub, which as a rule was not more than ten feet high, probably represented some eight or ten years' growth.

It was on the eastern side of the camp on dry gently sloping ground immediately above the edge of the great gorge of the Dihang River that Peripatus was found.

Solitary individuals were occasionally met with, but more usually two to four adults accompanied by a numer of young (sometimes as many as six) were collected together.
Further reading

Some videos to see