No. 4 September 1993
Editor and publisher: J. Monge-Nájera.
Editorial Board: B. Morera, C.E. Valerio, J.A. Vargas
As we reach the fourth year of publication, we are happy to see that the newsletter has fulfilled its goal of communicating professionals and "fans". Of course the most outstanding event in many years was the celebration of the first world meeting on onychophorans last September in Leicester, England. This was the result of much enthusiasm and even more work by Muriel Walker, who is now preparing some of the papers for a special issue of the Zoological Journal published by the Linnean Society of London. This issue of the Newsletter is chiefly dedicated to presenting the results to those who could not attend. For financial reasons I was one of them and want to thank Muriel for nevertheless allowing the presentation of a paper in absentia. ""Merci" also to the organizers of this year's Congress of Myriapodology in Paris for the same favor. Since the last issue, I had the honor of hosting, from Germany, Volker Storch, Hilke Ruhberg, Wolfgang BÆckeler and associates, and Ines and Gero Hilken; from the United States Rick Gore and Louis Mazzatenta (fromNational Geographic) and from Austria Gunther Pass and several colleages. Perhaps you, dear reader, will be the next to visit us in our beautiful onychoporan habitat ... Until next time, best wishes to all of you.
An Overview Of Leicester's "Onychophora 92" With Up-date Notes
During the Leicester meeting, Hilke Ruhberg (Hamburg) went directly to the rub when she presented her qualified review of the "genus" concept in onychophorans. She explained that morphological characters traditionally used to erect genera are often problematic, and that we must look not only closer, but from different angles, before delimiting genera. A closer look often (but not always) means electron microscopy, and new angles include biochemical and chromosome analysis.
Just as M. Read did about eight years ago for feeding behavior, Jonathan Wright (Ontario) put more accurate numbers to what we already knew about water exchange in onychophorans (he used Peripatopsis capensis ). As all previous authors, he found that onychophorans are highly sensitive to dehidration. Interestingly, experiments reported recently in Paris (Myriapodology Congress) by Monge-NÆjera, suggest that Epiperipatus biolleyi is unable to assess humidity in the absence of light and air currents. Perhaps (and just perhaps) avoiding air currents and strong light equaled protection from dehydration throughout onychophoran evolution and there was no need to develop additional humidity sensors.
Volker Storch (Heidelberg) reported that while onychophoran spermatozoa are not morphologically very different from other organisms, spermatogenesis is atypical. He opposed the now less popular view that onychophorans are closely related to the Pentastomida.
The fruitful cooperation of Muriel Walker (England) and Sylvia Campiglia (Brazil) which previously mentioned the possibility of a fully new view of the onychophoran "placenta" as a simple anchor, now produced a very detailed acount of embryo development in one of the most intensively studied species: Peripatus acacioi. Their new evidence indicates that material may indeed be taken from the maternal haemocoel, stored in the placenta and released into the embryo cavity: then, the placenta is more than an anchor.
Walker also revisited the embryogenesis of South African Opisthopatus cinctipes , which is atypical because the embryo elongates without any visible segmental boundaries. This apparently is an autapomorphy of "recent" origin: no more than 30 million years BP, according to their allozymes.
D. Stanton and colleagues (USA and Canada) reported that the mitochondrial genome size of Plicatoperipatus is only 14.6 kilobases long, very near the minimum possible size to code enough data for cell respiration, a fact which leaves us almost breathless...
Australian researchers Tait, Briscoe and colleagues presented several papers on genetic make up. Australian peripatopsids vary in caryotype size from (2N=) 18 to 42 chromosomes. Sex chromosomes are either indistinguishable or of the XY type. In general, variability is high and evidence suggests that isolated morphological study is likely to fail in distinguishing closely related species. This reports are all but happy news to those who need reliable identifications as a basis for physiological, ethological and ecological research, for example. A safe working rule for onychophorologists seems to be "limit yourself to a small area and deposit vouchers". This will reduce the danger of later discovering that one lumped together data from several species!
Isolation in moist mountains separated by a sea of arid land is a fact for Cephalofovea tomahmontis and may in time lead to divergent speciation of this strange species for which an extraordinary mating mechanism was hypothetized in a previous issue of this newsletter. Isolation is also a key word for the species of New Zealand and Tasmania. The first shares only one species with Australia, with which it has not been terrestrially connected for many millions of years. In contrast, Tasmania has repeatedly been connected and has the taxon "Euperipatoides leuckartii", which ranges to various parts of Australia and may in fact represent several sibbling taxa. From the other extreme of the World came Marielos Mora and Pedro Morera's (Costa Rica) study of E. biolleyi's genome. It has a haploid DNA value of 4.7 pg and a bimodal karyotype with many small and a few large chromosomes. The content of guanine and cytosine is very low and there are repeated sequence families. Preliminary evidence suggests the ocurrence of antennapedia genes, a statement that may appear uninteresting unless one mentions that if these authors are right, they will re-date evolution of such genes by more than 100 million years!
A good advise for the person who wants to study onychophorans is "first find some". Yet collecting them has never been easy (except perhaps in parts of South Africa) because they are rare. The time has come unfortunately to add a seccond reason for failing to find them: population reduction and even possible extinction caused by humans. Onychophoran conservation was analysed by Robert Mesibov and T.R. New, both from Australia. They concluded that assessing population trends and mapping distribution were of key importance and should be followed by habitat management. Mesibov, whose pioneering work deserves much praise, adds that mapping and management "are being done relatively cheaply in Tasmania", and with the financial support that onychophorology receives worldwide, "cheap" is a key word...
Hou Xianguang and Jan BergstrÆm (Nanjing and Stockolm) presented evidence favouring the identification of Cambrian oncopodophore animals (also known as "lobopods") as early members of the Onychophora clade. Although this view will not necessarily be accepted by everyone, the balance at the moment is that general morphology, skin structure, size and the newly discovered mandibles of Chinese specimens are identical to those of living onychophorans. Hopefully a more decisive argument will result from the ongoing joint project between Hou and Monge (Costa Rica), in which a morphometric comparison is being applied to fossil and living taxa.
At Leicester, Monge presented a cladistic study of living and fossil genera, suggesting that the ancestral onychophoran was a predatory marine species related to the polychaeta, with long oncopods, plate armouring and an annulated body. Apparently the phylum colonized the land in the late Cambrian or early Ordovician, developed the adhesive glands to capture prey and soon divided into the two current families. The presentation included a vicariant biogeographic analysis and a list of inbreeding adaptations found in some species, but the key feature of the paper was the attempt to put morphological, physiological and genetic information consistently in an evolutionary perspective.
Elaine Robson«s abstract does not have enough information for inclussion here, but Ballard et al.'s claim of RNA indicating that onychophorans are modified arthropods deserves comment. Their report probably was received with a distrust smile by onychophorologists, because it contradicts most morphological and physiological evidence. Time will probably show that genetic evidence is fallible and should complement rather than substitute a sound body of knowledge from other fields. That is exactly what happened to embryology which twenty years ago made the same claims to support the Uniramia hypothesis, an idea which has very few supporters (if any) today.
You Can Protect Onychophorans: The Conservation Questionaire
A questionnaire on endangered onychophoran populations is circulating. Interested readers may contact Dr. Robert Mesibov, P.O. Box 700, Burnie, Tasmania 7320, Australia. Please transmit this information to museum curators, universities and societies within your geographic area!
A New Onychophoran Family?
Muriel Walker has suggested that some pecculiarities of Opisthopatus may justify erection of a new family and she wisely stated that a concensus would be necessary to make such a significant modification. She welcomes opinions.
Hilke Ruhberg is creating a collection of onychophoran photographs which will be available to serious researchers and the like. You should send her duplicates of all you got, properly labelled.
Mario Vargas (Costa Rica) is organizing the first Art-Science Photo Expo event showing photographs of onychophorans selected for art's sake. The models will be E. biolleyi and Epiperipatus isthmicola.
Onychophoran Curiosities In Coronado, Costa Rica
While doing field work, the editor has learned that (quite unespectedly) onychophorans have some local folklore in Costa Rica. One person in Coronado said that their adhesive secresion eliminates warts and another explained that it can make snakes loose their skin. The origin of these beliefs is not hard to imagine: independently of onychophoran presence, warts are related to viruses which reflect physiological effects of stress and thus easily appear and disappear. Snakes shed their old skins periodically: probably someone put onychoporans and snakes together in a bag, saw the snake discard its old skin, and jumped to conclusions. Finally, we are pleased to report that our local guide bought a young milking cow with the money he has saved from onychophoran tours for visiting scientists. Perhaps "Peripata" would be a proper name for the cow...