Number 8, February 2001
Editor and publisher: Julián Monge-Nájera, Biología Tropical, Universidad de Costa Rica 2060 San José, Costa Rica. Published since 1987.
Editorial Board: Bernal Morera (Barcelona, Spain), Zaidett Barrientos and Carlos Valerio (INBio, Costa Rica) and José Vargas (Universidad de Costa Rica).
Onychophora research at the end of the 20th century
The last five years of the 20th century were not the best in terms of the number of studies that were published, but in compensation, findings have been varied and very interesting. Among them, I can mention the proposal of two new families of onychophorans, the deactivation of the "Cambrian explosion" bomb, the rediscovery of Indian onychophorans, the raise of the total number of described species to 140 and the online publication of a large bibliography (nearly 1000 references) that hopefully will end the bloopers of papers that "rediscover warm water" (as we say in Spanish) when authors miss pertinent papers. The Onychophora Newsletter is approaching 15 years of publication: again I thank you all for your continued interest, for your support messages, for the reprints and for everything else. I hope to continue serving you for at least another 15 years. As usual, keep up the good work and your interest in velvet worms.
Two new families in the Onychophora
G. Poinar (USA) has described Tertiapatus dominicanus n.g., n.sp. (Tertiapatidae n.fam.) and Succinipatopsis balticus n.gen., n.sp. (Succinipatopsidae n.fam.) (Lobopodia: Onychophora), the first Tertiary fossils of the Lobopodia, from Dominican and Baltic amber; respectively. Fossil onychophorans are rare and these are the only known from amber. They show important differences from modern species, particularly in their legs. If accepted by the scientific community, the proposed two new families will double the current number of onychophoran families.
The Cambrian "explosion": where is the bomb?
Julián Monge-Nájera (Costa Rica) and Hou Xianguang (China) (Revista de Biologia Tropical / International Journal of Tropical Biology and Conservation 48 (2/3): 333-351, 2000) found that a mature ecological community structure was generalized throughout the world's tropics during the Cambrian (even biodiversity and equitability indices were surprisingly close to modern values) and that the morphological diversity and geographic distribution of onychophorans indicate a significant pre-Cambrian evolutionary history which does not support the "explosion" hypothesis. They add that disparity within the phylum was greater than it is today and its reduction may have been associated with migration into the sediment when large predators evolved.
Onychophorans and the evolution of arthropods
Jan Zrzavy and colleagues in the Czech Republic (Cladistics 14(3) 249-285) did a cladistic analysis of traditional (i.e. morphological, developmental, ultrastructural) and molecular (18S rDNA) data sets (276+501 informative characters) to study the relationships of all metazoan higher taxa and grouped the Onychophora with Tardigrada and Arthropoda. Although based on the infamous 18 S rDNA analysis, the study deserves some confidence because it takes into account morphological evidence and because it does not deviate from the traditional cladogram for this three groups, in which the Tardigrada are the weakest member (few characters support its presence here).
Andrés de-Haro in Barcelona, Spain (Boletin de la Real Sociedad Espanola de Historia Natural Seccion Biologica. 94 (1-2) 103-113) finished his comparative study of the cephalic region of Arthropoda, Onychophora, Annelida and Lophophorata. A common origin is proposed for them in a Coelomate trimeric organism. He added "that Onychophora is an adelphotaxon of Arthropoda".
Invertebrate Phylogeny for computers
D. Dudley Williams of the University of Toronto (firstname.lastname@example.org www.citd.scar.utoronto.ca/CITDPress/) has published the CD Invertebrate Phylogeny, a very innovative multimedia tool to teach invertebrate zoology. The Onychophora section is very good, updated to the year 2000 and illustrated with many color photographs. To study invertebrate evolution, the student navigates in a phylogenetic tree. Interactivity, the color illustrations and the automatically self-grading tests are an important advance over traditional textbooks.
Reproductive anatomy of Brazilian onychophorans
Muriel Walker and Sylvia Campiglia (Journal of Morphology. 237 (2) 127-136) studied the seminal receptacula of Brazilian Peripatus acacioi and found that it has a good oxygen supply. The ultrastructure of the epithelium lining the seminal receptaculum indicates that these cells secrete the material that forms the luminal matrix that surrounds and provides nutrition for the stored spermatozoa.
Indian onychophorans rediscovered
The Indian Peripatus, Typhloperipatus weldoni, has seldom been seen or collected and is also as misterious as the tropical African onychophorans. However, Indian zoologist A. Raghuvarman and colleagues recently rediscovered it and reported that males shed their sperm on the dorsal and ventral surface of the females (Journal of Endocrinology and Reproduction 1 (2) 80-85), just as occurs in some South African species. Then the spermatozoa may digest and dissolve the thin cuticle of the micropores by hyaluronidase that is probably present in the sperm heads and reaches the ovaries for fertilization.
Sympatric cryptic species in New Zealand onychophora
Steven A. Trewick (Biological Journal of the Linnean Society 63 (3) 307-329 used allozyme electrophoresis to study live-bearing Peripatopsid Onychophora from the North Island of New Zealand. Peripatoides suteri had little intraspecific genetic variation but within P. novaezealandiae five genetically differentiated species were identified although none showed any consistent morphological differentiatio. New Zealand authors normally enphasize the active geophysical history of the region and Trewick is no exception, discussing how this complex may result from interaction of geologic history and low vagility in onychophorans.
Onychophora of South Africa revisited
M. L. Hamer and colleagues (Annals of the Natal Museum 38 (0) 283-312) reviewed the nine described species of South Africa, two in Opisthopatus Purcell, 1899 and seven in Peripatopsis Pocock, 1894. These species are redescribed, illustrated and keyed to facilitate future ecological and biodiversity studies. The authors suggest that at least another five undescribed species exist. In the past, South Africa was a leader in the study of onychophorans, but production greatly decreased after the Second World War. The country has, however, a powerful scientific establishment and this revision should allow a revival of onychophoran studies in the land of Mandela.
Intensive research on Australian onychophorans
The last years have been marked by a steady flow of papers about Australian onychophorans: Australia has replaced Costa Rica as the most productive country for this group. Here is a summary of work on down-under species.
P. Sunnucks and several Australian colleagues (Journal of Zoology 250: 447-460) have reviewed the reproductive biology of the ovoviviparous peripatus Euperipatoides rowelli which was found to comply with the general trends published six years ago for the phylum in general (Monge-Nájera, J. 1994. Reproductive trends, habitat type and body characteristics in velvet worms (Onychophora). Rev. Biol. Trop. 42 (3): 611-622). A female can harbour one developed and one undeveloped batch of embryos in each uterus. Excesses of developed embryos in one uterus are counterbalanced by deficits of undeveloped ones, indicating that females can use their paired reproductive tracts independently. Gestation may require six months or more and sperm is stored in good conditions for at least 9.5 months.
N. Curach & P Sunnucks (Molecular Ecology 8: 1375-1386) believe that cryptic species are common and studied the high local endemism of Australian onychophoran, Euperipatoides rowelli. They found that more than 70% of females had broods with multiple paternity and suggested that this may increase the genetic diversity of offspring, possibly to compensate for the low genetic diversity at the population level.
P. Sunnucks and A. C. C. Wilson (Molecular Ecology 8: 899-900) discovered that genetic work with onychophorans can be very difficult. Despite extensive optimization of many primer pairs, only five useable loci were obtained in Euperipatoides rowelli. Under standard conditions, only loci P6 and P23 gave scoreable polymorphic patterns of the expected size. Nevertheless, they concluded that E. rowelli is a species complex because adjacent populations can differ by 20% or more in mtDNA COI sequence.
K. Bittner and colleagues (Acta-Zoologica 79 (4) 267-275 have studied the ultrastructure of Austroperipatus aequabilis and found that, like Neotropical onychophorans, it has the "upside down" cell that has regularly been found in all sensilla bearing a sensory peg (apart from the sensilla they also occur within the labial epidermis. Since most sensilla contain several different receptor cells, these authors consider them to be complex sense organs, but the physiological-ethological work that would complement this type of observations is still scanty and much needed.
C. Brockmann and colleagues (Entomologica Scandinavica Supplement. 1997; is. 51: 319-329) studied the morphology of Ooperipatellus decoratus (Baehr, 1977) and found that the genital tract of adult females lacks the receptacula seminis found in juvenile females. Albeit they lacked exact egg-laying dates, their observations provide some support for a 19th century report that eggs might require as much as about one year to hatch.
The Onychophora of Mexico
In Arthropods of Mexico, published in the year 2000 by the Universidad Nacional Autónoma de México, the very poorly studied onychophoran fauna of that large neotropical country was treated by J. Monge-Nájera. Only three species have been described from Mexico: Oroperipatus eisenii (Wheeler, 1898), Oroperipatus goudoti (Bouvier, 1899) and Macroperipatus perrieri (Bouvier, 1899), while at least 14 species are expected to exist. The area around Mazatlán should receive special attention in future surveys to better establish the northern limit of the phylum in the American continent. Onychophorans probably arrived in Mexico from South America in the last five million years. The chapter also analyses the economic potential of onychophorans in ecotourism, as specimens for zoology courses and in microsurgery. Onychophora Bibliography approaches the 1000 references
A frequent problems with onychophoran papers, particularly acute in North America, is their poor review of the literature. Pertinent papers are not cited, and worse, the information they contain is clearly unknown by authors in detriment of their own work. Since 1999 I have tried to solve this problem by including abstracts and a bibliography in my web site Onychophora Online (See "Organisms" in Tropiweb, www.ots.ac.cr). The bibliography was kindly prepared by M. T. Ghiselin. Now an updated Onychophoira Bibliography compiled by Michael T. Ghiselin (California Academy of Sciences) and Michael L. Grieneisen (email@example.com, Scientific Reference Resources) is available and has 957 references, from "Aguinaldo, A.M.A.; Turbeville, J.M.; Linford, L.S.; Rivera, M.C.; Garey, J.R.; Raff, R.A.; Lake, J.A. (1997) Evidence for a clade of nematodes, arthropods and other moulting animals. Nature 387(6632): 489-493" to "Zrzavy, J.; Stys, P. (1995) Evolution of metamerism in Arthropoda: Developmental and morphological perspectives. Quarterly Review of Biology 70(3): 279-295. You can use (even search) that bibliography free of charge.
Onychophora Mailing List and new CIM web page
Michael L. Grieneisen has established an Onychophora mailing list for exchange of ideas, questions, answers and news.
If you wish to participate, please visit http://www.onelist.com/community/onychophora. Additionally, the Centre International de
Myriapodologie (Paris) has established a web page that you should see at: www.mnhn.fr/assoc/myriapoda/INDEX.HTM
It includes a section on Onychophora. The CIM also publishes a bulletin with yearly bibliographies, an interesting "In memoriam" section, news about workshops and congresses, a directory of members, etc. The bulletin is "a must" for anybody interested in myriapods in general.