NEWS AND VIEWS DAEDALUS------,------Coelenterates (2) modified . Such an idea fits ----{===== (4) well enough with the evidence that mol­ r (4) Catching the eye ------ luscs are primitively metameric, but it 1------ does not fit traditional ideas on the de­ DAEDALUS once invented a novel women's ,------Chelicerate velopment of the coelomic body cavity. anti-wrinkle face cream, inspired by those ,.....----- (3) ,-----Oligochaete Annelid worms have a capacious spectacle lenses that darken in sunlight. Its 1-----Polychaate annelid coelom, as do , but arthropods fast-acting pigment lightened in the L.....r----- Pogonophore and molluscs have only rudimentary shadowed crevices of the wearer's face, but Braohiopod CMon coelomic cavities, generally interpreted as darkened on the smooth well-lit areas -""1---Nudibranch ~use reduced or vestigial. The major body between them. This abolition of optical Bivalve molluscs (2) cavity in arthropods is the haemocoel, a contrast made the wearer's wrinkles almost Sipunculid capacious blood which impossible to detect. Unfortunately, it also FIG . 2 Topology interpreted from two trees8 in some arthropods and molluscs serves abolished perception of her facial style and calculated by evolutionary parsimony from the much the same function - a hydrostatic expression. The new cosmetic turned the same alignment of 18S rRNA as Fig. 1, with skeleton - as does the coelom in an­ most vivacious woman into a sort of dead­ the addition of three sequences (a nelids. The most widely accepted schemes pan zombie. Bafflingly, it sold mainly to conchostracan, a notostracan and a pen• of coelomate history treat arthropods and men - government spokesmen, tastomid19) . Numbers in brackets after group psychia­ names indicate the number of species molluscs as derived from annelid-like an­ trists, police interrogators, and others sampled . The tree is rooted on the coelenter• cestors by reduction of the coelom of the anxious to give nothing away. 8 20 ates. In the published tree the three longest circulatory system into a haemocoel'· • But So Daedalus is now turning the idea on its (most rapidly evolving) branches are Droso• Lake's tree implies that a haemocoel is head. Some pigments, like thionine, amplify phila, the sipunculid Golfingia and the tuni• primitive for (Fig. 2, insect optical contrast: they are bleached by light, cate Styela, respectively with about 56, 55 and below) because haemocoelic and darkened by shade. DREADCO's new and 37 transversions per 1,000 nucleotides. branch off at each of the first three nodes. 'Eyecatcher' cosmetics use this effect to Echinoderms (a crinoid , an echinoid, a brit• In dealing with relationships as remote enhance the optical contrast of a woman's tlestar and a starfish) did not emerge as as those between arthropods and other face, giving her an appealing facial live­ monophyletic in the published tree. phyla, we are certainly asking about liness and dynamism. Contrast amplifica­ more, but it has not yet been put to work). events in the , because tion is fast, but limited to the red region of In many-taxon problems, Lake gets round arthropods, molluscs and are the spectrum, so that blushing and other this disadvantage by repeated sampling, all known in early rocks. Inter­ dynamics of complexion are emphasized, 20 calculating four-taxon trees, retaining all estingly, Valentine , in a recent analysis while the wrinkles are largely left alone. those with a central branch supported at of late Precambrian metazoan trace and Daedalus is even formulating an Eye­ the level of 5 per cent significance, and body fossils, concluded that the haemocoel catcher face cream for men, with a promise combining taxon pairs that are supported preceded the coelom, that arthropods did of added cragginess, stubblier stubble, and in every four-taxon tree containing them. not replace a capacious coelom but never heightened moodiness of expression. And Lake's metazoan tree (Fig. 2) shows the had one, and that arthropods did not arise for actors, Eyecatcher grease-paint wiJJ Deuterostomia (Echinodermata + Chor­ "from some plexus of annelid precursors, convey the most subtle nuances of dramatic data) as monophyletic, as does parsimony but that arose from among a anguish to the cheapest and most distant 6 analysis of the same data'· • Because plexus of ancestors". Such seats. evolutionary parsimony deals only with ideas seem best tested by analysis of fur­ Eyecatcher colours should also prove unrooted trees ( as do all methods of ther sequences from molecules conserved popular in clothing. Their exaggeration of analysing sequence data, unless one roots since the Precambrian, and 28S (large contrast between highlight and shadow on a particular taxon), Lake used coelen­ subunit) rRNA is an obvious target. D would subtly emphasize the contours and terates as the outgroup and looked for dynamics of the wearer's figure. This cun­ roots significant at the 5 per cent level. All Colin Patterson is in the Department of Pal• ning anti-camouflage would call attention aeontology, The Natural History Museum, five of those roots render arthropods London SW7 580, UK. to the body far more beguilingly than con­ paraphyletic, but one (Fig. 2) matches the ventional fluorescent colours. Joggers, traditional dichotomy between deutero­ 1. Field , K.G. et al. Science 239. 748-753 (1988). exhibitionists, entertainers and their many stomes and protostomes. Within pro­ 2. Walker, W.F. Science 243, 548-549 (1989). imitators would welcome Eyecatcher cloth­ tostomes, this makes the two uniramians 3. Bode , H.R & Steele, R.E. Science 243, 549 (1989). 4. Ax , P. in TheHierarchyofLife (edsFemholm, B., Bremer, ing, and so would hikers or explorers ( + myriapods) in this sample, in­ K. & Jornvall, H.) 229-245 (Excerpta Modica , Amster• setting out into dangerous wildernesses. dividually or together, the sister-group of dam, 1989). Mothers, teachers and prison governors 5 . Ghiselin, M.T. Oxford Survs £vol. Biol. 5, 66-95 (1988). the remaining arthropods (, 6 . Patterson, C. in The Hierarchy of life (eds Femholm, B., would also be keen to issue it to their more Crustacea) plus the annelids, pogono­ Bremer, K. & Jornvall , H.) 471-488 (Excerpta Medica, furtive and evasive charges. Amsterdam, 1989). phore, , molluscs and sipun­ 7. Lake, J.A. in The Hierarchy of Life (eds Femholm, B .. In the form of paints and decorative culid. Further, the most probable position Bremer, K. & Jornvall, H.) 273-278 (Excerpta Medica, material, Eyecatcher dyes would give of the sipunculid is as the sister of bivalve Amsterdam, 1989). 8 . Lake, J.A. Proc. natn. Acad. Sci. U.S.A. 87, 763-766 a splash of added drama and impact to molluscs, so rendering the para­ (1990). everything they touched. The depth of con­ phyletic (molluscs did not emerge as 9 . Manton, S.M. The Arthropoda (Clarendon, Oxford, trast that gives the sunlit tropics their sharp 1977). monophyletic in any of the distance or 10. Boudreaux, H.B. Arthropod Phylogeny with Special and almost passionate surreality, could be 6 parsimony trees,. ). Reference to Insects (Wiley, New York, 1979). magicaJJy imported into a misty northern 11. Lake, J.A. Mo/. Biol. £vol. 4, 167-191 (1987). In the more distal part of the 18S rRNA 12. Jin , L. & Nei, M. Mo/. Biol. £vol. 7 , 82-102 (1990). townscape or a quiet domestic interior. 19 tree, Abele and others have used Lake's 13. Li , W.H, Wolfe, K.H., Sourdis, J. & Sharp, P.M . Cold Eyecatcher varnish would bring out the method to confirm (P < 0.04) that the Spring HartJ. Symp. quant. Biol. 52, 84 7--856 (1987). 14. Penny, D. Nature 331, 111- 112 (1988). surface detail of engineering components Pentastomida ( worms), parasites 15. Lake, J.A. Nature 343, 418-419 (1990). under inspection. And antique dealers of tetrapod vertebrates usually given a 16. Gouy, M. & Li, W.H. Nature 343,419 (1990). would craftily apply it to their more bat­ 17. Felsenstein, J. Nature 335, 188 (1988). of their own, are modified crust­ 18. Cavender, J.A. Mo/. Biol. £vol. 6, 301-316 (1989). tered offerings, to point up cracks, warp­ aceans. Lake's tree might be read as 19. Abele, L.G., Kim, W. & Felgenhauer, B.E. Mo/. Biol. £vol. ing, grain, worm-holes and the other 6, 685----691 (1989). indicating that in cladistic terms annelids, 20. Valentine, J.W. Proc. natn. Acad. Sci. U.S.A. 88, 2272- authenticating stigmata of great age. molluscs and the other minor phyla are 2275 (1989). David Jones 200 NATURE · VOL 344 · 15 MARCH 1990