Development Genes and Evolution

, Volume 216, Issue 7–8, pp 481–491 | Cite as

Hox genes in sea spiders (Pycnogonida) and the homology of arthropod head segments

  • Michaël ManuelEmail author
  • Muriel Jager
  • Jérôme Murienne
  • Céline Clabaut
  • Hervé Le Guyader
Original Article


The pycnogonids (or sea spiders) are an enigmatic group of arthropods, classified in recent phylogenies as a sister-group of either euchelicerates (horseshoe crabs and arachnids), or all other extant arthropods. Because of their bizarre morpho-anatomy, homologies with other arthropod taxa have been difficult to assess. We review the main morphology-based hypotheses of correspondence between anterior segments of pycnogonids, arachnids and mandibulates. In an attempt to provide new relevant data to these controversial issues, we performed a PCR survey of Hox genes in two pycnogonid species, Endeis spinosa and Nymphon gracile, from which we could recover nine and six Hox genes, respectively. Phylogenetic analyses allowed to identify their orthology relationships. The Deformed gene from E. spinosa and the abdominal-A gene from N. gracile exhibit unusual sequence divergence in their homeodomains, which, in the latter case, may be correlated with the extreme reduction of the posterior region in pycnogonids. Expression patterns of two Hox genes (labial and Deformed) in the E. spinosa protonymphon larva are discussed. The anterior boundaries of their expression domains favour homology between sea spider chelifores, euchelicerates chelicerae and mandibulate (first) antennae, in contradistinction with previously proposed alternative schemes such as the protocerebral identity of sea spider chelifores or the absence of a deutocerebrum in chelicerates. In addition, while anatomical and embryological evidences suggest the possibility that the ovigers of sea spiders could be a duplicated pair of pedipalps, the Hox data support them as modified anterior walking legs, consistent with the classical views.


Arthropoda Chelicerata Development Evolution Homology Hox genes Pycnogonida Segments 



We thank the Station Biologique de Roscoff for providing lab facilities for specimen collection and preparation. We are grateful to Jean Deutsch, Eric Quéinnec and Nicolas Rabet for advice and discussion, to Pierrette Lamarre for technical help, and to Thierry Jafredo for lab facilities. This work was founded by CNRS and the French Ministry of Research.

Supplementary material

427_2006_95_MOESM1_ESM.jpg (179 kb)
Fig. S1

Colossendeis bicincta, picture showing the proximal part of the proboscis and the anterior region of the cephalosoma, with the insertion of pedipalps (pd) and ovigers (ov) on a common basis (JPEG 183 kb)

427_2006_95_MOESM2_ESM.jpg (278 kb)
Fig. S2

The position of Endeis and Nymphon in the pycnogonid tree derived from the combined analysis of 18S and 28S rDNA and morphological data (Arango 2003). The two species investigated in the present study, Endeis spinosa (male individual) and Nymphon gracile, are illustrated on the right side of the tree. cho chelifore, ov oviger, pd pedipalp (JPEG 284 kb)

427_2006_95_MOESM3_ESM.doc (82 kb)
Fig S3 Amino-acid sequence alignment of pycnogonid Hox genes with representative genes from several panarthropods and other bilaterians, classified by groups of orthology. The alignment comprises, from left to right, eight positions of the hexapeptide region, six positions in the N-terminal region flanking the homeodomain, the 60 aa of the homeodomain, and ten positions in the C-terminal region flanking the homeodomain. Dashes indicate gaps inserted to align the sequences; blanks correspond to missing data. Black shading indicates amino-acid identity; grey shading indicate amino-acid similarity (for both, the threshold for shading was 40% of the sequences). In the homeodomain, helix 1 spans from position 10 to position 22, helix 2 from 28 to 37 and helix 3 from 42 to 58. Abbreviations of taxon names as in Fig. 3 (DOC 84 kb)
427_2006_95_MOESM4_ESM.jpg (454 kb)
Fig. S4

Maximum Likelihood analysis of the 60-aa (homeodomain) Hox gene dataset. Genes from Endeis spinosa are labelled in red; genes from Nymphon gracile are labelled in blue. ML bootstraps (300 replicates) are indicated above the branches. The scale bar indicates the number of nucleotide substitutions per position in the sequences. LogL=−2262.20753, gamma shape=0.457, proportion of invariant sites=0.041 (JPEG 464 kb)

427_2006_95_MOESM5_ESM.doc (18 kb)
Table S1 Supplement table (DOC 18 kb)


  1. Abzhanov A, Kaufman T (1999) Homeotic genes and the arthropod head: expression patterns of the labial, proboscipedia, and Deformed genes in crustaceans and insects. Proc Natl Acad Sci USA 96:10224–10229PubMedCrossRefGoogle Scholar
  2. Abzhanov A, Popadic A, Kaufman TC (1999) Chelicerate Hox genes and the homology of arthropod segments. Evol Dev 1:77–89PubMedCrossRefGoogle Scholar
  3. Arango CP (2003) Molecular approach to the phylogenetics of sea spiders (Arthropoda: Pycnogonida) using partial sequences of nuclear ribosomal DNA. Mol Phylogenet Evol 28:588–600PubMedCrossRefGoogle Scholar
  4. Averof M (1998) Origin of the spider’s head. Nature 395:436–437PubMedCrossRefGoogle Scholar
  5. Babu KS (1965) Anatomy of the central nervous system of arachnids. Zool Jb Anat 82:1–154Google Scholar
  6. Bain BA (2003a) Larval types and a summary of postembryonic development within the pycnogonids. Invertebr Reprod Dev 43:193–222Google Scholar
  7. Bain BA (2003b) Postembryonic development in the pycnogonid Austropallene cornigera (Family Callipallenidae). Invertebr Reprod Dev 43:181–192Google Scholar
  8. Behrens W (1984) Larvenentwicklung und Metamorphose von Pycnogonum litorale (Chelicerata, Pantopoda). Zoomorphology 104:266–279CrossRefGoogle Scholar
  9. Borradaile LA, Potts FA, Eastham LES, Saunders JT, Kerkut, GA (1961) The invertebrata: a manual for the use of students, 4th edn. Cambridge University Press, LondonGoogle Scholar
  10. Boyan G, Reichert H, Hirth F (2003) Commissure formation in the embryonic insect brain. Arthropod Struct Dev 32:61–77CrossRefGoogle Scholar
  11. Brauer A (1894) Beiträge zur Kenntnis der Entwicklungsgeschichte des Skorpions I. Z Wiss Zool 57:402–432Google Scholar
  12. Brusca RC, Brusca GJ (2003) Invertebrates, 2nd edn. Sinauer, Sunderland, MassachusettsGoogle Scholar
  13. Budd GE (2002) A palaeontological solution to the arthropod head problem. Nature 417:271–275PubMedCrossRefGoogle Scholar
  14. Budd GE, Telford MJ (2005) Along came a sea spider. Nature 437:1099–1102PubMedCrossRefGoogle Scholar
  15. Bullock TH, Horridge GA (1965) Structure and function in the nervous systems of invertebrates, vol II. Freeman, San Francisco and LondonGoogle Scholar
  16. Burke AC, Nelson CE, Morgan BA, Tabin C (1995) Hox genes and the evolution of vertebrate axial morphology. Development 121:333–346PubMedGoogle Scholar
  17. Carroll SB (2005) The new science of Evo Devo: endless forms most beautiful. Norton and Co, New York, LondonGoogle Scholar
  18. Carroll SB, Grenier J, Weatherbee SD (2005) From DNA to diversity: molecular genetics and the evolution of animal design, 2nd edn. Blackwell, LondonGoogle Scholar
  19. Chen J, Waloszek D, Maas A (2004) A new “great-appendage” arthropod from the lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero-ventral appendages. Lethaia 37:3–20CrossRefGoogle Scholar
  20. Colgan DJ, McLauchlan A, Wilson GDF, Livingston S, Edgecombe GD, Macaranas J, Cassis G, Gray MR (1998) Histone H3 and U2 snRNA sequences and arthropod molecular evolution. Aust J Zool 46:419–437CrossRefGoogle Scholar
  21. Coyne JA (2005) Switching on evolution. Nature 435:1029–1030CrossRefGoogle Scholar
  22. Damen WGM, Hausdorf M, Seyfarth E-A, Tautz D (1998) A conserved mode of head segmentation in arthropods revealed by the expression pattern of Hox genes in a spider. Proc Natl Acad Sci USA 95:10665–10670PubMedCrossRefGoogle Scholar
  23. Deutsch JS, Mouchel-Vielh E (2003) Hox genes and the crustacean body plan. BioEssays 25:878–887PubMedCrossRefGoogle Scholar
  24. Doyle JJ, Doyle JL (1987) A rapid DNA isolation procedure for small quantities of fresh leaf tissue. Phytochem Bull 19:11–15Google Scholar
  25. Duboule D (1994) Guide book to the homeobox genes. Oxford University Press, OxfordGoogle Scholar
  26. Dunlop JA, Arango CP (2004) Pycnogonid affinities: a review. J Zool Syst Evol Res 43:8–21CrossRefGoogle Scholar
  27. Edgecombe G, Wilson GDF, Colgan DJ, Gray MR, Cassis G (2000) Arthropod cladistics: combined analysis of histone H3 and U2 snRNA sequences and morphology. Cladistics 16:155–203CrossRefGoogle Scholar
  28. Eriksson BJ, Tait NN, Budd GE (2003) Head development in the onychophoran Euperipatoides kanangrensis with particular reference to the central nervous system. J Morphol 255:1–23PubMedCrossRefGoogle Scholar
  29. Frohman MA, Dush MK, Martin GR (1988) Rapid production of full-length cDNAs from rare transcripts: amplification using single gene-specific oligonucleotide primer. Proc Natl Acad Sci USA 85:8998–9002PubMedCrossRefGoogle Scholar
  30. Gilbert SF (2003) Developmental biology, 7th edn. Sinauer, Sunderland, MassachusettsGoogle Scholar
  31. Giribet G, Edgecombe GD, Wheeler WC (2001) Arthropod phylogeny based on eight molecular loci and morphology. Nature 413:157–161PubMedCrossRefGoogle Scholar
  32. Giribet G, Edgecombe GD, Wheeler WC, Babbitt C (2002) Phylogeny and systematic position of Opiliones: a combined analysis of chelicerate relationships using morphological and molecular data. Cladistics 18:5–70PubMedGoogle Scholar
  33. Guindon S, Gascuel, O (2003) A simple fast and accurate algorithm to estimate large phylogenies by Maximum Likelihood. Syst Biol 52:696–704PubMedCrossRefGoogle Scholar
  34. Hassanin A (2006) Phylogeny of arthropoda inferred from mitochondrial sequences: strategies for limiting the misleading effects of multiple changes in pattern rates of substitution. Mol Phylogenet Evol 38:100–116PubMedCrossRefGoogle Scholar
  35. Hassanin A, Léger N, Deutsch J (2005) Evidence for multiple reversals of asymmetric mutational constraints during the evolution of the mitochondrial genome of Metazoa, and consequences for phylogenetic inferences. Syst Biol 54:277–298PubMedCrossRefGoogle Scholar
  36. Hughes CL, Kaufman TC (2002a) Hox genes and the evolution of the arthropod body plan. Evol Dev 4:459–499PubMedCrossRefGoogle Scholar
  37. Hughes CL, Kaufman TC (2002b) Exploring the myriapod body plan: expression patterns of the ten Hox genes in a centipede. Development 129:1225–1238PubMedGoogle Scholar
  38. Jager M, Hassanin A, Manuel M, Le Guyader H, Deutsch J (2003) MADS-box genes in Ginkgo biloba and the evolution of the AGAMOUS family. Mol Biol Evol 20:842–854PubMedCrossRefGoogle Scholar
  39. Jager M, Murienne J, Clabaut C, Deutsch J, Le Guyader H, Manuel, M (2006) Homology of arthropod anterior appendages revealed by Hox gene expression in a sea spider. Nature 441(7092):506–508PubMedCrossRefGoogle Scholar
  40. Jarvis JH, King PE (1978) Reproductive biology of British pycnogonids (oögenesis and the reproductive cycle). Zool J Linn Soc 63:105–131Google Scholar
  41. Jones DT, Taylor WR, Thornton JM (1992) The rapid generation of mutation data matrices from protein sequences. CABIOS 8:275–282PubMedGoogle Scholar
  42. Leach WE (1814) The zoological miscellany, vol. 1, pp 33–34, 43–45Google Scholar
  43. Mallatt JM, Garey JR, Shultz JW (2004) Ecdysozoan phylogeny and bayesian inference: first use of nearly complete 28S and 18S rRNA gene sequences to classify the arthropods and their kin. Mol Phylogenet Evol 31:178–191PubMedCrossRefGoogle Scholar
  44. Maxmen A, Browne WE, Martindale MQ, Giribet G (2005) Neuroanatomy of sea spiders implies an appendicular origin of the protocerebral segment. Nature 437:1144–1148PubMedCrossRefGoogle Scholar
  45. Meisenheimer J (1902) Beiträge zur Entwicklungsgeschichte der Pantopoden. I. Die Entwicklung von Ammothea echinata Hodge bis zur Ausbildung der Larvenform. Z wiss Zool 72:191–248Google Scholar
  46. Mittmann B, Scholtz G (2003) Development of the nervous system in the “head” of Limulus polyphemus (Chelicerata: Xiphosura): morphological evidence for a correspondence between the segments of the chelicerae and of the (first) antennae of Mandibulata. Dev Genes Evol 213:9–17PubMedGoogle Scholar
  47. Montagu G (1808) Description of several marine animals found on the South Coast of Devonshire. Trans Linn Soc London 9:81–113Google Scholar
  48. Mouchel-Vielh E, Rigolot C, Gibert JM, Deutsch JS (1998) Molecules and the body plan: the Hox genes of cirripedes (Crustacea). Mol Phylogenet Evol 9:382–389PubMedCrossRefGoogle Scholar
  49. Mouchel-Vielh E, Blin M, Rigolot C, Deutsch JS (2002) Expression of a homologue of the fushi tarazu (ftz) gene in a cirripede crustacean. Evol Dev 4:76–85PubMedCrossRefGoogle Scholar
  50. Murtha M, Leckman JF, Ruddle FH (1991) Detection of homeobox genes in development and evolution. Proc Natl Acad Sci USA 88:10711–10715PubMedCrossRefGoogle Scholar
  51. Page DT (2004) A mode of arthropod brain evolution suggested by Drosophila commissure development. Evol Dev 6:25–31PubMedCrossRefGoogle Scholar
  52. Pavlopoulos A, Averof M (2002) Developmental evolution: Hox proteins ring the changes. Curr Biol 12:R291–R293PubMedCrossRefGoogle Scholar
  53. Pearse V, Pearse J, Buchsbaum M, Buchsbaum R (1987) Living invertebrates. Blackwell/Boxwood, Pacific Grove, CaliforniaGoogle Scholar
  54. Popadic A, Panganiban G, Rusch D, Shear WA, Kaufman TC (1998) Molecular evidence for the gnathobasic derivation of arthropod mandibles and for the appendicular origin of the labrum and other structures. Dev Genes Evol 208:142–150PubMedCrossRefGoogle Scholar
  55. Quéinnec E (2001) Insights into arthropod head evolution. Two heads in one: the end of the “endless dispute”? Ann Soc Entomol Fr 37:51–69Google Scholar
  56. Regier JC, Shultz J (2001) Elongation factor-2: a useful gene for arthropod phylogenetics. Mol Phylogenet Evol 20:136–148PubMedCrossRefGoogle Scholar
  57. Ronshaugen M, McGinnis N, McGinnis W (2002) Hox protein mutation and macroevolution of the insect body plan. Nature 415:914–917PubMedCrossRefGoogle Scholar
  58. Sanchez S (1959) Le développement des pycnogonides et leurs affinités avec les arachnides. Thèses CNRS, ParisGoogle Scholar
  59. Sandeman DC, Scholtz G, Sandeman R (1993) Brain evolution in decapod crustacea. J Exp Zool 295:112–133CrossRefGoogle Scholar
  60. Scholtz G, Edgecombe GD (2005) Heads, Hox and the phylogenetic position of trilobites. Crustac Issues 16:139–165Google Scholar
  61. Shultz JW, Regier JC (2000) Phylogenetic analysis of two nuclear protein-encoding genes in arthropods supports a crustacean-hexapod clade. Proc R Soc Lond B 267:1011–1019CrossRefGoogle Scholar
  62. Simonnet F, Deutsch J, Quéinnec E (2004) hedgehog is a segment polarity gene in a crustacean and a chelicerate. Dev Genes Evol 214:537–545PubMedCrossRefGoogle Scholar
  63. Telford MJ, Thomas RH (1998) Expression of homeobox genes shows chelicerate arthropods retain their deutocerebral segment. Proc Natl Acad Sci USA 95:10671–10675PubMedCrossRefGoogle Scholar
  64. Vilpoux K, Waloszek D (2003) Larval development and morphogenesis of the sea spider Pycnogonum litorale (Ström, 1762) and the tagmosis of the body of Pantopoda. Arthropod Struct Dev 32:349–383CrossRefGoogle Scholar
  65. Waloszek D, Dunlop JA (2002) A larval sea spider (Arthropoda: Pycnogonida) from the Upper Cambrian ‘orsten’ of Sweden and the phylogenetic position of pycnogonids. Palaeontology 45:421–446CrossRefGoogle Scholar
  66. Waloszek D, Chen J, Maas A, Wang X (2005) Early Cambrian arthropods—new insights into arthropod head and structural evolution. Arthropod Struct Dev 34:189–205CrossRefGoogle Scholar
  67. Weygoldt P (1985) Ontogeny of the arachnid central nervous system. In: Barth FG (ed) Neurobiology of arachnids. Springer, Berlin Heidelberg New York, pp 20–37Google Scholar
  68. Winter G (1980) Beiträge zur Morphologie und Embryologie des vorderen Körperabschnitts (Cephalosoma) der Pantopoda Gerstaecker, 1863. Z Zoolog Syst Evol Forsch 18:27–61Google Scholar
  69. Zrzavy J, Hypsa V, Vlaskova M (1998) Arthropod phylogeny: taxonomic congruence, total evidence and conditional combination approaches to morphological and molecular data sets. In: Fortey RA, Thomas RH (eds) Arthropod relationships. Chapman & Hall, London, pp 97–107Google Scholar

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • Michaël Manuel
    • 1
    Email author
  • Muriel Jager
    • 1
  • Jérôme Murienne
    • 2
  • Céline Clabaut
    • 3
  • Hervé Le Guyader
    • 1
  1. 1.UMR 7138 “SAE” CNRS UPMC MNHN ENS IRDUniversité Pierre et Marie Curie-ParisParisFrance
  2. 2.Muséum National d’Histoire Naturelle, UMR 5202 CNRSDépartement Systématique et EvolutionParisFrance
  3. 3.Evolutionary Biology, Department of BiologyUniversity of KonstanzKonstanzGermany

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