A conserved mode of head segmentation in arthropods revealed by the expression pattern of Hox genes in a spider

• Published in: Proceedings of the National Academy of Sciences - PNAS 1998-09, Vol.95 (18), p.10665-10670
• Main Authors: Damen, W.G.M. (Zoologisches Institut der Universitat Munchen, Munchen, Germany.), Hausdorf, M, Seyfarth, E.A, Tauta, D
• Format: Article
• Language: English
• Subjects: ADN; AMINO ACID SEQUENCES; Animals; ARANEAE; ARN MENSAJERO; ARN MESSAGER; Arthropods; Biological Sciences; Brain; CABEZA; Cambrian; CHEMICAL COMPOSITION; COMPLEMENTARY DNA; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; Crustaceans; Ctenidae; CUPIENNIUS; CUPIENNIUS SALEI; DESARROLLO EMBRIONARIO; DEVELOPPEMENT EMBRYONNAIRE; DNA; Drosophila; EMBRYONIC DEVELOPMENT; Embryonic growth stage; EMBRYOS; Evolution; Evolution, Molecular; Exoskeletons; EXPRESION GENICA; EXPRESSION DES GENES; FACTEUR DE TRANSCRIPTION; FACTORES DE TRANSCRIPCION; Ganglia; GEN HOMEOTICO; GENBANK/AJ007431; GENBANK/AJ007432; GENBANK/AJ007433; GENBANK/AJ007434; GENBANK/AJ007435; GENBANK/AJ007436; GENBANK/AJ007437; GENE; GENE EXPRESSION; GENE HOMEOTIQUE; GENES; Genes, Homeobox; HEAD; Head - growth & development; HOMEOTIC GENES; Insect genetics; Insect morphology; MESSENGER RNA; MOLECULAR SEQUENCE DATA; NUCLEOTIDE SEQUENCE; REGULATORY GENES; SECUENCIA NUCLEOTIDICA; SEQUENCE NUCLEOTIDIQUE; Spiders; Spiders - embryology; Spiders - growth & development; TETE; TRANSCRIPTION FACTORS
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.18.10665

Chelicerates constitute a basic arthropod group with fossil representatives from as early as the Cambrian period. Embryonic development and the subdivision of the segmented body region into a prosoma and an opisthosoma are very similar in all extant chelicerates. The mode of head segmentation, however, has long been controversial. Although all other arthropod groups show a subdivision of the head region into six segments, the chelicerates are thought to have the first antennal segment missing. To examine this problem on a molecular level, we have compared the expression pattern of Hox genes in the spider Cupiennius salei with the pattern known from insects. Surprisingly, we find that the anterior expression borders of the Hox genes are in the same register and the same relative segmental position as in Drosophila. This contradicts the view that the homologue of the first antennal segment is absent in the spider. Instead, our data suggest that the cheliceral segment is homologous to the first antennal segment and the pedipalpal segment is homologous to the second antennal (or intercalary) segment in arthropods. Our finding implies that chelicerates, myriapods, crustaceans, and insects share a single mode of head segmentation, reinforcing the argument for a monophyletic origin of the arthropods