Research ArticleEVOLUTIONARY BIOLOGY

Canadia spinosa and the early evolution of the annelid nervous system

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Science Advances  11 Sep 2019:
Vol. 5, no. 9, eaax5858
DOI: 10.1126/sciadv.aax5858
  • Fig. 1 General anatomy of C. spinosa.

    (A) USNM83929C, counterpart in dorsal view, polarized light, specimen underwater. (B) USNM277933, lateral view, note ventrally curved tips of notochaetae, polarized light, dry. (C) Elemental map for carbon of gill from USNM83929C part, position of equivalent gill of counterpart shown in (A). (D) Close-up view of head of USNM83929C, and anterior appendages, polarized light, dry. (E) Close-up view of anterior region of USNM83929D, polarized light, dry. (F) SEM backscatter image of median antenna of USNM83929D [area outlined in (E)]. (G) ROMIP65172.1 showing median antenna, reflected light, specimen under alcohol. (H and I) ROMIP65173, dorsal view. (H) Close-up view of palp and thick carbon band in palp, polarized light, specimen under ethanol. (I) SEM backscatter image showing carbon in the palp. Dashed boxes indicate positions of close up images. ma, median antenna; mo, mouth; nech, neurochaetae; noch, notochaetae; pa, palps; pagr, palp groove.

  • Fig. 2 Anterior nervous system of C. spinosa.

    (A and B) USNM83929B, part in dorsal view. (A) Anterior region, polarized light, specimen under alcohol. (B) SEM-EDX map for carbon. (C) USNM83929B, counterpart, anterior region, cross-polarized light, specimen under alcohol. (D) USNM83929B, counterpart, SEM-EDX map for carbon. (E and F) Close-up view of region shown in box with dashed outline shown in (D). White arrowheads indicate carbonaceous preservation of the parapodial margin. (E) Cross-polarized light under ethanol. (F) SEM backscatter. (G to I) USNM275517, specimen in dorsal view. (G) Anterior segments, reflected light underwater. (H) Close-up view of head, SEM backscatter. (I) Close-up view of palp showing feeding groove/innervation. (J and K) Close-up view of anterior region of ROMIP65174, specimen in dorsal view. (J) Reflected light under ethanol. (K) SEM backscatter. (L and M) ROMIP65175, part, specimen in dorsal view. (L) Anterior region, polarized light, photographed under ethanol. (M) Close-up view of head, SEM-EDX map for carbon. (N and O) ROMIP65176, juvenile in dorsal view. (N) Anterior segments, cross-polarized light under ethanol. (O) Close-up view of head and three anterior segments, SEM backscatter [area outlined in (N)]. (P) Confocal microscope image of Neanthes arenaceodentata (Aciculata) acetylated α-tubulin immunoreactivity is red, and cell nuclei are blue, refigured and modified from (50). Dashed boxes indicate positions of close-up images. an, antenna; cc, circumoral connective; cs, commissure; mo, mouth; nech, neurochaetae; noch, notochaetae; nop, notopodium (numbered by chaetiger); nph, nephridia; pa, palp; pan, parapodial nerve (numbered by chaetiger); pn, palp nerve; pyc, pygidial cirrus; sog, supraesophogeal ganglion; tnc, tentacular cirrus.

  • Fig. 3 Preservation of nervous tissue in C. spinosa in specimens preserved in ventral view.

    (A to H) ROMIP56972, specimen in ventral view. (A) Complete specimen, reflected light, specimen underwater. (B) Anterior region, SEM-EDX elemental map for carbon. (C) SEM backscatter image showing ventral and parapodial nerves. (D) SEM backscatter image showing palp and right circumoral connective. (E) SEM backscatter image showing palp nerve and left circumoral connective. (F) Posterior segments, photographed in reflected light underwater. (G) SEM EDX map for carbon of region shown in (F). (H) SEM backscatter of boxed region in (G), arrowheads demark the outline of the gut superimposed on the ventral nerve cord. (I to K) GSC8232A, specimen in ventral view. (J) SEM backscatter showing ventral nerves and ventral nerve cord of boxed region in (I). (K) Close-up view of parapodial nerve and parapodial outlines preserved carbonaceously, arrowheads indicate the body margin. cc, circumoral connective; ga, ganglion; pa, palp; pan, parapodial nerve; pn, palp nerve; sn, segmental nerve; vnc, ventral nerve cord.

  • Fig. 4 Reconstruction and schematic reconstructions of annelid nervous systems plotted on a simplified phylogeny.

    (A) Reconstruction by M. Collins © Royal Ontario Museum, all rights reserved (see also movie S1). (B) Simplified phylogeny of Annelida with C. spinosa recovered in the annelid stem group (see also the Supplementary Materials for the full phylogenetic results). Topology is based on the analysis using phylogenetic constraints based on recent phylogenomic trees. Proposed nervous system synapomorphies are shown at nodes, and inferred losses are shown along branches as cross marks. cc, circumoral connectives; ga, segmental ganglion; ma, median antenna; pan, parapodial nerve; pa, palp; sn, segmental nerve; sog, supraesophegeal ganglion; vnc, ventral nerve cord.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/9/eaax5858/DC1

    Supplementary Text

    Fig. S1. Additional specimens of C. spinosa showing details of overall anatomy.

    Fig. S2. Morphology of the palps of Canadia spinosa and Kootenayscolex barbarensis.

    Fig. S3. Gill morphology and attachment in Canadia spinosa.

    Fig. S4. Additional images and camera lucida drawings of anterior and axial nervous system of C. spinosa.

    Fig. S5. Elemental map of USNM83929C.

    Fig. S6. Additional elemental maps of USNM83929B showing the same region as Fig. 2A.

    Fig. S7. Phylogenetic position of C. spinosa based on morphological character matrix using the mkv + gamma model and ancestral state reconstruction.

    Fig. S8. Three-dimensional reconstructions of C. spinosa by Lars Fields.

    Table S1. Details of fossil material analyzed.

    Movie S1. Movie of three-dimensional reconstruction of C. spinosa by Lars Fields.

    Data file S1. Character taxon matrix in NEXUS format.

    References (5176)

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Text
    • Fig. S1. Additional specimens of C. spinosa showing details of overall anatomy.
    • Fig. S2. Morphology of the palps of Canadia spinosa and Kootenayscolex barbarensis.
    • Fig. S3. Gill morphology and attachment in Canadia spinosa.
    • Fig. S4. Additional images and camera lucida drawings of anterior and axial nervous system of C. spinosa.
    • Fig. S5. Elemental map of USNM83929C.
    • Fig. S6. Additional elemental maps of USNM83929B showing the same region as Fig. 2A.
    • Fig. S7. Phylogenetic position of C. spinosa based on morphological character matrix using the mkv + gamma model and ancestral state reconstruction.
    • Fig. S8. Three-dimensional reconstructions of C. spinosa by Lars Fields.
    • Table S1. Details of fossil material analyzed.
    • Legend for movie S1
    • References (5176)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mov format). Movie of three-dimensional reconstruction of C. spinosa by Lars Fields.
    • Data file S1. Character taxon matrix in NEXUS format.

    Files in this Data Supplement:

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