5 Metazoan Complexity
171
on the basis of such comparisons, and with the help of the molecular toolboxes used
to dissect the developmental regulatory networks acting in these tissues, it also starts
to become possible to identify the molecular correlates involved in the emergence
and modification of body plans, and to study the molecular correlates of visible
morphological features. Ultimately, these lines of research therefore aim to provide
a link between the genome and the features it encodes and that traditionally have
been used to discriminate between species.
Understanding animal diversity: The new marine model systems outlined in this
chapter already significantly broaden our view of evolutionary principles, but still,
they represent only a very small subset of the wealth of species living in the ocean.
There is great potential for the use of the new genomic approaches to address questions related to the diversity of animal groups. On the one hand, sequence data
available for reference models allows us to address how phenotypic differences (e.g.
in form or colour) are encoded on the molecular level. On the other hand, there also
appear to exist intriguing differences in the genetic networks even between closely
related, morphologically similar species. In both fields, genomic techniques already
provide a very useful basis for molecular analysis, and also hold a lot of potential
for future studies. Such studies will hopefully help us to re-draw, at some point, a
more accurate version of Haeckel’s tree of life that reflects better the true origins
of the different animals, along with the evolutionary paths that brought them into
existence.
Acknowledgements The authors wish to thank Ferdinand Marlétaz and Benjamin Backfisch for
critical reading of the manuscript, and Hanno Sandvik for help in locating the original lithograph
reproduced in Fig. 5.1. Research in F.R.’s laboratory is supported by a start-up fund of the Max
F. Perutz Laboratories.
References
Abedin M, King N (2008) The premetazoan ancestry of cadherins. Science 319: 946–948
Aburomia R et al (2003) Functional evolution in the ancestral lineage of vertebrates or when
genomic complexity was wagging its morphological tail. J Struct Funct Genomics 3: 45–52
Ackermann C (2002) Markierung der Zellinien im Embryo von Platynereis. In: Fachbereich
biologie, ed. Mainz: Johannes Gutenberg-Universität
Adamska M et al (2007a) Wnt and TGF-β expression in the sponge Amphimedon queenslandica
and the origin of metazoan embryonic patterning. PLOS One 2: e1031
Adamska M et al (2007b) The evolutionary origin of hedgehog proteins. Curr Biol 17: R836–R837
Adell T et al (2003) Isolation and characterization of two T-box genes from sponges, the
phylogenetically oldest metazoan taxon. Dev Genes Evol 213: 421–434
Adell T, Müller WEG. (2004) Isolation and characterization of five Fox (Forkhead) genes from the
sponge Suberites domuncula. Gene 334: 35–46
Adell T, Müller WEG. (2005) Expression pattern of the Brachyury and Tbx2 homologues from the
sponge Suberites domuncula. Biol Cell 97: 641–650
Aguinaldo AM et al (1997) Evidence for a clade of nematodes, arthropods and other moulting
animals. Nature 387: 489–493
Amerongen HM, Peteya DJ (1980) Ultrastructural study of two kinds of muscle in sea anemones:
the existence of fast and slow muscles. J Morphol 166: 145–154
171
on the basis of such comparisons, and with the help of the molecular toolboxes used
to dissect the developmental regulatory networks acting in these tissues, it also starts
to become possible to identify the molecular correlates involved in the emergence
and modification of body plans, and to study the molecular correlates of visible
morphological features. Ultimately, these lines of research therefore aim to provide
a link between the genome and the features it encodes and that traditionally have
been used to discriminate between species.
Understanding animal diversity: The new marine model systems outlined in this
chapter already significantly broaden our view of evolutionary principles, but still,
they represent only a very small subset of the wealth of species living in the ocean.
There is great potential for the use of the new genomic approaches to address questions related to the diversity of animal groups. On the one hand, sequence data
available for reference models allows us to address how phenotypic differences (e.g.
in form or colour) are encoded on the molecular level. On the other hand, there also
appear to exist intriguing differences in the genetic networks even between closely
related, morphologically similar species. In both fields, genomic techniques already
provide a very useful basis for molecular analysis, and also hold a lot of potential
for future studies. Such studies will hopefully help us to re-draw, at some point, a
more accurate version of Haeckel’s tree of life that reflects better the true origins
of the different animals, along with the evolutionary paths that brought them into
existence.
Acknowledgements The authors wish to thank Ferdinand Marlétaz and Benjamin Backfisch for
critical reading of the manuscript, and Hanno Sandvik for help in locating the original lithograph
reproduced in Fig. 5.1. Research in F.R.’s laboratory is supported by a start-up fund of the Max
F. Perutz Laboratories.
References
Abedin M, King N (2008) The premetazoan ancestry of cadherins. Science 319: 946–948
Aburomia R et al (2003) Functional evolution in the ancestral lineage of vertebrates or when
genomic complexity was wagging its morphological tail. J Struct Funct Genomics 3: 45–52
Ackermann C (2002) Markierung der Zellinien im Embryo von Platynereis. In: Fachbereich
biologie, ed. Mainz: Johannes Gutenberg-Universität
Adamska M et al (2007a) Wnt and TGF-β expression in the sponge Amphimedon queenslandica
and the origin of metazoan embryonic patterning. PLOS One 2: e1031
Adamska M et al (2007b) The evolutionary origin of hedgehog proteins. Curr Biol 17: R836–R837
Adell T et al (2003) Isolation and characterization of two T-box genes from sponges, the
phylogenetically oldest metazoan taxon. Dev Genes Evol 213: 421–434
Adell T, Müller WEG. (2004) Isolation and characterization of five Fox (Forkhead) genes from the
sponge Suberites domuncula. Gene 334: 35–46
Adell T, Müller WEG. (2005) Expression pattern of the Brachyury and Tbx2 homologues from the
sponge Suberites domuncula. Biol Cell 97: 641–650
Aguinaldo AM et al (1997) Evidence for a clade of nematodes, arthropods and other moulting
animals. Nature 387: 489–493
Amerongen HM, Peteya DJ (1980) Ultrastructural study of two kinds of muscle in sea anemones:
the existence of fast and slow muscles. J Morphol 166: 145–154