MCCLINTOCK, J.M.*; JOZEFOWICZ, C.; CARLSON, R.; MANN, D.J.; PRINCE, V.E.: Hox gene patterning and fish evolution We are using the zebrafish to investigate the evolution of Hox gene patterning functions. Whereas tetrapods possess 4 clusters of Hox genes, zebrafish have 7 distinct clusters. This condition is most likely due to a whole genome duplication, which […]

JEFFERY, J.E.*; BININDA-EMONDS, O.R.P.; COATES, M.I.; RICHARDSON, M.K.: Heterochrony in Amniote Evolution Heterochrony is thought to be a major link between developmental mechanisms and the emergence of phenotypic difference above the species level (macroevolution). Heterochronies affecting the timing of discrete events are of particular importance during organogenesis. Within vertebrates, this is the mid-embryonic period when […]

SHAPIRO, M.D.: Developmental morphology and gene expression in lizard digit reduction Evolutionary digit loss in lizards has been attributed to truncations in ancestral developmental programs, while another hypothesis refutes this idea. However, neither hypothesis has been tested in a developmental framework. Among living tetrapods, Australian skinks may offer the best examples of graded limb reduction. […]

Pizer, M.*; Wray, G.A.: The Evolution and Development of Left-Right Asymmetry in Echinoderms Echinoderms have a bilaterally symmetrical larva that becomes left-right asymmetric when adult structures begin to develop. These structures form primarily on the left side of the larva, eventually producing a pentaradially symmetrical adult. This unusual symmetry transition is one of the most […]

SEAVER, E.C.*; PAULSON, D.; IRVINE, S.Q.; MARTINDALE, M. Q.: Sequence and developmental expression of the engrailed gene in the polychaete Chaetopterus The number of times a segmented body plan has evolved in the metazoa is a currently debated issue. We are interested in understanding whether the annelids and arthropods share a common segmented ancestor and […]

deMaintenon, M.J.: Patterns of reproductive system development in the caenogastropods; systematic and evolutionary implications. The reproductive system is one of the most complex and variable of gastropod organ systems, and is often also the last organ system to develop. The level of anatomical variation of the reproductive system, coupled with its late development, renders it […]

Golenberg, E.M.: Floral Developmental Regulation and Sexual Lability in Spinach In dioecious, cultivated spinach, Spinacia oleracea, the presence or absence of reproductive organs is determined by organ primordia initiation rather than by degeneration of existing organ primordia as found in maize, sorrel, and campion. Male and female flowers differentiate morphologically early in floral morphogenesis (stage […]

NEDERBRAGT, A.J.*; DICTUS, W.J.A.G.; VANLOON, A.E.: Conserved Gene Networks in Development: The Engrailed and Dpp Homologues in Molluscan Shell Development During Drosophila development the engrailed/hedgehog/decapentaplegic gene network functions in setting up boundaries between different compartments, e.g. between anterior and posterior compartments in imaginal discs. Here, engrailed is expressed in cells on one side of the […]

FREEMAN, G.: A Developmental Basis for the Cambrian Explosion: Evidence from Extant Brachiopods Paleontological evidence indicates that a large number of new animal phyla, in addition to classes and orders within phyla, were first observed during the Cambrian. One possible basis for the genesis of new morphologies during this period may have been the ease […]

GILBERT, S.F.*; LOREDO, G.A.; BRUKMAN, A.; TUAN, R.: Studies in Turtle Shell Development: Osteogenesis of an Evolutionarily Novel Structure The turtle shell is an evolutionary novelty, a development of the osseous skeleton unique among vertebrates. The turtle shell is composed of a dorsal carapace, a ventral plastron, and a lateral bridge. The carapace contains fifty […]