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| Knopf, F.; Koenemann, S.; Schram, F.R.; Wolff, C.. |
| We have examined the caudal regions of diverse peracarid and pancarid malacostracans using light and scanning electronic microscopy. The traditional view of malacostracan posterior anatomy is not sustainable, viz., that the free telson, when present, bears the anus near the base. The anus either can occupy a terminal, sub-terminal, or mid-ventral position on the telson; or can be located on the sixth pleomere – even when a free telson is present. Furthermore, there is information that might be interpreted to suggest that in some cases a telson can be absent. Embryologic data indicates that the condition of the body terminus in amphipods cannot be easily characterized, though there does appear to be at least a transient seventh segment that seems to fuse... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Anus; Pancarida; Peracarida; Pleomeres; Proctodaeum; Teloblasts; Telson; Urosome; 42.74. |
| Ano: 2006 |
URL: http://www.repository.naturalis.nl/record/210767 |
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| Biggelaar, J.A.M. van den; Edsinger-Gonzales, E.; Schram, F.R.. |
| Recent discoveries in the field of developmental genetics have lead to the resurrection of the old idea, first proposed in the early 19th century, that the dorso-ventral axis of deuterostomes, such as vertebrates, has been inverted during the course of evolution from that noted in protostomes, i.e., what in deuterostomes is dorsal, is in protostomes ventral. However, while attractive in its simplicity, such a suggestion ignores the real events of embryogenesis. During the onset of gastrulation in deuterostomes as well as in protostomes a blastopore is formed with exactly the same embryonic, antero-posterior/dorso-ventral polarity. Subsequent differences in the patterns or morphogenetic movement in gastrulation result in a spatial inversion of this... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Amphistomy; Axis inversion; Deuterostomes; Spiral cleavage; Protostomes; Gastrulation. |
| Ano: 2002 |
URL: http://www.repository.naturalis.nl/record/534350 |
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| Schram, F.R.. |
| The study of biogeography was once a pillar of evolution science. Both Darwin and especially Wallace found great inspiration from the consideration of animal distributions. However, what is to happen to this discipline in a time of global trade, mass movement of people and goods, and the resulting globalization of the planet’s biota? Can we still hope to delve into the fine points of past geography as it affected animal and plant evolution? Maybe we can, but only with careful study of life forms that suffer minimal affects – at present – from globalization, viz., marginal faunas of quite inaccessible environments. Two examples taken from syncarid crustaceans illustrate this point. Bathynellacea provide insight into ancient patterns of distribution and... |
| Tipo: Article / Letter to the editor |
Palavras-chave: Anaspidacea; Bathynellacea; Globalization; Historical biogeography; Vicariance; 42.74. |
| Ano: 2008 |
URL: http://www.repository.naturalis.nl/record/280481 |
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