Article Abstract:
It has been possible to identify Hox genes from two previously unsampled phyla, a priapulid (Priapulus caudatus) and a lophophorate (the brachiopod Lingula anatina). An extensive Hox gene data set has also been collected from a polychaete annelid (Nereis virens), along with partial data from a gastropod mollusc (the limpet Patella vulgata). The stem lophotrochozoan had a least 10 Hox genes, while the stem ecdysozoan had at least eight. The common protostome ancestor also had at least eight Hox genes, with the common bilaterian ancestor having at least seven.
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Article Abstract:
An analysis of existing research on crustaceans including fossil records and morphological data indicates that homeotic or hox genes play a role in normal adaptive evolution. Differences in hox gene regulation among the different crustaceans are related to the evolutionary transformation of their anterior thoracic limbs into feeding appendages. Because a common structure for morphological comparison between crustaceans and insects is lacking, the analysis concentrates on comparisons between different subgroups of crustaceans.
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Article Abstract:
The expression of four Hox genes in the branchiopod crustacean Artemia franciscana have been compared with Hox gene patterns from insects to investigate the macroevolutionary changes in body architecture. Though crustaceans and insects share a common origin of segmentation, the specialized trunk segments may have independent origins. The three trunk genes in Artemia, Antp, Ubx, and abdA, have largely overlapping domains in the uniform thoracic region. In insects these genes form distinct segment types in thorax and abdomen.
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