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Independent Acquisition (independent + acquisition)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Embryonic development of verongid demosponges supports the independent acquisition of spongin skeletons as an alternative to the siliceous skeleton of sponges

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009
MANUEL MALDONADO
Approximately 85% of extant sponges (phylum Porifera) belong to the class Demospongiae, which contains 14 taxonomic orders. In the orders Verongida, Dictyoceratida, and Dendroceratida, jointly referred to as ,keratose demosponges', the skeleton does not contain siliceous spicules but only spongin fibres. This shared trait has encouraged placement of these orders together within Demospongiae, although their relationships remain uncertain. The present study documents for the first time embryo development in the order Verongida (Aplysina aerophoba), providing some clues for phylogenetic inference. Spawned eggs were enveloped by a follicle of maternal cells. Embryos and larvae were chimeric organisms, the blastocoel of which was filled with symbionts and maternal cells migrated from the follicle. The ultrastructure of epithelial larval cells revealed: (1) a basal apparatus characterized by a peculiar, angling accessory centriole; (2) a pear-shaped nucleus with a protruding beak connected to the rootlets of the basal body; and (3) a distinctive Golgi apparatus encircling the nuclear apex. Developmental and ultrastructural findings support the concept, in congruence with recent molecular studies, that Verongida are more closely related to Halisarcida (askeletal sponges) and Chondrosida (askeletal sponges + sponges with spongin + spiculate sponges) than to the remaining ,keratose' orders, making a monophyletic ,supra-ordinal unit' equivalent to a subclass (Myxospongia, new subclass). Hence, spongin skeletons have evolved at least twice in Demospongiae. Independent acquisition of ,corneous' materials as an alternative to silica could have been stimulated by the radiation of diatoms at the Cretaceous,Tertiary boundary (approximately 65 Mya), which depleted silicon in the photic zone of the world's ocean. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 427,447. [source]

Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra

JOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2003
G. A. Thomson
Abstract A Raman microscope was modified to allow the independent acquisition of two orthogonally polarized components of a Raman spectrum in a single measurement. Preliminary performance was demonstrated by simultaneously measuring the intensity of both polarized components of the silicon Raman band at 520 cm,1 as a silicon wafer was rotated through 360° under a polarized laser Raman probe. Polarization-resolved Raman spectra of a complex molecular crystal are also presented, illustrating the increase in spectral information available with the modified system. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Embryonic development of verongid demosponges supports the independent acquisition of spongin skeletons as an alternative to the siliceous skeleton of sponges

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009
MANUEL MALDONADO
Approximately 85% of extant sponges (phylum Porifera) belong to the class Demospongiae, which contains 14 taxonomic orders. In the orders Verongida, Dictyoceratida, and Dendroceratida, jointly referred to as ,keratose demosponges', the skeleton does not contain siliceous spicules but only spongin fibres. This shared trait has encouraged placement of these orders together within Demospongiae, although their relationships remain uncertain. The present study documents for the first time embryo development in the order Verongida (Aplysina aerophoba), providing some clues for phylogenetic inference. Spawned eggs were enveloped by a follicle of maternal cells. Embryos and larvae were chimeric organisms, the blastocoel of which was filled with symbionts and maternal cells migrated from the follicle. The ultrastructure of epithelial larval cells revealed: (1) a basal apparatus characterized by a peculiar, angling accessory centriole; (2) a pear-shaped nucleus with a protruding beak connected to the rootlets of the basal body; and (3) a distinctive Golgi apparatus encircling the nuclear apex. Developmental and ultrastructural findings support the concept, in congruence with recent molecular studies, that Verongida are more closely related to Halisarcida (askeletal sponges) and Chondrosida (askeletal sponges + sponges with spongin + spiculate sponges) than to the remaining ,keratose' orders, making a monophyletic ,supra-ordinal unit' equivalent to a subclass (Myxospongia, new subclass). Hence, spongin skeletons have evolved at least twice in Demospongiae. Independent acquisition of ,corneous' materials as an alternative to silica could have been stimulated by the radiation of diatoms at the Cretaceous,Tertiary boundary (approximately 65 Mya), which depleted silicon in the photic zone of the world's ocean. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 427,447. [source]

Opsin gene polymorphism predicts trichromacy in a cathemeral lemur

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 1 2009
Carrie C. Veilleux
Abstract Recent research has identified polymorphic trichromacy in three diurnal strepsirrhines: Coquerel's sifaka (Propithecus coquereli), black and white ruffed lemurs (Varecia variegata), and red ruffed lemurs (V. rubra). Current hypotheses suggest that the transitions to diurnality experienced by Propithecus and Varecia were necessary precursors to their independent acquisitions of trichromacy. Accordingly, cathemeral lemurs are thought to lack the M/L opsin gene polymorphism necessary for trichromacy. In this study, the M/L opsin gene was sequenced in ten cathemeral blue-eyed black lemurs (Eulemur macaco flavifrons). This analysis identified a polymorphism identical to that of other trichromatic strepsirrhines at the critical amino acid position 285 in exon 5 of the M/L opsin gene. Thus, polymorphic trichromacy is likely present in at least one cathemeral Eulemur species, suggesting that strict diurnality is not necessary for trichromacy. The presence of trichromacy in E. m. flavifrons suggests that a re-evaluation of current hypotheses regarding the evolution of strepsirrhine trichromacy may be necessary. Although the M/L opsin polymorphism may have been independently acquired three times in the lemurid,indriid clade, the distribution of opsin alleles in lemurids and indriids may also be consistent with a common origin of trichromacy in the last common ancestor of either the lemurids or the lemurid,indriid clade. Am. J. Primatol. 71:86,90, 2009. © 2008 Wiley-Liss, Inc. [source]