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Strigamia Maritima (strigamia + maritima)
Selected AbstractsAn early temperature-sensitive period for the plasticity of segment number in the centipede Strigamia maritimaEVOLUTION AND DEVELOPMENT, Issue 4 2010Vincent Vedel SUMMARY Geophilomorph centipedes show variation in segment number (a) between closely related species and (b) within and between populations of the same species. We have previously shown for a Scottish population of the coastal centipede Strigamia maritima that the temperature of embryonic development is one of the factors that affects the segment number of hatchlings, and hence of adults, as these animals grow epimorphically,that is, without postembryonic addition of segments. Here, we show, using temperature-shift experiments, that the main developmental period during which embryos are sensitive to environmental temperature is surprisingly early, during blastoderm formation and before, or very shortly after, the onset of segmentation. [source] Temperature-dependent plasticity of segment number in an arthropod species: the centipede Strigamia maritimaEVOLUTION AND DEVELOPMENT, Issue 4 2008Vincent Vedel SUMMARY The evolution of arthropod segment number provides us with a paradox, because, whereas there is more than 20-fold variation in this character overall, most classes and orders of arthropods are composed of species that lack any variation in the number of segments. So, what is the origin of the higher-level variation? The centipede order Geophilomorpha is unusual because, with the exception of one of its families, all species exhibit intraspecific variation in segment number. Hence it provides an opportunity to investigate how segment number may change in a microevolutionary context. Here, we show that segment number can be directly altered by an environmental factor (temperature),this is the first such demonstration for any arthropod. The direction of the effect is such that higher temperature during embryogenesis produces more segments. This potentially explains an intraspecific cline in the species concerned, Strigamia maritima, but it does not explain how such a cline is translated into the parallel interspecific pattern of lower-latitude species having more segments. Given the plastic nature of the intraspecific variation, its link with interspecific differences may lie in selection acting on developmental reaction norms. [source] Expression of trunk Hox genes in the centipede Strigamia maritima: sense and anti-sense transcriptsEVOLUTION AND DEVELOPMENT, Issue 3 2006Carlo Brena SUMMARY We report the coding sequence and embryonic expression of the four trunk Hox genes Antennapedia (Antp), Ultrabithorax (Ubx), abdominal-A (abd-A), and Abdominal-B (Abd-B) in the geophilomorph centipede Strigamia maritima. In geophilomorph centipedes, all leg-bearing segments (LBS) are generated during embryogenesis, allowing us to define expression in relation to the full extent of the forming trunk. Persistent Antp expression characterizes the maxillipedal (poison claw) segment, whereas all LBS express the three Hox genes Antp, Ubx, and abd-A. Abd-B is never detectably expressed in segmented tissue, but is restricted to a zone around the proctodaeum that contributes to the hindgut. Expression of all these Hox genes initiates in the unsegmented tissue of the blastodisc, with expression of Antp respecting a sharply defined anterior border before the appearance of morphological segmentation in the trunk. The accumulation of Hox gene transcripts is strongly modulated by the maturing segment pattern, suggesting regulatory interactions with multiple levels of the segment patterning machinery. For one of these genes, Ubx, we detect both sense and anti-sense transcripts. The anti-sense transcripts originate 3, to the Ubx coding sequence and overlap the homeobox exon; they are expressed earlier than the Ubx coding transcripts and persistently, in an axially restricted pattern comparable to but distinct from those of the Hox coding transcripts. The pattern of accumulation of Ubx sense and anti-sense transcripts is strikingly complementary, suggesting the possibility of anti-sense regulation of Ubx expression. [source] Early development and segment formation in the centipede, Strigamia maritima (Geophilomorpha)EVOLUTION AND DEVELOPMENT, Issue 2 2004Ariel D. Chipman Summary Geophilomorph centipedes exhibit a number of unique characteristics that make them of particular developmental and evolutionary interest. Segment numbers in geophilomorphs are higher than in any other centipedes, ranging from 27 to 191. They may be constant within a species, presenting in extreme form the "counting" problem in development, or they may vary,a situation that provides us with the opportunity to study naturally occurring variation in segment numbers. All their segments are generated during embryogenesis, a situation unlike that in the more basal centipede orders, which generate only a fraction of their 15 trunk segments in the embryo and develop the rest postembryonically. Here we provide a foundation for further developmental studies of the Geophilomorpha, building on the one study that has been conducted to date, on the coastal species Strigamia maritima. Development begins with the migration of nuclei to the surface of the egg, which then condense to form an embryonic rudiment of more than 20,000 cells, covering an entire hemisphere. During early development, the embryo can be divided into two distinct areas: a large terminal disc of apparently undifferentiated tissue and the germ-band, which has a clear anteroposterior axis and differentiated segments. The germ-band forms from the anterior of the terminal disc and extends anteriorly as the disc contracts. New segments are formed at the posterior margin of the germ-band. Once the process of segmentation ends, the germ-band folds and sinks into the yolk. We note that the classic description of centipede development, by Heymons more than a century ago, contains a fundamental error in the identification of the axes and hence in the interpretation of early segmentation. [source] A study of the diversity and geographical variation in numbers of leg-bearing segments in centipedes (Chilopoda: Geophilomorpha) in north-western EuropeBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010STYLIANOS M. SIMAIAKIS Five species of geophilomorphs, Strigamia maritima (Leach, 1817), Geophilus flavus (De Geer, 1778), Geophilus truncorum Bergsøe and Meinert, 1866, Geophilus proximus C. L. Koch, 1847, and Pachymerium ferrugineum (C. L. Koch, 1835), from various sample sites in north-western Europe were examined for numbers of leg-bearing segments. Where data was adequate, mean segment numbers were correlated with latitudinal gradients for each species. Solely in S. maritima and some populations of P. ferrugineum did the results show a highly significant geographic pattern towards more leg-bearing segments in southern populations of both sexes. As concerns G. proximus, we presented for the first time a remarkable geographic shift towards an increased number of pairs of legs in northern populations. Contrary to the conventional geographic pattern, we found that G. flavus and G. truncorum did not exhibit a north,south increase or decrease in segment number. Although there was no general/universal evidence supporting the occurrence of a significant regression slope between mean segment number and latitude/temperature, more information shows that the overall region-to-region segment variation was highly significant in both sexes. In S. maritima and P. ferrugineum mean segment number was correlated with the north,south temperature cline. The same was not observed in G. proximus. Parthenogenesis in G. proximus, and a series of ecological characteristics such as habitat preferences, spatial distribution, and fragmented populations could explain the presence or absence of a geographic patterning of segment number variation along a latitudinal cline. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 899,909. [source] | ||||||||||