Trunk anomalies in the centipede Stigmatogaster subterranea provide insight into late-embryonic segmentation

Leśniewska, Małgorzata; Bonato, Lucio; Minelli, Alessandro; Fusco, Giuseppe

doi:10.1016/j.asd.2009.05.001

Cited by 39 publications

(28 citation statements)

References 19 publications

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“…Defects include deformities of the head, abdominal epimera, pleopods, telson, and uropods in crustaceans (Fernandez et al 2011). Centipedes may have mispaired tergites, shrunk segments, variously deformed sclerites, bifurcated trunk, and defects of spiracles (Leśniewska et al 2009). In insects, a majority of anomalies affect antennae, mandibles, legs, and the exoskeleton (Asiain and Márquez 2009).…”

Section: Discussionmentioning

confidence: 99%

Morphological and anatomical changes related to leg anomalies in Tegenaria atrica

2015

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A range of leg anomalies was detected in embryos of the Tegenaria atrica spiders exposed to alternating temperatures of 14 and 32 °C. Multiple anomalies were observed in 13 individuals. This study is based on five individuals: two individuals affected by oligomely combined, respectively, with heterosymely and polymely, one affected by polymely with heterosymely, one by complicated polymely (accompanied by the reduction in length and malformations of the distal parts of the legs), and one individual with pure polymely. Changes in the central nervous system of these five individuals were described in detail on the basis of histological sections. The changes were mainly related to the number of neuromeres. Individuals affected by polymely had additional ganglia corresponding to the number of additional appendages, whereas the absence of a leg (oligomely) was associated with the absence of a ganglion. Histological analysis showed the fusion of ganglia in the three polymelic specimens, even though additional appendages were not fused.

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Section: Discussionmentioning

confidence: 99%

Morphological and anatomical changes related to leg anomalies in Tegenaria atrica

2015

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“…[24,25]). There is a problem, however, in mining the literature for this kind of evidence, because the most interesting examples, those for which we could nowadays formulate tentative explanatory hypotheses in terms of gene (mis)expression, are often concealed under poorly informative terminology and are seldom described in satisfactory detail.…”

Section: Discussionmentioning

confidence: 99%

Segmentation of the millipede trunk as suggested by a homeotic mutant with six extra pairs of gonopods

2014

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BackgroundThe mismatch between dorsal and ventral trunk features along the millipede trunk was long a subject of controversy, largely resting on alternative interpretations of segmentation. Most models of arthropod segmentation presuppose a strict sequential antero-posterior specification of trunk segments, whereas alternative models involve the early delineation of a limited number of ‘primary segments’ followed by their sequential stereotypic subdivision into 2n definitive segments. The ‘primary segments’ should be intended as units identified by molecular markers, rather than as overt morphological entities. Two predictions were suggested to test the plausibility of multiple-duplication models of segmentation: first, a specific pattern of evolvability of segment number in those arthropod clades in which segment number is not fixed (e.g., epimorphic centipedes and millipedes); second, the occurrence of discrete multisegmental patterns due to early, initially contiguous positional markers.ResultsWe describe a unique case of a homeotic millipede with 6 extra pairs of ectopic gonopods replacing walking legs on rings 8 (leg-pairs 10-11), 15 (leg-pairs 24-25) and 16 (leg-pairs 26-27); we discuss the segmental distribution of these appendages in the framework of alternative models of segmentation and present an interpretation of the origin of the distribution of the additional gonopods.The anterior set of contiguous gonopods (those normally occurring on ring 7 plus the first set of ectopic ones on ring 8) is reiterated by the posterior set (on rings 15-16) after exactly 16 leg positions along the AP body axis. This suggests that a body section including 16 leg pairs could be a module deriving from 4 cycles of regular binary splitting of an embryonic ‘primary segment’.ConclusionsA very likely early determination of the sites of the future metamorphosis of walking legs into gonopods and a segmentation process according to the multiplicative model may provide a detailed explanation for the distribution of the extra gonopods in the homeotic specimen. The hypothesized steps of segmentation are similar in both a normal and the studied homeotic specimen. The difference between them would consist in the size of the embryonic trunk region endowed with a positional marker whose presence will later determine the replacement of walking legs by gonopods.

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“…Moreover, this apparent desynchronization is reversible: The PSM cells gradually lost synchrony while the coupling was blocked, and after washing out the DAPT and re-engaging cell–cell coupling, the cyclic gene wave patterns sharpened as the oscillators gradually restored synchrony. In arthropods and annelids, a type of segmental anomaly, termed helicomery or “spiral segmentation”, was frequently observed in trunk regions (Leśniewska et al., 2009), and multiple developmental defects were suggested to be associated with. The genetic causes of helicomery haven't been identified; thus, testing whether Notch signalling is involved in the formation or helicomery is still an open question.…”

Section: A Three-tier Model Of the Segmentation Clockmentioning

confidence: 99%

Delta-Notch signalling in segmentation

Liao

Oates

2017

Arthropod Structure & Development

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Modular body organization is found widely across multicellular organisms, and some of them form repetitive modular structures via the process of segmentation. It's vastly interesting to understand how these regularly repeated structures are robustly generated from the underlying noise in biomolecular interactions. Recent studies from arthropods reveal similarities in segmentation mechanisms with vertebrates, and raise the possibility that the three phylogenetic clades, annelids, arthropods and chordates, might share homology in this process from a bilaterian ancestor. Here, we discuss vertebrate segmentation with particular emphasis on the role of the Notch intercellular signalling pathway. We introduce vertebrate segmentation and Notch signalling, pointing out historical milestones, then describe existing models for the Notch pathway in the synchronization of noisy neighbouring oscillators, and a new role in the modulation of gene expression wave patterns. We ask what functions Notch signalling may have in arthropod segmentation and explore the relationship between Notch-mediated lateral inhibition and synchronization. Finally, we propose open questions and technical challenges to guide future investigations into Notch signalling in segmentation.

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Trunk anomalies in the centipede Stigmatogaster subterranea provide insight into late-embryonic segmentation

Cited by 39 publications

References 19 publications

Morphological and anatomical changes related to leg anomalies in Tegenaria atrica

Morphological and anatomical changes related to leg anomalies in Tegenaria atrica

Segmentation of the millipede trunk as suggested by a homeotic mutant with six extra pairs of gonopods

Delta-Notch signalling in segmentation

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