What's in this crab? MRI providing high-resolution three-dimensional insights into recent finds and historical collections of Brachyura.
TL;DR: Magnetic resonance imaging may open up extensive possibilities to study evolutionary and ecological questions by utilizing the immense wealth of natural historical collections without any destruction of the items.
About: This article is published in Zoology.The article was published on 2017-04-01. It has received 14 citations till now.
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TL;DR: The present study combines advances in micro-computed tomography (micro-CT) and histology to study the internal morphology of decapod larvae, using the common spider crab as a model and resolving the individual limitations of these techniques.
Abstract: Traditionally, the internal morphology of crustacean larvae has been studied using destructive techniques such as dissection and microscopy The present study combines advances in micro-computed tomography (micro-CT) and histology to study the internal morphology of decapod larvae, using the common spider crab (Maja brachydactyla Balss, 1922) as a model and resolving the individual limitations of these techniques The synergy of micro-CT and histology allows the organs to be easily identified, revealing simultaneously the gross morphology (shape, size, and location) and histological organization (tissue arrangement and cell identification) Micro-CT shows mainly the exoskeleton, musculature, digestive and nervous systems, and secondarily the circulatory and respiratory systems, while histology distinguishes several cell types and confirms the organ identity Micro-CT resolves a discrepancy in the literature regarding the nervous system of crab larvae The major changes occur in the metamorphosis to the megalopa stage, specifically the formation of the gastric mill, the shortening of the abdominal nerve cord, the curving of the abdomen beneath the cephalothorax, and the development of functional pereiopods, pleopods, and lamellate gills The combination of micro-CT and histology provides better results than either one alone
23 citations
TL;DR: This study presents the first description of a hermit crab in which a majority of taxonomic details are illustrated through 3D volume-rendered illustrations, and the South African taxon was confirmed to be genetically distinct from all species tested.
Abstract: A new species of hermit crab, Pagurus fraserorum n. sp. (family Paguridae) is described from rocky subtidal reefs off KwaZulu-Natal, South Africa, and illustrated using both conventional drawings and colour photographs, and via three-dimensional (3D) X-ray micro-computed tomography (μCT). Because of the limitation μCT has in detecting very fine and soft structures, a novel approach of manually drawing setation and spinulation onto the two-dimensional images of the 3D visualizations was used to illustrate the pereopods. In addition, an interactive figure and rotation movie clips in the supplement section complement the species description, and the 3D raw data of the 3D type data are downloadable from the Gigascience Database repository. The new species is the sixth species of Pagurus Fabricius, 1775 reported from South Africa and is closely allied to the Indo-Pacific P. boriaustraliensis Morgen, 1990 and P. pitagsaleei McLaughlin, 2002, from which it differs by its shorter ocular peduncles, by the armature of the carpus of the right cheliped, and also in colouration. This study presents the first description of a hermit crab in which a majority of taxonomic details are illustrated through 3D volume-rendered illustrations. In addition, colour photographs and COI molecular barcodes are provided, and the latter compared to COI sequences of specimens from Western Australia previously identified as P. boriaustraliensis and of specimens of P. pitagsaleei from Taiwan, as well as to three additional South African members of the genus. The South African taxon was confirmed to be genetically distinct from all species tested.
8 citations
TL;DR: By minimizing individual variability, at least for aquatic arthropods, this pioneer study aims for the inference of method-based conversion factors in the future, providing a valuable tool for reducing quantitative neuroanatomical data already published to a common denominator.
Abstract: In the field of comparative neuroanatomy, a meaningful interspecific comparison demands quantitative data referring to method-specific artifacts. For evaluating the potential of state-of-the-art imaging techniques in arthropod neuroanatomy, micro-computed X-ray microscopy (μCT) and two different approaches using confocal laser-scanning microscopy (cLSM) were applied to obtain volumetric data of the brain and selected neuropils in Procambarus fallax forma virginalis (Crustacea, Malacostraca, Decapoda). The marbled crayfish P. fallax cf. virginalis features a parthogenetic reproduction generating genetically identical offspring from unfertilized eggs. Therefore, the studied organism provides ideal conditions for the comparative analysis of neuroanatomical imaging techniques and the effect of preceding sample preparations of nervous tissue. We found that wet scanning of whole animals conducted with μCT turned out to be the least disruptive method. However, in an additional experiment it was discovered that fixation in Bouin's solution, required for μCT scans, resulted in an average tissue shrinkage of 24% compared to freshly dissected and unfixed brains. The complete sample preparation using fixation in half-strength Karnovsky's solution of dissected brains led to an additional volume decrease of 12.5%, whereas the preparation using zinc-formaldehyde as fixative resulted in a shrinkage of 5% in comparison to the volumes obtained by μCT. By minimizing individual variability, at least for aquatic arthropods, this pioneer study aims for the inference of method-based conversion factors in the future, providing a valuable tool for reducing quantitative neuroanatomical data already published to a common denominator. However, volumetric deviations could be shown for all experimental protocols due to methodological noise and/or phenotypic plasticity among genetically identical individuals. MicroCT using undried tissue is an appropriate non-disruptive technique for allometry of arthropod brains since spatial organ relationships are conserved and tissue shrinkage is minimized. Collecting tissue-based shrinkage factors according to specific sample preparations might allow a better comparability of volumetric data from the literature, even if another technique was applied.
6 citations
Cites methods from "What's in this crab? MRI providing ..."
...…the removal of the cuticle or dissection of the nervous tissue, thus an analysis of the brain within the animal is only feasible by using X-ray -or magnetic resonance imaging techniques (Brinkley et al., 2005;Herberholz et al., 2004; Köhnk et al., 2017, and reviewed in Ziegler et al., 2011)....
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TL;DR: The protocol described here is also applicable for larger specimens of a variety of species and spans over 2-3 days resulting in an image stack ready for postprocessing and visualization.
Abstract: Micro-computed X-ray tomography (μCT) coupled with visualization techniques such as three-dimensional reconstruction of internal morphological structures has opened up new pathways for analyzing the anatomy of nervous systems in intact specimens. The possibility for combining μCT with other techniques is one of the major advantages of μCT scanning, and the technical development of higher resolutions in lab-based μCT-scanners allows for investigating the anatomy of specimens in the sub-milimeter range. The European shore crab Carcinus maenas features a larval development over four zoeal and one megalopal stage with body lengths ranging from 500 μm to 2000 μm. The developing nervous system in the larvae of C. maenas is organized into a central brain which is connected via esophageal connectives with a ventral nerve chord and segmental ganglia. Since soft tissues such as the nervous tissues feature low contrasts compared to other tissues such as muscles or cuticularized body parts, the interpretation in μCT scans is challenging and needs some practice. The protocol described here is also applicable for larger specimens of a variety of species and spans over 2-3 days resulting in an image stack ready for postprocessing and visualization.
5 citations
TL;DR: The morphological distinction between the Austinograea species is supported by molecular analyses, for A. williamsi, A. alayseae, and A. rodriguezensis from the western Indian Ocean.
Abstract: Two new species of the genus Austinograea Hessler & Martin, 1989 (Bythograeidae Williams, 1980), distinct from A. williamsi Hessler & Martin, 1989 and A. alayseae Guinot, 1990, are here reported from hydrothermal vent fields of the southwestern Pacific: A. hourdezi n. sp. and A. jolliveti n. sp., both in the Lau and North Fiji Back-Arc Basins. Austinograea hourdezi n. sp. is characterised by two depressions appearing as dark spots on the palm of both chelipeds in males and differs from the more northern A. williamsi and the Indian A. rodriguezensis Tsuchida & Hashimoto, 2002, which show only one spot on the male chelae, near the base of the dactylus. Some individuals exhibiting all morphological characters of A. hourdezi n. sp. bear only one spot on the chelae, near the base of dactylus; the fact that most are left-handed corresponds to the presence of a regenerated cheliped, with handedness reversal after the accidental loss of the major cheliped: these atypical individuals are here treated as A...
5 citations
References
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TL;DR: Molecular evidence is presented that Jamaican land crabs represent a single adaptive radiation from a marine ancestor that invaded terrestrial habitats only 4 million years ago and probably reflects the Mid-Tertiary inundation of that island.
Abstract: Crabs of the family Grapsidae are abundant organisms in most intertidal communities. However, relatively few species live in complete independence of the sea1. Of those species that do, Jamaica's nine endemic species of land crabs are unique in their exceptional adaptations to terrestrial life, which include the only active brood-care for larvae and juveniles known in crabs2,3,4,5,6. These adaptations, and the morphological similarity to a group of southeast Asian land-dwelling crabs, have raised the question of the number and age of land invasions of the Jamaican species. Here we present molecular evidence that Jamaican land crabs represent a single adaptive radiation from a marine ancestor that invaded terrestrial habitats only 4 million years (Myr) ago. A Late-Tertiary origin has also been found for lizards and frogs of Jamaica7,8,9 and probably reflects the Mid-Tertiary inundation of that island10.
458 citations
"What's in this crab? MRI providing ..." refers background in this paper
...Decapods have populated habitats ranging from the deep sea to freshwater systems, and the land up to the tree crowns of tropical rainforests (Hessler and Martin, 1989; Schubart et al., 1998; Magalhaes and Türkay, 2008)....
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TL;DR: Micro-CT has the potential to replace serial histology as the reference standard in many in vitro studies, and provides a practical approach to obtain quantitative information during some longitudinal investigations in vivo.
343 citations
"What's in this crab? MRI providing ..." refers methods in this paper
...…analysis including X-ray computerized tomography has been successfully used in this context (Noever et al., 2016) but with same limitations (including high doses of ionizing radiation and in many cases the need for additional contrast agents) (Holdsworth and Thornton, 2002; Schambach et al., 2010)....
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TL;DR: The objectives are to familiarize the reader with the basics of muCT techniques, to present the type of experimental designs currently used, and to highlight limitations, future directions, in muCT-scanner research applications, and experimental methods.
306 citations
"What's in this crab? MRI providing ..." refers methods in this paper
...…analysis including X-ray computerized tomography has been successfully used in this context (Noever et al., 2016) but with same limitations (including high doses of ionizing radiation and in many cases the need for additional contrast agents) (Holdsworth and Thornton, 2002; Schambach et al., 2010)....
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31 Dec 1991
114 citations