A micro X-ray computed tomography dataset of South African hermit crabs (Crustacea: Decapoda: Anomura: Paguroidea) containing scans of two rare specimens and three recently described species

Abstract

BackgroundAlong with the conventional deposition of physical types at natural history museums, the deposition of 3-dimensional (3D) image data has been proposed for rare and valuable museum specimens, such as irreplaceable type material.FindingsMicro computed tomography (μCT) scan data of 5 hermit crab species from South Africa, including rare specimens and type material, depicted main identification characteristics of calcified body parts. However, low-image contrasts, especially in larger (>50 mm total length) specimens, did not allow sufficient 3D reconstructions of weakly calcified and fine characteristics, such as soft tissue of the pleon, mouthparts, gills, and setation. Reconstructions of soft tissue were sometimes possible, depending on individual sample and scanning characteristics. The raw data of seven scans are publicly available for download from the GigaDB repository.ConclusionsCalcified body parts visualized from μCT data can aid taxonomic validation and provide additional, virtual deposition of rare specimens. The use of a nondestructive, nonstaining μCT approach for taxonomy, reconstructions of soft tissue structures, microscopic spines, and setae depend on species characteristics. Constrained to these limitations, the presented dataset can be used for future morphological studies. However, our virtual specimens will be most valuable to taxonomists who can download a digital avatar for 3D examination. Simultaneously, in the event of physical damage to or loss of the original physical specimen, this dataset serves as a vital insurance policy.

Three phyla—Two type specimens—One shell: History of a snail shell revealed by modern imaging technology

“…Therefore, the anteriormost section of the body that is visible is a large sternal sclerite (endosternite) located dorso‐anteriorly to the first pereiopods (Pilgrim, ), and the stumps of pereiopods 1 and 2. This sclerite has a very similar shape and position to that of Diogenes albimanus , for which µCT data of the holotype is available (http://gigadb.org/dataset/100364; Landschoff, Du Plessis, & Griffiths, , ), albeit without the degree of asymmetry indicative of the “left‐handedness” of this particular Diogenes species (Figure c). Conversely, in our specimen this asymmetry is not apparent, making the hermit crab “equal‐handed.” Moreover, the front edge of the soft part of a hermit crab carapace is well‐recognizable showing its typical composition of sclerites and soft connectors in between.…”

“…sclerite has a very similar shape and position to that of Diogenes albimanus, for which µCT data of the holotype is available (http:// gigadb.org/datas et/100364;Landschoff, Du Plessis, & Griffiths, 2018a, 2018b, albeit without the degree of asymmetry indicative of the "left-handedness" of this particular Diogenes species (Figure S3c). Conversely, in our specimen this asymmetry is not apparent, making the hermit crab "equal-handed."…”

MicroCT imaging applied to description of a new species of Pagurus Fabricius, 1775 (Crustacea: Decapoda: Anomura: Paguridae), with selection of three-dimensional type data

“…female 2.4 mm, SAMC MB-A066770) was wrapped in parafilm (Bemis NA, Neenah, WI, United States), mounted on rigid foam, which itself was glued to the top of a plastic rod, and scanned at 5 μm voxel resolution. In a datanote, Landschoff et al [50] give detailed information on data acquisition and processing for species descriptions.…”

“…Because in Paguridae the chelipeds have significant identification characters, through the rotation movies the viewer can gain even more insights into the armature and appearance. All scan raw data are publicly available for download from the GigaScience Database (GigaDB) online depository [60], and more detailed information on scanning parameters and data quality can be retrieved from the accompanying datanote [50]. …”