The osteology of the Mediterranean and African dwarf goby Corcyrogobius (Teleostei: Gobiidae) – Testing the limits of μCT-Scanning

Within the past decade, Micro-CT-Scanning and 3D-Rendering have become established methods in palaeontology for both actualistic and fossil studies. While this non-destructive procedure has yielded impressive, species-identifying traits for many fossil and recent organisms, we asked whether it could also accurately reconstruct the delicate skeletons of one of Earth’s smallest vertebrates: dwarf gobies. The material presented here includes the three species of Corcyrogobius Miller, 1972, rare cryptobenthic dwarf gobies of the Adriatic Sea and West African coasts. The specimens, ranging in size between 12 and 25 mm, come from the collection of the British Museum of Natural History, London (BMNH), and the Zoological State Collection, Munich (ZSM). They were micro-CT-scanned, visualized using Amira 3D-rendering and compared with x-ray images and isolated otoliths (hearing stones). Despite common artifacts and dislocations due to scanning errors, the scans revealed a surprising amount of intricate detail. The taxonomically important otoliths could be rendered with high resolution. Even closely overlapping bones, such as gill covers (opercle, subopercle), could be separated using Amira’s segmentation tool. Moreover, previously unknown differences between the three species were detected in the jaw bones, pelvis and vertebral column. A frequently encountered downside was the sometimes poor resolution of the scans and, as a result, of the segmented bones. Additionally, the program had difficulties distinguishing weakly ossified bones from soft tissue.

At this small scale, Micro-CT-scanning presents challenges and may produce misleading results. Nevertheless, our work with Corcyrogobius demonstrates that even miniature vertebrates can be successfully analyzed using this technique.