Spine skeleton morphogenesis during regeneration in clypeasteroid and camarodont sea urchins
The process of skeleton morphogenesis is described for broken and totally removed spines in clypeasteroid (hollow spine) and camarodont (solid spine) sea urchins. Spine regeneration after total spine removal is completed in 40–45 days in clypeasteroids and in 60–70 days in camarodont sea urchins. Along with common stages of formation of longitudinal ribs in both hollow and solid spines, fundamental differences were found between the initial stages of reparative growth of the spine shaft. The spine shaft is formed from a single median process in clypeasteroids and from many simultaneously growing processes in camarodont sea urchins. Reparative morphogenesis of totally removed and partly broken spines in clypeasteroid sea urchins and totally removed spines in camarodont sea urchins leads to the formation of a skeletal structure identical to the intact spine. However, during the regeneration of broken camarodont spines, lateral growth is markedly retarded. As a result, the regenerated part of the spine shaft has a smaller diameter when the initial spine length is achieved. A hypothesis is proposed on a paedomorphic origin of spines in the clypeasteroid sea urchins on the basis of the juvenile stage of definitive spines in the camarodont sea urchins.
Tissue and spine regeneration in the temperate sea urchin Psammechinus miliaris
Abstract The tissue regenerative capabilities of echinoderms are well known at the morphogenic level, yet significant knowledge gaps remain concerning the molecular control of these processes. This pilot study assayed two pharmacological agents (vincristine sulphate and DAPT) injected directly into the body cavity of specimens of the temperate echinoid Psammechinus miliaris which had had their spines and tube feet deliberately amputated. Vincristine sulphate, which is a generalised mitotic inhibitor, was used as a positive control, whereas DAPT is a y-secretase inhibitor known to block sea urchin embryo development and suppress echinoid regeneration by interfering with Notch signalling pathways. Significant differences in regeneration rate became apparent in both treatments 29 days post amputation with both inhibitors slowing regeneration of tube feet (0.6 μg/g vincristine sulphate by 44.4% relative to controls; 4 μg/g DAPT by 55.6% relative to controls) and spines (0.6 μg/g vincristine sulphate by 53.3% relative to controls; 4 μg/g DAPT by 66.7% relative to controls). Vincristine sulphate was more clearly dose-dependent than DAPT. This initial inhibition-based approach allows inferences to be made concerning possible molecular pathways controlling regeneration within P. miliaris and adds further support to the hypothesis that Notch signalling plays a major role in regulating regeneration in echinoids.
Archaeological Survey of Dangoyama Kofun by 3DGPR
We presented a three-dimensional ground penetrating radar (3DGPR) system for the archeological investigation in a harsh site, where we have to deal with many trees and/or great topographic variations. This system consists of a commercial GPR system with a laser positioning system. With this system, we can move the GPR antenna freely, on which a positioning detector can record accurate position for each GPR data trace. We applied our 3DGPR system at Dangoyama Kofun, a burial mound, in Fukushima prefecture, Japan. A lot of trees and bushes covered the survey area and cannot be cut. We acquired six datasets in two days in this area. We successfully imaged the boundary between the original surface of the burial mound and the covering soil clearly at about 0.3 m depth around the mound. Furthermore, we found some strong reflections appeared at 0.8 m depth in the top area of the mound, which can be from the artificial parts of the burial mound. The results would greatly aid the following archaeological excavation. In addition, we compared the non-interpolated depth slice with interpolated depth slice at same position and demonstrated that the interpolation process on threedimensional GPR data may introduce some artifacts which might mislead our interpretation.