Symmetry of echinoderms: From initial bilaterally-asymmetric metamerism to pentaradiality

Echinoderm radial symmetry has first appeared in the ambulacral system, when the ambulacral channel assumed the shape of a closed ring or a horseshoe with approximated ends, and then spread onto other organ systems. Its origin was a natural consequence of a steady increase of the original asymmetry of bilaterally-asymmetric three-segmented ancestors of echinoderms, culminated by closing of the ancestral linear metamerism into radiality. The evolutionary transformation from a simple pouchlike hydrocoel with one side channel to an elongated hydrocoel (located under the oesophagus) with two side channels, and finally to a nearly closed horseshoeshaped hydrocoel with three radial channels can be reconstructed based on the theca structure and the number of ambulacra in the row SolutaCincta-Helicoplacoidea. After the hydrocoel with three outbound ambulacral channels circled around the oesophagus as a horseshoe, it either closed into a ring, or its ends became closely approximated. This has determined the primary triradiate symmetry, which quickly transformed into pentaradial symmetry of the 2-1-2 type as a result of branching of two of the three primary radial channels. This occurred no earlier than the Late Vendian, when the first bilaterians appeared to have begun to acquire body appendages, and no later than the Early Cambrian, when the first skeletal remains of echinoderms entered the fossil record (in the Atdabanian). The 2-1-2 pentaradial symmetry evolved into the true pentaradiality as a result of shifting the timing of tentacle branching to earlier stages of ontogenesis and even spreading of the five tentacle primordia over the ambulacral ring. This occurred during the Ordovician.

Hyperspectral Imaging Technology for Revealing the Original Handwritings Covered by the Same Inks

This manuscript presents a preliminary investigation on the applicability of hyperspectral imaging technology for nondestructive and rapid analysis to reveal covered original handwritings.The hyperspectral imager Nuance‑Macro was used to collect the reflected light signature of inks from the overlapping parts.The software Nuance1p46 was used to analyze the reflected light signature of inks which shows the covered original handwritings.Different types of black/blue ballpoint pen inks and black/blue gel pen inks were chosen for sample preparation.From the hyperspectral images examined,the covered original handwritings of application were revealed in 90.5%,69.1%,49.5%,and 78.6%of the cases.Further,the correlation between the revealing effect and spectral characteristics of the reflected light of inks at the overlapping parts was interpreted through theoretical analysis and experimental verification.The results indicated that when the spectral characteristics of the reflected light of inks at the overlapping parts were the same or very similar to that of the ink that was used to cover the original handwriting,the original handwriting could not be shown.On the contrary,when the spectral characteristics of the reflected light of inks at the overlapping parts were different to that of the ink that was used to cover the original handwriting,the original handwriting was revealed.