Anterior regeneration after fission in the holothurianCladolabes schmeltzii(Dendrochirotida: Holothuroidea)

Abstract

The regeneration of the anterior portion of the body after fission was studied in the holothurian Cladolabes schmeltzii using electron microscopy methods. Following fission, the posterior portion of the digestive tube, cloaca, and respiratory trees remain in the posterior fragment of the body. The regeneration comprises five stages. In the first stage, connective-tissue thickening (an anlage of the aquapharyngeal bulb) occurs on the anterior end between the torn-off ends of the ambulacra. Most of the lost anterior organs developed in the second and third stages. The structures of water-vascular system and nerve ring form through dedifferentiation, proliferation, and migration of cells of the radial water-vascular canals and the radial nerve cords, correspondently. The lost digestive system portion is restored through the formation and merging of two anlagen. The digestive epithelium of the esophagus and pharynx develops from lining cells of microcavities near the central portion of the connective-tissue thickening, which probably migrate from the epidermis. The second gut anlage develops through transformation of the anterior gut remnant portion. The enterocytes partly dedifferentiate, but the epithelium retains integrity. The gut anlage grows down the mesentery and joins the regenerating aquapharyngeal bulb. In the fourth and fifth stages, all lost organs are formed and have nearly normal structure. The regeneration was concluded to occur through morphallactic rearrangements of the remaining parts of organs. Epithelial morphogenesis is the key development mechanism of the digestive, water-vascular, and nervous systems.

Molecular mechanisms of fission in echinoderms: Transcriptome analysis

“…In this regard, the factors that could be related to asexual reproduction and regeneration were analyzed. In holothurians, asexual reproduction occurs by the architomy type, and regeneration of the lost structures begins only after fission [ 3 , 16 , 20 , 21 ]. Nevertheless, products of the genes of 26 transcription factors that are related to regulation of morphogenesis are detected only in dividing C .…”

“…To date, no studies of the cellular and molecular mechanisms of fission in echinoderms have been conducted. There are a few publications on morphology of dividing individuals and regeneration of fragments after fission [ 17 – 21 ].…”

“…We have recently found that the holothurian Cladolabes schmeltzii shows the capability of transverse division [ 58 , 59 ]. The structure of internal organs and their post-fission regeneration in this species have been studied in detail [ 20 , 21 , 60 ]. The present study considers a comparative analysis of transcriptome of tissues in intact holothurians and individuals in the process of fission.…”

Neurons and Glia Cells in Marine Invertebrates: An Update

“…Developing mechanisms of NS are better understood where cellular division, differentiation, and cellular migration are relevant processes required in both vertebrates and invertebrates (Anderson et al, 1980;Bulloch, 1985). Respect to the regeneration processes in the NS of marine organisms, the process have been observed for years (Weis and Weis, 1978;Ladurner et al, 2000;Dahlberg et al, 2009), and now some key molecules are used as regeneration factors (Bailly et al, 2014;Joly, 2017;Kamenev and Dolmatov, 2017).…”

Morphogenesis and histogenesis during the arm regeneration in a basket star Astrocladus dofleini (Euryalida, Ophiuroidea, Echinodermata)

“…In sea lilies, regeneration speed of arms were examined based on fossil records (Syverson & Baumiller, 2018), although no histological examination has so far been carried out on the branched‐arm regeneration in the extant taxa. In sea cucumbers, studies on the regeneration of internal organs have been carried out in several species (Dolmatov, 2014; Garcia‐Arraras & Dolmatov, 2010; Kamenev & Dolmatov, 2015, 2016; Odintsova, Dolmatov, & Mashanov, 2005; Okada & Kondo, 2019).…”