Utilisation of Titanium and Titanium Dioxide as Scaffolds for Proliferating Coral Reef

Estimated 30 percent or more of coral reefs are now in danger of extinction by coastal construction increases and global temperatures rise. Several restoration techniques such as fragmentation, forming, Biorock have been developed in the past few years. In vertebrates such as mammals, osteoblast is known to form the bones composed of hydroxyapatite. Therefore, bone substitutional devices are generally surface modified to improve the adhesion of osteoblasts on the surfaces. Titanium dioxide film is often employed as the surface material for hard tissue substitutes made of titanium and its alloys. In hard corals, on the other hand, the soft tissue covered on the skeletons made of calcium carbonate has osteoblasts as well. The purpose of this work was to investigate the potential of titanium (Ti) and titanium dioxide (TiO2) as scaffolds for proliferating coral reefs by analysing the several interfacial reactions. The rods of pure Ti were anodised in aqueous phosphoric acid at a constant voltage of 80 V. The surfaces were confirmed to be anatase type TiO2. The coral fragments were kept in contact with the rods in a lab-scale aquarium with artificial seawater for several days. The colony of polyps vigorously expanded on the surfaces. Fragments of coral were placed on pure Ti, TiO2 coated pure Ti in Petri dishes and were reared in artificial seawater. Fine spherical precipitates of calcium carbonate with aragonite structure, which is the same inorganic substance as corals, were observed radially and regularly on the surfaces of TiO2. In addition, the adherence of planula larva to the sputtered TiO2 film was observed by using a QCM (Quartz Crystal Microbalance) method. The approach and adhesion of planula larva to the surface could be detected by monitoring the resonance frequency and resistance. The surfaces might have a great potential in coral reef regenerations.

Cell shape changes during larval body plan development in Clytia hemisphaerica

The cnidarian “planula” larva shows radial symmetry around a polarized, oral-aboral, body axis and comprises two epithelia cell layers, ectodermal and endodermal. This simple body plan is set up during gastrulation, a process which proceeds by a variety of modes amongst the diverse cnidarian species. In the hydrozoan laboratory model Clytia hemisphaerica, gastrulation involves a process termed unipolar cell ingression, in which the endoderm derives from mass ingression of individual cells via a process of epithelial-mesenchymal transition (EMT) around the future oral pole of an epithelial embryo. This contrasts markedly from the gastrulation mode in the anthozoan cnidarian Nematostella vectensis, in which endoderm formation primarily relies on cell sheet invagination. To understand the cellular basis of gastrulation in Clytia we have characterized in detail successive cell morphology changes during planula formation by Scanning and Transmission Electron Microscopy combined with confocal imaging. These changes successively accompany epithialization of the blastoderm, EMT occurring in the oral domain through the bottle cell formation and ingression, cohesive migration and intercalation of ingressed cells with mesenchymal morphology, and their epithelialization to form the endoderm. From our data, we have reconstructed the cascade of morphogenetic events leading to the formation of planula larva. We also matched the domains of cell morphology changes to the expression of selected regulatory and marker genes expressed during gastrulation. We propose that cell ingression in Clytia not only provides the endoderm, but generates internal forces that shape the embryo in the course of gastrulation. These observations help build a more complete understanding of the cellular basis of morphogenesis and of the evolutionary plasticity of cnidarian gastrulation modes.

Uji Peptida Komersial Hym-248 terhadap Metamorfosis dan Penempelan Planula yang berasal dari Slick (Testing of Commersial Peptide Hym-248 on Metamorphoses and Settlement of Planulae Collected from Slick)

Metamorfosis dan penempelan merupakan proses yang amat penting dalam siklus hidup koloni karang. Koloni karang hanya akan terbentuk jika larva planula berhasil bermetamorfosis dari larva planktonik menjadi bentik dan menempel pada substrat untuk kemudian bertumbuh menjadi koloni baru. Induktor berperan merangsang metamorfosis dan meningkatkan persentase jumlah zigot yang menempel dan berkembang menjadi koloni baru. Peptida komersial adalah neuropeptida golongan GLWamida yang bertindak sebagai hormon pemicu terjadinya metamorfosis planulae larva. Hasil penelitian menunjukkan, Hym-248, peptida komersial anggota GLWamida, mampu menginduksi metamorfosis dan penempelan planula yang berasal dari slick (kumpulan gamet yang terapung-apung di permukaan laut setelah dilepaskan koloni karang pada peristiwa spawning multispesifik). Slick dikoleksi dari Pulau Sambangan, Kepulauan Karimunjawa saat spawning masal terjadi pada bulan Maret. Seluruh dosis yang dicobakan mampu menginduksi proses metamorfosis dan settlement planula larva setelah planula diinkubasi dalam media yang telah diberi Hym-248. Hasil ini memberi peluang dilakukannya pembenihan larva planulae secara masal untuk keperluan restorasi terumbu karang dan budidaya karang. Kata kunci: metamorfosis, settlement, budidaya karang, Acropora, spawning masal, slick Settlement and metamorphosis, which leads to the formation of primary polyp, are critical steps in the life cycles of corals. Metamorphosis cue is necessary to create an internal trigger to initiate metamorphosis in coral larvae. Neuropeptides which act hormonally to induce metamorphosis, provide a reliable and efficient settlement cue for ex situ larval culture. Here we report that Hym-248, one member of GLWamide peptide can induce metamorphosis of planulae derived from collected slick. Experiments were done in Sambangan Island after March spawning event. The results showed that all applied doses of Hym-248 successfully induced the metamorphosis and settlement of planulae larvae produced from slick. The result of this study showed that coral propagules can be produced faster by applying the commercial peptide as the inducer which leads to mass production of coral propagules for coral culture. Key words: metamorphosis, settlement, coral culture, Acropora, mass-spawning, slick

Back in time: a new systematic proposal for the Bilateria

Conventional wisdom suggests that bilateral organisms arose from ancestors that were radially, rather than bilaterally, symmetrical and, therefore, had a single body axis and no mesoderm. The two main hypotheses on how this transformation took place consider either a simple organism akin to the planula larva of extant cnidarians or the acoel Platyhelminthes (planuloid–acoeloid theory), or a rather complex organism bearing several or most features of advanced coelomate bilaterians (archicoelomate theory). We report phylogenetic analyses of bilaterian metazoans using quantitative (ribosomal, nuclear and expressed sequence tag sequences) and qualitative (HOX cluster genes and microRNA sets) markers. The phylogenetic trees obtained corroborate the position of acoel and nemertodermatid flatworms as the earliest branching extant members of the Bilateria. Moreover, some acoelomate and pseudocoelomate clades appear as early branching lophotrochozoans and deuterostomes. These results strengthen the view that stem bilaterians were small, acoelomate/pseudocoelomate, benthic organisms derived from planuloid-like organisms. Because morphological and recent gene expression data suggest that cnidarians are actually bilateral, the origin of the last common bilaterian ancestor has to be put back in time earlier than the cnidarian–bilaterian split in the form of a planuloid animal. A new systematic scheme for the Bilateria that includes the Cnidaria is suggested and its main implications discussed.