Cell proliferation and migration during early development of a symbiotic scleractinian coral

In scleractinian reef-building corals, patterns of cell self-renewal, migration and death remain virtually unknown, limiting our understanding of cellular mechanisms underlying initiation of calcification, and ontogenesis of the endosymbiotic dinoflagellate relationship. In this study, we pulse-labelled the coral Stylophora pistillata for 24 h with BrdU at four life stages (planula, early metamorphosis, primary polyp and adult colony) to investigate coral and endosymbiont cell proliferation during development, while simultaneously recording TUNEL-positive (i.e. apoptotic) nuclei. In the primary polyp, the fate of BrdU-labelled cells was tracked during a 3-day chase. The pharynx and gastrodermis were identified as the most proliferative tissues in the developing polyp, and BrdU-labelled cells accumulated in the surface pseudostratified epithelium and the skeletogenic calicodermis during the chase, revealing cell migration to these epithelia. Surprisingly, the lowest cell turnover was recorded in the calicodermis at all stages, despite active, ongoing skeletal deposition. In dinoflagellate symbionts, DNA synthesis was systematically higher than coral host gastrodermis, especially in planula and early metamorphosis. The symbiont to host cell ratio remained constant, however, indicating successive post-mitotic control mechanisms by the host of its dinoflagellate density in early life stages, increasingly shifting to apoptosis in the growing primary polyp.

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

The enigmatic Ediacaran (late Precambrian) genus Rangea and related forms

The late Precambrian genus Rangea Gürich, 1929, a frond-like fossil composed of repeated foliate elements, is one of the first discovered forms belonging to the now widely known soft-bodied assemblages characterizing the Ediacaran Period. Rangea occurs together with the genera Pteridinium Gürich, 1933, and Ernietta Pflug, 1966, in the lower parts of the Nama Group, Namibia (South West Africa).Investigation of the preservation and structure of Rangea, utilizing a methodology similar to that established by Wade (1968, 1971), indicates that it was probably a colonial octocoral consisting of a large tapering primary polyp, or oozoid, and a number of leaf-shaped, conjoined fronds which bore the feeding polyps; it is suggested to belong to a group of early Ediacaran anthozoans which provide a fossil link between the still living Telestacea and Pennatulacea. Similar investigations of Pteridinium and Ernietta disclose that their structure is different from Rangea and does not support ideas that they are related to it.

The Life Cycle of a Gorgonian: Eunicella Singularis (Esper, 1794)

The life cycle of the gorgonian Eunicella singularis has been studied with emphasis on larval behaviour, metamorphosis and annual growth. Planulae are found to have a mobile phase lasting from several hours to several days. Once settled, they metamorphose into a complete primary polyp in approximately four days. In the first year, budding will yield colonies of a height between 10 and 30 mm. Subsequently, average growth rates range from 14 to 33 mm year-1. Death may be due to several causes. Predators may partly denude the gorgonian branches, thus facilitating the settlement of epibionts, which in turn may invade the entire skeleton, slowly pushing back the living tissue of the gorgonian. Colonies may also be torn off their substratum by wave or current action, this process sometimes being speeded up when tall epibionts such as fast growing bryozoans enhance resistance to water movement. Once toppled, the gorgonians die by necrosis of their living tissues, or by being buried under sediment. Colonies of E. singularis are estimated to reach an age of approximately 25 to 30 years. Some data have been obtained on growth rates and life spans of two other Mediterranean gorgonians, Lophogorgia ceratophyta and Paramuricea clavata.

On the Hydroid of Eutima Gracilis (Forbes and Goodsir)

In July 1938 I succeeded in rearing the hydroid of Eutima gracilis (Forbes and Goodsir) (also known as Saphenia gracilis) from adult medusae which liberated their eggs and sperm in finger-bowls of sea water. These hydroids were only in the primary polyp stage, and I withheld publication hoping to repeat the work later and perhaps rear the hydroid to a more advanced stage. As it is unlikely that I may now have the opportunity of doing this it seems worth while to publish a short account with figures of the polyp.