Octocoral Guaiagorgia

 

大家好！我哋係來自中文大學 珊瑚學院嘅FYP學生，Alice同Anna今年我哋研究室收到改善海洋生態基金嘅資助，研究一種香港搵到但世界少見嘅柳珊瑚 — Guaiagorgia 。Alice會研究佢哋嘅繁殖，而Anna就會研究佢哋承受壓力嘅能力。

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Hi everyone! This is Alice and Anna and we are the final year project students in Coral Academy Lab, The Chinese University of Hong Kong. This year our lab received funding support from the Marine Ecology Enhancement Fund (MEEF) to look into a gorgonian coral, Guaiagorgia, which can be commonly found in some sites in Hong Kong but rarely in the world. Alice will investigate their reproductive biology, while Anna will study their environmental tolerance. 

 

你應該有聽過珊瑚，咁你又知唔知珊瑚可按觸手數目分為兩大類？珊瑚蟲的觸手數目為六或其倍數的分類為「六放珊瑚亞網」(Hexacorallia)；有八隻觸手則為「八放珊瑚亞網」(Octocorallia)。 六放珊瑚嘅成員包括石珊瑚同黑珊瑚，八放珊瑚嘅成員就包括軟珊瑚、柳珊瑚同海筆。而我哋研究嘅𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢就係柳珊瑚嘅其中一個屬(Genus)。

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Do you know that corals are divided into two groups? Corals with 6 or multiples of 6 tentacles in each polyp belongs to subclass Hexacorallia, and corals with 8 tentacles in each polyp belongs to subclass Octocorallia. Hard corals and black corals are hexacorals, while soft corals, gorgonian and sea fans are all octocorals. The coral we are studying, Guaiagorgia, is a genus of gorgonians.

 

八放珊瑚係濾食性動物，會捉水入面嘅浮游生物嚟食同石珊瑚唔同，八放珊瑚無外在嘅碳酸鈣骨骼，亦都唔會組成珊瑚礁。

 

Many octocorals are filter feeders and feed on plankton. Unlike hard corals, octocorals do not possess external calcium carbonate skeleton, nor form coral reefs.

 

根據目前文獻所記，𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢可以係香港西面同大嶼山北面一帶嘅海域搵到。過往調查發現，𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢係機場附近、大磨刀洲、馬灣同青衣一帶生長。佢地比起其他珊瑚更加適應香港西面嘅水文環境同鹽度變化，因而成為咗主要嘅物種。 希望日後會有更多嘅生態調查，俾我哋知多啲𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢係香港嘅分佈啦。

According to the present literature review, 𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 is abundant in western Hong Kong water and Northern Lantau Island. Previous surveys show that Guaiagorgia sp. colonies can also be found near Hong Kong International Airport, Tai Mo To, Ma Wan, and Tsing Yi. They adapt to Hong Kong western water and salinity change better than other corals and become dominant. Hopefully, we will learn more about their distribution as there is more ecological survey on the species.

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𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢係濾食者，唔似得石珊瑚，𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢同大多數軟珊瑚一樣，佢哋冇共生嘅蟲黃藻去提供養份，會主要用觸手捉以海洋裏面嘅浮游生物同埋微生物為食。

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𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 is a filter-feeder. Unlike hard corals, 𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 and many other octocorals do not obtain nutrients from photosynthetic symbionts. Instead, they mainly filter water and capture plankton and tiny particles as food with their tentacles. 

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喺實驗室入邊，我哋會餵佢哋食啱啱孵化嘅豐年蝦BB同埋粉狀嘅珊瑚食物。按下連結，喺條片度睇吓佢哋點樣捉嘢食啦！

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In the laboratory, they are fed with newly-hatched brine shrimp and powdered marine plankton. Click to see how they catch food with their tentacles!

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目前為止，香港已記錄嘅八放珊瑚一共有67個品種。究竟科學家係點分唔同品種嘅八放珊瑚嘅呢？🔍

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仔細啲睇，每個品種都細節多多！因此，科學家可以透過分析同比較呢啲特徵, 將珊瑚分類及命名。係海底入面，我哋可以睇到唔同八放珊瑚品種嘅群體同珊瑚蟲嘅特徵嘅唔同。但要比較骨針的話，就需要係實驗室用特定嘅儀器觀察。🔬

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So far, 67 species of octocorals have been recorded in Hong Kong. How do scientists differentiate octocorals species? 🔍

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If you take a closer look, each species has many unique details! Scientists analyze and compare these characteristics to classify and name corals. We can observe differences in the colonies and polyp features of various octocoral species underwater. However, comparing sclerites requires specific laboratory instruments. 🔬

以我哋研究嘅𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 sp. 為例，佢哋嘅珊瑚蟲係伸展嘅時候係呈長管狀，可以完全收縮入共肉組織。成個群體咁睇，佢哋嘅分枝比其他八放珊瑚零散同雜亂，枝條亦較幼而長。至於骨針，佢哋嘅骨針較小，一般少於0.3mm。佢哋表層骨針嘅形狀為多刺嘅紡綞形；珊瑚蟲入面嘅骨針就呈棒狀，表面有突起物。而隨著分子生物技術越來越進步，科學家亦會比較基因組DNA及粒線體DNA的序列，為八放珊瑚繪製親緣關係樹，進行品種鑑定及調整分類。

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Take Guaiagorgia anas for example, when its polyps are extended, they appear tubular and can fully retract into the coenenchyme. As a colony, its branches are more scattered and disorganized compared to other octocorals, and its branches are thinner and longer. Regarding sclerites, they are relatively small, generally less than 0.3mm. The surface sclerites are spiny and spindle-shaped, while those inside the polyps are rod-shaped with protrusions.

 

With advancements in molecular biology, scientists also compare genomic and mitochondrial DNA sequences to create phylogenetic trees for octocorals, aiding in species identification and refining classifications.

珊瑚既然係動物，究竟佢哋係點生育下一代架呢？🧑‍🍼🔍珊瑚嘅性別可以分兩種，有啲品種嘅珊瑚係雌雄同體，有啲則係雌雄異體。​

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ince corals are animals, how do they reproduce the next generation? 🧑‍🍼🔍 Coral sexes can be divided into two types: some species are hermaphroditic, while others are gonochoric (having separate male and female individuals).

珊瑚亦有兩種生殖模式，分別係排卵型同孵育型。唔同品種嘅珊瑚係會採取唔同嘅生育方式架！​

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Coral sexes can be divided into two types: some species are hermaphroditic, while others are gonochoric (having separate male and female individuals).

但值得留意嘅係，我哋無辦法從珊瑚嘅外表判斷佢哋嘅性別，需要用到組織學切片，睇到佢哋嘅生殖腺先決定到佢哋嘅性別。 咁我哋研究嘅𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 sp. 又係點繁殖呢？敬請留意下一集！​

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However, it's important to note that we can't determine a coral's sex just by looking at its appearance. It requires histological analysis to observe their gonads and identify their sex. So, how does Guaiagorgia sp. reproduce? Stay tuned for the next episode! 😊

除咗性別同生殖模式之外，科學家仲想知道珊瑚產卵嘅時間同頻率 ，呢個時候就要用到組織學嚟研究珊瑚嘅生殖部分。組織學切片結果話俾我哋知，𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 sp. 係雌雄同體嘅品種，而且好大機會係夏末產卵 。​

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Aside from sex and reproductive modes, scientists are also interested in the timing and frequency of coral spawning. This is where histological analysis comes into play to study the reproductive structures of corals. Histological findings reveal that Guaiagorgia sp. is a hermaphroditic species, with a high likelihood of spawning in late summer.

而為咗進一步證實𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 sp. 嘅生殖方式，研究人員係實驗室設立咗收集儀，希望收集到𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢 sp. 嘅卵子或者幼蟲 。 究竟我哋嘅收集儀能唔能夠成功收集卵子或幼蟲呢？敬請留意下一集！​

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To further confirm the reproductive mode of Guaiagorgia sp., researchers set up collection devices in the lab, aiming to capture its eggs or larvae. Will our collection devices successfully gather eggs or larvae? Stay tuned for the next episode! 😊

為咗進一步證實𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢嘅生殖方式，研究人員係實驗室設立咗收集儀，希望收集到𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢嘅卵子或者幼蟲 。 係上年夏天，我哋嘅收集儀成功收集到𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢嘅卵子呀！收集到卵子，就代表𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢係屬於排卵型嘅珊瑚。​

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To further confirm the reproductive mode of Guaiagorgia, researchers set up collection devices in the laboratory, aiming to capture its eggs or larvae. Last summer, our collection devices successfully collected eggs of Guaiagorgia! The presence of eggs confirms that Guaiagorgia sp. is a broadcast-spawning coral.

如是者，我哋探索到𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢嘅性別、生殖模式同產卵時間 —— 佢哋係係雌雄異體嘅排卵型珊瑚，一般係夏末產卵 。希望未來嘅研究可以更深入咁了解唔同因素對 𝘎𝘶𝘢𝘪𝘢𝘨𝘰𝘳𝘨𝘪𝘢繁殖嘅影響。​

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Through this, we uncovered the sex, reproductive mode, and spawning timing of Guaiagorgia — it is a gonochoric, broadcast-spawning coral that typically spawns in late summer. We hope future research can delve deeper into how various factors influence the reproduction of this species.

Guaiagorgia anas 是一種生長於香港西部水域的柳珊瑚。在短短二十年間，這些珊瑚已在香港國際機場的海堤上形成了超過六千個群落。它們為何能如此茂盛地生長？是否與其特殊的繁殖方式有關？

珊瑚學院獲得「改善海洋生態基金」的資助，開展了對該珊瑚繁殖特性的研究。研究珊瑚的繁殖過程通常需要使用組織學技術，通過顯微鏡觀察其生殖組織的發育情況以及每月的變化趨勢。當卵母細胞（即正在發育的卵子）逐漸增大並突然消失時，這通常意味著珊瑚已經進行了產卵。

研究結果顯示，Guaiagorgia anas是雌雄異體且採用排卵方式進行繁殖的珊瑚。它的群體分為雄性和雌性個體，並且會將精子和卵子排放至外部環境中。研究還發現，該珊瑚通常在夏末進行產卵活動。

這些研究成果為進一步探索 Guaiagorgia anas為何能在大嶼山水域茂盛生長提供了重要線索，並在制定相關的保育與修復計劃時，提供了關鍵的科學依據。​

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Guaiagorgia anas is a species of gorgonian coral found in the western waters of Hong Kong. Over just two decades, it has formed over 6,000 colonies along the seawalls of Hong Kong International Airport. What enables such prolific growth? Could it be linked to a unique reproductive strategy?  
 

With funding from the “Marine Ecology Enhancement Fund,” Coral Academy investigated the reproductive traits of this coral species. Researching coral reproduction typically involves histological techniques, where microscopic observations are made of the coral’s reproductive tissues and their monthly developmental changes. When oocytes (developing eggs) gradually grow in size and then suddenly disappear, it is often a sign that the coral has spawned.  

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The study revealed that Guaiagorgia anas is gonochoric, having separate male and female colonies. It also employs broadcast spawning for reproduction, where male and female colonies release sperm and eggs into the surroundings. Spawning events primarily occur in late summer.  

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These findings provide valuable insights into why Guaiagorgia anas thrives in the waters around Lantau Island and serve as a critical reference for developing conservation and restoration strategies for this coral species.