作者 克爾-紐曼黑洞
盡管海百合Cyathidium foresti與 巨型牡蠣Neopycnodonte zibrowii的緊密共生并非必然(海百合也可直接固著于基巖上),但這種關聯可能帶來多重益處:首先,牡蠣殼的生長持續為海百合提供新的固著空間,這對空間受限環境中的固著生物來說至關重要;其次,二者雖都以濾食浮游生物為食,但攝食策略不同——牡蠣會主動產生攝食水流,而海百合被動依賴環境水流,因此可能受益于牡蠣創造的水流環境。
N. zibrowii屬于繁盛于白堊紀和古近紀,現已基本滅絕的硬牡蠣類(pycnodontine);C. foresti是在侏羅紀至白堊紀期間多樣性高、數量豐富的海百合類群的孑遺。二者的共生關系同樣跨越了漫長的時光——在位于丹麥法克瑟(Faxe)的距今逾 6000 萬年的中丹尼階,即存在Cyathidium屬(該屬模式種C. holopus)和硬牡蠣(Pycnodontesp.)共生的化石。Nielsen 報道了法克瑟剖面大量原位保存在疑似硬底懸垂結構下的群體,描述了海百合C. holopus常棲于牡蠣殼上,而牡蠣又附著于珊瑚形成的崖壁,且C. holopus本身常被新生牡蠣覆著。Steenstrup 在描述C. holopus時即記載其常見于厚牡蠣殼上,Ravn 與 Hennig 均注意到海百合偏好以倒置姿態附著于牡蠣鉸合區最大凹面處。6000 萬年前的法克瑟牡蠣-海百合組合可能和現今的亞速爾群島組合一樣棲息于冷水深海珊瑚礁相伴的硬底懸崖與懸垂結構下。
丹麥法克瑟中丹尼階的Cyathidium holopus與牡蠣化石。A:成百個C. holopus化石;B:位于可能的懸垂結構下的大量C. holopus化石;C:固著于牡蠣殼內表面的海百合(示意圖);D、E:硬牡蠣殼內表面固著的處于不同個體發育階段的C. holopus/ Wisshak 等,2009b
這些事實對研究海百合和牡蠣演化具有重要意義——這些海百合為逃避“中生代海洋革命(the Mesozoic Marine Revolution)”期間增強的捕食壓力而向深海遷移。固著海百合在晚中生代至新生代早期幾乎從淺水完全消失,被無柄的羽星類海百合取代,后者具有活動能力且常嚴格夜行,因而能避開晝行性捕食者。最可能的潛在捕食者是具碎殼能力的真骨魚類,這類捕食者在馬斯特里赫特期至古新世經歷了重大輻射演化。從Cyathidium在塞諾曼階至馬斯特里赫特階的記錄來看,其生境遷移始于晚白堊世[巴黎盆地與英國南部盆地(Anglo-Paris Basin,法國庇卡底和英國普利茅斯一帶)坎帕階的新發現即為證據],而法克瑟的材料表明該過程到中達寧階已完成。這一時間線與真骨魚類輻射演化完美吻合。而牡蠣亦在逃避固著競爭或捕食壓力。此外,白堊紀末危機可能也促進了這一“生境逃離”過程,該事件最終導致了白堊紀-古近紀大滅絕。在捕食壓力相對較小的穩定深水環境中,Cyathidium-(Neo)pycnodonte組合不僅躲過了這次大滅絕事件,更在未留下任何已知化石記錄且未顯著改變形態的情況下延續了整個新生代,最終成為今天可供原位研究的“活化石群落”。[完]
參考文獻及圖片來源:
Soares M P, Roux M, Giusberti L, et al, 2024. New Eocene species of the crinoid generaHolopusandCyathidium(Cyrtocrinida: Holopodidae) from north-eastern Italy[J]. Zootaxa, 5541(4): 401-437.
Wisshak M, Correa M L, Gofas S, et al, 2009a. Shell architecture, element composition, and stable isotope signature of the giant deep-sea oysterNeopycnodonte zibrowiisp. n. from the NE Atlantic[J]. Deep Sea Research Part I Oceanographic Research Papers, 56(3): 374-407.
Wisshak M, Neumann C, Jakobsen J, et al, 2009b. The 'living-fossil community' of the cyrtocrinidCyathidium forestiand the deep-sea oysterNeopycnodonte zibrowii(Azores Archipelago)[J]. Palaeogeography, Palaeoclimatology, Palaeoecology, 271(1-2): 77-83.
Gale A S, Jagt J W M, 2024. The aberrant crinoidCyathidium(Echinodermata, Crinoidea, Cyrtocrinida) from lower Campanian phosphatic chalk in West Sussex (UK) and Picardie (France)[J]. Proceedings of the Geologists Association, 135(6): 631-638.
Heinzeller T, Fechter H, Ameziane N, et al, 1997. Development ofCyathidium foresti(Echinodermata: Crinoidea, Cyrtocrinida) from early attached larvae to adult-like juveniles[J]. Journal of Zoological Systematics and Evolutionary Research, 35(1): 11-21.
Heinzeller T, Fricke H, Bourseau J-P, et al, 1996.Cyathidium planteisp. n., an extant cyrtocrinid (Echinodermata, Crinoidea)—morphologically identical to the fossilCyathidium depressum(Cretaceous, Cenomanian)[J]. Zoologica Scripta, 25: 77-84.
Donovan S, Jakobsen S, 2004. An unusual crinoid‐barnacle association in the type area of the Danian (Paleocene), Denmark[J]. Lethaia, 37(4): 407-415.
Heinzeller T, Fechter H, 1995. Microscopical Anatomy of the CyrtocrinidCyathidium meteorensis(sive foresti) (Echinodermata, Crinoidea)[J]. Acta Zoologica, 76(1): 25-34.
Ameziane N, 1999. Les genresCyathidiumet Holopus au sein des Cyrtocrinida (Crinoidea; Echinodermata)[J]. Annals & Magazine of Natural History, 33(3): 439-470.
Syverson V J, Charles G M, Karl S, et al, 2015. Growth, injury, and population dynamics in the extant cyrtocrinidHolopus mikihe(Crinoidea, Echinodermata) near Roatan, Honduras[J]. Bulletin of Marine Science, 91(1): 47-61.
Zítt J, Vodrázka R, Zágorsek K, 2014. New observations on the holopodid crinoid genusCyathidiumSteenstrup from the lower Turonian of the Bohemian Cretaceous Basin, Czech Republic[J]. Cretaceous Research, 51: 56-69.
Manni R, 2005. The non-isocrinid crinoids of the Michelotti Collection[J]. Bollettino della Societa Paleontologica Italiana, 44(3): 211-218.
Donovan S K, Pawson D L, 2008. A new species of the sessile crinoid Holopus d'Orbigny from the tropical western Atlantic, with comments on holopodid ecology (Echinodermata: Crinoidea: Holopodidae)[J]. Zootaxa, 1717: 31-38.
Fechter H, 1973.Cyathidium meteorensisspec. nov. ein neuer Crinoie aus der Familie Holopodidae[J]. Helgolnder Wissenschaftliche Meeresuntersuchungen, 25(1): 162-169.
Grimmer J C, Holland N D, 2010. The Structure of a Sessile, Stalkless Crinoid (Holopus rangii)[J]. Acta Zoologica, 71(2): 61-67.
特別聲明:以上內容(如有圖片或視頻亦包括在內)為自媒體平臺“網易號”用戶上傳并發布,本平臺僅提供信息存儲服務。
Notice: The content above (including the pictures and videos if any) is uploaded and posted by a user of NetEase Hao, which is a social media platform and only provides information storage services.