木材通過河流輸入等因素進(jìn)入大海,并在被海水浸透后沉入深海,成為這片缺乏初級生產(chǎn)環(huán)境的特殊碳源。這些“有機(jī)島嶼”片段化且存在時間短暫,因此棲息于此的生物往往演化出長距離擴(kuò)散策略。許多食木蛤(約35%的物種)殼表都有不挖洞的微型生物個體固著。研究者曾認(rèn)為這些微型個體是食木蛤幼體,因此認(rèn)為它們具有育幼習(xí)性。但后來的研究證實這些微型個體實際上是食木蛤的矮雄。矮雄以足絲固定在較大個體體表,僅有胎殼,營濾食生活。一些物種如Xylophaga supplicata的大的挖洞個體則是先雄后雌的雌雄同體,但其矮雄不能轉(zhuǎn)變?yōu)榇蟮耐诙磦€體。另一些物種如Xylophaga dorsalis和Xylophaga depalmai則是雌雄異體。一些食木蛤的性別受環(huán)境影響,如雌雄異體的Xylonora atlantica在食物充足的新棲息地,性別比例會偏向雌性。隨著木材被第一世代持續(xù)消耗,食物與空間資源逐步減少,之后世代的雄性比例逐漸增加,最終導(dǎo)致幼體直接在雌性殼上定居,形成矮雄。
食木蛤的浮游幼體可以長時間維持浮游生活,大幅推遲變態(tài)時間。例如,Xylonora atlantica幼蟲可延遲變態(tài)達(dá)6個月之久,同時能進(jìn)入遠(yuǎn)離海底的上層海水。懸浮于海底上方20米水層中的木材仍可被大量食木蛤定殖,因此,一些物種分布范圍極廣,可跨海盆分布。但與此同時,由于深海沉木獲取困難,所以有大量食木蛤定殖的現(xiàn)象僅被發(fā)現(xiàn)過一次,有些物種甚至出現(xiàn)在遠(yuǎn)離陸地的深淵平原或海溝,這些區(qū)域的木材沉降事件是極其罕見的。
一些食木蛤會選擇棲居的木材,如Abditoconus brava幾乎僅生活于松木而非橡木中,另一些則沒有這種偏好。后者的貝殼形態(tài)會因木材種類不同導(dǎo)致的硬度不同而出現(xiàn)變化。水深也會影響貝殼形態(tài),但是食木蛤科本身的貝殼形態(tài)又高度趨同,因此僅依靠貝殼形態(tài)很難將食木蛤定種,而水管等軟體結(jié)構(gòu)及其蛀道外部形態(tài)成為重要的分類依據(jù)。
Abditoconus brava/ Romano et a,2020
Abditoconus investigatoris。A–B. 正模TMAG E58320;C. TMAG E59292;D. 副模 2 TMAG E58316 / MacIntosh et al,2021
Spiniapex gilsonorum(TMAG E58450)/ MacIntosh et al,2021
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