把木头当饭吃，它们是深海木材分解者（下）（克尔-纽曼黑洞）

木材通过河流输入等因素进入大海，并在被海水浸透后沉入深海，成为这片缺乏初级生产环境的特殊碳源。这些“有机岛屿”片段化且存在时间短暂，因此栖息于此的生物往往演化出长距离扩散策略。许多食木蛤（约35%的物种）壳表都有不挖洞的微型生物个体固着。研究者曾认为这些微型个体是食木蛤幼体，因此认为它们具有育幼习性。但后来的研究证实这些微型个体实际上是食木蛤的矮雄。矮雄以足丝固定在较大个体体表，仅有胎壳，营滤食生活。一些物种如Xylophaga supplicata的大的挖洞个体则是先雄后雌的雌雄同体，但其矮雄不能转变为大的挖洞个体。另一些物种如Xylophaga dorsalis和Xylophaga depalmai则是雌雄异体。一些食木蛤的性别受环境影响，如雌雄异体的Xylonora atlantica在食物充足的新栖息地，性别比例会偏向雌性。随着木材被第一世代持续消耗，食物与空间资源逐步减少，之后世代的雄性比例逐渐增加，最终导致幼体直接在雌性壳上定居，形成矮雄。

食木蛤的浮游幼体可以长时间维持浮游生活，大幅推迟变态时间。例如，Xylonora atlantica幼虫可延迟变态达6个月之久，同时能进入远离海底的上层海水。悬浮于海底上方20米水层中的木材仍可被大量食木蛤定殖，因此，一些物种分布范围极广，可跨海盆分布。但与此同时，由于深海沉木获取困难，所以有大量食木蛤定殖的现象仅被发现过一次，有些物种甚至出现在远离陆地的深渊平原或海沟，这些区域的木材沉降事件是极其罕见的。

一些食木蛤会选择栖居的木材，如Abditoconus brava几乎仅生活于松木而非橡木中，另一些则没有这种偏好。后者的贝壳形态会因木材种类不同导致的硬度不同而出现变化。水深也会影响贝壳形态，但是食木蛤科本身的贝壳形态又高度趋同，因此仅依靠贝壳形态很难将食木蛤定种，而水管等软体结构及其蛀道外部形态成为重要的分类依据。

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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