挑食！以死亡鱿鱼的喙为食的海螺(原创 克尔-纽曼黑洞)

1888年，摩纳哥王储阿尔贝于亚速尔群岛外海约780英寻（约相当于1427米）深度拖网获得一块头足类喙的残骸。残骸上栖息着许多微型笠螺，多个个体啃咬出与贝壳基部大小相当的凹坑，有时坑底仅存一层透明薄膜。12年后，Dautzenberg与Fischer根据这些标本建立渊喙螺科Bathysciadiidae。

渊喙螺科是种粒螺目Cocculinida仅有的3个科之一。全科共4属9种，大多栖息于数千米深的海底，加之其以死亡鱿鱼喙为食的习性，因此十分罕见。尽管曾有在一个大王乌贼喙上发现百余个渊喙螺Bathysciadium costulatum个体的记录，但据2023年的一篇论文统计，全世界记录在案的博物馆馆藏仅有35批。稀少的发现令渊喙螺的相关研究极少。

渊喙螺拥有标志性的具放射状流苏的壳皮，和蛏螂一样壳皮长于壳体，其作用也和蛏螂的相似——当动物抬高身体以便水流过贝壳与其基座之间时，这些流苏覆盖两侧，使得沉积物无法进入贝壳与基座之间。渊喙螺的足部会形成类似吸盘的结构，也是唯一完全缺失中肠腺的非寄生腹足类。渊喙螺壳体脆弱，以至于在干燥环境中，Bathysciadium costulatum的外壳会因壳皮收缩而碎裂。在Bathysciadium costulatum的胃中曾发现刮削下的头足类喙碎片，推测其依靠共生菌消化这些碎片。

Bathysciadium xylophagum是唯一被发现于木材上的渊喙螺，其栖息于船蛆的蛀洞中。这被认为是在首选基质不存在时的无奈选择。在葡萄牙西南部外海约瑟芬海山发现的Bathysciadiumcf.xylophagum则栖息于头足类喙上。除Bathysciadium xylophagum外，仅有2个来自科隆群岛（加拉帕戈斯群岛）的未命名Xenodonta属物种确认不以头足类的喙为食——它们附着在一个尖帽螺科Capulidae个体的壳上并吞噬了它的大部分壳皮。

Bathysciadium xylophagum/ 作者拍摄自有标本

Bathysciadium xylophagum（图中a、b）

Bathysciadiumcf.xylophagum（图中c、d）

Xenodonta bogasoni

Bathysciadium pacificum生活的深度范围极广，在5500米、4000米至2000米水深都有发现，甚至曾在一条捕获自549~594米水深处的太平洋油鲽Microstomus pacificus的消化道内发现过一个标本。太平洋油鲽栖息深度为10~1370米。考虑其在冬季才向深水产卵洄游，而含B. pacificum的标本于6月采集到，因此B. pacificum可能在500~800米也有分布。令人遗憾的是这枚标本已经遗失。

Bathysciadium pacificum/ Geiger et al, 2023

渊喙螺科的Pilus conicus

渊喙螺在生命早期就会失去胎壳，齿舌退化，齿数远少于正常的扇舌型古腹足类齿舌。鱿喙螺科Teuthirostriidae的Teuthirostria cancellata尽管同样栖息于头足类喙上，却拥有正常的种粒螺型齿舌。因此鱿喙螺科可能代表着种粒螺科Cocculinidae与渊喙螺科之间的过渡——一些种粒螺首先改变食性，以头足类喙为食，随后齿舌和消化道因此而退化。鱿喙螺科共2属3种，除T. cancellata外，其余2种均栖息于沉木上。

鱿喙螺科的Fedikovella beanii

鱿喙螺科的Fedikovella caymanensis

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