城里来了一种新的海蜘蛛
There's a new sea spider in town

原始链接: https://nautil.us/theres-a-new-sea-spider-in-town-1285470

研究人员在萨利希海发现了七种海蜘蛛,其中两种此前未知;这是该地区百年来首次发现新的海蜘蛛种类。这些动物是与蝎子、蜘蛛和鲎有关联的古老海洋蛛形动物,但尤为独特的是,它们最多有12条腿,通过皮肤呼吸,并利用称为“抱卵肢”的特化附肢携带卵。 研究人员利用扫描电子显微镜和DNA分析,确认了毛足海蜘蛛(*Callipallene pilosuspedes*),其“毛茸茸的脚”和触手状口器酷似微缩版的沙拉克;他们还发现了基新塔尼蛛(*Tanystylum kiixin*),其名称源自发现地点附近的一个原住民村庄。*T. kiixin* 的腿短而坚硬,能够收集碎屑和微型寄生虫,从而在身体上形成微型生态系统。这些发现凸显了这些常被忽视的生物在生态和演化上的奇特之处。

Hacker News 的一则讨论强调了海蜘蛛异常古老且稳定的体型结构。化石证据表明,海蜘蛛大约在 5 亿年前就已经出现,此后变化很小。这可能是因为它们的解剖结构达到了某种有效的“局部最优”,帮助它们挺过了多次大灭绝事件。 尽管外形相似,海蜘蛛其实与陆生蜘蛛只有较远的亲缘关系。陆生蜘蛛大约在 1.5 亿年后才演化出现,与蝎子的亲缘关系反而更近。海蜘蛛的身体非常小,呈枝条状,腿却极长,内部器官还会延伸进入腿中。它们通过皮肤呼吸,雄性则会把卵带在腿上。
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原文

What has hairy feet, legs dotted with eggs, and a mouth loaded with tentacles like a Sarlacc from Star Wars? 

That’s how researchers from the University of British Columbia describe seven such creatures from the Salish Sea in a new paper published in the journal Organisms Diversity & Evolution. They include five known species plus a couple of new ones, marking the first discovery in a century of new sea spiders in the region.

As ancient arachnids closely related to scorpions, spiders, and horseshoe crabs, sea spiders share some traits such as exoskeletons, jointed legs, and chelicerae-type mouthparts adapted for piercing or grabbing prey. But sea spiders also rank as weird for the way they sport up to 12 legs, breathe through their skin, and spawn eggs from their legs, traits they’ve honed during their 500 million years of ocean life.

Read more: “The Mystery of 111,000 Spiders Living in a Giant Subterranean Web”

“A lot of the shallow water species are quite small, and so they’ll live as parasites on larger organisms, and they use this weird apparatus called a proboscis to suck the juices out of their host,” explained lead author Cormac Toler-Scott.  

The researchers collected specimens from sites that represented the range of sea spider habitats in the Salish Sea, from depths of 0 to about 60 feet, which would be considered shallow waters for sea spiders. Using scanning electron microscopy and DNA analysis, they classified the sea spiders by species, detecting the two previously undescribed ones in the process. 

Callipallene pilosuspedes (“hairy feet”) joins 36 other species of Callipallene worldwide, which tend to be slender and without claws on the male’s “ovigers,” or the special appendages used by males to pluck eggs off females and stick them to their own body for rearing. It has a triangular mouth bounded by three lips and covered with sensory hairs that give it the Sarlacc appearance, albeit in miniature—after all, C. pilosuspedes is only about a centimeter long.

The three lips of the C. pilosuspedes. Credit: Cormac Toler-Scott

The other new species, Tanystylum kiixin, gets its name from an indigenous village near the discovery site. Its legs are too short and stiff for good hygiene, so it gets covered with debris. Amongst the body hairs and debris, the researchers found even tinier single-celled parasites, such that the sea spiders maintain ecosystems on their bodies.

Which is yet another reason why Toler-Scott and his fellow researchers consider these water-based arachnids “horrifyingly fascinating.”

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Lead Image: Cormac Toler-Scott

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