栉水母：波折的演化研究 Ctenophora: The turns of research

栉水母目前属于栉水母动物门（又译，栉板动物门，Ctenophora），是一类两胚层辐射对称的无脊椎动物。

Ctenophores, or comb jellies, belong to the phylum Ctenophora, which includes a diverse group of invertebrate animals. They are radially symmetrical, meaning their body parts are arranged around a central axis, and have two embryonic layers. 

它们原来与刺胞动物门（Cnidaria）一起分在腔肠动物门（Coelenterata）。而随着栉水母的独立分出，“腔肠动物”一词在动物学中研究基本已经停用，而现在在生产生活中，腔肠动物一词专指刺胞动物。

Ctenophores used to be grouped together with cnidarians, such as jellyfish, in the phylum Coelenterata. However, due to their unique characteristics, ctenophores are now classified as a separate phylum, and the term Coelenterata is no longer used to refer to these animals in scientific studies.

在这里，我们回忆一下，经典动物学研究认为刺细胞（Cnidocyte）的有无能够将栉水母动物与刺胞动物划分开。

One key feature that distinguishes ctenophores from cnidarians is the absence of cnidocytes, which are specialized stinging cells found in jellyfish and other cnidarians. 

顾名思义，栉水母的“栉”是梳子的意思，其英文俗名也叫“梳子水母”（梳子冻，Comb jellies）。有的中文媒体也介绍栉水母俗称为“海胡桃”，但在一些情况下，相比于胡桃（Walnut，胡桃属 Juglans）这种动物似乎更像杨桃（Averrhoa carambola）一些。

The name "ctenophore" comes from the Greek word for "comb," which refers to the rows of cilia, or hair-like structures, that run along their body.

In English, ctenophores are commonly known as "comb jellies" or "sea gooseberries," and they are sometimes referred to as "walnuts of the sea" in some Chinese media, although their appearance is more akin to that of a starfruit in certain cases.

与海绵动物充满争议的演化关系不同，栉水母动物是目前学界公认的，地球上最早的动物门类。

While the evolutionary history of sponges is still debated, ctenophores are widely recognized as one of the earliest animal phyla on Earth. 

在系统发育关系上，栉水母动物的演化途径和两侧对称动物极其不同，而很多结构比栉水母简单的动物因为某些特征尚未分化，反而与高等生物的发育关系更近。

Their evolutionary path is very different from that of bilateral animals, despite the fact that many simpler animals with less complex structures are actually more closely related to higher organisms due to shared characteristics.

值得注意的是，在神经系统发育上，栉水母动物演化出独特的机制及其系统，如谷氨酸的神经递质和特异的神经递质受体等等。

One notable feature of ctenophores is their unique nervous system, which has evolved distinct mechanisms and pathways, such as the neurotransmitter glutamate and specific neurotransmitter receptors. 

由于经典研究中，其他动物的神经系统都是由原始刺胞动物演化而来，可以说栉水母动物的神经系统，是完全独立于其他动物类群神经系统的一支奇葩。

While the nervous systems of other animals have evolved from primitive cnidarians in classic view, ctenophores have developed a unique and independent system, making them a true oddity in the animal kingdom.

近年来，通过全基因组测序，发现栉水母也许是最古老的动物（多细胞）。栉水母的分类之所以曲折，是因为其在动物演化树上的地位一直备受关注，而动物学的发展将会为我们提供更多关于这些神秘生物的信息，让我们去发现、去探究。

In recent years, through whole-genome sequencing, it has been suggested that comb jellies (ctenophores) may be the oldest multicellular animals. The convoluted classification of comb jellies arises from their debated position on the animal evolutionary tree. As zoology continues to advance, it promises to reveal more about these enigmatic creatures, inviting us to explore and unravel their mysteries!