Comparative Proteomic Analysis of Slime from the Striped Pyjama Squid, <i>Sepioloidea lineolata</i>, and the Southern Bottletail Squid, <i>Sepiadarium austrinum</i> (Cephalopoda: Sepiadariidae)

Sepioloidea lineolata, the striped pyjama squid (family Sepiadariidae), is a small species of benthic bobtail squid distributed along the Southern Indo-Pacific coast of Australia. Like other sepiadariid squids, it is known to secrete large volumes of viscous slime when stressed. In order to identify key proteins involved in the function of sepiadariid slimes, we compared the slime proteome of Sepioloidea lineolata with that of a closely related species, Sepiadarium austrinum. Of the 550 protein groups identified in Sepioloidea lineolata slime, 321 had orthologs in Sepiadarium austrinum, and the abundance of these (iBAQ) was highly correlated between species. Both slimes were dominated by a small number of abundant proteins, and several of these were short secreted proteins with no homologues outside the class Cephalopoda. No mucins were identified within either species’ slime, suggesting that it is structurally distinct from mucin polymer-based gels found in many vertebrate and echinoderm secretions. The extent of N-glycosylation in the slime of Sepioloidea lineolata was also studied via glycan cleavage with Peptide: N-glycosidase F (PNGase-F). Although very few (four) proteins showed strong evidence of N-glycosylation, we found that treatment with PNGase-F led to a slight increase in peptide identification rates compared with controls.条纹睡衣鱿鱼（striped pyjama squid）*Sepioloidea lineolata*隶属于耳乌贼科（Sepiadariidae），是一种小型底栖短尾乌贼，分布于澳大利亚南部印度-太平洋沿岸。与其他耳乌贼类群相似，该物种在受到胁迫时会分泌大量粘性黏液。为鉴定参与耳乌贼黏液功能的关键蛋白，本研究将条纹睡衣鱿鱼的黏液蛋白质组与近缘种澳洲耳乌贼（*Sepiadarium austrinum*）的进行了对比。在条纹睡衣鱿鱼的黏液中共鉴定出550个蛋白质群组，其中321个在澳洲耳乌贼中存在直向同源基因，且二者对应蛋白的丰度（iBAQ）在物种间呈现高度相关性。两种黏液均由少量高丰度蛋白主导，其中多个为短分泌蛋白，在头足纲（Cephalopoda）外无同源序列。两种物种的黏液中均未检测到黏蛋白（mucins），提示其结构与众多脊椎动物和棘皮动物分泌物中基于黏蛋白聚合物的凝胶存在显著差异。此外，本研究还通过肽:N-糖苷酶F（Peptide: N-glycosidase F，PNGase-F）裂解糖链的方法，探究了条纹睡衣鱿鱼黏液中的N-糖基化程度。尽管仅有4个蛋白表现出较强的N-糖基化证据，但研究发现经PNGase-F处理后，肽段鉴定率较对照组略有提升。