Department of Biology, University of Victoria, Victoria, British Columbia, Canada.
Proc Biol Sci. 2012 Jan 7;279(1726):77-83. doi: 10.1098/rspb.2011.0501. Epub 2011 May 18.
The venom gland of predatory cone snails (Conus spp.), which secretes neurotoxic peptides that rapidly immobilize prey, is a proposed key innovation for facilitating the extraordinary feeding behaviour of these gastropod molluscs. Nevertheless, the unusual morphology of this gland has generated controversy about its evolutionary origin and possible homologues in other gastropods. I cultured feeding larvae of Conus lividus and cut serial histological sections through the developing foregut during larval and metamorphic stages to examine the development of the venom gland. Results support the hypothesis of homology between the venom gland and the mid-oesophageal gland of other gastropods. They also suggest that the mid-region of the gastropod foregut, like the anterior region, is divisible into dorsal and ventral developmental modules that have different morphological, functional and ontogenetic fates. In larvae of C. lividus, the ventral module of the middle foregut transformed into the anatomically novel venom gland of the post-metamorphic stage by rapidly pinching-off from the main dorsal channel of the mid-oesophagus, an epithelial remodelling process that may be similar to other cases where epithelial tubes and vesicles arise from a pre-existing epithelial sheet. The developmental remodelling mechanism could have facilitated an abrupt evolutionary transition to the derived morphology of this important gastropod feeding innovation.
捕食性圆锥蜗牛（Conus spp.）的毒液腺分泌神经毒性肽，可迅速使猎物瘫痪，这是促进这些腹足类软体动物非凡进食行为的一个重要创新。然而，这种腺体的不寻常形态引发了关于其进化起源和在其他腹足类动物中可能同源结构的争议。本研究培养了活锥螺（Conus lividus）的摄食幼虫，并在幼虫和变态阶段通过连续的组织学切片穿过发育中的前肠，以检查毒液腺的发育。结果支持毒液腺与其他腹足类动物的中食道腺同源的假设。它们还表明，腹足类动物前肠的中区域，与前区域一样，可分为具有不同形态、功能和个体发生命运的背侧和腹侧发育模块。在活锥螺幼虫中，中前肠的腹侧模块通过从前肠中食道的主要背侧通道迅速分离，迅速转变为变态后阶段的解剖学上新颖的毒液腺，这是一种上皮重塑过程，可能与其他上皮管和囊泡从预先存在的上皮片中产生的情况相似。这种发育重塑机制可能促进了这种重要的腹足类进食创新的衍生形态的突然进化转变。
