Jabr Noura, Gonzalez Paul, Kocot Kevin M, Cameron Christopher B
Département de Sciences Biologiques, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC, H3C 3J7, Canada.
Computational and Statistical Genomics Branch, Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
Evodevo. 2023 Apr 19;14(1):6. doi: 10.1186/s13227-023-00212-0.
Schizocardium karankawa sp. nov. has been collected from subtidal muds of the Laguna Madre, Texas, and the Mississippi coast, Gulf of Mexico. The Texas population is reproductive from early February to mid-April. Gametes are liberated by a small incision in a gonad. Oocyte germinal vesicle breakdown is increased in the presence of sperm, and the highest fertilization success was in the artificial seawater Jamarin U. Manually dechorionated embryos develop normally. Development was asynchronous via a tornaria larva, metamorphosis and maintained to the juvenile worm 6 gill-pore stage. Phalloidin-labeled late-stage tornaria revealed retractor muscles that connect the pericardial sac with the apical tuft anteriorly, the oesophagus ventrally, and muscle cells of the early mesocoels. The muscle development of early juvenile worms began with dorso-lateral trunk muscles, lateral trunk bands, and sphincters around the gill pores and anus. Adult worms are characterized by a stomochord that bifurcates anteriorly into paired vermiform processes, gill bars that extend almost the entire dorsal to ventral branchial region resulting in a narrow ventral hypobranchial ridge, and an elaborate epibranchial organ with six zones of discrete cell types. The trunk has up to three rows of liver sacs, and lateral gonads. The acorn worm evo-devo model species Saccoglossus kowalevskii, Ptychodera flava, and Schizocardium californicum are phylogenetically distant with disparate life histories. S. karnakawa from S. californicum are phylogenetically close, and differences between them that become apparent as adult worms include the number of gill pores and hepatic sacs, and elaborations of the heart-kidney-stomochord complex. An important challenge for evolutionary developmental biology is to form links from phylogenetically distant and large-scale differences to phylogenetically close and small-scale differences. This description of the embryology, development, and adult morphology of S. karankawa permits investigations into how acorn worm development evolves at fine scales.
新物种卡兰卡瓦裂心虫（Schizocardium karankawa sp. nov.）采自墨西哥湾得克萨斯州马德雷湖和密西西比海岸的潮下带泥地。得克萨斯种群在2月初至4月中旬繁殖。配子通过性腺上的一个小切口释放。在有精子的情况下，卵母细胞生发泡破裂增加，在人工海水Jamarin U中受精成功率最高。人工去壳的胚胎发育正常。发育通过柱头幼虫异步进行，变态并发育至幼体蠕虫的6个鳃孔阶段。用鬼笔环肽标记的晚期柱头幼虫显示出牵缩肌，其将心包囊与前方的顶簇、腹侧的食管以及早期中胚层的肌肉细胞相连。早期幼体蠕虫的肌肉发育始于背侧-外侧躯干肌肉、外侧躯干带以及鳃孔和肛门周围的括约肌。成年蠕虫的特征在于口索向前分叉成成对的蠕虫状突起、鳃条几乎延伸至整个背腹鳃区从而形成狭窄的腹侧鳃下嵴，以及具有六个离散细胞类型区域的复杂鳃上器官。躯干有多达三排肝囊和侧性腺。橡实虫演化发育模型物种科瓦列夫斯基囊舌虫（Saccoglossus kowalevskii）、黄鳃头虫（Ptychodera flava）和加利福尼亚裂心虫（Schizocardium californicum）在系统发育上相距甚远且生活史不同。卡兰卡瓦裂心虫与加利福尼亚裂心虫在系统发育上相近，它们之间成年蠕虫时明显的差异包括鳃孔和肝囊的数量，以及心-肾-口索复合体的精细结构。进化发育生物学面临的一个重要挑战是建立从系统发育上相距甚远和大规模差异到系统发育上相近和小规模差异的联系。对卡兰卡瓦裂心虫胚胎学、发育和成年形态的描述有助于研究橡实虫发育在精细尺度上是如何演化的。
