Pennington J T, Tamburri M N, Barry J P
Biol Bull. 1999 Jun;196(3):245-256. doi: 10.2307/1542949.
Populations of the articulate brachiopod Laqueus californianus occur in dense single-species aggregations near the continental shelf/slope break (100-200 m) in Monterey Bay, California. The development of embryos and larvae of L. californianus has been examined by scanning electron microscopy. Fertilizable eggs are 130-140 {mu}m in diameter, and sperm are unmodified. Cleavage is holoblastic and radial. At 10{deg}C an up-swimming blastula develops by 18-h, and gastrulation occurs within 24-38 h. The embryo elongates on a new larval axis and the blastopore closes by 72 h. A trilobed articulate brachiopod larva forms by day 3-4, and a metamorphically competent larva with attachment disk is attained in 7 days. Competent larvae swim downwards. Effects of temperature on larval survival and development rate have also been examined. Larvae die within 1 day at 25{deg}C. At 20{deg}C, development appears normal but results in spontaneous abnormal settlement of larvae 5-6 days old. At 15{deg}, 10{deg}, and 5{deg}C, most larvae achieve competence in 5, 7, and 9 days, respectively. Many larvae survive for 71 days at 10{deg} and 15{deg}C. Patterns of larval settlement vary among substrates, but larvae show strong preference for shells of living conspecific adults. Settlement and metamorphosis can occur within 24 h upon exposure of larvae to substrate.
有铰腕足动物加州挂线贝的种群聚集在加利福尼亚州蒙特雷湾大陆架/陆坡交界处（100 - 200米）附近，形成密集的单物种群落。通过扫描电子显微镜对加州挂线贝的胚胎和幼虫发育进行了研究。可受精的卵直径为130 - 140微米，精子未发生变形。卵裂为全裂且呈辐射状。在10℃时，18小时后发育出向上游动的囊胚，原肠胚形成发生在24 - 38小时内。胚胎在新的幼虫轴上伸长，胚孔在72小时内关闭。3 - 4天时形成三叶状有铰腕足动物幼虫，7天时发育出具有附着盘的可变态幼虫。可变态幼虫向下游动。还研究了温度对幼虫存活和发育速率的影响。幼虫在25℃时1天内死亡。在20℃时，发育看似正常，但会导致5 - 6日龄幼虫自发异常附着。在15℃、10℃和5℃时，大多数幼虫分别在5天、7天和9天达到可变态状态。许多幼虫在10℃和15℃下能存活71天。幼虫附着模式因底物而异，但幼虫对同种成年活体的贝壳有强烈偏好。幼虫接触底物后24小时内即可发生附着和变态。
