Miyamoto Norio, Saito Yasunori
Shimoda Marine Reesearch Center, University of Tsukuba, Shimoda, Shizuoka, Japan.
Zoolog Sci. 2007 Dec;24(12):1278-85. doi: 10.2108/zsj.24.1278.
The morphology and development of a new species of the genus Balanoglossus belonging to the family Ptychoderidae are described in detail. This acorn worm was collected from the sandy seashore in the cove near Shimoda Marine Research Center, University of Tsukuba (Shimoda, Shizuoka Prefecture, Japan). This acorn worm is easily distinguished from other balanoglossids by a characteristic hepatic region. There are two kinds of hepatic saccules: large, dark-colored saccules in the anterior region and small, light-colored saccules in the posterior region. Between the two subregions of the hepatic region, there is a small region that has no or tiny saccules. This species does not form distinct burrows or mounds of casts. The breeding season is in winter. The process of embryogenesis from fertilization to metamorphosis was observed. A shift in seawater temperature from about 13 degrees C to about 9 degrees C induced gamete release. Two days after fertilization, embryos hatched and became typical feeding tornaria larvae. Two months after fertilization these larvae metamorphosed into juveniles and began their benthic life.
详细描述了帚鳃柱头虫科柱头虫属一个新物种的形态和发育情况。这种柱头虫是从筑波大学下田海洋研究中心附近海湾的沙滩上采集到的（日本静冈县下田）。这种柱头虫通过其独特的肝脏区域很容易与其他柱头虫科动物区分开来。肝脏有两种囊泡：前部区域的大而深色的囊泡和后部区域的小而浅色的囊泡。在肝脏区域的两个亚区域之间，有一个没有或只有微小囊泡的小区域。该物种不会形成明显的洞穴或粪便堆。繁殖季节在冬季。观察了从受精到变态的胚胎发育过程。海水温度从约13摄氏度降至约9摄氏度会诱导配子释放。受精两天后，胚胎孵化并变成典型的摄食柱头幼虫。受精两个月后，这些幼虫变态成为幼体并开始底栖生活。
