Marine ribbon worms in the class Hoplonemertea were presumed to have lecithotrophic development until the recent discovery of predatory larvae in several species, including Emplectonema viride Stimpson, 1857: a common NE Pacific intertidal nemertean. This study reports the complete life cycle of E. viride in the laboratory from fertilization to sexual maturity, which took ~ 9.5 months at 12 − 15 °C. Predatory larvae of this species were successfully raised to metamorphosis on a diet of planktonic crustaceans, including barnacle nauplii and cyprids, and an occasional calanoid copepod. The larvae swam and grew for 3−4 months in lab culture with abundant food, before settling as juveniles and starting to feed on adult barnacles. Settlement was accompanied by a subtle but definite metamorphosis, which included shortening of epidermal cilia, loss of the caudal ciliary cirrus, and behavioral changes. Larvae were positively phototactic, whereas juveniles were negatively phototactic. A pelagic larval duration of several months provides abundant opportunities for dispersal, and likely results in high genetic connectivity among populations. Population genetic studies on other hoplonemertean species reveal higher-than-expected gene flow, suggesting that planktotrophic macrophagy (predatory larvae), as described here for E. viride, may be widespread within the class.

海洋带状蠕虫被认为具有卵磷脂发育，直到最近在几个物种中发现捕食性幼虫，包括Emplectonema viride Stimpson, 1857：一种常见的东北太平洋潮间带纽虫。这项研究报告了E. viride的完整生命周期在实验室中，从受精到性成熟，在 12 – 15 °C 下需要大约 9.5 个月的时间。该物种的掠食性幼虫以浮游甲壳类动物为食，包括藤壶无节幼体和鲤鱼，以及偶尔的桡足类动物，成功地使其变态。幼虫在具有丰富食物的实验室培养物中游泳和生长 3-4 个月，然后定居下来并开始以成年藤壶为食。定居伴随着微妙但明确的变态，包括表皮纤毛缩短、尾部纤毛卷毛消失和行为改变。幼虫具有正趋光性，而幼虫具有负趋光性。浮游幼虫长达数月的生存期为传播提供了充足的机会，并可能导致种群之间的高度遗传连通性。E. viride，可能在该类中广泛存在。