The diversity of tropical marine invertebrates is poorly documented, especially those groups for which collecting adults is difficult. We collected the planktonic tornaria larvae of hemichordates (acorn worms) to assess their hidden diversity in the Neotropics. Larvae were retrieved in plankton tows from waters of the Pacific and Caribbean coasts of Panama, followed by DNA barcoding of mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA to estimate their diversity in the region. With moderate sampling efforts, we discovered six operational taxonomic units (OTUs) in the Bay of Panama on the Pacific coast, in contrast to the single species previously recorded for the entire Tropical Eastern Pacific. We found eight OTUs in Bocas del Toro province on the Caribbean coast, compared to seven species documented from adults in the entire Caribbean. All OTUs differed from each other and from named acorn worm sequences in GenBank by >10% pairwise distance in COI and >2% in 16S. Two of our OTUs matched 16S hemichordate sequences in GenBank: one was an unidentified or unnamed Balanoglossus from the Caribbean of Panama, and the other was an unidentified ptychoderid larva from the Bahamas. The species accumulation curves suggest that nearly all the species have been collected and only one more species might still remain undetected in the Pacific. In contrast, the Caribbean species accumulation curve suggests that further sampling could yield more than 10 additional OTUs. Tornaria from the 14 OTUs exhibited typical planktotrophic morphologies, and, in some cases, may be distinguished by differences in pigmentation and by the number of telotrochal ciliary bands, but in general, few diagnostic differences were detected.

中文翻译：

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来自新热带地区的半脊索动物幼虫的意外分子和形态多样性

热带海洋无脊椎动物的多样性记录很少，尤其是那些难以收集成虫的群体。我们收集了半脊索动物（橡子蠕虫）的浮游 Tornaria 幼虫，以评估它们在新热带地区的隐藏多样性。从巴拿马太平洋和加勒比海岸水域的浮游生物拖带中回收幼虫，然后对线粒体细胞色素 c 氧化酶亚基 I (COI) 和 16S 核糖体 DNA 进行 DNA 条形码编码，以估计它们在该地区的多样性。通过适度的采样工作，我们在太平洋沿岸的巴拿马湾发现了六个操作分类单元 (OTU)，这与之前记录的整个热带东太平洋的单一物种形成鲜明对比。我们在加勒比海岸的博卡斯德尔托罗省发现了八个 OTU，相比之下，整个加勒比地区的成年人记录的七个物种。所有 OTU 彼此不同，与 GenBank 中命名的橡子蠕虫序列的 COI 成对距离 >10%，16S 中 >2%。我们的两个 OTU 与 GenBank 中的 16S 半脊索动物序列匹配：一个是来自巴拿马加勒比海的未鉴定或未命名的 Balanoglossus，另一个是来自巴哈马的未鉴定的 ptychoderid 幼虫。物种积累曲线表明，几乎所有物种都已被收集，太平洋中可能只有一种物种仍未​​被发现。相比之下，加勒比海物种积累曲线表明，进一步采样可能会产生 10 多个额外的 OTU。来自 14 个 OTU 的 Tornaria 表现出典型的浮游生物形态，并且在某些情况下，