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The morphological diversity of marine annelid larvae is stunning. Although many of the larval forms have been categorized as trochophores or modified trochophores, there are a few groups with distinctive larval features that make them easy to distinguish from other annelid larvae. We collected 252 annelid larvae from the plankton, with particular emphasis on oweniids, polygordiids, and thalassematids (i.e., echiurans) and sequenced fragments of their cytochrome c oxidase subunit 1 and 16S ribosomal RNA genes. We found six oweniid, five polygordiid, and eight thalassematid OTUs. Thalassematids were found only in samples from the Pacific, and oweniids were found only in Caribbean samples. Among the oweniids we found two distinct morphotypes, one with a narrow, cloche shape and another that had a wider and more rectangular shape with clearly developed lappets. Among the polygordiids, we identified one larva as Polygordius eschaturus and several larvae as Polygordius jenniferae. All larvae, except for the P. eschaturus, which was at a stage too early to make a determination, were endolarvae. Among the thalassematids, we identified larvae of Ochetostoma edax and found seven unidentified OTUs. Finally, 150 miscellaneous polychaete larvae were sequenced, representing ~76 OTUs. Four rostraria larvae from the Caribbean, whose sequences confirm the long‐held assumption that they are amphinomids, could not be identified to species. In total only 5% of these OTUs could be identified to species with known sequences, and most could not be identified to genus or even family with reasonable certainty. It is clear that this poor coverage in the reference databases will limit metabarcoding efforts to document numbers of OTUs, and that DNA barcodes will be of limited use for identifying neotropical marine annelids until reference databases have improved their coverage of this group. [ABSTRACT FROM AUTHOR]

As part of a project to document the diversity of larval invertebrates on both coasts of Panama, we collected and photographed 141 larval asteroids and sequenced fragments of their mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA. We uncovered 10 Caribbean operational taxonomic units (OTUs) and five Pacific OTUs. We could identify six of the 15 OTUs based on >99% similarity with reference sequences in GenBank: The Pacific species Astropecten verrilli and Pentaceraster cumingi and the Caribbean species Astropecten marginatus, Astropecten antillensis, Oreaster reticulatus, and Mithrodia clavigera. Two other OTUs were placed in BINs in the Barcode of Life Database (BOLD) with unpublished sequences that were identified as Pharia pyramidata from the Pacific and Valvaster striatus, now known from the Caribbean as well as the Indo‐West Pacific. The remaining seven species appear likely to belong to Luidia, as 16S sequences from each have 87%–95% identity with various species of Luidia, and the sequences nest among species of Luidia in neighbor‐joining trees. The low diversity of asteroid larvae reflects ~10% of the diversity of adult sea stars reported from Panama, and highlights the need for broader collection efforts and improved coverage of DNA barcode reference sequences for Luidia and other soft‐bottom species. [ABSTRACT FROM AUTHOR]

The identity of wild cloning sea star larvae has been a mystery since they were first documented in the Caribbean. The most commonly collected cloning species was thought to belong to the Oreasteridae, on the basis of similarity with sequences from Oreaster reticulatus and Oreaster clavatus. This larval form has recently been linked to a rare benthic juvenile. As part of two larger DNA barcoding projects, we collected cloning asteroid larvae from the Caribbean coast of Panama and compared them to a large reference database of tropical echinoderms. Morphological and DNA barcode data from the cytochrome c oxidase subunit I gene demonstrated that Panamanian larvae belonged to the same operational taxonomic unit as those recovered in previous studies of cloning larvae from the Caribbean. Much to our surprise, sequences from these larvae clearly identified them as belonging to Valvaster striatus , a species typically considered to be endemic to the Indo-West Pacific. A lineage of Mithrodia clavigera that occurs in both the Caribbean and the Indo-West Pacific also has cloning larvae, suggesting that this unusual life history has allowed larvae to pass around the Cape of Good Hope and the Benguela upwelling region, which is a barrier to dispersal for most tropical marine invertebrates. [ABSTRACT FROM AUTHOR]

Surveys of larval diversity consistently increase biodiversity estimates when applied to poorly documented groups of marine invertebrates such as phoronids and hemichordates. However, it remains to be seen how helpful this approach is for detecting unsampled species in well‐studied groups. Echinoids represent a large, robust, well‐studied macrofauna, with low diversity and low incidence of cryptic species, making them an ideal test case for the efficacy of larval barcoding to discover diversity in such groups. We developed a reference dataset of DNA barcodes for the shallow‐water adult echinoids from both coasts of Panama and compared them to DNA sequences obtained from larvae collected primarily on the Caribbean coast of Panama. We sequenced mitochondrial cytochrome c oxidase subunit I (COI) for 43 species of adult sea urchins to expand the number and coverage of sequences available in GenBank. Sequences were successfully obtained for COI and 16S ribosomal DNA from 272 larvae and assigned to 17 operational taxonomic units (OTUs): 4 from the Pacific coast of Panama, where larvae were not sampled as intensively, and 13 from the Caribbean coast. Of these 17 OTUs, 13 were identified from comparisons with our adult sequences and belonged to species well documented in these regions. Another larva was identified from comparisons with unpublished sequences in the Barcode of Life Database (BOLD) as belonging to Pseudoboletia, a genus scarcely known in the Caribbean and previously unreported in Panama. Three OTUs remained unidentified. Based on larval morphology, at least two of these OTUs appeared to be spatangoids, which are difficult to collect and whose presence often goes undetected in standard surveys of benthic diversity. Despite its ability to capture unanticipated diversity, larval sampling failed to collect some species that are locally common along the Caribbean coast of Panama, such as Leodia sexiesperforata, Diadema antillarum, and Clypeaster rosaceus. [ABSTRACT FROM AUTHOR]

Previous research focusing on pelagic gastropods in the open ocean has demonstrated that many morphospecies comprise multiple distinct clades or cryptic species that can be distinguished with DNA sequence data. To date, the genetic diversity of the pelagic gastropod fauna of the tropical East Pacific, especially in shallow coastal waters, remains largely unexplored. To document the diversity of pterotracheoids (formerly heteropods) from the coastal waters of the Bay of Panama, we collected, photographed and sequenced fragments of mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal DNA for 60 atlantids, 3 carinariids and 6 pterotracheids. In addition to the COI barcode, our results include the first published 16S sequences for these groups. We found 11 operational taxonomic units (OTUs): 9 in the genus Atlanta, 1 Carinaria and 1 Firoloida. We report the presence of Atlanta oligogyra (Clades A and B), Atlanta turriculata, Atlanta lesueurii, Atlanta helicinoidea (Clade B), Atlanta plana, Atlanta echinogyra, Atlanta inflata and Atlanta frontieri through comparisons of our sequences with previously published sequences. We did not find Atlanta gaudichaudi, Atlanta inclinata, Atlanta tokiokai, Atlanta gibbosa, Atlanta peronii, or Oxygyrus inflatus, which have previously been reported from the region. Haplotype networks and estimates of ΦST illustrate how some species show population differentiation across the tropical Indo‐Pacific region, whereas others show little apparent population structure. For example, the most common haplotypes of A. inflata and of A. turriculata occur in the Indian Ocean, the Central and West Pacific and the tropical East Pacific, whereas individuals of A. frontieri from the Indian Ocean do not share haplotypes with individuals of A. frontieri from the Pacific Ocean. Analyses were limited by sample sizes, but these data suggest that population genetics approaches may be useful for reconstructing population histories of these important, but overlooked, components of the plankton. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Phoronid larvae, actinotrochs, are beautiful and complicated organisms which have attracted as much, if not more, attention than their adult forms. We collected actinotrochs from the waters of the Pacific and Caribbean coasts of Panama, and used DNA barcoding of mtCOI, as well as 16S and 18S sequences, to estimate the diversity of phoronids in the region. We discovered three operational taxonomic units (OTUs) in the Bay of Panama on the Pacific coast and four OTUs in Bocas del Toro on the Caribbean coast. Not only did all OTUs differ from each other by >10% pairwise distance in COI, but they also differed from all phoronid sequences in GenBank, including the four species for which adults have been reported for the Pacific of Panama, Phoronopsis harmeri, Phoronis psammophila, Phoronis muelleri, and Phoronis hippocrepia. In each ocean region, one common OTU was more abundant and occurred more frequently than other OTUs in our samples. The other five OTUs were relatively rare, with only one to three individuals collected during the entire project. Species accumulation curves were relatively flat but suggest that at least one more species is likely to be present at each site. Actinotrochs from the seven sequenced OTUs had morphologies typical of species with non‐brooded planktotrophic development and, in some cases, may be distinguished by differences in pigmentation and the arrangement of blood masses. We found one larva with morphology typical of brooded planktotrophic larvae for which sequencing failed, bringing the total number of potential species detected to eight and representing >50% of the adult species currently recognized globally. [ABSTRACT FROM AUTHOR]

Lingulids and discinids are the only brachiopods that exhibit life histories that include a feeding planktonic stage usually referred to as a "larva". We collected planktotrophic brachiopod larvae from the Pacific and Caribbean coasts of Panama and took a DNA barcoding approach with mitochondrial cytochrome c oxidase subunit I (COI), mitochondrial ribosomal 16S, and nuclear ribosomal 18S genes to identify those larvae and to estimate their diversity in the region. We observed specimens from both coasts with distinct morphologies typical of lingulid and discinid larvae. COI and 16S were sequenced successfully for the lingulid larvae but failed consistently for all discinid larvae. 18S was sequenced successfully for larvae from both families. Sequence data from each gene revealed one lingulid operational taxonomic unit (OTU) from Bocas del Toro on the Caribbean coast, and one lingulid OTU from the Bay of Panama on the Pacific coast. These OTUs differed by >20% for COI, >10% for 16S and ~0.5% for 18S. Both OTUs clustered with GenBank sequences of Glottidia species, the only genus of lingulids in the Americas, but were distinct from G. pyramidata the only species reported for the Caribbean. Analysis of 18S sequence data for discinid larvae recovered 2 OTUs, one exclusively from the Pacific and one with a mixture of Pacific and Caribbean larvae. The 18S marker does not provide enough resolution to distinguish between species, and comparisons with GenBank sequences suggest that one OTU includes Pelagodiscus species, while the other may include Discradisca species. When compared with other marine invertebrates, our surveys of brachiopod larvae through DNA barcoding show relatively low levels of diversity for Panama. [ABSTRACT FROM AUTHOR]