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More than 2,500 species of copepods (Class Maxillopoda; Subclass Copepoda) occur in the marine planktonic environment. The exceptional morphological conservation of the group, with numerous sibling species groups, makes the identification of species challenging, even for expert taxonomists. Molecular approaches to species identification have allowed rapid detection, discrimination, and identification of species based on DNA sequencing of single specimens and environmental samples. Despite the recent development of diverse genetic and genomic markers, the barcode region of the mitochondrial cytochrome c oxidase subunit I (COI) gene remains a useful and - in some cases - unequaled diagnostic character for species-level identification of copepods. This study reports 800 new barcode sequences for 63 copepod species not included in any previous study and examines the reliability and resolution of diverse statistical approaches to species identification based upon a dataset of 1,381 barcode sequences for 195 copepod species. We explore the impact of missing data (i.e., species not represented in the barcode database) on the accuracy and reliability of species identifications. Among the tested approaches, the best close match analysis resulted in accurate identification of all individuals to species, with no errors (false positives), and out-performed automated tree-based or BLAST based analyses. This comparative analysis yields new understanding of the strengths and weaknesses of DNA barcoding and confirms the value of DNA barcodes for species identification of copepods, including both individual specimens and bulk samples. Continued integrative morphological-molecular taxonomic analysis is needed to produce a taxonomically-comprehensive database of barcode sequences for all species of marine copepods.

High-frequency acoustic scattering techniques have been used to investigate dominant scatterers in mixed zooplankton populations. Volume backscattering was measured in the Gulf of Maine at 43, 120, 200, and 420 kHz. Zooplankton composition and size were determined using net and video sampling techniques, and water properties were determined using conductivity, temperature, and depth sensors. Dominant scatterers have been identified using recently developed scattering models for zooplankton and microstructure. Microstructure generally did not contribute to the scattering. At certain locations, gas-bearing zooplankton, that account for a small fraction of the total abundance and biomass, dominated the scattering at all frequencies. At these locations, acoustically inferred size agreed well with size determined from the net samples. Significant differences between the acoustic, net, and video estimates of abundance for these zooplankton are most likely due to limitations of the net and video techniques. No other type of biological scatterer ever dominated the scattering at all frequencies. Copepods, fluid-like zooplankton that account for most of the abundance and biomass, dominated at select locations only at the highest frequencies. At these locations, acoustically inferred abundance agreed well with net and video estimates. A general approach for the difficult problem of interpreting high-frequency acoustic scattering in mixed zooplankton populations is described.

Aim: To apply a new paradigm using transient changes to visual scenes to explore information processing biases relating to "social" levels of alcohol and cannabis use., Participants: Male and female student volunteers (n = 200) not self-reporting substance-related problems., Setting: Quiet testing areas throughout the university campus., Design: A flicker paradigm, for inducing change blindness with lighter and heavier social users of alcohol (experiment 1, n= 100) and social users and non-users of cannabis (experiment 2, n= 100), explored the associations between habitual level of use and the latency to detection of a single substance-related or neutral change made to a scene of grouped substance-related and neutral objects., Measurements: Alcohol use was measured as the number of units of the heaviest drinking day from the previous week; cannabis use as the number of months of use in previous 12. Change-detection latency comparisons were used to evaluate processing biases., Findings: In both experiments, (i) heavier social users detected substance-related changes quicker than lighter and non-users; (ii) lighter and non-users detected substance-neutral changes quicker than heavier users; (iii) heavier social users detected substance-related quicker than substance-neutral changes; and (iv) lighter and non-users detected substance-neutral changes quicker than substance-related changes., Conclusions: Alcohol and cannabis processing biases are found at levels of social use, have the potential to influence future consumption and for this reason merit further research.