Segmented worms (Phylum Annelida): a celebration of twenty years of progress through Zootaxa and call for action on the taxonomic work that remains.

Zootaxa has been the leading journal on invertebrate systematics especially within Annelida. Our current estimates indicate annelids include approximately 20,200 valid species of polychaetes, oligochaetes, leeches, sipunculans and echiurans. We include herein the impact of Zootaxa on the description of new annelid species in the last two decades. Since 2001, there have been over 1,300 new annelid taxa published in about 630 papers. The majority of these are polychaetes (921 new species and 40 new genera) followed by oligochaetes (308 new species and 10 new genera) and leeches (21 new species). The numerous papers dealing with new polychaete species have provided us a clear picture on which polychaete families have had the most taxonomic effort and which authors and countries have been the most prolific of descriptions of new taxa. An estimated additional 10,000+ species remain to be described in the phylum, thus we urge annelid workers to continue their efforts and aid in training a new generation of taxonomists focused on this ecologically important group.

The common ecotoxicology laboratory strain of Hyalella azteca is genetically distinct from most wild strains sampled in eastern North America.

The amphipod Hyalella azteca is commonly used as a model for determining safe concentrations of contaminants in freshwaters. The authors sequenced the mitochondrial cytochrome c oxidase subunit I (COI) gene for representatives of 38 populations of this species complex from US and Canadian toxicology research laboratories and eastern North American field sites to determine their genetic relationships. With 1 exception, all US and Canadian laboratory cultures sampled were identified as conspecific. In 22 wild populations spanning 5 US states and 1 Canadian province, the commonly occurring laboratory species was found only in northern Florida, USA. Therefore, the diversity of the H. azteca species complex detected in the wild is not accurately represented in North American laboratories, questioning the reliability of H. azteca cultures currently in use to accurately predict the responses of wild populations in ecotoxicological assays. The authors also examined the utility of different COI nucleotide fragments presently in use to determine phylogenetic relationships in this group and concluded that saturation in DNA sequences leads to inconsistent relationships between clades. Amino acid sequences for COI were not saturated and may allow a more accurate phylogeny estimate. Hyalella azteca is crucial for developing water-quality regulations; therefore, laboratories should know and standardize the strain(s) they use to confidently compare toxicity tests across laboratories and determine whether they are an appropriate surrogate for their regions.