Molecular taxonomy and description of a new species of Limnodrilus (Naididae, Clitellata, Annelida) in China

The freshwater annelid worm genus Limnodrilus, including the widely distributed L. claparedianus Ratzel, 1868, is common in Chinese freshwater ecosystems. One species, previously recognized as morphologically intermediate between L. claparedianus and the North American taxon L. cervix Brinkhurst, 1963, is here described as a new species, L. paraclaparedianus Zhou & Cui n. sp., using both molecular and traditional taxonomy. Comparisons of sequences of the Cytochrome Oxidase subunit I (COI) mtDNA in a sample of Limnodrilus species showed that the distances between species were generally higher than the divergences within them. Phylogenetic analysis of COI as well as 16S mtDNA and Internal Transcribed Spacer 2 (ITS2) nDNA confirmed that the new species is an independent lineage. Moreover, morphological differences in the prostomium, characteristics of the chaetae and internal genitalia support the separation of the species.

The putative Ordovician annelid worm Haileyia adhaerens Ruedemann, 1934 is not a recognizable fossil

A number of putative annelid worms have been described from Ordovician strata, and these records are included in large-scale compilations of paleontological data. If these fossils are worms, they may yield important phylogenetic information; conversely, if they are not worms, they should not be included in large-scale databases. In either case, restudy of the type material of these supposed annelids is useful. The type material (holotype and one paratype) of one of these putative annelids, Haileyia adhaerens Ruedemann, 1934, from the Middle Ordovician Normanskill Shale of Idaho, USA, is re-described and re-illustrated. The original description stated that the species is segmented, with parapodia, papillae, and setae, and lived attached to graptolites. Upon re-examination, the setae could not be detected, and the segmentation, parapodia, and papillae are herein re-interpreted as taphonomic, rather than biological, features. The supposed attachment of Haileyia to graptolites is likely to represent fortuitous bedding-surface associations. There is no evidence that Haileyia adhaerens is an annelid, or even a recognizable fossil.

High-throughput live-imaging of embryos in microwell arrays using a modular, inexpensive specimen mounting system

Live-imaging embryos in a high-throughput manner is essential for shedding light on a wide range of questions in developmental biology, but it is difficult and costly to mount and image embryos in consistent conditions. Here, we present OMMAwell, a simple, reusable device that makes it easy to mount up to hundreds of embryos in arrays of agarose microwells with customizable dimensions and spacing. OMMAwell can be configured to mount specimens for upright or inverted microscopes, and includes a reservoir to hold live-imaging medium to maintain constant moisture and osmolarity of specimens during time-lapse imaging. All device components can be cut from a sheet of acrylic using a laser cutter. Even a novice user will be able to cut the pieces and assemble the device in less than an hour. At the time of writing, the total materials cost is less than five US dollars. We include all device design files in a commonly used format, as well as complete instructions for its fabrication and use. We demonstrate a detailed workflow for designing a custom mold and employing it to simultaneously live-image dozens of embryos at a time for more than five days, using embryos of the cricket Gryllus bimaculatus as an example. Further, we include descriptions, schematics, and design files for molds that can be used with 14 additional vertebrate and invertebrate species, including most major traditional laboratory models and a number of emerging model systems. Molds have been user-tested for embryos including zebrafish (Danio rerio), fruit fly (Drosophila melanogaster), coqui frog (Eleutherodactylus coqui), annelid worm (Capitella teleta), amphipod crustacean (Parhyale hawaiensis), red flour beetle (Tribolium castaneum), and three-banded panther worm (Hofstenia miamia), as well mouse organoids (Mus musculus). Finally, we provide instructions for researchers to customize OMMAwell inserts for embryos or tissues not described herein.Summary StatementThis Techniques and Resources article describes an inexpensive, customizable device for mounting and live-imaging a wide range of tissues and species; complete design files and instructions for assembly are included.