The use of hand-sanitiser gel facilitates combined morphological and genetic analysis of shelled pteropods

Abstract

There is a lack of standardised imaging methods for marine zooplankton due to the difficulty of manipulating small and often fragile specimens. Yet, standardised 2D photographs and 3D scans provide important morphological information to accompany DNA-barcoded specimens for reference databases such as the Barcode of Life Data System (BOLD). Shelled pteropods are considered as bio-indicators to study impacts of ocean acidification, and thus, it is especially important to obtain high-quality records of their fragile aragonitic shells. We used alcohol-based hand sanitiser gel as a medium for photographing pteropods of the genus Limacina prior to micro-CT scanning and destructive DNA analysis. The high viscosity and transparency of the hand sanitiser enabled easy handling of the specimens so that they could be positioned in a standardised orientation and photographed with a stacking microscope. The high-quality photographs provide a record of morphology and allow for subsequent geometric morphometric analyses. This method did not impact the downstream micro-CT and molecular analyses of the same specimens and resulted in publicly available 2D and 3D digital vouchers as well as ten reference DNA barcodes (partial Cytochrome Oxidase I gene sequences). While alcohol-based hand sanitiser entered our daily lives due to a distressing pandemic, we could make use of it as a cheap and easily available resource to make high quality voucher photographs of shelled pteropods. Digital vouchers serve as a record of their morphology for further taxonomic analyses and facilitate studies assessing shell growth and impacts of ocean acidification.