The application of established cell viability assays such as the commonly used trypan blue staining method to coral cells is not straightforward due to different culture parameters and different cellular features specific to mammalian cells compared to marine invertebrates. Using Pocillopora damicornis as a model, we characterized the autofluorescence and tested different fluorescent dye pair combinations to identify alternative viability indicators. The cytotoxicity of different representative molecules, namely small organic molecules, proteins and nanoparticles (NP), was measured after 24 h of exposure using the fluorescent dye pair Hoechst 33342 and SYTOX orange. Our results show that this dye pair can be distinctly measured in the presence of fluorescent proteins plus chlorophyll. P. damicornis cells exposed for 24 h to Triton-X100, insulin or titanium dioxide (TiO2) NPs, respectively, at concentrations ranging from 0.5 to 100 µg/mL, revealed a LC50 of 0.46 µg/mL for Triton-X100, 6.21 µg/mL for TiO2 NPs and 33.9 µg/mL for insulin. This work presents the approach used to customize dye pairs for membrane integrity-based cell viability assays considering the species- and genotype-specific autofluorescence of scleractinian corals, namely: endogenous fluorescence characterization followed by the selection of dyes that do not overlap with endogenous signals.

The application of established cell viability assays such as the commonly used trypan blue staining method to coral cells is not straightforward due to different culture parameters and different cellular features specific to mammalian cells compared to marine invertebrates. Using Pocillopora damicornis as a model, we characterized the autofluorescence and tested different fluorescent dye pair combinations to identify alternative viability indicators. The cytotoxicity of different representative molecules, namely small organic molecule, protein and nanoparticles (NP), was measured after 24 hours of exposure using the fluorescent dye pair Hoechst 33342 and SYTOX® orange. Our results show that this dye pair can be distinctly measured in the presence of fluorescent proteins plus chlorophyll. P. damicornis cells exposed for 24 hours to Triton-X100, insulin or titanium dioxide (TiO2) NPs, respectively, at concentrations ranging from 0.5-100 µg/mL, revealed a LC50 of 0.5 µg/mL for Triton-X100, 20 µg/mL for TiO2 NPs and an average 20% reduction in viability at 100 µg/mL for insulin. The workflow presented here provides a general framework for customizing dye pairs for cell viability assays considering the species- and genotype-specific autofluorescence of scleractinian corals.

Species are usually described by morphological terms. In order to simplify and shorten descriptions these are often abbreviated (e.g., SVL for snout-vent-length). However, there has been no systematic attempt to define and standardize such terms or their abbreviations. Here we present an initial list of 594 unique abbreviations from a total list of 1,223 abbreviations collected from >50 reptile species descriptions, resulting in a non-redundant list of 344 abbreviations. Most of these abbreviations describe either meristic characters such as scale counts (46%) or measurements such as SVL (snout-vent-length) (30%). The remainder describe presence/absence states, colors, or formulas such as ratios. We highlight the common problem of synonyms and homonyms, i.e., different terms and abbreviations for the same character or the same term for different characters. We propose to standardize definitions of terms and abbreviations in future species descriptions. In order to future-proof species descriptions for machine-readability such as text-mining, standardization is needed for all species descriptions in biology, not just reptiles.