Welcome on Teratotheca

This interactive, collaborative interface aims to document diatom teratologies, by collecting pictures of deformed specimens and describing the associated environmental conditions.

What are diatoms?

Diatom picture

Diatoms, unicellular microscopic algae that are ubiquitous in aquatic environments, are used as bioindicators of water quality in rivers and lakes. Diatom species can be identified by the shape and ornamentation of their siliceous skeleton, the frustule.

Why take an interest in teratologies?

Various studies indicate that frustule deformations in diatoms are characteristic of toxic stress. In the corpus of publications mentioning deformed diatoms (from Lavoie et al. 2017 and Falasco et al. 2021), the presence of toxic contaminants (red bars in the graph) is indeed preferentially mentioned as the probable cause of the appearance of teratologies.

Probable origin of teratologies indicated in published papers
Source: adapted from Falasco et al. (2021)

Teratology: a question of species, typology and severity

Deformations involve alterations to the contour of individuals (loss of symmetry in particular) or to the ornamentation of the frustule. The tendency to deform, and the ability to display one or the other of the types of frustule anomalies, seem to depend on the species (Falasco et al. 2021). Thus, Lavoie et al. (2017) suggested considering the taxonomic dimension in addition to the frequency of teratology in all species when diagnosing toxic pollution. Recent morphometric analysis work also suggests that the severity of deformations could reflect the intensity of the level of toxic pollution (Olenici et al. 2017, Cerisier et al. 2019).

Bioindication and consideration of teratology

Given the observed increase in the frequency of anomalies under conditions of toxic exposure, some diatom indices consider the relative abundance of teratological diatoms as a downgrading criterion for the quality of the environment (e.g. IBD, Coste et al. 2009, graph below), by attributing a specific profile to deformed specimens. If the percentage of deformations is not taken into account, the index scores may be overestimated (Olenici et al. 2020) and thus overestimate the quality of the environment.

Presence probability of normal (NPAL) and abnormal (NPTR) forms of Nitzschia palea
Presence probability of normal (FCAP) and abnormal (FCAT) forms of Fragilaria capucina
Source: figures from Coste et al. (2009)

Despite their relevance, deformations are generally poorly documented, mainly because of the lack of documentation on existing abnormal shapes and the difficulty for operators to draw the line between normality and subtle deformation.

Our goals

  • Create a reference iconography for identifying deformed diatoms
  • Collect images of deformed diatoms, together with their environmental data, using a collaborative approach
  • Use this dataset to establish correlations between deformations and associated stress factors

More info

Vallanzasca I., Boutry S., Laviale M., Quinton E., Morin S. 2023. Development of a collaborative web platform documenting the diversity and extent of diatom deformities. Botany Letters. DOI : 10.1080/23818107.2023.2183898

References

  • Cerisier A., Vedrenne J., Lavoie I., Morin S. 2019. Assessing the severity of diatom deformities using geometric morphometry. Botany Letters 166:32-40. DOI : 10.1080/23818107.2018.1474800
  • Coste M., Boutry S., Tison-Rosebery J., Delmas F. 2009. Improvements of the Biological Diatom Index (BDI): Description and efficiency of the new version (BDI-2006). Ecological Indicators 9:621-650. DOI : 10.1016/j.ecolind.2008.06.003
  • Falasco E., Ector L., Wetzel C.E., Badino G., Bona F. 2021. Looking back, looking forward: a review of the new literature on diatom teratological forms (2010–2020). Hydrobiologia 848:1675–1753. DOI : 10.1007/s10750-021-04540-x
  • Lavoie I., Hamilton P.B., Morin S., Kim Tiam S., Kahlert M., Gonçalves S., Falasco E., Fortin C., Gontero B., Heudre D., Kojadinovic-Sirinelli M., Manoylov K., Pandey L.K., Taylor J.C. 2017. Diatom teratologies as biomarkers of contamination: Are all deformities ecologically meaningful? Ecological Indicators 82:539-550. DOI : 10.1016/j.ecolind.2017.06.048
  • Olenici A., Blanco S., Borrego-Ramos M., Momeu L., Baciu C. 2017. Exploring the effects of acid mine drainage on diatom teratology using geometric morphometry. Ecotoxicology 26:1018–1030. DOI : 10.1007/s10646-017-1830-3
  • Olenici A., Baciu C., Blanco S., Morin S. 2020. Naturally and Environmentally Driven Variations in Diatom Morphology: Implications for Diatom-Based Assessment of Water Quality. In: Cristóbal, G., Blanco, S., Bueno, G. (eds) Modern Trends in Diatom Identification. Developments in Applied Phycology vol 10. Springer, Cham. DOI : 10.1007/978-3-030-39212-3_4

Funding

This project is funded by the Office Français de la Biodiversité (OFB) through the Aquaref 2022-2024 programme (Theme B).