Larval Biometry as an Endpoint in Chronic Sea Urchin Assays Echinometra lucunter (Linnaeus, 1758)
Test based on the biometrics of E. lucunter larvae
DOI:
https://doi.org/10.5132/eec.2024.01.01Keywords:
Echinodermata, Larval biometry, Endpoint, ReproducibilityAbstract
This study was carried out with the aim of contributing to the improvement of the evaluation of sea urchin embryo-larval tests, reducing its analysis subjectivity and also to solve the problems associated with the morphology of different Echinodermata larvae used in ecotoxicological tests. In this regard, the larval size technique (biometrics) was applied as an endpoint in sub-lethal assays using the reference toxicants zinc sulfate and potassium dichromate as a standard for calibrating the EC50 estimate (Median Effective Concentration) and NOEC (No Observed Effect Concentration). The tests, using the sea urchin species Echinometra lucunter, were carried out between the years 2017 to 2019 and were analyzed by two methods, the traditional one (counting normal larvae and those with developmental delay) and biometrics based on the maximum length of the larvae obtained in the treatments. It was established that the minimum number of measurements of the different stages of development (egg, embryo and larva) was 35 (n) per replicate. For the tests carried out over 15 months, it was verified, based on the Wald Test, that there is a seasonality in the sizes of the larvae. The EC50 of the metals tested was similar between the traditional and biometric methods when adopting the size of 18-hour-old larvae as a reference for 100% effect, but there was disagreement between the methods when the size of the eggs is considered as the total effect. On the other hand, the estimates of the NOEC were more sensitive by the biometry method, in disagreement with the traditional method.
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