Spawning and multiple end points of the embryo-larval bioassay of the blue mussel Mytilus galloprovincialis (Lmk)

Abstract

Since the 1960s, little has been done to improve and simulate the use of short-duration chronic bioassays of bivalve embryos, particularly in mussels. However, these test organisms offer great advantages in relation to other groups, due to the ease of obtaining breeders in cultivation systems, in the environment and any time, and due to their high sensitivity to chemicals or contaminants. To contribute some methodological aspects, this study uses techniques to stimulate spawning or improve the obtaining of gametes for use in bioassays with the mussel Mytilus galloprovincialis. It also evaluates different criteria for determining the effect on the larvae, for estimation of EC and NOEC values, based on morphological analysis of developmental delay and the biometrics of the larvae. KCl proved to be a reliable inducer of spawning, with positive responses in 10 of the 12 months of the year tested. Moreover, this chemical, in association with NHCl, demonstrated the capacity to activate immature oocytes obtained from extirpated gonads, enabling an improvement in fertilization rates. The different criteria adopted to determine the effects on the larvae in the assays with reference toxicants (SDS and KCrO) resulted in EC and NOEC values without significant differences, indicating reliability in the results and freedom in the choice of criteria of effect to be adopted in the trials.

Exposure to Plasticiser DEHP Affects Eggs Spawned by Blue Mussels: A Possible Risk to Fertilisation?

“…During the fertilisation event, eggs are released as an intermittent pink cloud, while sperm is released in a thin, steady stream through the exhaling syphon cloud [ 69 ]. The KCl method from [ 70 ] was chosen as a spawning inductor, and carried out as follows: mussels were injected with 2 mL of 0.5 M KCl into the valve cavity and left for 2 h outside water. Then, they were randomly divided into 5 tanks for each treatment (n = 6 per replicate tank in a final volume of 2 L), considering that preliminary tests showed that mussels were more likely to spawn when placed with conspecifics and not in individual jars.…”