# In vitro culture media type impacts gene expression in the freshwater mussel Lampsilis siliquoidea (Bivalvia: Unionidae)

## TL;DR

This study shows that the type of culture media used affects gene expression in freshwater mussel larvae during metamorphosis.

## Contribution

The study is the first to compare gene expression in freshwater mussel glochidia across different in vitro culture media.

## Key findings

- 1.2% of the transcriptome showed significantly altered gene expression in different culture media.
- 86% of differentially expressed transcripts were consistent across L-15 and lipid-supplemented M199 media.
- Gene Ontology analysis revealed environmental impacts on physiology and juvenile survival.

## Abstract

Artificial propagation is an important conservation technique to mitigate the loss of native freshwater mussel diversity. In vitro propagation is an alternative method of metamorphosing freshwater mussel larvae (glochidia) to juveniles without a host fish, but the methodology is still evolving in its rates of metamorphosis. This study provides the first comparison of gene expression in freshwater mussel glochidia metamorphosed in different culture media: M199, L-15, and M199 supplemented with lipids. Compared to the commonly used M199, 1.2% of the transcriptome of glochidia reared in the other culture media showed significantly altered expression levels. Of these differentially expressed transcripts, 86% were the same regardless of whether glochidia were metamorphosed in the different basal culture medium L-15 or in M199 supplemented with lipids. We discuss the Gene Ontology categories with the highest number of differentially expressed transcripts, as well as those categories that were over-represented in the different culture media compared to the whole transcriptome. Our results suggest that the external environment can have a significant impact on the physiology of metamorphosing glochidia and may potentially impact the health and survival of juveniles.

The online version contains supplementary material available at 10.1186/s41065-025-00589-z.