# Safety Assessment of the Extract of Phycobiliproteins Derived From Arthrospira platensis: Acute Toxicity Studies in Pacific Oysters

## TL;DR

This study assesses the safety of phycobiliprotein extract from Arthrospira platensis on Pacific oysters, finding low toxicity at most concentrations.

## Contribution

The study provides the first acute toxicity assessment of phycobiliprotein extract in Pacific oysters.

## Key findings

- No treatment-related mortality or apoptosis was observed in oysters at tested concentrations.
- High-dose PBP extract caused genotoxicity and reduced esterase activity in hemocytes.
- HSP90 expression was up-regulated in gills after exposure to PBP extract.

## Abstract

Since shellfish farming has the potential to help feed a growing human population, it is crucial to anticipate new opportunities to improve the health of bivalves on farms and hatcheries. Phycobiliproteins (PBPs), natural nutritional components, are considered promising as immunomodulatory feed additives for aquaculture. The aim of this study was to examine the acute toxicity of a PBP extract obtained from Arthrospira platensis biomass for commercially important bivalve species, the Pacific oyster (Magallana gigas (Thunberg, 1793)). The PBP extract was added to water at final concentrations of 2, 20, and 200 μg/mL for a 24 and 48‐h exposure period. Compared to the control group, there were no treatment‐related biological effects on oyster mortality or induction of apoptosis or cellular death of hemocytes. However, exposure to the PBP extract significantly increased the respiratory rate of the oysters for 24–48 h. In the high‐dose group (200 μg/mL), a reduction in the activity of nonspecific cytoplasmic esterases and an increase in DNA damage levels in hemocytes were observed. Examinations of heat shock protein expression (HSP70 and HSP90) in the gills showed up‐regulation of HSP90 at a 200 μg/mL extract concentration after a 24 h exposure period and at all studied concentrations after 48 h of exposure. Although oysters in the high‐dose group displayed signs of genotoxicity and reduced nonspecific esterase activity of hemocytes, other parameters measured indicated low toxicity of the extract. The no‐observed‐adverse‐effect level of the PBP extract for adult Pacific oysters was determined as a concentration in water below 200 μg/mL.