Assessment of the cytotoxicity of an aqueous extract of phycobiliproteins, a promising feed additive for the giant oyster Magallana gigas (in vitro model)

The sustainable development of the aquaculture of the giant oyster (Magallana gigas) in Russia is facing a number of constraints, the main of which are the shortage of available juveniles raised in Russian nurseries and high dependence on imports of spath from abroad. To overcome these obstacles, it is necessary not only to expand the network of specialized nurseries, but also to introduce innovative technologies that help improve the conditions of maintenance and the physiological state of the breeding stock in the pre-spawning period. One of the promising areas is the use of natural biologically active substances as functional feed additives. In particular, phycobiliproteins (FBPs) extracted from the microalgae Arthrospira platensis (spirulina) have pronounced antioxidant, anti-inflammatory, and immunomodulatory properties. Their inclusion in the diet of the broodstock of juvenile producers is promising to reduce the negative consequences of keeping nurseries in an artificial environment during the pre-spawning period. The aim of the study was to evaluate the acute toxicity of the aqueous FBP extract to oyster hemocytes in vitro and determine the range of safe concentrations at which there are no pronounced adverse effects at the cellular level. Hemocytes were incubated in sterile seawater with FBP extract at concentrations of 2, 20, and 200 micrograms/ml for 1 hour and 3 hours. FBP extract at a concentration of 2-200 micrograms/ml did not cause hemo-lymph cell death, did not affect their functional activity, and did not induce apoptosis in them. However, the addition of FBP extract at a concentration of 200 micrograms/ml led to DNA damage from the first hour of incubation. The results showed low cytotoxicity of the extract against hemocytes of the giant oyster at its concentration in the medium below 200 micrograms/ml.