## 3 Results and Discussion
### Growth and Shellfish Indices with the Addition of Lpb. plantarum I  
The growth rate in the weight and shell length of _Aequipecten opercularis_ was significantly higher after adding _Lpb. plantarum_ I (Figure 2). After one month, the scallops in the experimental tank fed with _Lpb. plantarum_ I grew more in weight (0.07 \(\pm\) 0.06 g day\({}^{-1}\)) and in length (0.08 \(\pm\) 0.06 mm day\({}^{-1}\)) than the scallops in the control tank fed only with a live algae mix culture (GRw 0.02 \(\pm\) 0.01%; GRl 0.01 \(\pm\) 0.01%). Compared with the control scallops, the specific growth rate weight and specific growth rate length were lower (0.02 \(\pm\) 0.001 mm day\({}^{-1}\); 0.82 \(\pm\) 1.12 g day\({}^{-1}\)) than in the scallops treated with _Lpb. plantarum_ I (0.20 \(\pm\) 0.006 mm day\({}^{-1}\); 4.21 \(\pm\) 4.90 g day\({}^{-1}\)) (Figure 3). Previous studies have reported positive effects of various LAB on the growth performance of both fish and shellfish. In a study conducted by [PERSON] et al. [29], it was observed that _Litopeneus vunnamei_ larvae fed with a diet supplemented with _Lactiplantibucillus plantarum_ 69 Cr, _Lactiplantibucillus fermentutum_ 101 Cc, and _Lactiplantibucillus casei_, exhibited improved growth performance and survivability. Similarly, the inclusion of the probiotic _Lactiplantibucillus acidophilus_ (FLa) in the diet of Siberian sturgeon (_Acipenser baerii_) resulted in enhanced growth indices, biochemical content, and blood composition [18]. Other studies have also reported higher growth performance in _Pagrus major_[23], _S. aurata_[21], and _C. caprio_[25], when fed diets fortified with LAB probiotics. Figure 2: Growth rate: (**a**) weight (GRw) and (**b**) length (GRl), of the control (CON) _A. opercularis_ and those exposed to LAB isolates (LAB), over four weeks. *_p_ < 0.001. Data on the condition index from scallops in the control (73.71 \(\pm\) 8.78%) and experimental tank (76.74 \(\pm\) 8.34%) yielded similar results (Figure 4, \(p\)\(>\) 0.05). Scallops in a tank fed with _Lpb. plantarum_ I gained, at the end of one month, a significantly higher meat yield (MY) (33.15 \(\pm\) 2.63%) compared with the control tank (29.66 \(\pm\) 2.87%). The muscle index and gonadosomatic index of the control and scallops fed additionally with _Lpb. plantarum_ I showed no significant differences (Figure 5). The improved growth performance of shellfish fed with a diet containing _Lpb. plantarum_ I can be attributed to the bacteria's ability to stimulate digestive enzymes. This stimulation enhances feed digestibility, resulting in increased energy benefits that ultimately lead to a higher growth rate. Furthermore, the notable increase in indices observed in scallops treated with LAB can enhance digestion and improve the absorption of nutrients from the diet. As a result, this contributes to enhanced growth performance and commercial quality of the shellfish. According to studies, supplementing potential probiotic LAB has been found to increase the specific activities of the digestive enzymes in various marine species, such as lions-paw scallop [47], Catarina scallop (_Argopecten ventricosus_) [48], and white shrimp (_Litopenaeus vannamei_) [49]. It has been proposed that LAB supplementation improves gut maturation, which could explain the increased digestive enzyme activity in firmed shellfish fed with LAB [27]. Research by [PERSON] et al. [50] has also confirmed the safety and effectiveness of _Lactobacillus_ spp. as a probiotic in aquaculture, as it can improve nutrient assimilation in the host. In addition, treatment with _Lactobacillus_ spp. isolated from lion's paw scallop has been shown to help maintain the integrity of internal tissues and increase tissue weight [29], which may be reflected in the condition index and meat yield of the scallops in our study. Figure 4: Commercial quality: (**a**) condition index (CI) and (**b**) meat yield (MY), of the control (CON) _A. opercularis_ and those exposed to LAB isolates (LAB), over four weeks. * \(p\)\(<\) 0.001.