Effect of homeopathic medicines on growth, survival and gastrointestinal microbiota of juvenile scallop Argopecten ventricosus

Objective. To study the effect of homeopathic medicines on growth, survival and gastrointestinal (GIT) microbiota of Catarina scallop Argopecten ventricosus. Materials and methods. Five homeopathic treatments (T1) ViP-ViA 1D, (T2) ViP-ViA 7C, (T3) AcF-MsS 1D, (T4) PhA-SiT 7C, (T5) ViT 31C and three controls: (C1) diluted ethanol 1:99, (C2) diluted/succussed ethanol 1C and (C3) distilled water were evaluated (21 days) in triplicate. Microbiota was analysed by sequencing the V3-V5 region of the 16S rRNA genes. Results. The best growth in shell-length corresponded to T1 (117 µm d-1) and T2 (108 µm d-1) and the highest survival (P ≤ 0.05) to T3 and T5, stating T3 as the best HOM-treatment. A clear separation was found in rarefaction curves of HOM-treated against un-treated control scallops. Significant differences (P ≤ 0.05) were found for Phyla (Proteobacteria> Actinobacteria> Firmicutes> Bacterloidetes>Chloroflexi and for Genera: Symbiobacterium> Microbacterium> Methylobacillus> Bacillus> Paenibacillus> Burkholderia> Nostoc> Methylobacterium> Leucobacter). The genus Symbiobacterium was dominant in the HOM-treatment T5 (Vidatox®), finding significant differences (P ≤ 0.05) with respect to all treatments. At species level, Microbacterium maritypicum (Actinobacteria) showed a greater relative abundance (P ≤ 0.05) in T1 and T3 and Symbiobacterium toebii (Firmicutes) was also significantly higher (P ≤ 0.05) in abundance in T5 and T2, both against initial T0. Conclusions. This study showed for the first time, the composition of the GIT microbiota in Catarina scallop A. ventricosus and focused on the potential applicability of homeopathic medicines to improve overall performance and modulate the GIT microbiota of the species.

FIRST EXPERIENCE OF CAGE CULTIVATION OF HATCHERY-PRODUCED JUVENILE SCALLOP MIZUHOPECTEN YESSOENSIS AT EASTERN COAST OF PRIMORYE

Yesso scallop Mizuhopecten yessoensis is the main object of aquaculture in Primorye with annual yield measured in hundreds ton. However, further development of its farming could be restricted by lack of the spat. Availability of the spat imported from China using for the scallop cultivation at the coast of Primorye is explored. The spat from Chinese hatchery located in Shandong province was supplied for one aquaculture company in Primorye in the volume of 660 . 106 ind. in 2018 and settled to hanging collectors (1000 ind. per bag), then to cages in the marine farm located north-eastward from the Moryak-Rybolov Bay. Survival and growth rate of the scallop juveniles were examined in early November 2018, when the water temperature was from 10.3–10.4 оС at the sea surface to 9.7–9.9 оС at the bottom, salinity was about 33.60 psu in the whole water column, chlorophyll a concentration varied in the range 0.4–0.8 mg/L with the maximum in the layer 8–24 m. The spat mortality during transportation was estimated as 15 %, but it increased to 56–90 % during its growing up in cages. This level of mortality is much higher than mortality of the spat collected from the coastal waters at southern Primorye. The highest mortality of artificial spat was observed for large-sized mollusks, whereas it was satisfactory for the small-sized ones. Possible reason of high mortality is too high density of juveniles and damaging of their soft tissues by other shells. The spat shells height did not exceed 5–10 mm in the collectors but increased during their growing in cages to 20–25 mm. This size is similar to the size of scallop growing from natural spat in southern Primorye. However, growth rate of the scallop growing at the Moryak-Rybolov Bay (2.0–2.7 mm/month) is lower than in Peter the Great Bay (3.0–3.5 mm/month) though higher than in the Vladimir Bay and Aniva Bay. Mean body weight of the cultivated scallop in November was 1.5 ± 0.1 g.