Aquaporins (AQPs) play crucial roles in osmoregulation, but the knowledge about the functions of AQPs in Sinonovacula constricta is unclear. In this study, Sc-AQP1, Sc-AQP8, and Sc-AQP11 were identified from S. constricta, and the three Sc-AQPs are highly conserved compared to the known AQPs. The qRT-PCR analysis revealed that the highest mRNA expressions of Sc-AQP1, Sc-AQP8, and Sc-AQP11 were detected in the gill, digestive gland, and adductor muscle, respectively. In addition, the highest mRNA expression of Sc-AQP1 and Sc-AQP11 was detected in the D-shaped larvae stage, whereas that of SC-AQP8 was observed in the umbo larvae stage. The mRNA expression of Sc-AQP1, Sc-AQP8, and Sc-AQP11 significantly increased to 12.45-, 12.36-, and 27.44-folds post-exposure of low salinity (3.5 psu), while only Sc-AQP1 and Sc-AQP11 significantly increased post-exposure of high salinity (35 psu) (p < 0.01). The fluorescence in situ hybridization also showed that the salinity shift led to the boost of Sc-AQP1, Sc-AQP8, and Sc-AQP11 mRNA expression in gill filament, digestive gland, and adductor muscle, respectively. Knockdown of the Sc-AQP1 and Sc-AQP8 led to the decreased osmotic pressure in the hemolymph. Overall, these findings would contribute to the comprehension of the osmoregulation pattern of AQPs in S. constricta.

Mariculture wastewater poses environmental challenges due to pollution and eutrophication. Targeted cultivation of diatoms in wastewater can help alleviate these issues while generating beneficial algae biomass, however reliable operating methods are lacking. We proposed a novel method for treating mariculture wastewater that employed UV-C irradiation and nutrient regulation to achieve targeted diatom cultivation. This study first examined growth of four diatom species (Nitzschia closterium, Chaetoceros muelleri, Cyclotella atomus, and Conticribra weissflogii) in mariculture wastewater. C. muelleri and C. weissflogii demonstrated better adaptability compared to N. closterium and C. atomus. Additionally, the growth and nutrient utilization of C. muelleri were studied under varying concentrations of silicate, phosphate, ammonium, and trace elements in wastewater. Optimal growth was observed at 500 μmol/L silicate, 0.6 mg/L phosphate, and 4 mg/L ammonium. Ammonium proved to be a more effective nitrogen source than urea and nitrate in promoting growth at this low level. Surprisingly, trace element supplementation did not significantly impact growth. Finally, this study utilized UV-C irradiation as a pre-treatment method for wastewater prior to nutrient adjustment, significantly enhancing the growth of C. muelleri. Overall, this study provides guidance on regulating key nutrients and pre-treatment method to optimize diatom biomass production from mariculture wastewater. This approach not only addresses environmental challenges associated with mariculture but also contributes to sustainable aquaculture practices through the recovery of valuable aquatic resources.

The razor clam Sinonovacula constricta, is one of the most commercially important cultured bivalves in China and Southeast Asia, while S. rivularis is its closer relatives discovered more than a decade ago. In order to obtain offspring with faster growth rate and stronger salt tolerance of S. constricta and S. rivularis, interspecific hybrids were produced, and the hybridity of the interspecific hybrids was confirmed by microsatellite markers. Microsatellite markers exhibit a high potential for transfer through cross-amplification in related species, and the transferability of 48 pairs of microsatellite marker primers from S. constricta were assessed in S. rivularis. Here, 24 universal microsatellite markers were successfully amplified in S. rivularis, of which 18 were polymorphic with the allele number from 2 to 5. The genetic diversity of two razor clams evaluated by 18 polymorphic microsatellite markers indicated that two species were both above the middle level, with a relatively higher genetic diversity, while S. constricta showed higher genetic diversity than S. rivularis according to the genetic parameters of Na, Ho, He and PIC. Furthermore, a total of two species-specific microsatellite markers were screened, which could be used for quick genetic identification of S. constricta, S. rivularis and their hybrids. The results suggest the induced interspecific hybrids are true hybrids between S. constricta and S. rivularis, which provide a basis for breeding, subsequent protection, and germplasm resources utilization of the razor clams.

Excessive ammonia accumulation poses a significant threat to aquatic species. Potamocorbula ustulata, known for its burrowing behavior and high population density, may experience elevated ammonia levels in its environment. However, its ammonia stress response mechanisms remain unclear. This study investigates the physiological and molecular responses of P. ustulata to acute ammonia exposure. Antioxidant enzyme activity was significantly altered in the gills and hepatopancreas, with GS, GDH, and ARG levels markedly increasing in the hepatopancreas. Transcriptome analysis revealed that after 24 h of exposure, differentially expressed genes (DEGs) were enriched in apoptosis and inflammation-related pathways (MAPK, NF-kB, NOD-like receptor signaling). By 96 h, DEGs in the gills were associated with nitrogen metabolism and transport, while those in the hepatopancreas were linked to oxidative phosphorylation and amino acid metabolism. Key ammonia transport and excretion genes, including V-type H⁺-ATPase, Ammonium transporter Rh, and Na⁺/K⁺-ATPase, were significantly upregulated in the gills, while glutamine synthetase and glutamate dehydrogenase were upregulated in the hepatopancreas (p < 0.05). These findings suggest that ammonia stress disrupts antioxidant defense, triggers inflammation and apoptosis, and enhances ammonia tolerance through excretion, glutamine conversion, and urea synthesis. This study provides insights into the molecular mechanisms underlying ammonia tolerance in bivalves.

This study investigated the effects of culture density on the phytoplankton communities in an integrated culture model of the blood clam Tegillarca granosa and Pacific white shrimp Litopenaeus vannamei. Two treatments were set up: L (L. vannamei 18 ind/m², T. granosa 33 ind/m²) and H (L. vannamei 36 ind/m², T. granosa 66 ind/m²). The management methods were the same during the experimental period, and the feed intake was determined according to L. vannamei. The results showed that there were more than 38 species of phytoplankton in the ponds, belonging to six phyla and 28 genera; the diversity index of the phytoplankton was higher in the early stage of the experiment and lower in the later stage; the average biomass of phytoplankton was 21.74 × 10⁴ ind/L; and the culture density had no significant effect on water quality. This study showed that a reasonable increase in culture density would not cause significant adverse effects on the environment. It is possible to increase the stocking density of shrimp with the mollusk without causing inadequate conditions for the phytoplankton community and water quality.