Crustins form a large family of antimicrobial peptides (AMPs) in crustaceans composed of four sub-groups (Types I-IV). Type II crustins (Type IIa or “Crustins” and Type IIb or “Crustin-like”) possess a typical hydrophobic N-terminal region and are by far the most representative sub-group found in penaeid shrimp. To gain insight into the molecular diversity of Type II crustins in penaeids, we identified and characterized a Type IIb crustin in Litopenaeus vannamei (Crustin-like Lv) and compared Type II crustins at both molecular and transcriptional levels. Although L. vannamei Type II crustins (Crustin Lv and Crustin-like Lv) are encoded by separate genes, they showed a similar tissue distribution (hemocytes and gills) and transcriptional response to the shrimp pathogens Vibrio harveyi and White spot syndrome virus (WSSV). As Crustin Lv, Crustin-like Lv transcripts were found to be present early in development, suggesting a maternal contribution to shrimp progeny. Altogether, our in silico and transcriptional data allowed to conclude that (1) each sub-type displays a specific amino acid signature at the C-terminal end holding both the cysteine-rich region and the whey acidic protein (WAP) domain, and that (2) shrimp Type II crustins evolved from a common ancestral gene that conserved a similar pattern of transcriptional regulation.

This work aimed to evaluate Nannochloropsis spp. as feed additive in the diet of Pacific white shrimp for their effect on midgut microbiology, thermal shock resistance and immunological parameters. Initially, the digestibility of the microalgae meal was assessed, and the apparent digestibility coefficient (ADC) was determined. The ADC was, in general, high in lipids (78.88%) and eicosapentaenoic fatty acid (73.86%). Then, Nannochloropsis spp. were included in diets at four levels (0, 0.5, 1 and 2% inclusion). The shrimp were reared in 500 L clear water tanks containing 20 shrimp per tank with an initial weight of 6.05 ± 0.06 g and fed four times a day. Shrimp fed with supplemented diets containing Nannochloropsis spp. (0.5 and 2%) presented higher resistance to thermal shock when compared to the non-supplemented group (control). Shrimp fed with 1 and 2% of algae inclusion had a higher production of reactive oxygen species (ROS) when compared to other treatments. No statistical difference was observed in the immunological parameters and microbiology of the intestinal tract. Thus, the inclusion of Nannochloropsis spp. in shrimp diets at 0.5 and 2% levels increases resistance to thermal shock and ROS production in shrimp.

The present study aimed to evaluate the effects of thermal variation on the green and brown strains of Kappaphycus alvarezii cultivated under laboratory conditions. The seaweeds were maintained in two cultivation regimes for 42 days: a control group at 26 ± 0.5°C and an experimental group subjected to a gradual decrease from 24 ± 0.5°C to 14 ± 0.5°C, with a 2°C reduction per week. Growth was monitored weekly and documented with photographic records. Biomass samples were collected at 22, 18, and 14 ± 0.5°C for analyses of photosynthetic pigments and phenolic compounds, while morphological evaluations using optical microscopy were carried out after exposure to 18 and 14 ± 0.5°C. The gradual decrease in temperature impaired daily growth in both strains, with a pronounced reduction from 18 ± 0.5°C and minimum values at 14 ± 0.5°C. The green strain maintained greater growth stability, while the brown strain preserved photosynthetic pigments more effectively under control conditions and exhibited higher levels of phenolic compounds at low temperatures. In addition, significant interactions between strain and treatment were observed for phycobiliproteins (phycoerythrin and phycocyanin), indicating that the response to cold stress results from the combination of these factors. These findings highlight that the green and brown strains exhibited distinct physiological, morphological, and biochemical responses to thermal stress, reinforcing the importance of selecting cold-tolerant strains to optimize productivity and mitigate seasonal risks in regions with harsh winters.