This study aimed to document the seasonal cycle of steroid levels in the plasma and ovary, including testosterone (T), estradiol-17β (E₂) and 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) in relation to ovarian development in wild populations of female blue tang fish. The gonadosomatic index (GSI%) maintained high values from April to July and increased from the II to IV ovarian stages and dropped in the V stage. Levels of plasma, ovary T and E₂ and DHP were high from March to July. Plasma T and E₂ levels were low in the II stage when most oocytes were previtellogenic, reaching a peak during spawning, and decreased in the V stages when fish were going to late spawning and termination. DHP was detected in all stages of the ovary with a higher level in spawning fish but decreased after spawning. These results revealed that T, E₂ and DHP could be involved in ovarian development and DHP may play a significant role as a maturational inducing hormone in blue tang fish.

This study investigates the sustainable extraction of nano-Hydroxyapatite (nano-HAp) from Lates calcarifer fish bones, a by-product of the seafood industry, through thermal calcination. Nano-HAp was synthesized at two temperatures (650 °C and 700 °C), resulting in rod-like (42 nm) and spherical (98 nm) particles, respectively. Both samples were identified as B-carbonated HAp, with Ca/P molar ratios of 1.842 for HAp 650-4 h and 1.856 for HAp 700-4 h, confirming the presence of B-type HAp, which has higher Ca/P ratios than the standard HAp found in bones and teeth (1.67). Cytotoxicity tests showed that both samples exceeded the ISO 10993-5:2009 standard, with L929 cell viability above 70% at concentrations up to 2 mg mL⁻¹. Notably, the study emphasizes that the size and morphology of nano-HAp play a critical role in its biological activity. Larger spherical particles (HAp 700-4 h) enhanced the proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) more effectively than smaller rod-like particles (HAp 650-4 h), suggesting their greater potential for tissue engineering and bone regeneration applications. This work demonstrates the promising biocompatibility of fish bone-derived nano-HAp and its potential for sustainable biomedical applications.

On 5 November 2020, a poisoning event involving four people by the consumption of moray eel occurred in Khanh Hoa Province, Viet Nam, with signs indicative of ciguatera. The remaining moray portion was confiscated for identification of causative species and responsible toxins. The phylogenetic study based on COX1 identified the moray as Gymnothorax javanicus Bleeker (1859). Out of 17 marine lipophilic toxins (MLPs) that were analyzed using LC-MS/MS, only Pacific ciguatoxin-1 (P-CTX-1) was detected in the moray’s flesh at 1.30 ± 0.004 ng/g ww, while no toxin was found in the skin. The N2a assay’s ciguatoxicities in the skin and flesh were 0.69 ± 0.075 and 2.49 ± 0.216 ng P-CTX-1/g ww equivalent, respectively. In the N2a assay, the P-CTX-1 amount in the moray flesh was 1.9 times greater than that determined by LC-MS/MS, indicating the presence of additional sodium channel activators or a matrix effect. The P-CTX-1 amount in the moray flesh was at a level that generates major ciguatera poisoning (CP) symptoms in humans (1.0 ng/g P-CTX-1), makes sense given that four consumers experienced the onset of poisoning symptoms. This study is significant for the management of seafood safety since it is the first scientific report on the species and toxin in a moray causing ciguatera in Viet Nam.

Fisheries and Aquatic Sciences

This paper is concerned with composition and antibacterial activities of ethyl acetate extracts from 3 species of Laurencia (Rhodophyta): Laurencia papillosa, Laurencia flexilis and Laurencia cartilaginea collected from the southern coasts of Vietnam. The results showed that ethyl acetate (EtOAc) extracts of these species displayed antibacterial activities against Salmonella typhimurium, Escherichia coli and Bacillus subtilis. The qualitative investigations revealed the presence of two sesquiterpene secondary metabolites Elatol and Palisadin A in EtOAc extracts from the three above- mentioned Laurencia species.