Molting is a key biological process in crustaceans, with impacts on their growth, development and reproduction. Extracellular vesicles (EVs) serve as bio-cargo carrying such as nucleic acids, proteins, and lipids which mediate intercellular communication and participate in various cell biological processes. In this study, we obtained hemocyte transcriptome data during the intermolt, premolt, and postmolt stages of the mud crab Scylla paramamosain. We analyzed the differentially expressed genes in the three stages of molt and identified a number of immune-related genes and structural cuticle genes. We then isolated and characterized the EVs from the hemolymph of S. paramamosain and sequenced their miRNA. In total, we characterized 89 EVs microRNAs (miRNAs) targeting 1447 genes that are potentially involved in the molting process of S. paramamosain. The EVs miRNAs mainly regulated the immune-related genes and affected the molting process by mediating ecdysone signaling and insulin signaling pathways during the mud crab molt cycle. This is the first study of EVs miRNAs and their interaction with mRNA to identify important candidate genes associated with, or regulating, the molting process. This study provides a better understanding of, and novel insights into, the molting cycle of crustaceans and offers baseline information for further studies in the mechanisms regulating molt.

Pseudomonas plecoglossicida infection, which causes visceral white spot disease, is a significant and economically devastating disease in aquaculture. In this study, we investigated the impact of bacterial infection on the protein composition of exosomes derived from the surface mucus of the hybrid grouper Epinephelus fuscoguttatus♀ × E. lanceolatus♂. Two hundred healthy fish were randomly separated into challenge and control groups. Fish from the challenge group received 10³ CFU/g of the bacterial pathogen P. plecoglossicida via intraperitoneal injection, while sterile PBS was used as a negative control. After injection, the mucus was collected and the exosomes were extracted for proteomic analysis. The results of proteomic analysis revealed that P. plecoglossicida infection significantly increased the levels of innate immune proteins, including lysosomal and peroxisomal proteins, within the exosomes. Furthermore, the CAD protein was found to play a pivotal role in the protein interaction networks involved in the response to P. plecoglossicida infection. Intriguingly, we also observed a significant increase in the levels of metal-binding proteins within the exosomes, providing important evidence of nutritional immunity on the surfaces of the fish hosts. Notably, several proteins, such as plasma kallikrein, Annexin A5, eukaryotic translation initiation factor 3 subunit M, and S-methyl-5-thioadenosine phosphorylase, exhibited a remarkable increase in abundance in exosomes after infection. These proteins show promising potential as noninvasive biomarkers for the diagnosis of visceral white spot disease. The study contributes to the understanding of the host response to P. plecoglossicida infection and may aid policymakers in implementing appropriate intervention measures for effective risk management of this devastating disease.

Members of the genus Crassicauda (Nematoda: Spirurida) are macroparasites infect the body tissues of whales and dolphins. However, limited information is available on morphological descriptions and phylogenetic studies of the worms. In present study, we report the first complete mitochondrial genome of Crassicauda magna from Neophocoena sunameri in Ningbo, Zhejiang Provence, China. The mitogenome has 13,605 base pairs (74.97% A + T content) and is made up of a total of 36 genes (12 protein-coding, 22 transfer RNAs, and 2 ribosomal RNAs). This study will provide useful molecular information for addressing taxonomic and evolutionary issues in Crassicauda sp..