<i>Dazl</i> and <i>dnd</i> Identify Both Embryonic and Gonadal Germ Cells in Chinese Hook Snout Carp (<i>Opsariichthys bidens</i>)

In recent years, the Chinese hook snout carp (Opsariichthys bidens) is becoming increasingly popular due to its high nutritional value and delicious taste. However, anthropogenic influences have caused a rapid reduction in its population. Considering long-term development sustainability, it is essential to conduct research on its reproductive development. In this study, the germ-cell related genes dazl (Obdazl) and dnd (Obdnd) were cloned, and their expression patterns were revealed. RT-PCR analysis indicated that Obdazl and Obdnd were specifically expressed in gonads. In the testis, Obdazl and Obdnd RNAs have a similar expression pattern: their transcripts were abundant in spermatogonia, gradually decreased, and eventually disappeared during spermatogenesis. Early oocytes in the ovary exhibited strong expression of Obdazl and Obdnd RNAs and reduced remarkably after peak expression at III oocytes. Surprisingly, Obdazl RNA was dynamically found in perinuclear spots that finally aggregated into the Balbiani body (Bb) in the early oocytes. Moreover, Obdazl 3′ UTR enabled the reporter gene to be expressed stably in medaka PGCs, suggesting that dazl was identified as the germ cell marker in O. bidens, which may provide perspectives for further studies on the development of PGCs in the future

Isolation and characterization of a novel temperate bacteriophage infecting Aeromonas hydrophila isolated from a Macrobrachium rosenbergii larvae pond

Aeromonas hydrophila is an opportunistic pathogen that frequently leads to significant mortality in various commercially cultured aquatic species. Bacteriophages offer an alternative strategy for pathogens elimination. In this study, we isolated, identified, and characterized a novel temperate A. hydrophila phage, designated as P05B. The bacteriophage P05B is a myovirus based on its morphological features, and possesses the capability to lyse A. hydrophila strains isolated from shrimp. The optimal multiplicity of infection (MOI), adsorption rate, latent period, and burst size for phage P05B were determined to be 0.001, 91.7 %, 20 min, and 483 PFU/cell, respectively. Phage P05B displayed stability across a range of temperatures (28–50 °C) and pH values (4.0–10.0). Sequence analysis unveiled that the genome of phage P05B comprises 32,302 base pairs with an average G + C content of 59.4 %. A total of 40 open reading frames (ORF) were encoded within the phage P05B genome. The comparative genomic analyses clearly implied that P05B might represent a novel species of the genus Bielevirus under Peduoviridae family. A phylogenetic tree was reconstructed, demonstrating that P05B shares a close evolutionary relationship with other Aeromonas and Aeromonas phages. In conclusion, this study increased our knowledge about a new temperate phage of A. hydrophila with strong lytic ability