SummaryThe Chinese sturgeon, Acipenser sinensis, is a large-sized panadromous cartilagous fish and requires more than ten years to reach sexual maturity. An understanding of the reproductive organs and fertilization process is a precondition for controlled reproduction of this endangered species. The developing oocyte is surrounded by an extracellular matrix composed of the zona pellucide (ZP) protein in several isoforms, all of which play important roles in fertilization and embryo protection. The present study reports the identification of two ZP genes, AsZPAX and AsZPB, in this fish. The full-length cDNAs of AsZPAX and AsZPB were 2950 base pairs (bp) and 1832 bp, predicting proteins of 946 and 592 amino acid residues, respectively. Both proteins have a conserved ZP domain. In a gene tree, AsZPAX and AsZPB were respectively clustered with their counterparts in other vertebrates. Tissue distribution analysis demonstrated that the AsZPAX RNA was transcribed in both the ovary and the liver, while AsZPB was transcribed exclusively in the ovary. RNA in situ hybridization revealed apparent RNA expression of both AsZPAX and AsZPB in growing oocytes of the 4-year-old ovary.

Summary Somatolactin (SL) is a pituitary hormone specific to fish and is reported in a variety of teleost species. Although it appears to be involved in many different physiological processes, its biological functions are poorly understood in Acipenseriformes. In this paper the expression pattern of this protein is characterized in Chinese sturgeon (Acipenser sinensis). Structure analysis showed that AsSL had a 24aa signal peptide and a 208aa mature protein, one N‐glycosylation site at positions 145‐147 and seven Cys residues conserved with other SLs. The antiserum was raised against a 15 aa antigen, derived from the Chinese sturgeon somatolactin (AsSL) amino acid sequence. Western blot analysis showed the pituitary‐specific expression of AsSL. In situ hybridization revealed that the mRNA of AsSL was expressed mainly in pars intermedia (PI), although also slightly in proximal pars distalis (PPD), cells expressing AsSL disperse throughout the pars intermedia. These findings provide useful information for future physiological research in Chinese sturgeon.