Using laboratory choice experiments, behavioural preferences of the early juvenile mudskipper Boleophthalmus pectinirostris for temperature, salinity and sediment were observed. The temperature preference experiments were conducted in an annular chamber with a thermal gradient of 27 to 34°C, and the fish selected a mean AE S.D. temperature of 31Á2 AE 0Á5°C. The salinity preference experiments were conducted in an aquarium with decreasing salinity from 20 to 15, 10, 5 and 0Á5, and significantly more (P < 0Á05) fish were found in water with a salinity of 5. The sediment preference experiments were tested in circular tanks which contained four types of sediment (medium sand, fine sand, muddy sand and sandy mud), and the fish showed a clear preference for sandy mud. These results indicated that early juvenile B. pectinirostris showed behavioural preference for microhabitats. Temperature and salinity probably set large-scale boundaries on distribution, but sediment should be a critical factor for determining the distribution of the mudskipper.

Ovulation is a remodeling process including blood capillary rupture and coagulation. Until now, there is no regulation and functional studies of coagulation factors in ovulation. Here, we report dramatic increases of coagulation factors (f5, f3a) in zebrafish preovulatory follicles. This upregulation was induced by progestin (DHP: 17α, 20β-dihydroxy-4-pregnen-3-one), a native ligand for nuclear progestin receptor (Pgr) that is essential for ovulation in zebrafish; but was abolished in pgr-/-. In addition, promoter activities of f5 and f3a were significantly enhanced by progestin via zebrafish Pgr. Similarly, we found promoter activities of human F5 were significantly stimulated by progesterone (P4) via human PGRB. Moreover, a dramatic increase of erythrocyte numbers in capillaries on ovarian follicles was associated with ovulation. Importantly, heparin, an anticoagulant, inhibited ovulation. Furthermore, reduced fecundity and impaired ovulation were observed in f5+/- female zebrafish. Together, our results provide plausible evidence for an exceptional function of coagulation factors in ovulation.Significance StatementPrecise activation of metalloprotease is essential for ovulation. This activation is controlled by serum-derived protease inhibitors. However, the association between coagulation factors and ovulation is unclear. We demonstrated that nuclear progestin receptor (Pgr), a well-established initiator for ovulation, was a major regulator for a dramatic increase of coagulation factors (f5 & f3a) in preovulatory follicles of zebrafish. Blood coagulation in the capillaries of preovulatory follicles occurred prior to follicular rupture in wildtype zebrafish. Interestingly, this blood coagulation was blocked in Pgr knockout fish, which can’t ovulate. Inhibition of blood coagulation significantly reduced ovulation. Decreased fertility was also found in F5 heterozygous zebrafish. Our findings reveal critical roles of steroid receptor-regulated coagulation factors in blood coagulation that controls ovulation.

Both the mudskipper Boleophthalmus pectinirostris and Chinese black sleeper Bostrichthys sinensis live in the intertidal zone, but their feeding habits are different. The adult B. pectinirostris is herbivorous, whereas the adult B. sinensis is carnivorous; however, differences between the two species are not clear with regard to distribution patterns and activities of the intestinal enzymes. This study thus investigated the distribution patterns and specific activities of four disaccharidases (maltase, sucrase, lactase and trehalase), two proteases [leucine-amniopeptidase (LAP) and c-glutamyltranspeptidase (c-GT)] and an alkaline phosphatase (ALP) in brush border membrane fractions obtained from three purified intestinal sections of the two species. The highest activities of the four disaccharidases were found in the midgut of B. pectinirostris and in the foregut of B. sinensis. Highest activities of the two proteases and ALP occurred in the hindgut of B. pectinirostris and in the midgut of B. sinensis. The activities of the four disaccharidases in each intestinal section of B. pectinirostris were significantly (P < 0.05) higher than in those of B. sinensis. The levels of LAP, c-GT and ALP activities in the three intestinal sections varied in B. pectinirostris and B. sinensis, suggesting that the primary regions for disaccharide digestion were in the midgut in B. pectinirostris and in the foregut in B. sinensis, and that the hindgut of B. pectinirostris and the midgut of B. sinensis should play important roles in final protein digestion and nutrient absorption, respectively. The activities of the four disaccharidases in the two species were well correlated with their feeding habits. However, no clear-cut correlation between the activities of the two proteases and diet could be concluded from the present study.

Summary Chinese black sleeper (Bostrychus sinensis) is a burrow‐dwelling fish found in intertidal mudflats. As a commercially important fish in southern China, the nursing of B. sinensis fry is a critical step for its farming. The growth and survival of B. sinensis fry are closely related to the stocking density, shelter and diet. In this study, 1575 healthy fry were used to investigate the effects of three factors, namely: diet, stocking density, and shelter on the survival rate (SR), specific growth rate (SGR) and condition factor (CF). The optimal combinations of three levels of each of these three factors (A1‐3, B1‐3 and C1‐3) were also determined, using an orthogonal array design of OA9 (34). After 50 days of nursing, the results showed that: (i) the best combinations for the three factors at their optimal levels were A1B1C2 or A1B1C3; (ii) factor A was the most important factor and had significant effects (P < 0.05) on the SR and SGR of the fry, while the other factors had no significant effects (P > 0.05); (iii) the SGR, SR and CF of fry fed with commercial formulated feed (CFF) were significantly higher (P < 0.05) compared to those of fry fed with minced trash fish (MTF); and (iv) the fry fed with MTF mixed with antimicrobial peptides (MTF+AMP) showed higher SGR, SR and CF than those fed with MTF alone, which indicated that the antimicrobial peptides had positive effects on the growth and survival of the fry.