Qiyong Zhang

Why does the mudskipper Boleophthalmus pectinirostris form territories in farming ponds

The mudskipper Boleophthalmus pectinirostris maintained territories in farming ponds during the cold season between November and February. There were two types of territory, one was surrounded by mud-walls, and the other was without mud-walls. Both types of territory were entirely covered by shallow water. The area of walled territories was significantly bigger than that of non-walled ones. The nearest neighbour distance of walled territories was significantly shorter than that of non-walled territories. In January, fish surface activity occurred between 1200 and 1500 hours at which time the territorial water temperature reached a maximum, being significantly higher than that of the air, mud surface or deep burrow. The territorial sediments exhibited a significantly greater benthic microalgal biomass (chlorophyll- a and total chlorophyll- a ) as compared to the non-territorial sediments. The present study indicates that B. pectinirostris forms a territory during the cold season to keep a pool of water that encourages diatom growth and enables the fish to engage in surface activity.

Hypoxic tolerance of Chinese black sleeper Bostrichthys sinensis embryos at heartbeat stage

Tolerance of hypoxia in Chinese black sleeper ( Bostrichthys sinensis ) embryos at heartbeat stage was examined at different oxygen concentrations. Embryonic response to hypoxic conditions was expressed in terms of the intensity of variation in heartbeat rate ( V ). Exposure of the embryos at 25°C to 0.5, 1.0 and 1.5 mg/l dissolved oxygen (DO), caused bradycardia, which was developed within the first 10 min of hypoxia, followed by a plateau, and lasted until termination of the hypoxia. The V values were significantly affected by DO concentrations ( P P P V values were significantly lower than the V values of average heartbeat rates ( P V values were not significantly different between primary heartbeat rate and average heartbeat rate after 90 min exposure ( P >0.05).