Internal sperm storage after mating is important for insect reproduction, because it permits delayed fertilisation, and post-copulatory mate choice in polyandrous females. The polyandry is common in many animal taxa including insects, because it increases female fitness by reducing the risk of infertility and providing opportunities for sperm competition and choice. The reproductive success of males, on the other hand, often depends upon avoidance of sperm competition by preventing mated females from copulating and receiving sperm from other male suitors. A widespread strategy used by males is the use of the male seminal fluid proteins (SFPs) that form the mating plug and alter female behaviors, for example by suppressing mating receptivity and elevating egg-laying. Under these circumstances, females are expected to evolve mechanism(s) to control exposure to the male SFPs in order to maximize fitness by balancing the positive and negative impacts of polyandry. Here, we discover that Drosophila melanogaster females eject male ejaculates 1-6 h after mating with a stereotypic behaviour, and that this is regulated by a brain neuropeptide pathway composed of diuretic hormone 44 (Dh44), and its receptor Dh44R1. We showed that suppressing Dh44 or Dh44R1 signals in the brain expedites sperm ejection, whereas enhancing Dh44 or Dh44R1 signals delays sperm ejection. This study uncovers a molecular mechanism by which females can influence sperm competition and selection, and counter actively the negative impact of polyandry.

Recently it was known that the problems of nearshore processes and damage of berth and counter facilities frequently had appeared at the small fishery port, such as Daebang near Samcheonpo city, Korea. Here we try to analyze the impact of the rearrangement of counter facilities and berth layout adopted for tranquility of its inner harbor. Because this harbor is being connected to Daebang channel, the rearrangement of the structures might affect to the current speed and direction and wave height, so do to the sea bottom undulation. Therefore, we made model test for the several layouts of the berth and breakwater in this area. Numerical model result shows that the bottom was eroded by 1m by tidal currents and the speed of flow did not shrink, even after the construction work was completed. The direction of the sand movement was downdrift. Although the model study gave reasonable description of beach processes and approach channel sedimentation mechanism, it is necessary to compare with the field history, including the records of waves, tides and bottom materials, etc. for better prediction.

Gunsan-Janghang Harbor is located at the mouth of Gum River, on the central west coast of Korea The harbor and coastal boundaries are protected from the effects of the open ocean by natural coastal islands and shoals due to depositions from the river, and two breakwaters. The navigation channel commences at the gap formed by the outer breakwater and extends through a bay via a long channel formed by an isolated jetty. For better understanding and analysis of wave transformation process where a wide coastline changes appear due to on-going reclamation works, we applied the spectral wave model including wind effect to the related site, together with the energy balance models. This paper summarizes comparisons of coastal responses predicted by several numerical wave predictions obtained at the coastal waters near Gunsan-Janghang Harbor. Field and numerical model investigations were initially conducted for the original navigation channel management project. We hope to contribute from this study that coastal engineers are able to use safety the numerical models in the area of port and navigational channel design.