Behavioral assay and chemical characters of female sex pheromones in the hermit crab Pagurus filholi

Males of the hermit crab Pagurus filholi perform assessment behavior toward females, as a preliminary step of precopulatory guarding, during the reproductive season. It is known that such behavior is elicited by female sex pheromones, but the compounds involved have never been characterized in this species. Several experiments were conducted to develop a reliable bioassay along with purification procedures to identify potential compounds with pheromonal activity in Pagurus filholi. We developed a bioassay protocol to assess pheromonal activity by using an empty shell with cotton containing either artificial seawater (control) or test water. We measured and compared the time duration of male assessment behavior toward each shell if the test water contained female sex pheromones. Ultra-filtering of seawater samples potentially containing pheromones showed that the compound was < 1 kDa in molecular weight. Males showed precopulatory assessment behavior toward "female conditioned" water samples treated with open column purification and eluted with MeOH, suggesting that compounds triggering male behavior were low polar molecules. Molecules with pheromonal activity were not volatile after freeze drying, effective even after heating to 90 A degrees C, and remained active in seawater at 12 A degrees C even after 6 days from sample collection, which suggests a rather stable characteristic of the female sex pheromones of this species

津軽海峡における鯨類目視調査

津軽海峡の鯨類に関する知見は極めて乏しい。本研究では津軽海峡の鯨類の鯨種，それらの出現頻度を明らかにするため，2003年4月から2004年11月まで函館・青森間を運行するフェリーからの目視調査を実施した。58日6,102kmの目視調査により，合計415群3,010 個体の鯨類の発見があった。発見はカマイルカが優占し，マイルカ，イシイルカ，ハンドウイルカ、ネズミイルカ、コビレゴンドウ等が発見された。カマイルカの来遊のピークは5～6月の年一回であった