Identification and characterization of ice nucleators transmitting from prey to predator

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As the first step to identify the exgenous ice nucleators of the house spider, Achaearanea tepidaroirum, location of ice nucleators in the body of prey animals (Porcellio scaber) and its heat susceptibility were examined. Ingestion of the isopod's gut elevated the spider's supercooling point from -5 to -9C and this effect was comparable to that of whole body of the prey. This means that the ice nucleators exist at least in the alimentary canal of the prey animals, thus suggesting that the prey animals incorporate them in the process of feeding. Spiders that fed on a heated isopod's gut had a lower supercooling point than those fed on an unheated gut. Thus, the ice nucleators transmitting from prey to predator were susceptible to heat, thus suggesting that it is organic in origin.To characterize the ice nucleators, their seasonal and geographical abundance in the field was examined. I found that the ice nucleators occur whole the year round and wide geographical range from northern to southern Japan. Almost all field-collected prey animals such as cricket, ants and isopods contain them. These observatons strongly suggest that the ice nucleators transmitting from prey to predator are common in the field. Because of the ubiquity, ice nucleating active microorganism such as bacteria can be the candicates as the ice nucleator.