SOME PROBLEMS ON MARINE BIOGEOGRAPHICAL MICRO- 

 PROVINCES SURROUNDING JAPAN 



By Tadasige Habe^ Tokubei Kuroda and Denzaburo Miyadi 



Zoological Institute, Science College 



Kyoto University, Kyoto, Japan 



Three characteristic aspects of marine Httoral fauna, which have 

 bearings on biogeographical segmentation of Japanese seas, are discussed 

 in this paper. 



1) We recognize the continental coastal elements in Japanese bay 

 fauna. These elements have their chief distribution area on the Asiatic 

 coast and, unlike the littoral fauna of open sea coast, their distribution 

 is scarcely influenced by oceanic currents. 



2) A large part of the continental coastal fauna has recently de- 

 clined or become extinct in Japan, and its relics have important meaning 

 on the establishment of biogeographical micro-provinces of the Japanese 

 coast. 



3) The benthic communities of bays show regionally different dis- 

 tribution types on the Pacific and Japan Sea sides. We think that typo- 

 logical biogeography is no less important than taxonomic biogeography. 



Biogeographical Significance of the Bay Fauna as Compared 

 WITH the Littoral Fauna of the Open Sea 



It is generally accepted that the oceanic current with its own tem- 

 perature range is the chief factor to determine the biogeographical 

 provinces of the sea. In Japan, the warm Kuroshio Current and the cold 

 Oyashio Current define the biogeographical micro-provinces both hor- 

 izontally and vertically. The influence of oceanic current is more prom- 

 inent on the littoral fauna than on the deep sea fauna. Although a 

 distinct boundary between southern and northern faunas is recognized 

 near Inubo-saki, not far from Tokyo, where the Kuroshio CuiTent turns 

 its coastal course to off-shore course, the faunal provinces of the deep 

 sea are less distinct and have wider extent. 



The influence of oceanic current on the faunal distribution, how- 

 ever, seems more or less limited to open sea coast, and the bay fauna is^ 

 quite independent from it in the biogeographical sense. The mollus- 

 can species characteristic of Japanese bays have much wider ranges in 

 comparison with those of open sea coast, and Inubo-saki has little mean- 

 ing as a barrier for their distribution. In this respect the bay fauna 



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