日本およびその周辺水域における浮遊性カイアシ類の動物地理 <総説>

Zoogeography of pelagic copepods in Japan and its adjacent waters

Ohtsuka Susumu

Ueda Hiroshi

日本プランクトン学会報

The zoogeography of marine and freshwater pelagic copepods occurring in Japan and its adjacent waters is reviewed. Recent human activities have drastically changed pelagic copepod communities. For example, the introduction of neritic and brackish-water copepods into new habitats via ship ballast water has been increasingly reported. And the introduction of foreign fishes into ponds and lakes has caused great changes in the species composition of copepods. Hence it is important to recognize the original distributions and origins of pelagic copepods.

Extensive studies on oceanic copepods have revealed that among both epipelagic and meso/bathypelagic oceanic copepods many show restricted, non-cosmopolitan distributions. In the Euchaetidae some are distributed locally in highly productive waters as numerically important species while others have a wide distribution in oligotrophic waters at low population densities. In the Pacific Ocean and the Sea of Japan, warm-water species and cold-water species exhibit different vertical distributions, which are seasonally variable owing to the direction and strength of currents. The present distributions of deep-sea copepods seem to have been established after the Miocene when oxygenated deep waters were restored.

Neritic and inlet species in Japanese waters can be classified into six categories: (1) East Asian initial endemic element; (2) Indo-West Pacific element; (3) arctic-temperate element; 4) Okhotsk-Bering Sea element; (5) circumtropical element; (6) bipolar element. Taxa belonging to the first three categories are predominant. Neritic and inlet species also exhibit a distinct horizontal zonation, which is mainly influenced by salinity, food concentration, and predator pressure. According to their distribution pattern, they can be empirically grouped into four habitat groups: oligohaline neritic, eutrophic neritic, mesotrophic neritic, and oligotrophic neritic species. Brackish-water copepods are also divided among the first four biogeographic categories, but mainly comprise East Asian initial endemic species. Most freshwater planktonic cyclopoids in Japan are still identified as cosmopolitan species or those with wide geographical ranges, despite current doubts about cosmopolitanism in freshwater zooplankton. The recent introductions of brackish-water, inlet, and neritic copepods from East Asia into new habitats via ship ballast water are summarized and their influences on their new habitats are discussed.

copepods

カイアシ類

zoogeography

動物地理

introduction

移入

Tethys Sea

テーチス海

East China Sea

東シナ海

Zoology [ 480 ]

jpn

日本プランクトン学会

Copyright (c) 1999 The Plankton Society of Japan

[ISSN] 0387-8961

[NCID] AN00197015