DISTRIBUTION OF PACIFIC DEEP-SEA ANIMALS 369 



The details will be found in the forthcoming scientific reports. 

 There is a good general agreement with Zenkevitch's statement (1953) , 

 translated from German: "In the greatest depths the holothurians ex- 

 ceed 90 per cent of the bio-mass, followed by sponges, which tlo not 

 reach 7000 meters. The Asteroidea do not reach 8000 meters, and 

 between 8000 and 9000 meters disappear Octocorallia, Amphipodn and 

 Isopoda, somewhat deeper than 9000 m. Actinia and Mollusca. In the 

 greatest depths (9800 meters), studied by us by trawling, was only found 

 Polychaeta, Echiuroidea, Holothuroidea, and Pogonophora." 



The food supply varies very much from one place to another; its 

 origin may as a rule be from the production of phytoplankton, in which 

 case deep-sea areas close to regions with up-welling water will have fau- 

 nas rich both as regards the number of species and the quantity present, 

 as in the Eastern Pacific along the subtropical and tropical American 

 coasts. 



In other areas a considerable amount of terrigeneous debris brought 

 out by rivers or from mangiove swamps is a very important addition; 

 this has been foiuid in inland seas like the Sulu, Celebes, and Banda 

 Seas. 



In certain areas with a very special circulation of the deep water, 

 causing a much higher temperature as in the Sulu Sea (about 10° C), the 

 composition of the fauna may be quite different, but this remains still 

 to be studied. 



The general conclusion about the Pacific abyssal fauna would there- 

 fore be that it is part of the Cosmopolitan deep-sea fauna and that dif- 

 ferences in composition from one area to another would mainly be due 

 to ecological factors, primarily depth and food supply; only the trench 

 faunas may have develo23ed endemisms. 



List of Literature 



Bruun, a. F. 1937: Contributions to the Life Histories of the Deep Sea 

 Eels: Synaphobranchidae. Dana-Report No. 9, 1937. Copenhagen. 



1951: The Philippine Trench and its Bottom Fauna. Nature, vol. 



168. London. 



1953a : Problems of Life in the Deepest Deep Sea. The Geograph- 

 ical Magazine, vol. 26. London. 



1953b: Dybhavets Dyreliv. In Bruun, Greve, Mielche & Sparck: 



Galatheas Jordomsejiing 1950-52. Copenhagen. 

 Dahl, E. 1953: The Distribution of Deep Sea Crustacea. XIV Intern. Zool. 



Congress Copenhagen. TUBS Colloquium. 

 Ekman, S. 1953a: Zoogeography of the Sea. London. 

 1953b: Beti-achtungen iiber die Fauna der abyssalen Ozeanboden. 



XIV Intern. Zool. Congress Copenhagen. lUBS Colloquium. 

 Face, L. 1953a: Remarques sur les Conditions de Vie de la Faune Benthique 



Abyssale. XIV Intern. Zool. Congress Copenhagen. lUBS Colloqium. 



