MARINE AMPHIPODA IN MICRONESIA — BARNARD 461 



increased temperature or whether this diversification is associated 

 with the richer epif aunal habitats of the tropics. No comparisons of the 

 tropical Indo-Pacific with the eastern Pacific and Atlantic Oceans can 

 be made. 



Tropical indo-pacific amphipod fauna. — A smnmary of the 

 gammaridean Amphipoda of the tropical Indo-Pacific is presented 

 in table 1. It is restricted to species fomid between the Tropics of 

 Cancer and Capricorn from the east shores of Africa to the Marquesas 

 Islands and includes the Red Sea. It contains species found inter- 

 tidally and subtidally down to depths of 200 feet. Not included are 

 the terrestrial species of the Talitridae nor oceanic pelagic species. 



Of shallow water marine faunas it has been presumed that the 

 Indo-Pacific represents the longest known belt of relatively uniform 

 environment in terms of narrow temperature range and so it is ex- 

 pected that a large proportion of species ranges throughout the Indo- 

 Pacific. Barriers to dispersal of animals are most notable in the eastern 

 part of the Indo-Pacific where long stretches of open sea separate 

 archipelagoes. 



Amphipoda are crustaceans brooding their eggs and hatching their 

 young as miniature adults so that dispersal is not accomplished by 

 pelagic larvae. That so many species of Amphipoda, not only in the 

 tropics but in colder regions, have been disposed over widespread areas 

 attests to their dispersive success, regardless of the lack of larvae. 

 A number of species appears to be transported successfully on floating 

 algae. Through the courtesy of Dr. Torben WoM, the writer exam- 

 ined samples of floating seaweed collected by the Galathea Expedition 

 in the Indo-Pacific region, in the Mozambique Channel, Seychelles, 

 Celebes, and Philippine Sea. Amphipods often were collected from 

 these materials in great abundance, especially Ampithoe ramondi, 

 Cymadusa Jilosa, Elasmopiis pectenicrus (note that E. ecuadorensis 

 appears to be a variety of this), and Stenothoe gallensis. All of these 

 species are widely spread in the intertidal of the Indo-Pacific and 

 probably they form a normal faunal component on floating seaweeds, 

 perhaps in greater density than that found on attached plants. Ex- 

 peditions should be advised to collect more surface flotsam to discover 

 other amphipods being dispersed in this manner. 



Amphipods dwelling on intertidal algae probably are more widely 

 distributed in the Indo-Pacific because of accidental dispersal by 

 means of flotsam than are those species living on the sublittoral ben- 

 thos and building tubes or nestling among fixed bits of hard substrate. 

 Nevertheless, many sublittoral amphipods span deep barriers. 



Although many groups of animals have been studied extensively 

 in the tropics, little effort has been expended on the Amphipoda. 

 One problem is that amphipods are quite small in the tropics M. L. 



