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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



A remarkable incident occurred in connection 

 with Lepidapedon nicolli and Prosorhynchus ozakii. 

 These two species, new at the time, both occurred 

 at Tortugas at 90 fathoms in the same individual 

 fish, a snowy grouper, Epinephelus niveatus. In 

 1934, I collected these same two species again 

 from a single fish, an "unidentified, spotted, 

 grouper-like fish" from the Pacific Ocean at Isabel 

 Island, Mexico. It is unfortunate that this fish 

 could not be further identified. As far as I can 

 learn, Epinephelus niveatus does not occm- in the 

 Pacific. 



TREMATODES FROM SURFACE WATER FISHES 



A comparison of 142 species of trematodes from 

 less than 50 fathoms at Tortugas with faunas 

 known elsewhere reveals, in general, (1) that the 

 Tortugas fauna is very unlike that of the coast of 

 Maine or Massachusetts, the European Atlantic 

 or the Mediterranean, and (2) it is strikingly 

 similar to the fauna at Bermuda and the tropical 

 Amercian Pacific. 



Of the 142 species at Tortugas, 28 species (19.8 

 percent) occur at Bermuda (Hanson 1950). 

 This similarity is to be expected since many of 

 the same species of fishes occur in both regions. 

 In fact, at least 21 of the 28 species of trematodes 

 occur in the same host species in both regions. 



The only other part of the world where such 

 trematodes have been collected sufficiently to 

 give adequate sampling and which compares with 

 the similarity to Bermuda is the tropical American 

 Pacific. Considering species from 50 fathoms or 

 less, 24 or 16.8 percent of 142 Tortugas species 

 occur in the American Pacific. Also, there is 

 reason to believe this similarity is even greater 

 than this figure indicates. Three additional 

 species in the Pacific occur in Bermuda fishes which 

 occur at Tortguas ; still three more species are now 

 reported (Pearse 1949) from Beaufort, N. C, in 

 fishes which occur at Tortugas. Thus, the 

 probable total is at least 30 species, a figure 

 practically identical with that derived from com- 

 parison with Bermuda. Furthermore, if fishes 

 down to 100 fathoms were considered, the Pacific 

 percentage would be slightly higher. 



Thus, based on our present knowledge, one can 

 conclude that the Tortugas trematode faima of 

 surface-water fishes is very similar to that of 

 Bermuda, as would be expected, and equally as 

 similar to that of the tropical American Pacific, 



as might not be expected. There is one striking 

 difference among these regions. Whereas at 

 Bermuda the species of host fishes are, in general, 

 identical with those involved at Tortugas, in the 

 Pacific the hosts are, with very few exceptions, 

 different but related species. As far as the 

 trematodes are concerned, the tropical American 

 Pacific occupies a position comparable to that 

 of Bermuda in relation to Tortugas, almost as 

 though there were no land barrier between the two 

 oceans. It is well known that this land barrier has 

 not always existed. Have the trematode parasites 

 retained their specific identity while their hosts, 

 perhaps both fish and molluscan, have evolved 

 into slightly different species? Trematode dis- 

 tribution suggests that just as the Gulf Stream 

 has made Bermuda practically an outpost of the 

 Gulf of Mexico and Caribbean faunas, the 

 tropical and subtropical American Pacific is also 

 such an outpost persisting as evidence of the 

 prehistoric continuity of the two oceans. 



Further evidence of an ancient influence of 

 inter-oceanic continuity is the relative dissimilar- 

 ity of the Tortugas fauna to such adjacent regions 

 as Beaufort, N. C. Here the trematodes have 

 been as well sampled as in the Pacific, and only 15 

 of the Tortugas species are known there. This 

 number is hardly more than half the number known 

 to occur in the Pacific. If the trematodes were 

 accidentally distributed by migrants such as 

 birds, this difference would not be expected. 

 Fourteen Tortugas species, from less than 50 

 fathoms, occur at Woods Hole, Mass. Eleven 

 occur in Japanese waters. This extension of 

 species far into the Pacific is reflected in the 

 Bermuda fauna. Five of the Bermuda species 

 occur in Japan and six in the tropical American 

 Pacific, as compared with seven at much nearer 

 Woods Hole, six at Beaufort, three in the European 

 Atlantic, and three in the Mediterranean (Hanson 

 1950). This greater affinity of the Bermuda 

 trematodes for Japanese than for European waters 

 is better understood ia the light of the Pacific 

 affiinities of the Tortugas fauna. 



The distribution of these trematodes is, of 

 course, a result of numerous and complex factors. 

 For example, a few of the species considered here 

 are parasites of open sea fishes with a very wide 

 range. Their parasites would be expected to 

 have a wide distribution. Omission of these 

 species, however, would not materially change the 



