GULF OF MEXICO 



345 



proportional figures. The species from deeper 

 water were considered separately because parasites 

 from these depths have not been studied in most 

 regions. Presumably, these species have a wide 

 distribution at appropriate depths. If sufficient 

 numbei"s of species are involved, the exceptional 

 cases or errors in identification will be minimized. 

 In most cases, such factors would probably more 

 or less balance one another in the various localities. 

 However, it seems to me that the figures available 

 are not suitable for statistical analysis because of 

 factors which cannot be given numerical value. 

 For example, from purely geographical considera- 

 tions one would expect the Pacific fauna to be 

 very different from Tortugas, separated as it is 

 by a land barrier and with practically no pos- 

 sibility of contact by way of the Antarctic or the 

 partly fresh-water Panama Canal. More com- 

 plete knowledge of these parasites in all regions 

 is needed. As this knowledge is gained it seems 

 probable that a very interesting host-parasite- 

 distribution picture will unfold, particularly at 

 the specific and generic levels. 



TREMATODES OF TURTLES 



Four species of marine turtles occur in the Gulf 

 of Mexico. These are the loggerhead turtle, 

 Caretta caretta, the green turtle, Chelonia mydas, 

 the hawk-bill turtle, Erctmochelys imbricafa, and 

 the leathery or leatherback turtle, Dermochelys 

 coriacea. All four of these turtles have a very 

 wide distribution in warm seas. They are very 

 favorable hosts for trematodes, some of which also 

 appear to be widely distributed, others being 

 reported as yet only from certain localities. The 

 actual distribution of these trematodes can be 

 known only after the examinations made in various 

 regions are more or less equivalent. Until then, 

 the presence of a species is more significant than 

 its apparent absence. With only two exceptions, 

 the trematodes described from marine turtles are 

 all Digenea. Since a moUuscan host is also re- 

 quired in their life cycle it is probable that a 

 number of these trematodes will have a distribu- 

 tion limited by the distribution of the molluscan 

 host. 



Considering the wide individual range of these 

 turtles in the open sea, a surprising variety of 

 trematodes succeed in parasitizing them. Fifty- 

 one species have been reported from Chelone 

 mydas, 30 from Caretta caretta, and 9 from Eretmo- 



chelys imbricata. It is an interesting fact that 

 none of these trematodes is known to occur as an 

 adult parasite of fishes.' Furthermore, despite 

 the aquatic life of the turtles, these trematodes 

 belong to reptilian parasitic groups (families and 

 genera). Turtles have no representatives of such 

 common trematode families of fishes as Hemi- 

 uridae, Opecoelidae, Fellodistomatidae, etc. A 

 similar situation exists in connection with the 

 trematodes of marine mammals which are quite 

 different from species occurring in either turtles 

 or fishes. 



Only a few turtles from the Gulf have been 

 examined for parasites. Additional records, par- 

 ticularly from Chelone and Eretmochelys , could 

 easily be made. Such records would make pos- 

 sible comparisons between the parasites of this 

 region and other seas. 



TREMATODES OF CARETTA CARETTA 



Fifteen species of trematodes from (\retta 

 caretta at Tortugas, Fla., have been reported by 

 Linton (1910), Pratt (1914), Manter (1932), and 

 Luhman (1935). These are as follows: 

 ASPIDOGASTREA 



ASPIDOGASTRIDAE 



1. Lopholaspis vallei (Stossich, 1899) Looss, 



1902. 



DIGENEA 



Pronocephalidae 



2. C.ricocephalns albus (Kuhl & van Hasselt, 



1822) Looss, 1899. 



3. Diaschislorchis pandus (Braun, 1901) Johns- 



ton, 1913. 



4. Pleurogonius trigonocephalus (Rud., 1809) 



Looss, 1901. 



5. Pyetosomum longicaecum Luhman, 1935. 

 Brachycoeliidae 



6. Cymatocarpus undulatus Looss, 1899. 



7. Orchidasma amphiorchis (Braun, 1899) 



Braun, 1901. 

 Plagiorchidae 



8. Pachypsolus ovalis Linton, 1910. 



9. Pachypsolus tertius Pratt, 1914. 



10. Styphlotrema solitarius (Looss, 1899) 

 Odhner, 1910. 



Rhytidodidae 



11. Rhytidodes secundus Pratt, 1914. 



GORGODERIDAE 



12. Phyllodistomum cymbiforme, (Rud., 1819) 



Braun, 1899. 



I The presence of a single specimen ol Orckidasma amphiorchis in Coryphaena 

 hippuTus reported by Manter (1931) is without doubt an accidental and 

 temporary condition probably due to recent ingestion of a young turtle by 

 the fish. 



