GULF OF MEXICO 



319 



single species was reported from Sumatra and 

 Texas. 



Due to the scarcity of qualified American 

 workers the fauna of the European coasts is far 

 better known than the Gulf fauna, and this 

 probably explains the predominance of Europeaa 

 forms among species recorded from more than one 

 locality. Allgen (1947b) reported numerous 

 species from the western coast of North America, 

 and these differ from the eastern fauna, as would 

 be expected. 



ECOLOGY AND LIFE HABITS 



Most marine nematodes are bottom dwellers 

 or live in association with algae, sponges, colonial 

 hydroids, bryozoa, mollusks, decapods, ascidians, 

 and othei-s. Because of their inability to swim 

 freely for long periods of time, they are never 

 typically planktonic (i. e. holoplanktonic) . A 

 few nematodes appear capable of directed move- 

 ment; monhysterids in particular exhibit a very 

 rapid vibratory motion in which the body may 

 appear as an ellipse with two processes at each 

 end, but the worms cannot sustain these swimming 

 movements for more than several seconds. Most 

 nematodes have a slow serpentine motion which 

 is rather ineffective in locomotion without the 

 aid of a substrate for leverage. In their true 

 habitat, however, locomotion is quite efficient 

 (e. g., oncholaims can move rapidly among 

 filamentous algae). Bottom dwellers are usually 

 confined to a sharply restricted local area. 



Many European workers, notably Micoletzky 

 and Steklioven, have paid considerable attention 

 to ecological considerations, e. g., the association 

 of certain species with certain types of bottoms, 

 the frequency of species in a certain habitat, etc. 

 The largest nematode population is to be found 

 in mud rich in organic debris. Steklioven has 

 estimated that 500-600 nematodes per cubic 

 centimeter may be found Ln such a bottom. 

 Saprophagous species, carnivores, and algivorous 

 and diatomivorous species abound here. In 

 highly aerated regions such as breakwaters or 

 surf-beaten rocks there is a rich fauna of algivorous 

 species. 



There are numerous references in the literature 

 to the food of nematodes among the genera re- 

 ported from the Gulf of Mexico. Monhysterids 

 and chromadorids hi general feed on algae and 

 diatoms; Monhystera and Euckromadora feed 



especially on algae — unicellular and filamentous; 

 and Theristus on diatoms. The diatoms may be 

 almost half the diameter of the body. In the 

 anterior of the intestine they are filled with 

 bright green pigment, but when the shells are 

 rejected through the anus they usually contain 

 only a small amount of unabsorbed brownish 

 yellow pigment, proving that the diatoms are 

 actually being utilized as food. Chitwood (1951) 

 presumes that Paranticoma longicaudata feeds on 

 algae because of elongate, irregular, greenish 

 masses in the lumen and similarly colored cell 

 inclusions. Halichoanolaimus has been reported 

 several times as predatory on other nematodes. 

 The genus Halenchus belongs to a group primarily 

 parasites of terrestrial angiosperms, but the species 

 H. fucicola, first described by de Man (1892), is 

 a parasite of the brown alga, Fucus. Such nema- 

 todes have a strictly liquid diet, inserting their 

 hollow oral stylet into plant cells and predigesting 

 the contents to some extent. It would be in- 

 teresting to ascertain the host plant for H. mexi- 

 cantLS described from the Gulf of Mexico (Chit- 

 wood 1951). 



Herbivorous species may usually be recognized 

 as such by the pigments present either in the 

 intestinal lumen or as cell inclusions. Timm 

 (1951) has reinvestigated such cell inclusions in 

 Syringolaimus smarigdus which Cobb (1928) first 

 found associated with the common mud snail, 

 Nassa obsoleta. Cobb had reported that Syringo- 

 laimus was feeding on an encrusting orange alga 

 of the genus Raljsia growing on the shell of the 

 snail, but Timm showed by chemical tests of the 

 cell inclusions and contents of the lumen that this 

 worm feeds rather on the filamentous green alga 

 which forms a thick felt mat on the shell of Nassa. 

 The junior author has likewise observed the 

 feeding of Chromadora quadraline aides obtained in 

 the living state from Chesapeake Bay off Solomons 

 Island. Maryland. This nematode was found in 

 great abundance in association with the bright red 

 sponge, Microciona prolifera. Some worms were 

 apparently feeding off the epidermal substance of 

 the sponge through the action of their three, fine 

 teeth, because bright red, finely divided particles 

 were observed m the intestinal lumen. After 2 

 months in an unaerated aquarium the sponges 

 had died, but the chromadorids were still thriving 

 on small algae trapped by the coarse skeleton of the 

 sponge. 



