The nereid worms are evidently one of the staple items in the diet of 

 many of the birds, including the whooping crane. Nereids and fiddler 

 crabs are burrowers in the soft mud or sand of the salt flats. 



Seventeen species of invertebrates, which might be termed marine or 

 brackish water types, have been found in Aransas Refuge. These species 

 include the pulmonate Melampus coffeus , which is found only among the 

 salt marsh plants. It appears that the dominant invertebrate of the salt 

 flats is blue crab, Callinectes sapidus . Crabs were observed at all 

 stations, and their remains indicate their importance as a food item for 

 both birds and racoons. Almost of equal importance in species mass is 

 the shrimp Penaeus aztecus , but its occurrence is seasonal. Worms are 

 apparently the base of the food pyramid on the salt flats, for there is 

 little else on the bottom in the way of food for the crabs and shrimp, 

 except each other. 



The fauna of salt flat ponds is marine; above the three-foot contour 

 line, this fauna abruptly ends except for the sporadic forays of indi- 

 vidual blue crabs, and is replaced in the ponds and ditches of the higher 

 ground by a fauna composed of crayfish, aquatic insects, freshwater 

 entomostraca, ostracods, gammarids, and mollusks (H.D.) 



Keywords: marine invertebrate fauna, salt marshes, birds, Texas 



V-E-5 



MacDonald, K.B. 1969. Quantitative studies of salt marsh mollusc faunas 

 from the North American Pacific coast. Ecological Monographs 39:33-60. 



The Spartina-Salicornia salt marshes of the North American Pacific 

 Coast, and the tidal creeks that dissect them, contain distinctive 

 molluscan faunas. These faunas exhibit a characteristic "structure," 

 one or two species being widely distributed and very abundant while 

 the remaining species are all represented by small numbers of patchily 

 distributed individuals. When described in terms of the identity and 

 number of species present and their respective relative abundances and 

 size-frequency distributions, this "structure" remains fairly uniform 

 between different sites within the same faunal province. The creek 

 faunas usually contain more species and have a more variable species 

 composition than do the marsh faunas. 



The distribution of recurrent groups of species within the fauna 

 supports the classification of Pacific Coast molluscan provinces pro- 

 posed by Valentine (1966). There are some indications that both 

 salt marsh and tidal creek environments in the Californian Province 

 (27-34°N) contain a greater variety of species than do similar 

 environments in the Oregonian Province (34-50°N). 



Although the salt marsh molluscs occupy similar types of niches at each 

 site (i.e., all epifaunal species feeding on algae and plant detritus), 



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