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Niche Specificity of Neohaustorius Schmitzi and Haustorius SP. (Crustacea: Amphipoda) in North Carolina

Croker, Robert A.
Ecology 1967 v.48 no.6 pp. 971-975
Amphipoda, beaches, body length, digestive system, feces, fluorescent lighting, foods, invertebrates, laboratory experimentation, light microscopy, littoral zone, microorganisms, sand, seawater, Georgia, North Carolina
Neohaustorius schmitzi and the larger Haustorius sp. coexist in the upper intertidal zone of Georgia and North Carolina sand beaches. The kinds and sizes of foods ingested and the morphology, setation, and size ratios of maxillae were examined to determine the contribution of these factors to the niche specificity of these sympatric amphipods in North Carolina. The morphology and setation of the maxillae of both species were quite similar, although maxillae lengths of Haustorius sp. were about x2.3 the size of maxillae of N. schmitzi. Body length differences were about 25% less. Both species ingested materials considerably larger than the internal dimensions of the filter apparatus, although Haustorius sp. ingested interstitial invertebrates and larger plant remains that N. schmitzi did not. Detritus made up much of the volume of the gut contents of both species. Laboratory experiments showed that both species fed for short periods, but at frequent intervals, and produced about 1 fecal pellet/animal/hr in unfiltered sea water. Detrital masses with included microorganisms were identified in sea water, gut contents, and fecal pellets by white— and fluorescent light microscopy. Niche specificity is maintained primarily by a size difference between the species, and this is reflected in the size of the foods despite consierable overlap in the types of foods utilized.