Ecology of Amazonian needlefishes (Belonidae)

Abstract

The Amazon Basin has about 15 families and over 60 species of fishes whose relatives are mostly marine (Roberts, 1972 gives a slightly lower estimate for the species). Supposedly the freshwater forms were derived from marine taxa, or at least the'ir ancestors were. The Belonidae, or needlefishes, are represented by at least 10 genera and 32 species in the oceans and freshwaters of the world (Collette, 1974b; Nelson, 1976). South America has four freshwater belonid genera, three (Pota- morrhaphis, Pseudotylosurus and Belonion) of which are endemic and one (Strongylura) that 19 worldwide in marine, estuarine and freshwaters (Collette, 1974b). ln South America Pseudotylosurus appears to be the most widespread freshwater belonid genus, and is known from the Orinoco, Amazon and La Plata drainage systems and from rivers in the Guianas region (Collette, 1974c). Pse~tdotylosurus microps is found in the Orinoco and Amazon basins and in the Guianas; P. eigenmanni is known from the Paraná-paraguay and upper Madeira areas (Collette, 1974c). Potamorrhap1vis is distributed in the Orinoco and Amazon basins and in the Guianas region; P. petersi is known from the Amazon and Orinoco basins, whereas P. guianensis is found in these two systems and in the Guianas (Collette, 1974a, 1982). The genus Belonion is known from the Orinoco and Amazon Basins; B. dibranchodon appears to be restricted to the Orinoco system, and likewjse, B. apodion to the Amazon drainage ( Collette, 1966). Needlefishes