Research Training Program

Raissa Menéndez-Delmestre
University of Puerto Rico, San Juan
San Juan, Puerto Rico

Bruce B. Collette, Ph.D.
Supervising Scientist
Department of Vertebrate Zoology
Division of Fishes

"...the investigation I have conducted under the supervision of Dr. Bruce B. Collette has helped me understand some of the methods used in systematic research."

Revision of freshwater needlefish genus Xenentodon. The needlefish family Belonidae is composed of approximately 32 species. Elongate tooth-studded upper and lower jaws, as well as an elongate body distinguish these fishes from other families. Needlefishes live in the upper 10m of tropical waters. Some species inhabit marine waters while other inhabit freshwater. There are four genera of freshwater needlefishes, three in South America, and one, Xenentodon, in East Asia. These fish are considered aquarium species, and are commercially important in some countries (e.g. India) as food. Until recently most scientists that have studied the genus Xenentodon in East Asia, have considered this genus to have only one species. In 1989, Tyson Roberts indicated that this might have not only one species, but rather three. The purpose of this revision of the genus Xenentodon is to clarify how many species exist in the genus. To do this revision, some of the characters that Roberts used were studied. Counts of the pre-dorsal scales, vertebrae and fin rays where recorded for specimens found in the National Museum of Natural History collection and some borrowed from other institutions. In order to count the vertebrae and the fin rays, radiographs were taken of each of the specimens studied. The data obtained was analyzed by groups corresponding to the drainage in which the fish were caught. The data was plotted into graphs to observe if there was a division that might separate the specimens studied into different species. There was no division apparent that this might indicate a division in the genus, but rather a large range for total vertebrae and pre-dorsal scales. Other characters need to be studied to clarify the number of species in the genus Xenentodon.