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aqua 2(3)_Paratrygon

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SINGLE PAPER

Volume 2, Issue 3 – April 1997

Lasso, C. A., A. Rial B. and O. Lasso-Alcala: Notes on the biology of the freshwater stingrays Paratrygon aiereba (Muller & Henle, 1841) and Potamotrygon orbignyi (Castelnau, 1855) (Chondrichthyes: Potamotrygonidae) in the Venezuelan llanos, pp. 39-50.

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SINGLE PAPER

Volume 2, Issue 3 – April 1997

Lasso, C. A., A. Rial B. and O. Lasso-Alcala: Notes on the biology of the freshwater stingrays Paratrygon aiereba (Muller & Henle, 1841) and Potamotrygon orbignyi (Castelnau, 1855) (Chondrichthyes: Potamotrygonidae) in the Venezuelan llanos, pp. 39-50.

Abstract

The ontogenetic development, reproduction, feeding habits and habitats and habitat of the stingrays Paratrygon aiereba and Potamotrygon orbingyii from the Venezuelan Ilanos (Apure river basin) were studied. According to the ontogenetic development, four stages were considered. Fetuses, immatures, sexually maturing and mature individuals. The variation of 12 measurements and their development in relation to disk width are described. P. aiereba attained greater size (780 mm DW) and weight (25 kg) than P. orbignyi (325 mm DW) and weight (2 kg). In P. aiereba males, sexual maturity is apparently reached at a size larger than 410 mm DW, whereas in P. orbingyi sexual maturity is attained at 230 DW. Females show signs of sexual maturation at 370 and 185 mm DW in P. aiereba and P. orbignyi respectively. Pregnancy and littering in both species goes on all year. Births seem to be more frequent during the rainy season. According to our data, the litter size varies between one and two young in each reproductive cycle in both species. P. aieereba is a piscivore even though shrimps are important items in this diet. P. orbignyi is essentially an insect feeder. P. aiereba has been observed only in the main channel of the Caño Guaritico (clear water) whereas P. orbignyi is usually found in a wide range of habitats and water types.

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