Larval Development of the Shorthead Redhorse (Moxostoma macrolepidotum) from the Susquehanna River

Abstract

Abstract Shorthead redhorse eggs hatched 8 days after fertilization at a mean temperature of 15.6 C. The total length (TL) of newly hatched larvae averaged 10.0 mm (range, 9.3–10.4 mm); their standard (notochord) length averaged 9.4 mm (range, 8.7–9.9 mm). They were melanophore-free, had slightly upturned urostyles, and incomplete mouths. Melanophores appeared for the first time in larvae of 10.2 mm TL. Fin rays were visible in caudal, dorsal, pectoral, anal, and pelvic fins by 12.9, 15.8, 16.0, 16.7, and 18.8 mm TL, respectively. Transformation of shorthead redhorse to the mesolarval phase occurred by 12.4 mm TL and to metalarval phase by 16.2 mm TL. Protolarvae of the shorthead redhorse can be distinguished from those of northern hog sucker (Hypentelium nigricans) from the Susquehanna River by their smaller standard (notochord) length and larger postanal length as percentages of TL, and their fewer preanal myomeres. Shorthead redhorse mesolarvae lack the melanophore-free area between the eyes found in n...