Mystus impluviatus: A New Species of Bagrid Catfish (Teleostei: Bagridae) from Eastern Borneo
A new species of bagrid catfish in the genus Mystus is described from the Mahakam River drainage in eastern Borneo. Mystus impluviatus closely resembles Mystus nigriceps and Mystus castaneus but differs in having a second posterior fontanel on the supraoccipital. It can be further distinguished from M. nigriceps and M. castaneus a combination of the following characters: maximum height of adipose fin 4.7–6.0% SL, length of adipose fin base 31.6–36.1% SL, long second and third dorsal fin rays, causing the dorsal fin to appear less rounded, maximum height of pectoral spine serrations 3.6–4.8% of spine length, a deeply forked caudal fin with a slender upper lobe, and a brown body with a distinct dark triangular patch on the base of the caudal peduncle.Abstract
Mystus impluviatus, paratype male, CAS 95035, 98.9 mm SL
Schematic illustration of dorsal views of heads of (A) Mystus impluviatus, CAS 97049, holotype, 87.0 mm SL; (B) Mystus castaneus and Mystus nigriceps (M. castaneus, UMMZ 155714, 77.9 mm SL illustrated), showing presence of second posterior fontanel on supraoccipital in M. impluviatus. Scale bar represents 10 mm
Schematic illustration of caudal fins of (A) Mystus impluviatus, CAS 95038, paratype, 83.0 mm SL; (B) Mystus castaneus, UMMZ 155714, 77.9 mm SL. Scale bar represents 5 mm
Map showing distribution of Mystus castaneus (▪), Mystus impluviatus (▴) and Mystus nigriceps (•). Base map courtesy of W. J. Rainboth
(A) Maximum height of the adipose fin (%SL) plotted against SL (mm) for Mystus castaneus and Mystus impluviatus; (B) Length of the adipose fin base (%SL) plotted against SL (mm) for M. impluviatus and Mystus nigriceps