Marbled Darter

Etheostoma marmorpinnum is distinguished from all other members of the species complexby higher percentage of belly covered by scales (60–80% vs. 10% or less); higher percentage of body area along the first dorsal-fin base covered with scales (100% vs. 70% or less); dark distinct marbling in second dorsal fin of nuptial males (vs. lighter diffuse marbling or marbling absent); narrower band width for caudal fin (range = 12–15% of fin length vs. 15–25%) and anal-fin (range = 29–33% vs. 33–58%); more scalesaround caudal peduncle (25 vs. 23 or 24); and higher first dorsal fin (D1H, =117 vs. 105 or less). The species is further distinguished from E. percnurum by fewer caudal fin rays (15 vs. 18); narrower distal band on pectoral fin (range = 17–20% vs. 27–32% of fin length) and second dorsal fin (14–21% vs. 23–25% of finheight); and by prominent tessellation of medial region of caudal fin of nuptial males (vs. uniformly dusky). Further distinguished from E percnurum and E. sitikuense by an intermediate number of pored lateral-line scales (27 vs. 22 or 33 respectively). Means of other measurements were also informative in distinguishing E. marmorpinnum from other members of the complex (Ref. 79849).

The marbled darter (Etheostoma marmorpinnum) is a species of freshwater ray-finned fish, a darter from the subfamily Etheostomatinae, part of the family Percidae, which also contains the perches, ruffes and pikeperches. It is endemic to the eastern United States. It occurs in Tennessee in the Little River drainage and formerly occurred in the Holston River where it is now extirpated, not having been collected there since the completion of the South Fork Holston Dam. This species can reach a length of 4.1 centimetres (1.6 in) SL.