Males of Rivulus carolinae n. spec., differ from other minute species in the subgenus

Owiyeye, also known as the “rectocaudatus species group”, by the following combination Thus of characters. Body slender and small, dorsal pointed with a small basis, reaching beyond the caudal-fin base; anal fin long but not pointed; pelvic fins exceptional long, reaching from ray 8 to 11 (occasionally to the end of the anal fin base ending) of the anal fin; caudal truncated with straight but “frayed” yellow-white posterior border and reticulated pattern in the central portion; dark stripe starting posterior to the eyes, fading posteriorly on a bright blue background; orange dots on the sides surrounded with fine dark borders; males never express a "Rivulus spot."

Females differ by having all fins rounded; a brown nearly black zone, starting posterior of the caudal peduncle covering one-third of the caudal; the dark zone is divided in two by a thin white line reaching from the dorsal- to the ventral border. Females also differ from those of all known congeners by evincing a rust-color on ventral fins and all unpaired fins as well, and a body with red spots surrounded by a thin black margin on a blueish background. A somewhat similar caudal fin pattern is seen on females of Rivulus uakti from the middle Rio Negro. However, in that species the caudal pattern only covers twothirds of the dorsoposterior portion of the caudal. It differs from R. carolinae n. spec., by evincing different body colors and shorter ventral fins and a dark margin at the anal of females caudal fin. The image to the right shows a variation seen in few wild males only and is likely the result of fighting and in the process of regeneration. (Ref. 130065).