Two new Rivulus killies named

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Killifish expert Wilson Costa has described two new species of Rivulus from the upper Paraguay River drainage in central Brazil.

The two new species, named Rivulus bororo and Rivulus paresi, belong to the subgenus Melanorivulus and are described in the latest issue of the journal Ichthyological Exploration of Freshwaters.

Rivulus bororoThis species is distinguished from other members of Melanorivulus in having 2+1 mandibular neuromasts (neuromasts are lateral line sensory organs), and a combination of the following characters: dark purplish grey spots on the caudal peduncle of both sexes, a bright greenish blue blotch on the humeral region in males, 8"9 dorsal-fin rays, 11"13 anal-fin rays, 30"31 scales in the longitudinal series, close red dots on the flank arranged in chevron-like series with the vertex on the mid-lateral line, and red bars on the caudal fin in males.

The species was collected from under dense marginal vegetation in a shallow (10"20 cm deep) swamp and is named after an indigenous tribe that formerly inhabited a large part of the Paraguay River drainage (where this species is found).

Rivulus paresiRivulus paresi is distinguished from other members of Melanorivulus in having small white spots that form a reticulate pattern on the dorsal fin and the basal portion of the anal fin, and forming narrow bars on the caudal fin in males, a narrow basihyal, and a combination of the following characters: a continuous dark gray mid-lateral stripe on flank, 30"31 scales in the longitudinal series, close red dots on the flank arranged in chevron-like series with the vertex on the mid-lateral line, and red bars on the caudal fin in males.

This species is named after an indigenous tribe that formerly inhabited the Parecis Hills in central Brazil, and has been collected in a shallow (10 cm deep) slightly inclined swamp with low current.

The author was unable to provide images for us to reproduce.

For more information, see the paper: Costa, WJEM (2007) Rivulus bororo and R. paresi, two new killifishes from the upper Paraguay River basin, Brazil (Teleostei: Rivulidae). Ichthyological Exploration of Freshwaters 18, pp. 351"357.