Taxonomy & naming
Cynodonichthys uroflammeus was described in 1980 by William A. Bussing, originally as Rivulus uroflammeus, within the same comprehensive treatment of Costa Rican freshwater fishes that also produced C. fuscolineatus and numerous other Central American rivulines. The specific epithet uroflammeus combines Greek and Latin elements referring to a flame-like colouration of the tail, presumably a bright orange or red caudal-fin marking noted in the original description. Following Costa's 2011 revision that split the old genus Rivulus into several regional lineages, this species was transferred to Cynodonichthys. Eschmeyer's Catalog of Fishes lists the valid combination as Cynodonichthys uroflammeus (Bussing, 1980), within the family Rivulidae.
Alongside its congener C. fuscolineatus, this species is part of the Central American radiation of Cynodonichthys, a genus of small, non-annual, forest-stream rivulines distributed from Mexico through Panama and into northern South America.
Morphology
Cynodonichthys uroflammeus is expected to share the general rivuline body plan of its genus: an elongate, cylindrical body, flattened head and dorsally set eyes adapted to surface ambush-feeding. Its defining feature, as suggested by the specific epithet, is a flame-coloured — likely orange or red — marking on the caudal fin, though a full modern description of this pattern and precise body measurements was not confidently available from the sources consulted here — data sparse.
Sexual dimorphism in the genus generally favours more vividly coloured males, and the caudal-fin "flame" marking referenced in the name may itself be a male secondary sexual character, though this has not been directly confirmed for this species.
Habitat
Cynodonichthys uroflammeus occurs in forest-stream habitat in Costa Rica, in keeping with the genus's general preference for small, shaded, slow-flowing watercourses with leaf-litter substrate. As a non-annual rivuline, it is presumed to occupy permanent rather than seasonal water bodies, unlike the temporary-pool annual killifish of South America.
Precise drainage-level distribution data for this species were not confidently available from the sources consulted here — data sparse.
Feeding
No dedicated dietary study of Cynodonichthys uroflammeus was located. As with other Rivulidae, a carnivorous, ambush-feeding diet of small aquatic and terrestrial invertebrates taken near the water's surface is inferred from the family rather than confirmed for this species specifically.
Mating
Courtship and spawning behaviour specific to Cynodonichthys uroflammeus have not been documented in the sources consulted. Non-annual Rivulidae generally are egg-scattering spawners, depositing adhesive eggs among leaf litter or fine plant roots over an extended period without elaborate courtship or nest-building — a pattern presumed for this species by analogy with its relatives.
Breeding
Published captive-breeding information specific to this species is data sparse. As with C. fuscolineatus and other non-annual Central American rivulines, breeding in captivity is generally considered approachable given soft, slightly acidic water and fine-leaved plants or leaf litter for egg deposition, without the diapause-and-dry-storage cycle required by true annual killifish. Specific parameters for C. uroflammeus were not confirmed here.
In the aquarium
Cynodonichthys uroflammeus is not established in the mainstream aquarium trade and is known mainly to specialist killifish keepers. General husbandry for the genus — soft, slightly acidic water, subdued lighting, dense planting or leaf litter, and a well-sealed lid — reflects the natural forest-stream habitat this genus favours, though species-specific care notes were not confirmed.
Conservation
Cynodonichthys uroflammeus is listed by the CARES Preservation Program at the Endangered (CEN) priority level. As with its congener C. fuscolineatus and other Costa Rican forest-stream killifish, the principal concern is habitat degradation from deforestation and the associated sedimentation and warming of small forest streams. Given its evidently restricted range, ongoing land-use pressure in Costa Rica is reason enough for the conservation concern reflected in this listing, even absent a detailed published population assessment specific to the species.