Taxonomy & naming
Cynodonichthys boehlkei was described by Huber and Fels in 1985, originally placed in the genus Rivulus — at the time the standard catch-all for Neotropical rivulines. The parentheses enclosing the authority signal that the species has since been transferred from its original genus. Wison J.E.M. Costa's 2011 revision of the Rivulidae (Ichthyologia Exploratoria Freshwatorum 22(3):233–249) formally reorganised the group into a series of more natural, morphologically cohered genera, validating Cynodonichthys as the name recognised by FishBase for this species. The American Killifish Association and a segment of the hobby literature instead use Anablepsoides, a genus name reinstated for a coherent group of non-annual rivulines across northern South America and the Lesser Antilles. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) is the governing authority for valid names; readers should note that both Cynodonichthys boehlkei and Cynodonichthys boehlkei appear in current literature for the same fish.
The type locality is a tributary of the Rio La Miel in the Magdalena drainage, Colombia, with collection code COGM 21-30. The type locality was rediscovered in 2008 by F. Vermeulen, who located the fish in swift, clear creeks approximately 17 mi upstream of the confluence at San Miguel — a significantly more montane setting than the lowland habitats typical of many congeners. FishBase also lists the species as "questionably non-annual", a note that likely reflects the limited wild data available, but all captive breeding accounts treat it as a non-annual plant spawner.
The species epithet boehlkei honours James E. Böhlke (1930–1982), an ichthyologist at the Academy of Natural Sciences of Philadelphia whose extensive work on Neotropical freshwater fishes made lasting contributions to the systematics of characins, catfishes, and gobies as well as killifish.
This fish was long listed as Anablepsoides boehlkei; Eschmeyer's Catalog of Fishes places the species in Cynodonichthys, and the current combination Cynodonichthys boehlkei is followed here.
Morphology
Cynodonichthys boehlkei is a small, slender rivuline reaching a maximum recorded total length of 1.8 in (FishBase). The body plan is typical of the genus: cylindrical and tapering, with a slightly superior to terminal mouth suited to surface and mid-water prey capture, moderately large cycloid scales, and a rounded caudal fin. The overall proportions are those of a streamlined micro-predator adapted to hunting in and among submerged vegetation and root mats.
Males are more vividly marked than females, as is standard for the group. The flanks show a pattern of small reddish or brownish spots on an olive-green to tan base, and the unpaired fins carry a degree of colour. Females are plainer — pale olive-brown with less fin pigmentation — and become noticeably deeper-bodied when gravid. Detailed published colour plates for this species are sparse, consistent with the small number of specimens collected and the limited time it has spent in hobbyist collections; the account in itrainsfishes.net and AKA records are the primary sources for its appearance in life.
Habitat
The Magdalena River is Colombia's principal river system, draining the inter-Andean valley between the Western and Central Cordilleras before flowing north to the Caribbean Sea. Cynodonichthys boehlkei is known from tributary streams of this basin — specifically swift, clear creeks in the upper Rio La Miel sub-drainage near San Miguel, at an Andean foothill elevation well above the broad lowland floodplain. The 2008 rediscovery by F. Vermeulen documented the species in fast-flowing, well-oxygenated stream habitat rather than the sluggish lowland pools more typical of many Neotropical rivulines.
As a non-annual killifish, C. boehlkei is associated with permanent or near-permanent watercourses. It does not depend on seasonally drying pools and lacks the diapausing egg adaptations of annual killifish. The swift, clear stream habitat documented at the type locality suggests cooler, better-oxygenated water than many lowland rivulines experience; exact temperature and chemistry data from the wild are not published in the available literature. Genus-wide, Anablepsoides species from comparable Neotropical stream habitats tend to occur in soft, slightly acidic to near-neutral water, but this should not be assumed for C. boehlkei specifically without field data.
The Magdalena basin has suffered severe deforestation and agricultural conversion across much of its catchment, making the conservation status of small, range-restricted endemic fishes such as this one a matter of ongoing concern even where direct population data are lacking.
Feeding
Cynodonichthys boehlkei is a generalised micro-predator, feeding on the small invertebrates available in its stream habitat: chironomid larvae, microcrustaceans, small aquatic insects, terrestrial invertebrates falling onto the water surface, and similar live prey. FishBase classifies it as benthopelagic — an indication that foraging occurs across the water column and at the surface film, as is typical of rivulines with a superior-to-terminal mouth position.
In captivity, the species accepts the standard killifish live and frozen diet: Artemia nauplii and adults, daphnia, cyclops, small bloodworm, and similar invertebrates. Itrainsfishes notes that rich live-food feeding stimulates sustained spawning activity, suggesting that diet quality has a direct influence on reproductive output. Prepared foods can be offered but should not form the bulk of the diet for best condition and colour.
Mating
Cynodonichthys boehlkei is a non-annual killifish and a continuous, plant or mop spawner. Rather than depositing eggs in moist substrate for dry-season diapause, pairs court and spawn repeatedly over days and weeks, attaching small batches of adhesive eggs to fine-leaved plants, floating roots, Java moss, or artificial spawning mops. Itrainsfishes documents approximately 5–10 eggs per day when the pair is well fed on live food — a rate consistent with the iterative, continuous-spawning strategy characteristic of non-annual rivulines from permanent water.
Courtship follows the typical Anablepsoides pattern: males display laterally to females, erecting the dorsal and caudal fins to present their colour pattern. Spawning acts are brief and repeated, with each act yielding one or a small cluster of eggs. Male aggression between spawning bouts may stress females in confined quarters; providing visual breaks or alternating access to the breeding mop helps maintain a sustainable spawning rate without injuring the female.
A single male and one or two females can be maintained together in a dedicated breeding set-up; trio arrangements with two females can reduce the intensity of male attention on any single female.
Breeding
Eggs are amber-coloured, approximately 0.06 in in diameter, and adhere individually or in small clusters to spawning mops, Java moss, or fine-leaved plants. Itrainsfishes records an incubation period of approximately 14 days in water — no dry incubation or peat transfer is required, which makes the species straightforward to breed compared to annual killifish. Eggs can be picked from the mop at intervals and incubated separately in small containers to prevent adult predation, or the adults can be removed and the mop left in place.
Fry are free-swimming at hatch and are large enough to take newly hatched Artemia nauplii immediately, which simplifies early rearing. Growth is steady when fed regularly on live or frozen micro-foods; itrainsfishes documents sexual maturity at approximately 4–5 months. Maximum captive lifespan is around 2 years, consistent with a non-annual life history that nevertheless operates on a relatively short generational timescale compared to longer-lived temperate fish.
One practical caution noted by hobbyists is that Cynodonichthys boehlkei — like most rivulines — is an excellent jumper and will exploit any gap in the aquarium cover. A tight-fitting lid is essential. Breeding tanks as small as 3 US gal have been used successfully when furnished with a dark substrate, subdued lighting, and a floating spawning mop.
In the aquarium
Cynodonichthys boehlkei is an uncommonly seen species in the hobby, primarily maintained by killifish specialists and AKA members rather than in the general aquarium trade. Its modest size — under 2 in — makes it suitable for small dedicated set-ups: a 3–5 US gal tank per pair or trio, well covered, with dark gravel or peat-based substrate, floating plants or a spawning mop, and subdued lighting. The species is peaceful toward its own kind in appropriately sized groups and should not be mixed with larger or aggressive fish.
Water conditions documented for captive breeding include soft, slightly acidic to near-neutral water at tropical room temperatures; the swift, clear Andean foothill streams of the type locality suggest that slightly cooler, well-oxygenated conditions may suit this species better than the warm, sluggish water preferred by many lowland rivulines. In practice, a temperature in the low-to-mid 20s °C and a pH in the 6.0–7.5 range with soft, clean water is a reasonable starting point. Regular small water changes and live-food feeding are the keys to sustained spawning.
The species' rarity in the trade is partly an artefact of how few export-licensed collection trips have targeted the upper Rio La Miel catchment. Hobbyists who do obtain it tend to distribute eggs through killifish society networks — the AKA and similar national clubs — rather than through commercial channels. Availability is therefore intermittent and usually network-dependent.
Conservation
The IUCN Red List assessment of October 2014 (published in version 2025-2, assessed by Mojica, Jimenez-Segura & Alonso) places Cynodonichthys boehlkei in the Data Deficient (DD) category. The listing reflects limited distributional data and the difficulty of making a meaningful population-trend assessment for a species known from only a small number of collections in the Magdalena River basin. Data Deficient status does not imply the species is secure — it means the data needed to assign a threatened category are absent.
The Magdalena basin context is concerning. The river system is one of South America's most heavily impacted: extensive deforestation across the inter-Andean slopes for cattle ranching and agriculture, water extraction for irrigation, and pollution from urban centres and extractive industries have degraded large portions of the catchment. Small endemic fishes with restricted ranges — particularly those confined to headwater and foothill tributary systems — are disproportionately vulnerable to the sedimentation, altered hydrology, and water-quality changes that accompany land clearance. C. boehlkei's confirmed range appears to be limited to a small area of the upper Rio La Miel sub-watershed, making any localised habitat disturbance a potential threat to the entire known population.
The species does not appear on the CARES (Conservation, Awareness, Responsibility, Empowerment, and Stewardship) priority list, and captive populations within the killifish hobby are small and inconsistently maintained. A formal distributional survey of the upper Magdalena tributaries, combined with an updated IUCN assessment incorporating recent field data, would substantially improve the basis for conservation decision-making for this and many other small endemic Magdalena basin fishes.