Taxonomy & naming
Nothobranchius krysanovi was described by Shidlovskiy, Watters, and Wildekamp in 2010 in the journal Zootaxa (volume 2724, pages 37–57), together with the closely related N. pienaari. The authors distinguished the new species from the superficially similar N. rachovii on the basis of coloration, meristics, and a markedly different karyotype: N. krysanovi carries 2n=18 chromosomes (karyotype formula 26 ft+8sm+2st/a, NF=34), whereas N. rachovii has 2n=16. The holotype is a male of 1 in SL deposited at MRAC as A4-039-P-0078, collected from 7 mi south of Nicuadala toward Quelimane in the Licungo River system (17°39.5'S, 36°51.5'E), Mozambique.
The species sits within subgenus Nothobranchius sensu stricto and is placed in the N. rachovii species group. Its closest associate in the wild is N. orthonotus, with which it co-occurs at approximately 87% of sampled sites — an unusually high syntopic rate within a genus whose members frequently partition seasonal pools by microhabitat.
Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong, continuously updated) records the valid combination as Nothobranchius krysanovi Shidlovskiy, Watters & Wildekamp, 2010. The species epithet honours a collector or contributor to the original study (the exact honoree is recorded in the original description). The name Nothobranchius krysanovorum is treated as a synonym of this species in Eschmeyer's Catalog of Fishes.
Morphology
Nothobranchius krysanovi is a diminutive killifish: maximum recorded standard length is 1 in in males and 1 in in females (FishBase). The body is moderately compressed, with a blunt snout and upturned mouth typical of the genus — an adaptation to surface feeding in shallow, plant-fringed pools.
Sexual dichromatism is pronounced. Males are vivid: the flanks carry alternating light-blue and orange-red oblique bars running from behind the pectoral fin to the caudal peduncle. The dorsal and anal fins mirror this barred pattern. The caudal fin is orange-brown, marked with a bright orange subterminal band and a black terminal band — a banding arrangement characteristic of the N. rachovii group. Females are cryptic by comparison, showing only faint brown oblique bars on the posterior flanks and plain, unmarked fins.
Meristically, dorsal-fin ray counts of 15–17 and anal-fin ray counts of 15–17 place N. krysanovi within the typical range of mid-sized Nothobranchius. The chromosomal difference from N. rachovii — 2n=18 versus 2n=16 — is detectable only cytologically but was pivotal in establishing the species as distinct.
Habitat
The species is native to the coastal lowland zone of east-central Mozambique, confined to the watersheds of the Kwa-Kwa (Cuacua) and Licuare rivers and their tributaries north of the lower Zambezi River. Elevations across the known range span roughly 3–285 ft above sea level (WildNothos). Biogeographically, the area falls within the Coastal East Africa freshwater ecoregion.
Habitat consists of ephemeral floodplain pools and seasonal swamps that fill with the rains and vanish completely during the dry season — the classic Nothobranchius landscape. Marginal grass vegetation fringes these pools, and aquatic macrophytes including Nymphaea, Ottelia, Lagarosiphon, and Utricularia are recorded within them. The surrounding terrain is low-lying coastal plain dominated by seasonally inundated grassland and, increasingly, irrigated rice paddies.
Water chemistry at sampled sites is moderately warm and near-neutral: temperatures of 84–90 °F, pH 6.9–7.3, and conductivity ranging widely from 100 to 1,480 µS/cm have been recorded. Water is typically turbid. These figures stand apart from the soft, acidic water associated with many West African Nothobranchius; the Mozambican coastal plain pools tend to accumulate more dissolved minerals from clay-rich soils before drying.
Feeding
Like other small Nothobranchius, N. krysanovi is a micro-predator and opportunistic omnivore in the wild. Seasonal pools of the Mozambican coastal plain support dense populations of small invertebrates — aquatic insect larvae, microcrustaceans, and worms — that constitute the bulk of the diet during the brief wet-season growing period. The upturned mouth is well suited to taking prey at or near the water surface.
In the aquarium, the species takes live and frozen foods readily: Artemia nauplii, Daphnia, Moina, bloodworm (Chironomus larvae), and grindal worm are all suitable staples. Dry foods are accepted by many individuals but are best used as a supplement rather than a primary diet, since the short lifespan of annual killies makes nutritional quality especially important. Varied, live-food-rich feeding supports colour intensity in males and reproductive condition in both sexes.
Mating
Nothobranchius krysanovi follows the classic annual Nothobranchius mating strategy. As the seasonal pools fill, males immediately establish loose territories and begin displaying to females. The male's coloration intensifies dramatically: the blue and orange-red bars on the flanks and fins become vivid advertisement signals directed both at rival males and prospective mates. Courtship involves the male positioning himself alongside the female, extending and spreading his fins to maximise the visual impression of the barred pattern.
When a female is receptive, the pair move to soft substrate — mud, detritus, or peat at the pool floor. The male curves his body around the female and the two drive together into the substrate with a brief, vigorous wriggle. This embrace deposits and fertilises one to a small cluster of eggs, which are buried in the substrate by the motion of spawning. The pair resurface and may spawn again immediately or after a short interval. There is no pair bond and no parental care; males will court multiple females over the course of the wet season.
Breeding
The diapausing eggs of N. krysanovi are the survival mechanism that bridges the dry season. Once buried in the substrate, the embryos enter diapause — a state of arrested development that confers resistance to desiccation as the pool dries to cracked mud. At WildNothos-documented temperatures, embryonic development in peat moss spans approximately five to seven months at room temperature before the eggs are ready to hatch. When the rains return and the pool refills, the embryos resume development and hatch rapidly, often synchronising with the rehydration event.
In the hobby, N. krysanovi is bred using the standard peat-spawning method: a shallow layer of boiled, dried, and sieved peat moss or coconut coir is provided as substrate in the breeding tank. After a few weeks of spawning, the peat is removed, gently squeezed to remove free water (not fully dried), packed into a bag or container, and stored dry at room temperature for three to five months. The peat is then re-wetted with soft, slightly acidic water and the fry emerge within hours to a few days. First foods are micro-worm and freshly hatched Artemia nauplii. The fry grow quickly — males colour up within weeks — and the fish can be back in spawning condition within a few months of hatching, reflecting the compressed annual life cycle.
The AKA collection code for this species is MOZ 04-10, indicating Mozambique provenance, and the species has been circulated in the killifish hobby. Its small size makes it manageable in modest aquarium setups compared with larger Nothobranchius.
In the aquarium
Nothobranchius krysanovi is a rewarding annual killifish for the specialist keeper, combining vivid coloration with a manageable size and a straightforward breeding protocol. A species or pair tank of 10–15 US gal is sufficient; males are aggressive toward one another and should not be housed together unless the tank is large with visual barriers. A trio of one male and two females distributes male attention and is a common working arrangement in the hobby.
Water conditions should reflect the near-neutral, warm parameters of the wild habitat: temperature 79–86 °F, pH 6.8–7.4, and moderate hardness are suitable. Regular small water changes maintain quality in the shallow, heavily stocked tanks typical of killifish breeding. A peat or coir substrate layer is provided at all times for spawning, or a separate container of substrate can be introduced for defined collection periods. Dense floating plants and a secure lid (killies can jump) complete the setup.
Because N. krysanovi is short-lived — wild fish rarely survive beyond one rainy season — the keeper's priority is to maintain a productive egg bank. Batches of incubated peat should be staggered so that hatches can be used to replenish the breeding population continuously. The species is available in specialist killifish circles through the AKA and similar associations; obtaining eggs or fry from established keepers is the typical entry point.
Conservation
The IUCN Red List assessed Nothobranchius krysanovi as Vulnerable (criterion B1ab(iii)) in 2018–2019. The assessment reflects the species' restricted range — confined to a cluster of seasonal wetland systems in a small area of coastal Mozambique — and the ongoing degradation of its floodplain marsh habitat. The primary driver is agricultural conversion: the low-lying coastal plains that support the ephemeral pools used by this species are also prime targets for irrigated rice cultivation. Drainage, levelling, and year-round water management eliminate the seasonal drying cycle on which annual killies depend, permanently removing habitat even when the land remains nominally 'wetland'.
The restricted extent of occurrence implied by criterion B1 means that even localised habitat changes have population-level consequences. The species has no buffer of large, stable water bodies and no populations in protected areas known to the original assessors. Its syntopic association with the more widespread N. orthonotus means that the two species' fates are tied in part — where N. orthonotus persists, conditions may still be adequate for N. krysanovi — but this co-occurrence provides no conservation shelter.
In the killifish hobby, the species is maintained by a small number of specialist keepers, primarily in Europe and North America, through AKA-registered strains under the MOZ 04-10 collection code. Ex-situ collections of this kind do not substitute for wild habitat protection but provide a degree of insurance against the extinction of the wild population. Long-term survival of this species depends on the preservation of seasonal floodplain wetlands in the Kwa-Kwa and Licuare basins.