Taxonomy & naming
Charles Tate Regan described this species in 1912 under the name Rivulus strigatus, with a type locality given as Rio da Prata, Pará State, Brazil — placing the type in the greater Amazon basin of eastern Brazil. The authority is presented in parentheses because the species has since been moved from the genus in which it was originally described. Eschmeyer's Catalog of Fishes (Fricke, Eschmeyer & Fong) records the valid combination as Laimosemion strigatum (Regan, 1912).
The transfer to Laimosemion was effected by Wilson J. E. M. Costa in a 2011 phylogenetic and taxonomic study of aplocheiloid killifishes. Costa resurrected Laimosemion and diagnosed the genus on two osteological characters: a well-developed dorsal process of the urohyal and an expanded lateral articular facet of the first hypobranchial. The genus as revised encompasses roughly 24 species distributed across northern South America. Molecular phylogeographic work on aplocheiloid killifishes confirms that Laimosemion strigatum belongs to the Neotropical Rivulidae clade centred on the Amazon and Guiana Shield drainages.
The specific epithet strigatus is the Latin past participle of strigare, meaning 'furrowed' or 'striped', alluding to the lateral colour pattern of horizontal lines or stripes that characterise the species in life.
This fish was long listed as Laimosemion strigatus; Eschmeyer's Catalog of Fishes places the species in Laimosemion, and the current combination Laimosemion strigatum is followed here.
Morphology
Laimosemion strigatum is a slender, laterally compressed rivuline with a maximum recorded standard length of 1.6 in (It Rains Fishes; Frans Vermeulen). The body proportions are typical for the genus: a relatively elongate form, a slightly upturned mouth positioned near the top of the head (an adaptation to surface feeding and egg-laying near the water surface), and a rounded caudal fin. Scales are moderately sized and cycloid.
Colouration in males is characteristically marked with a series of red or reddish-brown horizontal stripes or rows of dots along the flanks against an olive to golden-green background — the pattern the specific epithet references. The unpaired fins often carry red and blue pigment with a pale or hyaline outer margin. Females are less vividly pigmented, showing the lateral striping in a more subdued brownish tone, and lack the intense fin colouration of males. The dorsal fin is set well back on the body, near the caudal peduncle, a configuration common to many rivulines and associated with ambush-style surface predation.
Habitat
Laimosemion strigatum inhabits permanent freshwater environments in the eastern Amazon basin of Brazil. Documented localities include the Anapu River basin in Pará State (Freitas et al. 2019 length-weight study), consistent with the original type locality at Rio da Prata in the same state. It is not a species of ephemeral seasonal pools; the eScholarship dissertation survey (Furness, 2014) explicitly classifies it among non-annual killifishes inhabiting permanent water bodies.
Ecological trait studies in Amazon stream fish assemblages record the species in association with macrophyte beds and vegetated littoral zones of lowland forest streams — habitats that provide the floating plant cover and fine-leaved aquatic vegetation the species uses for egg deposition. Water in such Amazonian streams is typically warm, soft, and mildly acidic, though precise pH and hardness measurements specific to Laimosemion strigatum collection sites are not well documented in the available literature; the species is best regarded as a soft, warm-water fish appropriate to Amazonian lowland conditions.
Feeding
Like most rivulines, Laimosemion strigatum is a micro-predator that feeds near the water surface and in the upper water column. The upturned mouth morphology is consistent with targeting small invertebrates — aquatic insect larvae, microcrustaceans, small worms, and terrestrial insects that fall onto the water surface — as the primary prey in the wild.
In captivity the species adapts readily to a varied diet of small live and frozen invertebrates: Daphnia, Artemia nauplii, bloodworm (chironomid larvae), micro-worms, and white worms all constitute suitable foods. Dry foods in the form of fine flake or micro-pellets are accepted alongside live and frozen items, though a diet heavy in live or frozen invertebrates maintains condition and colour more effectively. As with all small killies, overfeeding should be avoided — the fish are active and efficient feeders and excess food quickly compromises water quality in the small, densely planted tanks typically used for the species.
Mating
Laimosemion strigatum is a non-annual killifish and a plant or mop spawner — it does not bury eggs in substrate peat for a dry-season diapause. Instead, pairs or small groups engage in repeated spawning acts near the water surface and among fine-leaved vegetation or fibres of a floating spawning mop, depositing a small number of adhesive eggs at each encounter over an extended period.
Males are territorial and can be aggressive toward one another, so housing arrangements should be considered carefully. In sufficient space, a colony of multiple males and females can coexist, but a single male kept with one or more females minimises aggression-related stress and injury. Conditioning on high-protein live foods — Daphnia, Artemia, bloodworm — stimulates spawning activity. The spawning embrace is brief; the pair press flanks and deposit eggs simultaneously among plant fibres or mop strands.
Breeding
Spawning by Laimosemion strigatum is continuous and incremental: a conditioned pair deposits 5 to 15 eggs per day on a floating mop or fine-leaved aquatic or artificial plants (It Rains Fishes, Frans Vermeulen). Eggs are approximately 0.06 in in diameter, amber in colour, and adhere to the spawning substrate. Unlike annual species, the eggs require no drying or peat burial — they incubate directly in water at the ambient temperature of the breeding tank, hatching after approximately 14 days.
Fry are small at hatching but free-swimming immediately and accept Artemia nauplii as first food from the outset. Growth is steady at warm temperatures; juveniles reach sexual maturity in 4 to 5 months. Adults in captivity are relatively long-lived for a killifish, surviving up to three years under good conditions. Because spawning is daily and ongoing, the most productive method for raising fry is to check the mop regularly — every two to three days — picking out eggs and incubating them separately in shallow containers to prevent predation by the adults. The species is rated easy to breed by experienced killifish keepers.
In the aquarium
Laimosemion strigatum is an excellent small killifish for the specialist: tractable, continuously spawning, and rewarding to observe at close range in a suitably furnished tank. A 8–11 US gal aquarium densely planted with fine-leaved species (Ceratophyllum, Myriophyllum, Java moss) supplemented with one or two floating spawning mops provides the cover and spawning sites the fish needs. Dark substrate — fine gravel over a peat layer or peat moss mixed into the substrate — enhances the colours of males noticeably. Floating cover is beneficial both as refugia and as spawning sites.
The species is an accomplished jumper, and a tight-fitting lid with no gaps is essential. Water should be soft to moderately soft and slightly acidic to neutral, warm (72–79 °F is a safe working range for an eastern Amazonian species), and well-filtered but with gentle flow — strong current is not appropriate. Laimosemion strigatum can be kept in a species tank as a colony or as a pair; it is too small and delicate to be housed with larger or boisterous fish. Compatible tankmates, if any, should be similarly sized peaceful species. Regular small partial water changes maintain the quality that the species — and its eggs — require.
The species has a modest but steady presence in the killifish hobby, traded among Killifish Association members and specialist importers rather than through mainstream retail channels. It is manageable for a hobbyist with some prior killifish experience.
Conservation
Laimosemion strigatum has not been formally assessed by the IUCN Red List and carries no conservation status designation. Its documented range centres on the Anapu River basin of eastern Pará State — a region within the so-called 'arc of deforestation' at the agricultural frontier of the Brazilian Amazon, where cattle ranching, soy cultivation, and illegal logging have driven some of the highest deforestation rates in Amazonia over the past three decades.
As a species of permanent lowland forest streams associated with macrophyte beds and vegetated littoral habitats, Laimosemion strigatum is vulnerable to the sediment loading, stream channel simplification, and riparian vegetation clearance that accompany land conversion. Small-bodied killifishes with restricted ranges are disproportionately susceptible to localised habitat loss; if the species' effective range is limited to a handful of drainages within Pará, even moderate habitat degradation could reduce populations significantly. A formal IUCN assessment would require more comprehensive distribution data than currently available, but precautionary concern is warranted given the habitat pressures operating across its known range.