Taxonomy & naming
The species was described by the Austrian zoologist Rudolf Kner in 1863 as Astronotus altifrons, on material from the rivers of Pacific Costa Rica and Panama. The epithet altifrons ('high forehead') refers to the steep, raised profile of the nape. Through the twentieth century it passed, like its relatives, through Cichlasoma, then Amphilophus and Astatheros, before being placed in the new genus Cribroheros when Říčan and colleagues (2016) restricted Astatheros to its single Pacific type species and erected Cribroheros for the substrate-sifting heroines. Cribroheros belongs to the heroine cichlids (tribe Heroini), the genus name referring to the sieve-like sifting feeding of the group. The fish is still seen in older references as 'Cichlasoma' or 'Amphilophus altifrons'.
Morphology
Cribroheros altifrons is a small cichlid, FishBase reporting a maximum of about 5 in SL. Its most distinctive feature is the high, rounded forehead and steep nape that name the species. The body is silvery-grey to olive or tan, marked with a row of dark blotches forming a broken midlateral line and a dark spot at the caudal-base, with the barring and a darker mask strengthening with mood and breeding condition; fine spangling and reddish fin margins appear in good colour. The mouth is sub-terminal, suited to sifting soft substrates. Sexual dimorphism follows the heroine pattern: mature males grow somewhat larger and develop more produced, pointed dorsal and anal fin tips, while ripe females are rounder-bodied and may show more contrasting flank markings when breeding.
Habitat
Cribroheros altifrons is a Pacific-slope species of southern Central America, occurring in the rivers of southeastern Costa Rica (the Térraba / Grande de Térraba drainage) and western Panama (the Chiriquí drainage). It inhabits warm lowland and foothill rivers and their pools and slower reaches, over substrates of sand, mud and gravel where it can sift for food, among rock and submerged wood. FishBase cites a temperature range of roughly 72–84 °F and neutral-to-alkaline water (pH from about 7.0 upward). It occupies the warm, productive lowland and lower-foothill waters of the southern Pacific versant, a region with its own distinct cichlid fauna of which this small sifter is a characteristic member.
Feeding
Cribroheros altifrons is a benthic omnivore and substrate-sifter, FishBase placing it at a trophic level near 2.9 — toward the lower, more herbivore- and detritivore-leaning end of the genus. It feeds on aufwuchs (the film of algae and micro-organisms on hard surfaces) and on aquatic invertebrates, including various aquatic insects, taking mouthfuls of soft sediment and sorting out the edible fraction in the winnowing manner that gives the genus its name. The sub-terminal mouth suits this bottom- and surface-grazing diet. In its river communities it functions as a small generalist forager of the substrate and aufwuchs zone.
Mating
As a heroine cichlid, Cribroheros altifrons is a monogamous, biparental species that pairs and defends a joint breeding territory. Pair formation follows the standard cichlid courtship — lateral display, fin-flaring, jaw contact and cooperative cleaning of a spawning surface — with the pair intensifying in colour and becoming territorial as spawning nears. As a small species it is only moderately aggressive, but a bonded pair defends its patch firmly during the breeding cycle. Pairs select and clean a hard surface in advance of spawning.
Breeding
Cribroheros altifrons is a biparental open substrate spawner. The female lays a clutch of adhesive eggs on a cleaned hard surface, and both parents share extended care: the female tends and fans the eggs while the male guards the territory, the roles converging as the brood develops; once free-swimming the fry are guarded as a school by both parents, who lead them over the soft bottom where they begin to forage. Clutch sizes in so small a fish are modest by genus standards (likely one to a few hundred eggs). Wild breeding behaviour is not exhaustively documented, but it follows the well-established biparental-substrate-spawner pattern of the group.
In the aquarium
Cribroheros altifrons is an uncommon aquarium fish, kept mainly by specialists in southern Central American cichlids. Its small adult size means modest space requirements — a tank of around 40–65 US gal suits a pair, with more for companions. Water should be warm (72–84 °F) and neutral to moderately alkaline (pH about 7.0–8.0); strong filtration and regular water changes keep it in condition. As a substrate-sifter it should be given a bed of fine sand, which lets it feed naturally and spares its gills the abrasion of gravel; furnish with rock and driftwood forming broken sight-lines and a flat stone as a spawning site, with hardy anchored plants. As a small, moderately aggressive species it mixes reasonably with other robust fish of similar size and water needs, with breeding pairs given space at spawning time. Feeding is straightforward — a quality sinking pellet plus frozen and live invertebrate foods and some vegetable or algae-based matter to match its aufwuchs-leaning natural diet. The main husbandry note is to provide sand and a varied, partly vegetable diet.
Conservation
The IUCN Red List classifies Cribroheros altifrons as Vulnerable, a more concerning category than the Least Concern rating this species carried previously. It occurs across Pacific-slope drainages of southern Costa Rica and western Panama, where the lowland and foothill rivers it depends on face the region's familiar pressures — deforestation and agricultural runoff (including from banana and pineapple cultivation in this part of Costa Rica), water extraction, sedimentation and introduced species. It carries no CITES listing. As with all of the genus, the health of its river system is the key determinant of its long-term status.