Taxonomy & naming
Guianacara dacrya was described in 2011 by Jessica H. Arbour and Hernán López-Fernández in the journal Neotropical Ichthyology, on material gathered during the Royal Ontario Museum and University of Toronto surveys of Guyanese rivers. The holotype (UG/CSBD 1666, ex ANSP 177130), a 3 in SL fish, was taken at Water Dog Falls on the Burro Burro River in the Essequibo drainage, with a large paratype series distributed among the ANSP, AUM, INPA and ROM collections. It belongs to the genus Guianacara, a compact radiation of 'bandit' or 'banded' acaras endemic to the Guiana Shield, and specifically to the nominotypical subgenus Guianacara, which is diagnosed by two supraneural bones, produced lappets on the front dorsal-fin spines, and a midlateral bar. The genus sits in the eartheater tribe Geophagini of the subfamily Cichlinae. Arbour and López-Fernández separated dacrya from every congener by two characters of fine anatomy: a distinctive infraorbital stripe that fades across the upper cheek in larger fish while staying dark over the preopercle and interopercle, and a uniquely shaped, partly toothless laminar expansion on the side of the lower pharyngeal jaw plate. The species has accumulated no synonyms since its description and remains valid in subsequent checklists of Guiana Shield cichlids. It has no established English common name; in the hobby it is sold, when it appears at all, simply as a Guianacara or 'bandit cichlid', and those trade labels are best left in quotation marks rather than elevated to a settled name.
Morphology
This is a small, fairly deep-bodied and laterally compressed cichlid that reaches about 4.5 in in standard length, with the type series running to roughly 3.5 in SL. The body is a warm tan to olive-brown crossed by a pattern of about nine darker vertical bars; the most conspicuous of these is the midlateral bar, a narrow black-to-brown band that descends from the base of the seventh to ninth dorsal spines. In Guianacara dacrya that bar is unusually thin — only about three scales wide where it crosses the upper lateral line, narrowing to one and a half or two scales below it — which is one of the features that separates it from the broader-barred congeners. When a midlateral spot is visible it is small and round and sits on and just below the upper lateral line. The diagnostic mark is on the face: a dark infraorbital stripe runs from beneath the eye toward the throat, growing fainter across the cheek in adults over about 2 in SL but staying black on the preopercle and interopercle, where it can broaden and round into a tear-drop shape — the 'weeping' look that names the fish. The three front dorsal spines and their lappets keep their juvenile dark coloration into adulthood, and white spots dot both the spiny and soft parts of the dorsal fin; the dorsal, anal and occasionally the caudal fin draw out into short filaments in mature fish. The describers reported no apparent sexual dimorphism, so the sexes are best told apart only by venting or by a ripe female's fuller body rather than by reliable external markings.
Habitat
Guianacara dacrya is a fish of the upland Guiana Shield, recorded from south-western and central Guyana from the Potaro River in the north to the Yukanopita Falls in the south, throughout the Essequibo basin — including its main tributaries the Rupununi, Siparuni and Kuyuwini — and across the low Rupununi divide into the Takutu and Ireng rivers, which drain to the rio Branco and so into the upper Amazon. The describers regarded northern-Brazilian records from the rio Uraricoera in the Branco basin as probable but not yet confirmed by sampling. It is most typical of clearwater streams with a moderate current, where it lives over sandy bottoms strewn with larger rocks; juveniles gather in great numbers in pebble-and-rock riffles over sand, often among leaf litter. During the wet season it also occupies the seasonally flooded lagoons of the Rupununi savanna, where there is no current at all. The water it was collected in is warm, well oxygenated and extremely soft: field measurements in the Rupununi and Pirara (Ireng) drainages gave temperatures of 77–83 °F, dissolved oxygen of 5.3 to 6.56 mg/L, and conductivity of only 27.1 to 34.5 µS/cm — the dilute, near-ion-free water characteristic of Guiana Shield uplands. These are shallow stream and shoreline habitats; depth was not given as a formal range but the recorded biotopes are wadeable, on the order of the upper metre or two of the water column.
Feeding
No dedicated gut-content study of Guianacara dacrya has been published, so its diet is inferred from its anatomy, its habitat, and the habits of its close relatives. FishBase places it at a trophic level of about 3.3, the value expected of a small benthic omnivore rather than a specialist predator or a strict herbivore. The genus belongs to the eartheaters (Geophagini), and like other Guianacara it is a bottom-oriented forager that picks and sifts through sand, fine gravel and leaf litter for small invertebrates — aquatic insect larvae, microcrustaceans and worms — together with organic detritus and incidental plant and algal material. The modified lower pharyngeal jaw that helped diagnose the species is part of the pharyngeal mill all cichlids use to process such prey. In its home streams it functions as one of the small benthic insectivore-omnivores of the sand-and-rock community, working the substrate alongside other shield fishes rather than competing as an open-water hunter.
Mating
The reproductive behaviour of Guianacara dacrya has not been described from the wild, and the species is uncommon enough in aquaria that detailed first-hand spawning accounts are scarce; what can be said is drawn from the well-documented habits of the genus, which are consistent across its members. Guianacara are biparental cichlids that form pairs and defend a shared territory around a chosen breeding site. Pair formation is preceded by mutual display, with the contrasting eye-mask and flank markings used in signalling, and a bonded pair will jointly hold and defend a patch of substrate. Keepers of the genus note that pairs are best formed by letting fish choose their own mates from a group, since arbitrarily paired adults can be aggressive toward one another, and that a harem arrangement — one male to several females, each holding a small territory — can also work. Outside of breeding the fish are comparatively peaceful and somewhat retiring, sticking close to rock and root cover.
Breeding
Direct breeding data specific to Guianacara dacrya are not available, but the genus's mode is well established and there is no reason to think dacrya departs from it. Guianacara are substrate-spawning, cave-and-cleft brooders: a pair cleans a sheltered surface — the underside of a rock, a crevice, or a cavity they excavate beneath stones — and the female deposits her eggs there while the male defends the surroundings. Both parents tend the brood, fanning and guarding the eggs and then shepherding the free-swimming fry, which are led out to forage over the substrate and herded back to cover at any disturbance. Egg counts for the genus are modest, on the order of a few dozen to around a hundred eggs per spawn (a genus-typical figure rather than a measured count for dacrya), and hobbyist reports note that the eggs are greenish. The fish are best regarded as careful biparental cave spawners whose success in captivity depends mainly on a compatible, self-selected pair and the soft, warm water of their home streams; given those conditions, broods are raised by the parents in the normal cichlid fashion.
In the aquarium
Guianacara dacrya is only occasionally available to hobbyists, and it is far less often kept than the better-known Guianacara sphenozona or Guianacara owroewefi that move through the trade as generic 'bandit acaras', so published husbandry is thin and largely generalised from the genus. The species stays modest in size — around 4.5 in — so a pair can be housed in a tank of roughly 47 in length (about 55–65 US gal), with more space needed if other cichlids are present or if a harem of several females is kept. The single most important point is to reproduce the water it comes from: warm, very soft, well-oxygenated clearwater. Aim for 77–84 °F, a pH on the acidic-to-neutral side (about 5.5–7.0), and genuinely low hardness and conductivity, with good circulation and high dissolved oxygen to echo the shield streams. A sand or fine-gravel substrate is essential, because these are eartheaters that work the bottom; furnish the tank with smooth rocks, driftwood and a few caves or rock clefts to serve as spawning sites and retreats, and keep some current moving across the sand.
Temperament is manageable but not trivial. Away from breeding the fish are relatively peaceful and even shy, and they coexist well with calm, similarly sized South American tankmates such as tetras, pencilfish, peaceful catfishes and other small-to-medium cichlids that will not bully them. The friction is intraspecific: a breeding pair becomes territorial, and unpaired or mismatched adults can quarrel, so the proven approach is to grow out a group and let pairs form on their own, or to run a one-male harem in a tank large enough that subordinate females can keep their distance. Feeding is straightforward — a varied diet of sinking pellets, frozen and live foods such as bloodworm, daphnia and brine shrimp, with the bottom-foraging behaviour catered to by offering food that reaches the substrate. The common mistakes are keeping the fish too hard and alkaline, skimping on the sandy bottom and cover, and forcing incompatible adults together; get the soft warm water, the sand and the social setup right and it is an undemanding, attractive shield cichlid.
Conservation
The IUCN Red List assesses Guianacara dacrya as Least Concern, in an assessment by R.G. Frederico dated 18 November 2020. The species is reasonably widespread across the Essequibo and Branco-headwater drainages of the Guiana Shield and is described as abundant within the Essequibo basin, so it is not considered threatened at present and it carries no CITES listing. Its range, however, lies largely in remote upland country whose rivers face the pressures common to the shield: gold-mining and the mercury and sedimentation that come with it, deforestation, and the prospect of altered flow regimes — none of them documented as a specific danger to this fish, but all part of the backdrop in the region. As a clearwater specialist tied to soft, low-conductivity streams, it would be more exposed than a habitat generalist to local degradation of water quality, which is the main reason to keep an eye on its strongholds even while its overall status remains secure.