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Mouthbrooder

A mouthbrooder is any fish species that exhibits mouthbrooding, a specialized form of parental care in which one or both parents incubate fertilized eggs or newly hatched fry within the buccal cavity of the mouth, providing protection and oxygenation until the offspring are capable of independent swimming.^[1] This behavior, observed in at least nine families of teleost fishes, evolved independently multiple times and typically lasts 10–14 days, during which the brooding parent ceases feeding to avoid ingesting the brood.^[1]^[2] Mouthbrooding is particularly prevalent among cichlid fishes of the family Cichlidae, especially in African Great Lakes such as Lakes Malawi, Tanganyika, and Victoria, where nearly all species employ maternal mouthbrooding as the primary reproductive strategy.^[3] In these systems, females typically collect 30–1,500 eggs (depending on body size) post-fertilization and retain them in the mouth, performing rhythmic pumping and churning motions to ventilate the eggs with oxygen-rich water while preventing fungal growth or suffocation.^[1]^[2] Paternal mouthbrooding occurs in other groups, such as cardinalfishes (family Apogonidae) and certain catfishes (e.g., cuckoo catfish, Synodontis multipunctatus), where males brood the eggs, sometimes incorporating parasitic strategies like laying eggs in the nests of mouthbrooding cichlids.^[2] Biparental mouthbrooding, though rarer, has been documented in some cichlid species.^[3] The physiological demands of mouthbrooding impose significant costs on the parent, including energy deficits from fasting that reduce ovarian development and alter hormone levels, such as decreased circulating estrogens and androgens in brooding females.^[2] Despite these trade-offs, the strategy enhances offspring survival rates by shielding vulnerable eggs and fry from predators and environmental hazards, contributing to the evolutionary success of mouthbrooding lineages in diverse aquatic habitats.^[1] Notable examples include the Nile tilapia (Oreochromis niloticus), an important aquaculture species where mouthbrooding supports rapid population growth.^[1]^[3]

Overview and Definition

Definition

Mouthbrooding, also known as oral or buccal incubation, is a reproductive strategy employed by certain fish species as a form of parental care, in which an adult fish—typically the female, though males in some cases—holds fertilized eggs or early-stage larvae in its oral cavity until they hatch or achieve independence. This internal brooding protects the developing offspring from predators, adverse water conditions, and other threats by maintaining them in a secure, oxygenated environment within the parent's mouth. The duration of mouthbrooding varies by species but often lasts from several days to weeks, during which the parent provides ventilation by periodically opening and closing its mouth to circulate water over the brood.^[2]^[1] This method contrasts sharply with other forms of parental care in fish, such as substrate guarding, where eggs are deposited and defended on surfaces like rocks or plants, or nest building, which involves constructing protective structures for external incubation. In mouthbrooding, eggs are typically deposited briefly externally for fertilization and then immediately ingested and retained by the parent, often minimizing the need for extended territorial defense of a spawning site. This distinction highlights mouthbrooding as an adaptation for species in high-predation environments, particularly among cichlids and other teleosts, where external brooding would expose vulnerable eggs to greater risks.^[4]^[5] Physiologically, mouthbrooding fish exhibit adaptations suited to this demanding role, including an enlarged buccal cavity capable of accommodating the brood without compromising essential functions like respiration. The parent's gills may shorten or adjust in structure to balance space for the eggs with oxygen exchange, creating a trade-off between brooding capacity and feeding efficiency. A key adaptation is the near-complete cessation of feeding during the brooding phase, as swallowing movements could harm the offspring; this fasting often results in significant body mass loss and delayed subsequent reproductive cycles.^[2]^[6]^[7] The behavior has long been recognized, with ancient Egyptian artifacts from as early as 2000 BCE depicting mouthbrooding tilapia as symbols of rebirth and fertility, indicating early human observation of this strategy in cichlids. Scientific documentation of mouthbrooding in cichlids emerged in the 19th century, as naturalists explored African freshwater systems and described the reproductive habits of species like those in the Great Lakes, laying the foundation for modern studies on fish parental care.

Types of Mouthbrooding

Mouthbrooding in fish is broadly categorized into egg brooding and larval brooding based on the developmental stage at which the parent assumes oral incubation. In egg brooding, also known as ovophile mouthbrooding, the parent—typically the female in cichlids—collects fertilized eggs immediately after spawning, holding them in the mouth until hatching without any external attachment to a substrate.^[8] This form is common among maternal mouthbrooders in the Cichlidae family, where eggs are often laid briefly in a pit or on a cleaned surface (substratum brooding variant) before being swiftly ingested for protection.^[9] In contrast, non-substratum egg brooding involves direct transfer of eggs into the parent's mouth during spawning, minimizing exposure, as observed in some species where fertilization occurs orally.^[10] Larval brooding, or larvophile mouthbrooding, occurs post-hatching, with the parent ingesting newly hatched larvae or early fry until they can feed independently, often after an initial period of substrate guarding.^[11] This delayed strategy is prevalent in certain cichlids like those in the genus Geophagus, where eggs are laid and guarded on the substrate until the larvae become mobile, at which point they are taken into the mouth.^[12] The distinction between these types reflects adaptations to environmental pressures, with egg brooding providing earlier protection against predation and larval brooding allowing for initial external development.^[10] Gender roles in mouthbrooding vary significantly across species, influencing the type and execution of care. Most cichlids exhibit maternal mouthbrooding, where females dominate egg or larval incubation, as seen in haplochromine species from African Great Lakes.^[10] In contrast, paternal mouthbrooding prevails in families like Apogonidae (cardinalfishes), where males hold eggs or larvae; examples include Sarotherodon melanotheron, which broods for 14–18 days.^[13] Biparental involvement, though less common, occurs in some cichlids, with both parents sharing duties sequentially or cooperatively.^[14] The duration of mouthbrooding typically spans 10–21 days in cichlids, varying by species, egg size, and factors like water temperature and oxygen levels; for instance, Astatotilapia burtoni females brood for about 14 days. In cardinalfishes, paternal brooding can extend longer to ensure larval independence.^[13] An analogous but distinct form is pouch brooding in syngnathids like seahorses (Hippocampus) and pipefishes (Syngnathus), where males incubate eggs in a specialized abdominal or tail pouch rather than the mouth, providing similar protective functions such as oxygenation and nutrient transfer.^[15] This viviparous-like strategy evolved independently and differs from true buccal incubation by involving a dedicated organ.^[15]

Behavioral Aspects

Parental Care Strategies

In many maternal mouthbrooding cichlids, the female releases eggs midwater or on a substrate, immediately taking them into her mouth where fertilization occurs orally as she inhales sperm released by the male. In species like the Nile tilapia, eggs are deposited on a substrate, fertilized externally by the male, and then collected by the female. In paternal mouthbrooders, the male collects the fertilized eggs into the buccal cavity by scooping or nuzzling. This uptake ensures protection from predators and environmental hazards right from the outset of development.^[16]^[3] During the incubation period, which can last from one to several weeks depending on species and temperature, the parent employs maintenance behaviors to support offspring viability. Aeration is achieved through rhythmic mouth movements or buccal churning, which circulates oxygenated water over the eggs and larvae while also facilitating gas exchange for the brood. Additionally, parents occasionally expel the brood briefly and re-ingest it to remove debris, fungal growth, or dead eggs, thereby maintaining hygiene and preventing infection. These actions, though essential, impose continuous physical demands on the parent.^[17]^[18]^[19] The physiological costs of mouthbrooding are substantial, primarily stemming from voluntary fasting and respiratory challenges. Parents cease or greatly reduce feeding to avoid ingesting offspring, leading to significant energy depletion and body mass loss; in some cichlid species, this can reach up to 14% over the brooding period. Oxygen deprivation arises as the expanded buccal cavity impairs normal gill ventilation, elevating metabolic stress and reducing the parent's aerobic capacity, particularly under hypoxic conditions. These trade-offs highlight the high investment in parental care.^[2]^[18]^[20] Offspring release occurs when larvae have sufficiently developed, typically after yolk sac absorption and the onset of independent feeding capability. Timing is often cued by internal developmental cues but can be influenced by external stimuli, such as deteriorating water quality or low oxygen levels, prompting premature expulsion to safeguard survival. In species exhibiting biparental care, such as certain tilapias, both parents may share incubation duties sequentially or cooperatively, intensifying care through divided labor and extended protection. This variation in intensity underscores the adaptability of mouthbrooding strategies across taxa.^[21]^[18]^[22]

Species-Specific Variations

Mouthbrooding behaviors exhibit notable variations among cichlid species, particularly between those from African rift lakes and Neotropical regions. In African rift lake cichlids, such as those in Lake Malawi, females typically engage in prolonged mouthbrooding lasting 2 to 3 weeks, during which the eggs hatch and juveniles periodically exit the mouth for feeding before returning for protection.^[23] In contrast, Neotropical cichlids often display shorter brooding periods; for instance, in species like Bujurquina vittata, brooding duties are shared after an initial 5 days by the male, with the larval phase concluding in about 5 days at 26°C.^[24]^[25] Cardinalfishes demonstrate a distinct paternal mouthbrooding strategy, where males incubate fertilized eggs in their mouths for approximately 3 to 4 weeks until hatching, followed by an additional period holding the larvae.^[26] Upon release, males often expel the young into sheltered crevices at night to minimize predation risk, with the process timed around sunset in some species like Apogon niger.^[27] In betta fish, mouthbrooding integrates with bubble nest construction in certain species, where males occasionally hold eggs or fry in their mouths as a supplementary protective measure alongside nest-based care.^[28] This hybrid behavior reflects an evolutionary transition from bubblenesting, allowing flexibility in brooding methods depending on environmental conditions or threats.^[29] Environmental factors, such as temperature, significantly influence brooding duration across species. For example, in Nile tilapia (Oreochromis niloticus), mouthbrooding typically lasts 10 to 14 days at around 28°C, with higher temperatures accelerating hatching but potentially shortening overall incubation if exceeding optimal ranges.^[30]^[31] Behavioral anomalies, including premature release of broods, can occur under stress, as seen in mouthbrooding cichlids and bettas where high disturbance leads to expulsion or consumption of eggs and fry to alleviate physiological strain.^[32]^[33] In such cases, inexperienced parents or community tank conditions exacerbate the risk, resulting in reduced offspring survival.^[34]

Evolutionary and Ecological Role

Evolutionary Origins

Mouthbrooding is thought to have originated within perciform fishes during the early Tertiary period, around 46-65 million years ago, aligning with the initial diversification of the Cichlidae family in the Eocene.^[35] This timing corresponds to the emergence of cichlids as a distinct lineage, where mouthbrooding likely evolved as an advanced form of parental care amid increasing ecological pressures in freshwater habitats.^[36] The behavior's association with the broader cichlid radiation underscores its role in enabling rapid speciation and adaptation in diverse aquatic environments. Convergent evolution has led to the independent development of mouthbrooding in multiple unrelated fish groups beyond cichlids, such as the perciform Apogonidae (cardinalfishes, where males brood eggs) and certain siluriform catfishes (e.g., Ariidae). These parallel origins, documented across at least nine teleost families, suggest that mouthbrooding arose as a response to similar selective pressures for offspring protection in predator-rich settings.^[37] The genetic underpinnings of mouthbrooding involve hormonal regulation, particularly prolactin, which modulates brooding instincts and parental behaviors in species like the biparental cichlid Astatotilapia burtoni.^[38] Prolactin levels rise during brooding phases, inhibiting feeding and promoting care, thereby linking physiological and behavioral adaptations.^[2] Direct fossil evidence for mouthbrooding is lacking, as the behavior cannot be preserved in the rock record; instead, its evolutionary history is inferred from morphological traits in extant species, such as expanded buccal cavities and reduced feeding structures in brooding adults.^[39] Evolutionary transitions to mouthbrooding appear to have occurred from ancestral external guarding strategies, including substrate brooding, with phylogenetic analyses indicating at least 10 independent shifts within cichlids alone.^[40]

Advantages and Disadvantages

Mouthbrooding provides significant advantages in offspring survival by offering direct protection from predators and environmental hazards. In field studies of open-water spawning cichlids from Lake Tanganyika, such as Cyprichromis leptosoma and C. microlepidotus, egg survival rates during brooding averaged 77.2% and 88.8%, respectively, due to the physical shelter of the parent's buccal cavity, which minimizes predation and dispersal losses.^[41] This protection also extends to pathogens, as the parent's mucus and oxygenation behaviors reduce exposure to waterborne infections compared to externally laid eggs.^[42] Despite these benefits, mouthbrooding imposes substantial costs on the brooding parent, primarily through reduced foraging and elevated energy demands. Brooding females typically cease or drastically limit feeding for 2-4 weeks, leading to significant body mass loss—up to 20-30% in some cichlid species—and reliance on stored reserves, which delays ovarian recrudescence and subsequent spawning.^[2] Additionally, the confined environment can foster fungal infections on eggs if parental health declines, as opportunistic fungi like Saprolegnia colonize weakened or dying embryos within the mouth cavity.^[43] Increased metabolic stress from hypoxia and immune suppression further exacerbates these risks during brooding.^[44] These costs result in key trade-offs, including higher per-clutch investment but fewer reproductive cycles per season. Mouthbrooders produce smaller clutch sizes of larger, yolk-rich eggs to compensate for extended care, limiting females to 1-2 broods annually versus multiple in non-brooding species, which aligns with life-history strategies in resource-limited habitats.^[3] Ecologically, mouthbrooding enhances population stability in predator-dense environments like the African Great Lakes, where it buffers against high juvenile mortality and supports sustained diversity in species-rich assemblages such as Lake Tanganyika's cichlid flocks.^[45] Comparative field data indicate hatch rates around 70-90% for mouthbrooders versus 40-60% for substrate-spawning cichlids in similar settings, underscoring the strategy's role in maintaining viable populations amid intense predation pressure.^[46]

Applications in Aquaculture

Benefits for Fish Farming

Mouthbrooding species, particularly tilapia (Oreochromis spp.) and certain cichlids, offer significant advantages in aquaculture due to their natural parental care behaviors, which enhance fry survival rates compared to species requiring artificial incubation. By incubating eggs and fry in the parent's mouth, these fish protect offspring from predators and environmental stressors, leading to higher hatching success and reduced early-stage mortality without the need for intensive hatchery interventions.^[47]^[48] This natural process minimizes labor costs associated with manual hatching and rearing, allowing farmers to allocate resources more efficiently toward grow-out phases.^[49] Tilapia, as a prominent mouthbrooding species, is one of the most important in global aquaculture production, with farmed output reaching approximately 7 million metric tons in 2024.^[50] Their suitability stems from rapid maturation and prolific reproduction, enabling scalable seed production that supports commercial operations in diverse environments. Economically, this translates to lower overall mortality costs—often below 10-20% in well-managed systems—and faster grow-out to market size (typically 6-8 months), boosting profitability for small-scale and industrial farms alike.^[51]^[47] Environmentally, mouthbrooding aligns with sustainable farming by mimicking natural reproductive cycles, reducing reliance on synthetic hormones or feeds for broodstock management and promoting biodiversity-friendly practices in integrated systems.^[49] In African contexts, tilapia aquaculture has thrived since the 1970s, exemplified by Egypt's expansion from research trials in the 1950s to over 1.1 million tons of tilapia annually by 2023, providing essential protein and income for rural communities while leveraging local water resources.^[52]^[53] Similar successes in Kenya and Nigeria highlight how mouthbrooding facilitates low-input farming, contributing to food security across the continent. Projections indicate global tilapia production will reach about 7.3 million tons in 2025, though challenges such as disease management in major producing countries continue to influence growth.^[54]

Cultivation Techniques

In aquaculture, cultivation of mouthbrooding fish, such as Nile tilapia (Oreochromis niloticus), often employs hapas—fine-mesh net enclosures suspended in ponds or tanks—to facilitate natural spawning and brooding while protecting eggs and fry from predation and dispersal. These hapas, typically measuring 1x1x1 m or larger (e.g., 40 m²), are stocked with mature broodstock at densities of 6 fish per m² and sex ratios of 3 females to 1 male, allowing females to mouthbrood eggs for 10-15 days before releasing fry directly into the enclosure for easy collection.^[55]^[30] To synchronize brooding cycles and enhance spawning efficiency, hormone induction is commonly applied using agents like Ovaprim (a synthetic GnRH analog combined with a dopamine inhibitor) or carp pituitary extract, administered via intramuscular injection at doses of 0.5-1.0 mL/kg body weight for females. These treatments promote ovulation within 6-12 hours, enabling timed mouthbrooding without disrupting the natural incubation process, and have been shown to increase spawning frequency in controlled setups compared to untreated groups.^[56]^[57] Post-brooding, fry are promptly separated from adults and graded by size (e.g., stocking at 2,500 fry/m² initially, then reducing to 1,500/m² after 7-10 days) in dedicated nursery hapas or tanks to minimize cannibalism, which can reach 30-35% under suboptimal feeding or density conditions. This management involves feeding high-protein diets (40-50% protein) 6-8 times daily from yolk-sac absorption, achieving survival rates above 90% when water quality is maintained (e.g., dissolved oxygen >5 mg/L).^[30]^[58]^[59] Challenges arise with non-brooding or low-performance strains, where females may release eggs prematurely or exhibit reduced parental care; these are addressed through selective breeding programs targeting reproductive traits, such as the Genetically Improved Farmed Tilapia (GIFT) strain, which enhances brooding reliability and overall seed quality via multi-generation selection.^[60]^[61] Optimized techniques in hapa systems can yield 1,000-2,000 viable fry per female per brooding cycle, depending on broodstock size (e.g., 200-500 g females) and nutrition, supporting scalable production of up to 10 million fry monthly from large operations.^[55]^[62]^[63]

Interactions with Brood Parasites

Parasitic Exploitation

Mouthbrooding fish, particularly cichlids in African rift lakes, are vulnerable to brood parasitism by the cuckoo catfish Synodontis multipunctatus, the only known obligate vertebrate brood parasite outside of birds. This species employs a cuckoo strategy, where groups of male and female catfish synchronize spawning with host cichlids, intruding on the spawning site to scatter their eggs among the host's clutch while simultaneously consuming some host eggs. The host female, driven by her mouthbrooding instincts to retrieve and incubate stray eggs, inadvertently takes up the catfish eggs into her buccal cavity alongside her own.^[64] The mechanism relies on exploiting the host's parental response to scattered offspring rather than visual or chemical mimicry, as catfish eggs differ markedly in size, shape, and appearance from those of cichlids—typically spherical and 2 mm in diameter compared to the larger, oval 4.5 mm eggs of hosts like Simochromis diagramma. Catfish embryos hatch approximately three days earlier than host eggs, at around 2 days post-fertilization, allowing the larger, predaceous catfish larvae (with wider jaws and more teeth adapted for predation) to consume the newly hatching cichlid young upon their release from the mouth. This predation often results in the complete elimination of the host's brood in parasitized clutches.^[64]^[65] Notable examples include parasitism of Simochromis diagramma and Cyprichromis coloratus in Lake Tanganyika, where catfish groups actively disrupt spawning to deposit 5–10 eggs per intrusion, leading to multiple parasite offspring per host brood in successful cases. In affected broods, host offspring survival is typically reduced to near zero, though rare mixed broods may occur if rejection behaviors intervene early; overall, this can diminish host reproductive success by up to 100% in parasitized instances, with median parasite yields of 6–7 young per event. Recent studies indicate low incidence of cannibalism among multiple parasitic embryos, enhancing overall parasite success.^[64]^[66]^[67]^[67] This form of parasitic exploitation is geographically prevalent in Lake Tanganyika, an African rift lake, where parasitism rates range from 5–15% of host broods across multiple cichlid species, reflecting an ongoing coevolutionary arms race. A 2023 analysis of 779 broods from 20 cichlid species found four frequently parasitized hosts with rates of 2–18%, indicating non-specialized host use. While not reported in other rift lakes like Malawi or Victoria, the specificity to Tanganyikan mouthbrooders underscores the localized evolution of this interaction.^[68]^[69]

Defense Mechanisms

Mouthbrooding fish employ several adaptive strategies to counter brood parasitism, particularly from species like the cuckoo catfish (Synodontis multipunctatus) in African Great Lakes ecosystems. These defenses primarily involve the recognition and expulsion of foreign eggs after uptake, as parasites often exploit the brief window when the brooding parent retrieves its clutch. Sympatric host species, such as the cichlid Simochromis diagramma, demonstrate a generalized rejection response to non-native eggs, distinguishing them based on physical characteristics like size and shape rather than species-specific mimicry. Catfish eggs, measuring approximately 2 mm in diameter, contrast with host eggs ranging from 2.5 to 4.5 mm, facilitating detection and selective ejection during incubation.^[68] Behavioral avoidance further enhances protection, with experienced females exhibiting heightened vigilance during spawning windows—periods when the mouth is periodically opened to aerate eggs. These parents selectively retrieve only verified own eggs, reducing opportunistic intrusions by parasites that synchronize their egg-laying with host spawning. A 2022 study showed that individual experience also improves parasite intrusion success, highlighting reciprocal learning in this arms race.^[70] Morphological adaptations in host eggs, such as robust surface structures and larger size, indirectly deter parasite adhesion and integration by making foreign eggs more conspicuous and easier to expel without damaging the clutch. In coevolved populations of Lake Tanganyika, this has spurred an evolutionary arms race, where mouthbrooding cichlids show 3-11 times lower parasitism rates (around 5.5%) compared to naïve allopatric hosts facing 17-63% infection. Parasites counter by refining intrusion tactics, but host defenses escalate through genetic and learned improvements in rejection efficiency. Empirical studies confirm high efficacy in experienced parents, with rejection rates of parasitic eggs reaching 80% in multiparous females, versus near-total acceptance (7%) in first-time breeders. This experience-dependent learning underscores the dynamic co-evolutionary pressures shaping mouthbrooding behaviors across lake populations.^[68]

Taxonomy

Mouthbrooding Families

Mouthbrooding occurs in at least nine families of teleost fishes, spanning freshwater, brackish, and marine environments, and involves either eggs, larvae, or both being incubated in the parent's buccal cavity.^[42] This parental care strategy has evolved independently multiple times, with paternal mouthbrooding documented in eight families and maternal or biparental forms in others.^[71] Collectively, these families encompass thousands of species, though not all members within each family exhibit mouthbrooding.^[72] The Cichlidae family, commonly known as cichlids, is the most prominent group of mouthbrooders, comprising approximately 1,800 species distributed primarily in freshwater systems across Africa, South America, and parts of Central America and Asia.^[73] Within this family, mouthbrooding is typically maternal, where females incubate fertilized eggs and sometimes early-stage fry, though paternal and biparental variants occur in select lineages; this behavior is especially prevalent among African rift lake species, such as those in Lakes Malawi, Tanganyika, and Victoria.^[10] Cichlids' mouthbrooding supports high offspring survival in predator-rich environments but often requires the brooding parent to abstain from feeding for weeks. Apogonidae, or cardinalfishes, represent another major mouthbrooding lineage with more than 370 species, nearly all of which are paternal larval brooders inhabiting coral reefs in the Indo-Pacific and tropical Atlantic oceans. Males in this family collect eggs post-fertilization and retain larvae in their mouths for up to several weeks, providing oxygenation and protection until the young are independent; this strategy is adapted to the high predation pressures of marine reef ecosystems.^[74] Additional families exhibiting mouthbrooding include Osphronemidae (gouramis and bettas), where select Southeast Asian species, such as certain Betta, engage in maternal mouthbrooding of eggs in freshwater habitats.^[75] Helostomatidae, represented by the kissing gourami (Helostoma temminckii), features paternal mouthbrooding by males in slow-moving Southeast Asian waters.^[76] Other notable groups are Ariidae (sea catfishes, paternal mouthbrooders in marine and estuarine settings), Bagridae (some paternal in Asian freshwater), Opistognathidae (jawfishes, paternal burrow-associated brooding in reefs), Eleotridae (sleepers, paternal in Indo-Pacific streams), and Pomacentridae (some damselfishes with paternal mouthbrooding).^[7] These families highlight the global distribution of mouthbrooding, with freshwater forms concentrated in Africa and South America via Cichlidae, and marine variants dominant in the Indo-Pacific through Apogonidae and allies.^[77]

Notable Species Examples

Oreochromis niloticus, commonly known as the Nile tilapia, exemplifies a commercially significant mouthbrooding species where females incubate fertilized eggs in their buccal cavity for approximately 12 days until hatching, after which they may continue to protect the yolk-sac larvae for a few additional days. This maternal mouthbrooding behavior enhances offspring survival in variable aquatic environments, contributing to the species' rapid reproduction and adaptability. As one of the most farmed fish globally, dominating tilapia aquaculture production (over 80% as of 2023 estimates) and ranking second in overall aquaculture volume, O. niloticus plays a crucial role in global food security and economic development in regions like Africa and Asia.^[78]^[79] In Lake Tanganyika's cichlid flock, Tropheus moorii stands out as an extreme specialist adapted to rocky, algal-rich habitats, with females engaging in prolonged maternal mouthbrooding lasting around 33 days on average. During this period, brooding females maintain feeding territories and periodically release fry to forage on algae, a behavior that supports their nutritional needs while minimizing predation risks in the lake's competitive ecosystem. This extended incubation duration, longer than in many other cichlids, reflects evolutionary adaptations to the stable but predator-dense environment of Lake Tanganyika, where T. moorii's territoriality and dietary specialization further underscore its ecological niche.^[80]^[80] The Banggai cardinalfish, Pterapogon kauderni, represents a rare case of paternal mouthbrooding among marine species, with males incubating eggs in their mouths for about 3-4 weeks until the young are free-swimming. Endemic to a restricted area in Indonesia's Banggai Archipelago, this behavior allows males to protect developing offspring in shallow, seagrass-dominated habitats vulnerable to currents and predators. Classified as Endangered by the IUCN Red List, P. kauderni faces severe threats from habitat degradation due to coastal development and destructive fishing, as well as overcollection for the aquarium trade, which has drastically reduced local populations.^[81]^[81]^[82] Conservation challenges extend across many mouthbrooding species, with habitat loss from deforestation, pollution, and water extraction posing major threats; for instance, approximately 26% of assessed freshwater fish, including numerous mouthbrooders, are now threatened with extinction according to 2025 IUCN evaluations. In the case of T. moorii and P. kauderni, localized declines highlight the vulnerability of endemic mouthbrooders to anthropogenic pressures in biodiverse hotspots like the African Great Lakes and Indonesian seas.^[83]^[84] Research on mouthbrooding genetics has advanced using model species like the African cichlid Astatotilapia burtoni, where studies identify key genes such as the pheromone receptor or113a, whose disruption triggers male mouthbrooding behavior typically reserved for females, revealing molecular mechanisms underlying parental care transitions. Transcriptomic analyses in A. burtoni further show upregulation of immune and stress-response genes during maternal mouthbrooding, linking nutritional trade-offs to offspring protection and providing insights into evolutionary conserved pathways for parental investment in teleost fishes. These findings from genetic and neural studies emphasize how brooding behaviors are regulated at the molecular level, informing broader understandings of reproductive strategies in mouthbrooding lineages.^[85]^[86]^[17]

References

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East African cichlid fishes | EvoDevo | Full Text - BioMed Central
Jan 5, 2023 · Parallel life history evolution in mouthbrooding cichlids from the African Great Lakes. Proc Natl Acad Sci. 2008;105:15475–80. Article CAS ...
[24]
https://cichlidae.com/article.php?id=183
[25]
Early development in the mouth-brooding cichlid fish - SciELO
Both juvenile and adult individuals with mouth-brooded offspring were collected along the basins of the Cuiabá and Manso Rivers in the state of Mato Grosso, ...
[26]
To feed or to breed: morphological constraints of mouthbrooding in ...
Feb 8, 2012 · Mouthbrooding was strongly associated with the morphology of the feeding apparatus in males. Male cardinalfishes possessed longer heads, snouts ...
[27]
Nocturnal hatching timing of mouthbrooding male cardinalfish ...
On the day of hatching, they released newly hatched larvae from their mouths on average 81 min after sunset. Semilunar hatching periodicity was significant, but ...<|separator|>
[28]
The Magnificent Mouthbrooding Bettas - Tropical Fish Hobbyist
Feb 1, 2020 · Mouthbrooding most likely evolved from bubblenesting, and many betta species are not restricted to one brooding process over another. For ...
[29]
When egg layers mouth brood | Betta Fish Forum
Oct 21, 2014 · Apparently, some males will hold eggs or small fry in their mouths for a long period of time, especially when they feel threatened.Missing: occasional mouthbrooding
[30]
10.8 Hatchery rearing of tilapia eggs and fry
The eggs of substrate spawners hatch within 48 h at 28°C, while mouth-brooded eggs hatch within 96 h. The larvae of all tilapia species have bulky yolks; unable ...
[31]
(PDF) EFFECTS OF TEMPERATURE ON THE EGG PRODUCTION ...
Egg production decreased with the increase of water temperature. Maximum number of eggs was produced at 25°C and minimum number at 33°C.
[32]
Some mouthbrooding fish eat their children to reduce stress
Nov 9, 2022 · Some cichlid fish mothers can boost their chemical defences by using antioxidants found in their own children.
[33]
Krabi Mouth Brooding Betta - Betta simplex Fish Profile & Care Guide
Jul 13, 2023 · Stress can lead to premature swallowing or release of eggs, particularly in inexperienced males. It is, therefore, preferable to leave the ...
[34]
Caring of Mouth Brooding Cardinalfish - Reef Central
Mar 30, 2016 · In my experience, when left in a community tank, the male will spit the eggs out long before they hatch - there is just too much stress from all ...
[35]
The fossil record and biogeography of the Cichlidae (Actinopterygii
Based on the biology and distribution of modern and fossil cichlids, it is more probable that they arose less than 65 million years ago, in the Early Tertiary, ...
[36]
Age of Cichlids: New Dates for Ancient Lake Fish Radiations
Mar 15, 2007 · Cichlids' global origins are estimated at 133.2 MYA, while fossil calibrations suggest African Eocene origins at 46.0 MYA.Missing: timeline | Show results with:timeline
[37]
Perciform - an overview | ScienceDirect Topics
Mouthbrooding has developed in several orders (Table 5), and different forms exist (Patzner, 2008): (a) the male (father) keeps the eggs; (b) the female ...
[38]
Evolution of mouthbrooding and life-history correlates in the fighting ...
The origin of and evolutionary transitions among the extraordinary diverse forms of parental care in teleost fish remain largely unknown.
[39]
The role of prolactin in the regulation of brood care in the ...
Jul 28, 2008 · The hormone prolactin (PRL) is important for the regulation of parental care in many species of mammals, birds and fish, ...
[40]
Cenozoic Cichlids of Africa (Cichlidae: Pseudocrenilabrinae) With ...
Apr 24, 2022 · If the vicariant event were the cause of the modern distribution, this would indicate an age for the family of at least 120 million years; ...
[41]
[PDF] Kinematics of mouthbrooding in Oreochromis niloticus (Cichlidae)
Evolutionary transitions from close guarding of the eggs in nests or crevices to mouthbrooding have occurred at least 10 times in the history of cichlids ...
[42]
Offspring mortality during mouthbrooding in two open-water ...
Oct 19, 2022 · Analyses of 279 and 263 mouthbrooding females showed that the average egg number decreased by 22.8% and 11.2% from spawning to hatching and ...Missing: scatter | Show results with:scatter
[43]
Proteomics of Buccal Cavity Mucus in Female Tilapia Fish ...
In comparison, known negative consequences of mouthbrooding include starvation, increased energy expenditure, hypoxia, decrease in immune function, limited ...
[44]
https://www.sciencedirect.com/science/article/abs/pii/S1095643310000863
[45]
Hypoxia and energetics of mouth brooding: Is parental care a costly ...
This study explores costs of mouth brooding and the response of parent and offspring to brooding under hypoxia in the maternal African mouth brooder ...
[46]
[PDF] Ecology and Evolution of the African Great Lakes and Their Faunas
Oct 28, 2014 · Overall, lakes could be categorized as more ecologically stable (e.g., Lake Tanganyika) or as systems with limited ecological stability (e.g., ...
[47]
Jul/Aug 2020 - Cichlid World - Tropical Fish Hobbyist
Aug 1, 2020 · Mouthbrooding likely originated from transportation (by mouth) of wrigglers between excavated pits during nursing in substrate-brooding species, ...<|separator|>
[48]
FAO Fisheries & Aquaculture
**Summary of Tilapia Nilotica from FAO Fisheries & Aquaculture:**
[49]
Mouthbrooding Fish Bring Child Care to a New Level
Mar 26, 2020 · Mouthbrooding is a strategy where parents keep eggs (and sometimes newly hatched fry) in—you guessed it—their mouths. Learn more here.Missing: biology | Show results with:biology
[50]
[PDF] WHY TILAPIA IS BECOMING THE MOST IMPORTANT FOOD FISH ...
The tilapias, with their unique mouth-brooding form of reproduction and extreme hardiness, allow farmers with the most meager resources an opportunity to rear ...
[51]
Annual farmed finfish production survey: A modest supply decline for ...
Oct 9, 2023 · Global production of farmed tilapia in 2023 is projected at 6.7 MMT, up about 5 percent over 2022 levels, and 7.03 MMT in 2024, up another 5 ...
[52]
How To Farm a Better Fish - National Geographic
A tilapia reveals a mouthful of eggs that will be extracted for hatching at a farm. Mouth brooding—along with rapid growth, a vegetarian diet, and the ability ...
[53]
Egypt's success with tilapia a blueprint for all Africa
Aug 7, 2017 · Aquaculture research started in the 1930s, while modern commercial tilapia culture started in the late 1950s. Nile tilapia is, essentially, the ...
[54]
From Africa to the world—The journey of Nile tilapia - El‐Sayed - 2023
Mar 5, 2023 · In recent history, the first tilapia culture trial dates back to 1924 in Kenya, when water ponds were stocked with different species of tilapias ...
[55]
Advances in tilapia broodstock management - Global Seafood Alliance
Oct 1, 2000 · Mouth brooding is one of the main causes of reduced seed productivity. Females typically spend 10 to 15 days incubating eggs and caring for fry.
[56]
Assisted reproduction in Nile tilapia Oreochromis niloticus
The synthetic hormonal product Ovaprime was used for the induced spawning of Cyprinus carpio, in comparison with the Pituitary gland extract. The study was done ...
[57]
Use of hCG hormone in the natural and artificial reproduction of Nile ...
Jul 29, 2021 · Protocols of spawning induction by hormones in Nile tilapia have been applied mainly for collecting of gametes in procedures of chromosome ...Missing: techniques | Show results with:techniques
[58]
[PDF] IJRA - v3n1 - Comparisons ofTilapia Seed Productio nUnder ...
... production. International Journal of Recirculating Aquaculture, Volume 3 11. Page 2 ... method as opposed to the natural mouth-brooding method ... Conference on ...Missing: techniques | Show results with:techniques
[59]
Size dependent cannibalism in juvenile Nile tilapia (Oreochromis ...
Dec 6, 2018 · Cannibalism among tilapia fry and fingerlings has been identified as one of the major problems by small-scale hatchery operators (Pantastico ...
[60]
Genetically Improved Farmed Tilapia: Benefiting aquatic food ...
Oct 5, 2022 · WorldFish has demonstrated that selective breeding is a feasible, cost-effective and sustainable approach to the genetic improvement of tilapia.
[61]
Selective Breeding for Genetic Improvement of Nile tilapia ... - MDPI
The review recommends purposive support for developing a systematic strain improvement breeding program, which will be a source of improved broodstock and seed ...
[62]
FAO - Oreochromis niloticus
Production of optimum-sized (<14 mm) fry ranges from 1.5 to 2.5 fry/m2/day (20 to 60 fry/kg female/day). In the South East Asian hapa method, fish are examined ...
[63]
[PDF] Nile Tilapia and Blue Tilapia Fry Production in a Subtropical Climate ...
Jun 9, 2015 · Ponds were harvested 13–20 d after stocking. Female buc- cal cavities were inspected prior to stocking to ensure none was incubating eggs/sac ...Missing: cultivation post-
[64]
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5931752/
[65]
Early life-history features associated with brood parasitism in the ...
Feb 11, 2019 · However, the ontogenetic features of the cuckoo catfish that enable this species to parasitize mouthbrooding cichlids have not been described.
[66]
Brood parasitism of an open-water spawning cichlid by the cuckoo ...
This study reports that the cuckoo catfish also parasitizes the open-water spawning Cyprichromis coloratus, although it may not be a regular host.
[67]
Low incidence of cannibalism among brood parasitic cuckoo catfish ...
Apr 8, 2023 · Parasitism involves intrusion by a group of cuckoo catfish into an ongoing cichlid host spawning, predation of some host cichlid eggs, and ...
[68]
Success of cuckoo catfish brood parasitism reflects coevolutionary ...
May 2, 2018 · In Lake Tanganyika, mouthbrooding cichlids are exploited by the only obligate nonavian vertebrate brood parasite, the cuckoo catfish Synodontis ...
[69]
To eat or not to eat: egg-based assessment of paternity triggers fine ...
Apr 21, 2010 · A direct mechanism to recognize own and foreign eggs is by cues from the eggs (e.g. olfactory or visual) themselves. Here, the ability to ...
[70]
Individual experience as a key to success for the cuckoo catfish ...
Mar 31, 2022 · More than one cuckoo catfish offspring often successfully develop in a parasitised host clutch, a situation also observed in some nonevicting ...
[71]
FAMILY Details for Cichlidae - Cichlids - FishBase
Nov 29, 2012 · Mouthbrooding species are usually biparental, and eggs are guarded on a substrate prior to oral incubation which starts with advanced eggs or ...
[72]
Relaxed Feeding Constraints Facilitate the Evolution of ...
Mouthbrooding, a form of parental care where offspring develop inside a parent's mouth, increases multifunctionality by adding a major function (reproduction) ...
[73]
Sexual Difference in Buccal Morphology of the Paternal ...
Among marine fishes, the largest group with mouth- brooding habit is the cardinalfish (Apogonidae), which con- sists of 300 species or more. In all the species ...
[74]
Sexual dimorphism in the buccal cavity of paternal mouthbrooding ...
Jul 21, 2005 · The mechanical basis of mouthbrooding in the coral reef cardinalfish (family Apogonidae) has yet to be established. Sexual dimorphism in the ...
[75]
Southeast Asian mouth-brooding Betta fighting fish (Teleostei
Southeast Asian mouth-brooding Betta fighting fish (Teleostei: Perciformes) species and their phylogenetic relationships based on mitochondrial COI and nuclear ...Introduction · Materials And Methods · ResultsMissing: families | Show results with:families
[76]
FAMILY Details for Helostomatidae - Kissing gouramies - FishBase
Nov 29, 2012 · Filter feeder and grazer on benthic algae. Etymology, : Greek, elos, -e, -on = stud, nail + Greek, stoma = mouth ( Ref. 45335) ...
[77]
Mouthbreeding in fishes - ScienceDirect.com
Mouthbreeding occurs in at least fifty-three genera of fishes (four orders, eight families) that inhabit marine, brackish and fresh water.
[78]
[PDF] Nile Tilapia (Oreochromis niloticus) - U.S. Fish and Wildlife Service
Mouthbrooding by females [Trewavas 1983].” “Sexual maturity is reached at 3-6 months depending on temperature, reaching about 30 g. Reproduction occurs only ...
[79]
Mating and Parental Care in Lake Tanganyika's Cichlids - PMC - NIH
Biparental mouthbrooding, whereby the female broods eggs and early fry before the male takes over all (or part, as in Microdontochromis rotundiventralis and ...
[80]
Banggai Cardinalfish, Pterapogon kauderni, Aquaculture Pledge
Aug 28, 2019 · The Banggai cardinalfish, Pterapogon kauderni, which is currently listed as Endangered by the IUCN Redlist and Threatened under the Endangered Species Act.
[81]
Banggai Cardinalfish | NOAA Fisheries
In 2016, NOAA Fisheries listed the species as threatened under the Endangered Species Act. Appearance. The species is differentiated from all other cardinalfish ...
[82]
[PDF] THE WORLD'S FORGOTTEN FISHES
Today, nearly a third of freshwater fish species are threatened with extinction due to a devastating combination of threats from damming rivers to draining ...
[83]
Summary Statistics - IUCN Red List of Threatened Species
The IUCN Red List is updated. For each Red List update, IUCN provides summaries of the numbers of species in each category, by taxonomic group and by country.
[84]
Genetic Mutation Prompts 'Deadbeat Dad' Fish to Start Raising Their ...
Aug 1, 2024 · A genetic mutation that disables a pheromone receptor, or113a, causes males to mouthbrood eggs, which is normally a female behavior.
[85]
Transcriptomic changes associated with maternal care in the brain ...
During this mouthbrooding behavior, which can last 2–3 weeks, mothers undergo voluntary fasting accompanied by loss of body mass and major metabolic changes.<|separator|>