Wrasse

Wrasses (family Labridae) are a diverse family of marine ray-finned fishes renowned for their ecological versatility and often striking coloration, comprising approximately 500 species across about 60 genera and inhabiting tropical and subtropical coastal waters worldwide.^[1][2] These fishes exhibit a broad range of body sizes, from just a few centimeters in small species like Minilabrus striatus to over 2 meters and 150 kilograms in the humphead wrasse (Cheilinus undulatus), the largest member of the family.^[2][1] Their bodies are typically elongate to oblong and slightly to strongly compressed, featuring a protrusible mouth with thick lips, one or two pairs of prominent forward-projecting canine teeth at the front of each jaw, and pharyngeal grinding plates for processing prey.^[2] A single continuous dorsal fin with 8 to 21 spines and large, smooth cycloid scales are diagnostic traits, while the lateral line may be straight, curved, or interrupted.^[2] Coloration varies dramatically, often with distinct juvenile, initial-phase (typically female or subordinate male), and terminal-phase (large dominant male) patterns that can include vibrant blues, greens, and reds.^[2][1] Wrasses are primarily associated with coral reefs, rocky substrates, seagrass beds, and sandy bottoms, ranging from intertidal tide pools to depths exceeding 100 meters, though most species prefer shallow, nearshore environments.^[2][1] Their global distribution spans all tropical seas, extending into temperate regions as far north as Norway and with the highest species diversity in the Indo-Pacific, particularly around Australia where over 165 species occur.^[2][1] Ecologically, wrasses occupy a wide array of trophic niches, with most species being diurnal carnivores or omnivores that feed on zooplankton, small fishes, crustaceans, mollusks, worms, echinoderms, fish eggs, parasites, and mucus, using their specialized jaws to crush hard-shelled prey or pick at substrates.^[2][3] Certain genera, such as Labroides (cleaner wrasses), engage in mutualistic cleaning symbiosis, removing ectoparasites from client fishes on reefs.^[2] A key life-history trait in most species is protogynous hermaphroditism, where functional females sequentially change sex to become males, often triggered by social cues in harem-like mating systems.^[2][1] As one of the most structurally and functionally diversified reef fish families, wrasses contribute significantly to ecosystem dynamics, including predation, cleaning, and habitat maintenance.^[3] Many wrasse species face threats from overfishing, habitat degradation, and the aquarium trade, with several listed as threatened on the IUCN Red List as of 2025, including the Endangered humphead wrasse due to its slow growth and high market value and the Vulnerable hogfish.^[4][5][1]

Etymology and Overview

Etymology

The word "wrasse" entered the English language in the 1670s, derived from the Cornish term wrach or wragh, meaning "old woman" or "hag."^[6] This Celtic root is cognate with the Welsh gwrach and Breton gwrac'h, both carrying similar connotations of an elderly woman or witch-like figure, possibly alluding to the fish's distinctive facial features or behaviors observed in local traditions.^[7][8] Early English usage of "wrasse" primarily referred to European species, such as the ballan wrasse (Labrus bergylta), documented in natural history texts from the late 17th century onward.^[6] The term's adoption reflects the influence of Cornish fishing communities, where the fish were commonly encountered along coastal waters.^[9] In other languages, wrasses bear varied regional names highlighting their diversity. In Spanish, they are known as lábridos, a direct adaptation from the family name Labridae, or papagallo for certain colorful species evoking parrot-like qualities.^[10][11] The family name Labridae itself stems from the Latin labrum, meaning "lip," in reference to the fishes' prominent protractile mouths.^[12]

General Characteristics

Wrasses belong to the family Labridae within the order Labriformes, a diverse group of marine ray-finned fishes (class Actinopterygii) that inhabit tropical and subtropical waters worldwide.^[13] As of 2025, the family comprises over 600 species distributed across approximately 82 genera, making it one of the largest and most speciose families of coral reef fishes.^[14] These fishes exhibit a wide range of body sizes, with most species being relatively small, typically measuring under 20 cm in total length, though they vary greatly in shape, from elongate to deep-bodied forms.^[13] The largest species, the humphead wrasse (Cheilinus undulatus), can reach up to 2.3 m in length and weigh as much as 191 kg, highlighting the family's morphological diversity.^[15] A defining characteristic of wrasses is their protractile mouth equipped with prominent canine-like teeth, which aids in capturing prey, paired with thick, often fleshy lips that can fuse with the snout in some species.^[13] They possess a continuous dorsal fin formed by the fusion or close adjacency of two dorsal elements, typically with IX-XII spines and 9-19 soft rays, contributing to their agile swimming in complex reef environments.^[13] Many species display vibrant coloration, with patterns ranging from iridescent blues and greens to bold stripes and spots, which serve functions in camouflage, mating, and species recognition.^[16] Additionally, a significant proportion of wrasses are protogynous hermaphrodites, meaning individuals develop as females first and may later transition to males, a reproductive strategy that enhances population flexibility in varying social conditions.^[13] As key inhabitants of coral reef ecosystems, wrasses play vital roles in maintaining biodiversity by occupying diverse trophic niches, from invertebrate feeders to cleaners and herbivores in some cases, thereby supporting the structural integrity and health of reef communities.^[17] Their abundance and ecological versatility contribute to the overall resilience of coral habitats, where they help control populations of small invertebrates and algae, indirectly benefiting coral growth and survival.^[18]

Taxonomy and Phylogeny

Classification

Wrasses belong to the phylum Chordata, class Actinopterygii, order Labriformes, and family Labridae, which encompasses the wrasses proper.^[19] Phylogenetically, the family Scaridae (parrotfishes) is nested within Labridae based on molecular data, though it is traditionally treated as a separate family due to distinct morphological and ecological traits.^[19] This placement reflects the family's position within the superorder Percomorpha, with Labriformes sister to the Centrogenys false scorpionfishes.^[19] The Labridae family comprises approximately 676 species across 83–85 genera. This total includes ~100 species of parrotfishes (Scarinae), nested within Labridae based on molecular phylogenies, increasing the count from the traditional ~576 wrasse species. These are organized into 12–13 major clades that function as subfamilies in the updated phylogenetic taxonomy.^[19] These include Hypsigenyinae (encompassing Odacini with 12 species), Clepticini, Cirrhilabrinae (89 species), Labrinae (true wrasses, 23 species), Cheilininae (24 species), Xyrichtyinae (47 species), Pseudolabrinae (38 species), and Julidinae (246 species, further divided into up to 23 subclades).^[19] This structure arises from synthetic phylogenies incorporating 590 species, highlighting the family's diversity in body form and habitat adaptation.^[19] Recent taxonomic revisions have added dynamism to Labridae classification, with 42 new species described in the past decade and over 150 genus-species combinations updated since 2000.^[19] Notable additions include Paracheilinus amanda (Amanda's flasher wrasse) from the Great Barrier Reef and Coral Sea in 2023, Iniistius bakunawa (eclipse-spot razor wrasse) from the Philippines and Western Australia in 2023, and Halichoeres sanchezi (tailspot wrasse) from Mexico's Revillagigedo Archipelago in 2024. Eleven genera have been elevated, such as Concholabrus (2 species) and Crassilabrus, while 17 species in Cirrhilabrinae have been proposed as synonyms.^[19] Prominent genera within Labridae illustrate the family's ecological breadth. Labroides, known for cleaner wrasses, includes 9 species that engage in symbiotic cleaning behaviors.^[19] Thalassoma encompasses approximately 27 species of active, predatory wrasses, though some have been reclassified into Gomphosus.^[19] Cheilinus features large-bodied species, such as the humphead wrasse (C. undulatus), adapted to coral reef environments.^[19] In 2025, phylogenetic taxonomy proposals by Brownstein et al. and Fricke et al. integrate extensive molecular data to refine Labridae structure, formally recognizing 12 major clades including Odacini and Clepticini for improved evolutionary alignment.^[19] These updates emphasize monophyly and provide a stable nomenclature that preserves established names while resolving polyphyletic groups.^[19]

Evolutionary History

The fossil record of the Labridae family, which includes wrasses, dates back to the Early Eocene, approximately 50 million years ago, with the earliest known specimens discovered in the Monte Bolca lagerstätte in northern Italy.^[20] These early forms, such as those from the genus Eocoris and related taxa, already exhibited characteristic protractile mouths adapted for feeding on small invertebrates and algae, indicating that key morphological features of modern wrasses were present in these ancient reef-associated fishes.^[21] At least five distinct labrid species have been identified from this site, providing evidence of an established presence in Eocene coral reef ecosystems.^[22] The family underwent rapid diversification during the Miocene epoch (approximately 23 to 5 million years ago), coinciding with the global expansion of coral reefs and the proliferation of reef habitats in the Indo-Pacific.^[17] A 2025 genome-scale phylogenomic study led by Yale researchers revealed "explosive evolution" in Labridae, with major clades experiencing accelerated speciation rates and pulses of morphological innovation, positioning wrasses and parrotfishes as one of the most species-rich families among modern reef fishes.^[23] This diversification was driven by ecological opportunities in expanding reef environments, where labrids adapted to diverse niches, contributing to their current global species count exceeding 600.^[14] Recent phylogenetic reconstructions have refined our understanding of Labridae's evolutionary history through node-stem definitions and phylogenomic analyses. A 2025 study published by the Peabody Museum of Natural History established comprehensive phylogenetic taxonomy for the family, delineating 12 major clades (such as Hypsigenyinae and Labrinae) based on ultraconserved genomic elements and fossil-calibrated trees, which trace the deep history of reef fish diversification.^[24] These analyses highlight convergent evolutionary patterns across lineages, integrating fossil data from the Eocene to Miocene to model the family's radiation.^[25] Key adaptations, such as protogynous sex change and tool use, emerged independently in multiple Labridae lineages, enhancing reproductive flexibility and foraging efficiency in complex reef settings. Sex change mechanisms, where females transition to males in response to social cues, evolved multiple times within the family, supported by genomic studies identifying novel genes and epigenetic reprogramming in species like the bluehead wrasse (Thalassoma bifasciatum).^[26] Similarly, tool use—such as anvil use by striking urchins against hard surfaces to access prey—has been documented in over five species of New World Halichoeres wrasses, with 2025 observations confirming independent origins in this clade, likely tied to Miocene ecological pressures.^[27]

Physical Description

Morphology

Wrasses exhibit an elongated, cylindrical body shape that is often laterally compressed, covered in cycloid scales that provide flexibility and smooth movement through water.^[1] This body form supports their agile navigation in complex reef environments, with sizes ranging from as small as 4 cm in the minute wrasse (Minilabrus striatus) to over 2 m in the humphead wrasse (Cheilinus undulatus).^[1] Their fins include a single continuous dorsal fin bearing 9 to 21 spines followed by soft rays, an anal fin with 3 spines and 8 to 12 soft rays, and paired pelvic fins typically with 1 spine each, all contributing to precise maneuvering and propulsion aided by well-developed pectoral fins.^[13] The lateral line system is either continuous or interrupted, enabling detection of water vibrations from nearby movements.^[13] The head features a protractile upper jaw equipped with thick, fleshy lips and prominent forward-pointing canine teeth adapted for grasping prey, complemented by specialized pharyngeal jaws that crush ingested items.^[1] The overall snout is pointed to facilitate probing crevices.^[28] Sensory adaptations include large eyes suited for vision in the low-light conditions of coral reefs, enhancing prey detection and spatial awareness.^[29] Coloration patterns, which can vary by sex, often feature intricate markings that align with these structural traits.^[1]

Sexual Dimorphism and Coloration

Wrasses display pronounced sexual dimorphism, particularly in size and coloration, where females and initial-phase (IP) males are generally smaller and exhibit drabber, more cryptic patterns, while terminal-phase (TP) males are larger and feature brighter, bolder markings. This dimorphism is especially marked in species confined to coral reefs, as phylogenetic comparative analyses reveal that reef exclusivity correlates strongly with the evolution of color differences, independent of other sexual selection factors.^[30] In many species, TP males attain lengths up to 20-30% greater than females, enhancing their competitive advantages in mating.^[1] Coloration in wrasses often involves vibrant hues of blue, green, and yellow, with TP males showing intensified pigmentation such as iridescent blues and greens alongside reduced white areas, in contrast to the countershading and mottled patterns of IP individuals that aid in blending with substrates. For instance, the Mediterranean rainbow wrasse (Coris julis) exemplifies this, with females displaying a brownish dorsum, yellowish flanks, and pale ventral region, whereas males exhibit a more vivid green-to-blue body accented by orange longitudinal bands.^[30][31] Similarly, in the humphead wrasse (Cheilinus undulatus), TP males develop a prominent forehead hump alongside brighter blue-green tones, a feature less pronounced or absent in females, correlating positively with body size. During protogynous sex reversal from female to TP male, wrasses undergo rapid physiological changes in pigmentation, shifting from IP drabness to TP vibrancy within days to weeks, reflecting hormonal influences on chromatophores. Cleaner wrasses, such as Labroides bicolor, demonstrate species-specific signals through subtle dimorphism, with males often showing more saturated blue heads and yellow tails compared to the grayer, striped females, aiding in pair recognition at cleaning stations.^[30][32]

Distribution and Habitat

Global Range

Wrasses (family Labridae) are predominantly distributed in tropical and subtropical marine waters worldwide, with the highest species diversity occurring in the Indo-Pacific region, where over 500 of the family's more than 600 species are found.^[1] In contrast, the Atlantic Ocean hosts fewer species, around 100, reflecting lower overall biodiversity in that basin.^[1] Some species extend into temperate waters, such as the ballan wrasse (Labrus bergylta), which ranges northward to the coasts of Norway.^[1] The centers of wrasse diversity are concentrated in biodiverse hotspots like the Coral Triangle, encompassing Indonesia and the Philippines, and the Great Barrier Reef, where numerous genera achieve peak species richness.^[33] Vagrant populations have also appeared in the Mediterranean Sea as Lessepsian migrants via the Suez Canal, including species such as Pteragogus pelycus and Pteragogus trispilus.^[34] High levels of endemism characterize many wrasse populations, particularly on isolated islands; for example, 16 of the 45 species recorded in Hawaiian waters are endemic to the archipelago, including the Hawaiian cleaner wrasse (Labroides phthirophagus).^[35] Recent discoveries underscore ongoing exploration in the Pacific, such as the eclipse-spot razor wrasse (Iniistius bakunawa), described in 2023 from specimens in the Philippines and Western Australia.^[36] Most wrasse species exhibit sedentary adult lifestyles, remaining closely tied to local reef habitats, though juveniles often disperse over long distances via ocean currents during their pelagic larval phase.^[37]

Ecological Niches

Wrasses primarily occupy a range of coastal marine environments, including coral reefs, rocky shores, and seagrass beds, spanning from intertidal zones to depths of up to 100 m. Temperate species extend into kelp forests, where macroalgae provides structural complexity similar to that of tropical reefs. These habitats offer the substrate proximity and structural diversity essential for the family's benthic-oriented lifestyle.^[1][2][38] Species-specific zonation is common, with juveniles frequently inhabiting shallow rubble, rock pools, and inshore areas for protection, while adults shift to outer reef slopes or deeper subtidal zones. This ontogenetic habitat partitioning allows juveniles to exploit less competitive microhabitats with abundant cover, such as seagrass or algal beds, before transitioning to more exposed, structure-rich sites like crevices and boulder fields on reefs. Preferences for complex substrates facilitate hiding from predators and access to prey, with many species avoiding open sand flats in favor of vegetated or rocky terrains.^[39][40][41] Adaptations to these niches include territorial behaviors, where individuals defend small areas within crevices or algal patches for foraging and shelter. For example, the goldsinny wrasse (Ctenolabrus rupestris) establishes territories of 0.7–2 m² amid rocks and eelgrass, relying on these refuges for site fidelity and predator avoidance; this species is particularly sensitive to variations in water quality, which can disrupt its crevice-dependent lifestyle. Such territoriality enhances resource monopolization in high-competition environments.^[38][42] Through their feeding habits as invertivores, wrasses play a key role in maintaining habitat integrity by regulating invertebrate abundances, which indirectly modulates bioerosion rates on reefs. Species like the ballan wrasse prey on sea urchins, preventing excessive grazing that could alter algal community structure and substrate stability. These interactions support overall reef health by promoting balanced benthic communities.^[38][1]

Behavior and Ecology

Feeding Strategies and Tool Use

Wrasses exhibit diverse feeding strategies adapted to their coral reef and benthic habitats, primarily targeting invertebrates such as crustaceans, mollusks, echinoderms, and fish eggs, alongside algae and occasionally small fish or corals.^[43] Their diets reflect trophic versatility, with many species acting as generalists despite specialized jaw morphologies; for instance, micro-crustaceans and macro-invertebrates like crabs and snails constitute major components in many examined species across the Great Barrier Reef.^[43] Feeding methods include precise pecking at sessile or slow-moving prey using protrusible jaws, and crushing hard-shelled items with robust pharyngeal jaws that function as a secondary grinding apparatus.^[44] Cleaner wrasses, such as Labroides dimidiatus, incorporate ectoparasites into their diet as a key food source.^[45] Foraging in wrasses is predominantly opportunistic and diurnal, with individuals actively searching reef crevices, seagrass beds, and algal mats during daylight hours to exploit available prey.^[46] Activity peaks shortly after dawn and tapers toward dusk, allowing efficient energy allocation in visually oriented predation.^[46] Some wrasse species employ mucus cocoons at night for protection during rest, underscoring their diurnal foraging rhythm while minimizing nocturnal vulnerability.^[47] A notable innovation among wrasses is tool use, observed in at least 26 species across multiple genera, where individuals strike hard-shelled prey against anvils such as rocks or coral to access nutritious interiors.^[27] This behavior, documented since the 1970s, involves deliberate selection of anvil sites and prey transport, demonstrating cognitive flexibility; for example, tuskfishes in the genus Choerodon routinely use coral heads to crack mollusks and crustaceans.^[48] Their strong pharyngeal jaws and mouth morphology facilitate prey manipulation during these strikes.^[27] Recent research has expanded evidence of anvil use in the genus Halichoeres, with a 2025 study documenting 19 observations across five New World species (H. bivittatus, H. brasiliensis, H. garnoti, H. poeyi, and H. radiatus), targeting prey like crabs, sea urchins, clams, and brittle stars against diverse anvils including rocks, coral, and even human debris.^[27] These findings, gathered via citizen science, highlight anvil use's prevalence in tropical reefs for overcoming prey defenses.^[27] Iconic examples include the humphead wrasse (Cheilinus undulatus), which preys on crown-of-thorns starfish (Acanthaster planci), helping control outbreaks that threaten coral ecosystems.^[49]

Cleaning Symbiosis

Cleaner wrasses, particularly the five species of the genus Labroides exemplified by Labroides dimidiatus, form mutualistic partnerships with a wide array of reef fish by establishing dedicated cleaning stations on coral reefs. At these stations, typically located in shallow waters 1-3 meters deep, cleaners meticulously remove ectoparasites such as gnathiid isopods, along with dead skin and mucus from the bodies, gills, and mouths of client fish. This behavior is obligate for Labroides species, meaning it constitutes their primary foraging strategy and social organization.^[50][51] The symbiosis yields clear benefits: client fish achieve improved hygiene and reduced parasite burdens, which can enhance their growth, survival, and overall fitness, while cleaners secure a reliable food supply from the ingested material. However, an element of conflict arises through "client manipulation," as cleaners preferentially consume protein-rich mucus over the less nutritious parasites, sometimes leading to shorter cleaning sessions that prioritize the cleaner's nutritional needs over the client's optimal parasite removal. This dynamic underscores the evolutionary tension in the mutualism, where clients may return despite occasional cheating due to the net health advantages.^[52][53][54] Cleaners advertise their services using vivid signals, including striking blue and yellow body colorations that distinguish them from predators and attract potential clients from afar. Upon approach, they perform rapid, tail-beating dances to initiate interactions and guide clients into position. A 2019 experiment demonstrated that L. dimidiatus passes the mirror self-recognition test by attempting to remove marks visible only in reflections, suggesting advanced cognitive abilities that may facilitate strategic decision-making during cleaning encounters.^[55][56] These cleaning stations function as defended territories, often maintained by a hierarchical group consisting of a dominant male overseeing multiple subordinate females, with the male aggressively repelling intruders to preserve access to clients. By curbing ectoparasite proliferation across the reef community, cleaner wrasses like L. dimidiatus play a pivotal role in ecosystem stability, promoting higher local fish diversity and abundance through indirect effects on client health and behavior.^[50][57][52]

Reproduction and Life History

Sexual Systems

Wrasses (family Labridae) exhibit diverse sexual systems, with the majority of species displaying sequential hermaphroditism, predominantly of the protogynous type, where individuals transition from female to male during their lifetime.^[58] In protogynous species, such as the bluehead wrasse (Thalassoma bifasciatum), all individuals initially develop as females, with the largest or socially dominant female undergoing sex change to become a functional male when conditions favor it.^[59] This transition involves rapid gonadal reorganization, typically completing within weeks to months, driven by a shift from ovarian to testicular tissue production. Recent studies, such as those on the ballan wrasse (Labrus bergylta) in 2023, have provided histological and endocrine insights into early gonad development in protogynous species.^[60][61] Protogyny is considered the ancestral condition in Labridae, correlating with social structures like harems where larger males monopolize mating opportunities.^[58] The sexual phases in protogynous wrasses are divided into the initial phase (IP) and terminal phase (TP). During the IP, individuals are either females or smaller "sneaker" IP males that mimic female behavior and coloration to opportunistically fertilize eggs, comprising a minority (often 4-10%) of the male population.^[61] TP males, known as "super-males," arise either as primary males (rarely born male) or through secondary sex change from females; they are larger, more aggressive, and display vibrant coloration to defend territories.^[62] Sex change is primarily triggered by social cues, such as the removal of a dominant TP male from a group, prompting the largest female to initiate the process to fill the reproductive vacancy.^[59] Hormonal mechanisms underpin this, including decreased levels of 17β-estradiol and increased 11-ketotestosterone, alongside potential roles for stress hormones like cortisol in mediating social stress responses.^[61] While protogyny dominates, exceptions exist within the family. Bidirectional sex change, allowing reversals between sexes, has been documented in select species like the saddle wrasse (Halichoeres trimaculatus), where social manipulations can induce changes in either direction.^[63] Additionally, gonochoristic species with fixed sexes occur, particularly among temperate wrasses such as the ocellated wrasse (Symphodus ocellatus), which lack hermaphroditic capabilities and maintain separate male and female lineages throughout life.^[64] These variations highlight the evolutionary flexibility of sexual systems in wrasses, influenced by ecological and social factors.^[58]

Reproductive Behaviors and Parental Care

Reproductive behaviors in wrasses (family Labridae) are diverse, reflecting their varied mating systems, which range from harem polygyny to lek-like aggregations. In harem systems, dominant terminal-phase (TP) males, often larger and more colorful, perform courtship displays involving rapid swimming, head shakes, and exaggerated body postures to attract and retain groups of females within defended territories, culminating in pair spawning where eggs and sperm are broadcast externally over the reef substrate.^[65] Lek-like systems, common in species like the bluehead wrasse (Thalassoma bifasciatum), feature TP males establishing transient spawning sites where they intensify displays—such as vertical rises and color flashes—to solicit females from passing schools, sometimes resulting in group spawning with multiple males competing.^[65] Initial-phase (IP) individuals, which may be females or smaller males, often engage in parasitic spawning by streaking into pairs to fertilize eggs undetected.^[65] Spawning in wrasses predominantly occurs in shallow, nearshore reef environments, where water currents aid in egg dispersal, and many species time these events with lunar cycles to optimize larval survival or sex ratios. For instance, the sixbar wrasse (Thalassoma hardwicki) preferentially spawns around the new moon, potentially linking light levels to offspring development, while other species like the bluehead wrasse exhibit year-round activity peaking in warmer months.^[66] In the Labrinae tribe, some species construct simple nests from algae or seagrass in sheltered crevices, where females deposit adhesive eggs for localized fertilization, contrasting with the pelagic broadcast typical of most labrids.^[1] These sites are selected for protection from predators and strong currents, ensuring higher egg viability.^[66] Parental care is rare among wrasses and limited to paternal efforts in select temperate and subtropical species, primarily within the genus Symphodus. Nesting males, such as those in the ocellated wrasse (Symphodus ocellatus), build and maintain nests from plant debris, fan eggs to oxygenate them, and vigorously defend against egg predators and intruding males, often at the expense of further mating opportunities.^[67] In the corkwing wrasse (Symphodus melops), larger males invest more time in nest guarding, correlating with higher hatching success, though care duration varies with environmental risks and male personality traits.^[68] Mouthbrooding is absent across the family, and in most tropical species, eggs are abandoned post-spawning, relying on high fecundity for recruitment.^[65] In protogynous wrasse species, sex change integrates seamlessly with reproductive behaviors, as transitioning individuals rapidly adopt male-typical aggression and courtship displays to compete for territories and mates. For example, in the bluehead wrasse, females induced to change sex by the removal of dominant males begin performing TP courtship rises and territorial patrols within hours, enhancing their access to harems.^[69] This behavioral plasticity, tied to the family's hermaphroditic systems, allows former females to shift from subordinate roles to dominant ones, often increasing reproductive output through harem formation.^[70]

Interactions and Significance

Parasites and Diseases

Wrasse in the family Labridae host a diverse assemblage of parasitic organisms, with 338 parasite records documented across 127 wrasse species globally.^[71] These include endoparasites such as trematodes (134 species) and nematodes (9 species), as well as ectoparasites like crustaceans, particularly copepods (44 species), and monogeneans (12 species) that commonly infest gills and skin.^[71] A representative nematode is Huffmanela ossicola, which embeds in the bones of labrid hosts, including branchial arches and spinal cords of species in the genus Bodianus, potentially causing structural damage to skeletal tissues. Parasitic infections in wrasse can impair host fitness by reducing growth rates through nutrient diversion and tissue damage, while severe infestations may induce sterility by disrupting reproductive organs or hormonal balance.^[72] Ecologically, these parasites integrate into reef food webs, where they may be transferred between hosts during interactions such as cleaning by mutualistic partners. In aquaculture contexts, wrasse face additional threats from diseases like viral nervous necrosis (VNN), caused by betanodaviruses, which has been identified in wild populations of species such as ballan wrasse (Labrus bergylta) and goldsinny wrasse (Ctenolabrus rupestris) along Norwegian and Swedish coasts, leading to central nervous system damage, behavioral abnormalities, and high mortality rates.^[73] Fungal infections, including those from Ichthyophonus hoferi, also affect stressed wrasse in farmed settings, manifesting as granulomatous lesions and elevated mortality in overcrowded or environmentally compromised populations.^[74] Host specificity is a prominent feature among wrasse parasites, with many taxa restricted to particular labrid species or genera, which enhances their utility in biodiversity assessments and phylogenetic analyses of coral reef fish communities.^[75]

Human Interactions and Conservation

Wrasses are harvested for various human uses, including as food fish in commercial fisheries. For instance, the tautog (Tautoga onitis), a North Atlantic wrasse, supports targeted fisheries where it is valued for its firm white flesh and caught using hook-and-line methods, contributing to regional seafood markets. Similarly, the humphead wrasse (Cheilinus undulatus) is prized in the live reef fish trade across Southeast Asia, where its flesh is considered a luxury delicacy and often transported alive to markets like those in Hong Kong for high-end consumption. Vibrant species such as the yellowbreasted wrasse (Anampses twistii) are popular in the marine aquarium trade, with approximately 90% of traded marine ornamental fish, including wrasses, sourced from wild coral reef habitats, potentially straining reef ecosystems. Additionally, species in the genus Labroides, known as cleaner wrasses, have been explored for use in aquaculture, though temperate wrasses like the goldsinny (Ctenolabrus rupestris) and ballan wrasse (Labrus bergylta) are more commonly deployed in salmon farms to control sea lice infestations by removing parasites from farmed Atlantic salmon (Salmo salar), reducing reliance on chemical treatments. Major threats to wrasse populations stem from overfishing, habitat degradation, and climate change. The humphead wrasse was assessed as Vulnerable by the IUCN in 1996 but has since declined sharply due to intense exploitation in the live reef trade, leading to its reclassification as Endangered on the IUCN Red List, with ongoing population reductions observed into 2025. Overfishing affects many wrasse species globally, including through destructive practices like cyanide fishing in reef areas. Habitat loss from coastal development and coral bleaching exacerbates these pressures, while climate change poses acute risks; a 2024 multi-stressor experiment revealed that the goldsinny wrasse exhibits high sensitivity to marine heatwaves, with 34% mortality under heat stress alone and 53% under combined warming, acidification, and hypoxia conditions. Conservation efforts for wrasses include international trade regulations and innovative monitoring technologies. The humphead wrasse (Cheilinus undulatus) has been listed on CITES Appendix II since 2004, requiring export permits to ensure trade does not threaten its survival and aiming to curb illegal international commerce. In 2025, a facial recognition application called Saving Face was launched in Hong Kong, utilizing AI to identify individual humphead wrasses by their unique facial patterns from photographs, aiding enforcement against illegal trade by verifying compliance with import permits. Protected marine areas also play a key role; the Great Barrier Reef Marine Park safeguards wrasse populations through zoning that prohibits fishing in no-take zones, supporting biodiversity and recovery for species like the Maori wrasse (Cheilinus chlorourus). Emerging issues include predation by invasive species and pathogen transmission from aquaculture. Invasive lionfish (Pterois volitans) in the western Atlantic heavily prey on the endangered social wrasse (Halichoeres socialis), comprising nearly half of their diet in Belizean reefs and compounding habitat threats to this narrowly ranged species. Furthermore, the use of farmed cleaner wrasses in salmon aquaculture risks spreading diseases to wild populations, as escaped or released fish can transmit pathogens like viral hemorrhagic septicemia to native wrasse stocks, highlighting the need for disease screening in aquaculture practices.