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Phenotypic macroevolutionary studies provide insight into how ecological processes shape biodiversity. However, the complexity of phenotype-ecology relationships underscores the importance of also validating phenotype-based ecological inference with direct evidence of resource use. Unfortunately, macroevolutionary-scale ecological studies are often hindered by the challenges of acquiring taxonomically and spatially representative ecological data for large and widely distributed clades. The South American cichlid fish tribe Geophagini represents a continentally distributed radiation whose early locomotor morphological divergence suggests habitat as one ecological correlate of diversification, but an association between locomotor traits and habitat preference has not been corroborated. Field notes accumulated over decades of collecting across South America provide firsthand environmental records that can be mined for habitat data in support of macroevolutionary ecological research. In this study, we applied a newly developed method to transform descriptive field note information into quantitative habitat data and used it to assess habitat preference and its relationship to locomotor morphology in Geophagini. Field note–derived data shed light on geophagine habitat use patterns and reinforced habitat as an ecological correlate of locomotor morphological diversity. Our work emphasizes the rich data potential of museum collections, including often-overlooked material such as field notes, for evolutionary and ecological research. [ABSTRACT FROM AUTHOR]

We used computer simulations of growth, mating and death of cephalopods and fishes to explore the effect of different life-history strategies on the relative prevalence of alternative male mating strategies. Specifically, we investigated the consequences of single or multiple matings per lifetime, mating strategy switching, cannibalism, resource stochasticity, and altruism towards relatives. We found that a combination of single (semelparous) matings, cannibalism and an absence of mating strategy changes in one lifetime led to a more strictly partitioned parameter space, with a reduced region where the two mating strategies co-exist in similar numbers. Explicitly including Hamilton’s rule in simulations of the social system of a Cichlid led to an increase of dominant males, at the expense of both sneakers and dwarf males (“super-sneakers”). Our predictions provide general bounds on the viable ratios of alternative male mating strategies with different life-histories, and under possibly rapidly changing ecological situations. [ABSTRACT FROM AUTHOR]

In biogeography, vicariance and long‐distance dispersal are often characterised as competing scenarios. However, they are related concepts, both relying on collective geological, ecological, and phylogenetic evidence. This is illustrated by freshwater fishes, which may immigrate to islands either when freshwater connections are temporarily present and later severed (vicariance), or by unusual means when ocean gaps are crossed (long‐distance dispersal). Marine barriers have a strong filtering effect on freshwater fishes, limiting immigrants to those most capable of oceanic dispersal. The roles of vicariance and dispersal are debated for freshwater fishes of the Greater Antilles. We review three active hypotheses [Cretaceous vicariance, Greater Antilles–Aves Ridge (GAARlandia), long‐distance dispersal] and propose long‐distance dispersal to be an appropriate model due to limited support for freshwater fish use of landspans. Greater Antillean freshwater fishes have six potential source bioregions (defined from faunal similarity): Northern Gulf of México, Western Gulf of México, Maya Terrane, Chortís Block, Eastern Panamá, and Northern South America. Faunas of the Greater Antilles are composed of taxa immigrating from many of these bioregions, but there is strong compositional disharmony between island and mainland fish faunas (>90% of Antillean species are cyprinodontiforms, compared to <10% in Northern Gulf of México and Northern South America, and ≤50% elsewhere), consistent with a hypothesis of long‐distance dispersal. Ancestral‐area reconstruction analysis indicates there were 16 or 17 immigration events over the last 51 million years, 14 or 15 of these by cyprinodontiforms. Published divergence estimates and evidence available for each immigration event suggests they occurred at different times and by different pathways, possibly with rafts of vegetation discharged from rivers or washed to sea during storms. If so, ocean currents likely provide critical pathways for immigration when flowing from one landmass to another. On the other hand, currents create dispersal barriers when flowing perpendicularly between landmasses. In addition to high salinity tolerance, cyprinodontiforms collectively display a variety of adaptations that could enhance their ability to live with rafts (small body size, viviparity, low metabolism, amphibiousness, diapause, self‐fertilisation). These adaptations likely also helped immigrants establish island populations after arrival and to persist long term thereafter. Cichlids may have used a pseudo bridge (Nicaragua Rise) to reach the Greater Antilles. Gars (Lepisosteidae) may have crossed the Straits of Florida to Cuba, a relatively short crossing that is not a barrier to gene flow for several cyprinodontiform immigrants. Indeed, widespread distributions of Quaternary migrants (Cyprinodon, Gambusia, Kryptolebias), within the Greater Antilles and among neighbouring bioregions, imply that long‐distance dispersal is not necessarily inhibitory for well‐adapted species, even though it appears to be virtually impossible for all other freshwater fishes. [ABSTRACT FROM AUTHOR]

This study investigates the morphological aspects of larval development in Maylandia estherae, an endemic cichlid species from Lake Malawi. Larvae obtained from mature broodstock were sampled daily from hatching until the juvenile stage, and their morphological development was observed under a microscope. Important morphological features such as mouth opening, exogenous feeding, free swimming, yolk sac, and pigmentation were observed and photographed. The findings indicate that M. estherae larvae reached the juvenile stage within approximately 20-25 days. Throughout larval development, it was determined that total length and mouth gape gradually increased, the yolk sac was depleted within 12-13 days, and exogenous feeding commenced alongside the development of free-swimming ability. Additionally, significant changes in fin differentiation and pigmentation were observed in the larvae. The larval development duration and morphological characteristics of M. estherae were found to be similar to those of other Malawi cichlid species. The findings of this study contribute to the understanding of the ontogenetic processes of M. estherae and have implications for aquaculture practices. Furthermore, the results provide a significant contribution to the literature on the larval development of Malawi cichlids and offer insights for future research. [ABSTRACT FROM AUTHOR]

In freshwater ecosystems, parasite infection patterns are influenced by factors including spatial–temporal variations, host diet, and habitat. Fish often change diets, affecting their parasite communities. This study focused on non-native host fish Geophagus sveni, aiming to characterize diet and endoparasitic helminth fauna patterns in the invaded area, investigating spatial and seasonal possible differences of endoparasite infections and correlating with host diet, in São José dos Dourados River and Tietê River areas. The host fish were collected in these areas during the dry and rainy season using gillnets. The endoparasites were collected and preserved in alcohol and identified using taxonomic methods, and stomach contents were examined for diet analysis. Parasitism descriptors were calculated and evaluated spatially and seasonally by ANOVA and the Kruskal–Wallis tests. PERMANOVA assessed G. sveni diet differences, and RDA correlated the endohelminth abundance with the host diet. Two endoparasites were recorded: metacercariae of Austrodiplostomum compactum (Trematoda) and larvae and adults of Raphidascaris (Sprentascaris) lanfrediae (Nematoda). Spatial differences were observed for the mean abundance and prevalence of R. (S.) lanfrediae and A. compactum prevalence. Seasonal variations of parasitic descriptors occurred for the nematode in the Tietê River area. The detritus and aquatic insects were the most consumed items by G. sveni. Detritus consumption positively correlates with nematode abundance. The findings indicate that factors such as artificial channels and rainfall, which can influence resource availability, may affect the fish’s diet and potentially influence the structure of its endoparasite community. The study emphasizes the importance of understanding trophic chain-transmitted parasites and calls for further research in Neotropical environments. [ABSTRACT FROM AUTHOR]

During courtship, prezygotic barriers are thought to maintain the diversity of species since differences in phenotypic traits and reproductive behaviours are likely to be involved in maintaining species boundaries. However, introgressive hybridization has been reported in many different taxa and the resulting hybrids usually possess phenotypic features, including behaviours, that are intermediate between those of the parents. The outcome of hybrids may depend on the interactions between the intrinsic viability of the hybrids, the ecological environment of the species, and the fitness of hybrids in that ecological context. In cichlids, the mechanism of hybridization is increasingly documented as an important factor in their evolutionary radiation since it may provide novel gene combinations that promote speciation and adaptive radiation by generating new transgressive phenotypes. Cichlid species are separated mostly by pre-mating isolating mechanisms. Like colour patterns, acoustic communication is involved in sexual selection, but this pattern has been much less studied and the outcome of hybridization on acoustic features has never been examined. To gain novel insights into the evolution of their acoustic communication behaviour, we performed a hybrid cross between Chindongo saulosi and Maylandia estherae. Qualitative examination of courtship showed that the three groups possess the same sequence of behaviours. However, sounds produced during courtship showed specific signatures since all three groups differ at the level of sound duration and pulse period, with both features being intermediate in hybrids in comparison to the two parent species. Colour patterns in hybrids were also different from those of the parent species. These results show that hybridization can affect at least two kinds of prezygotic barriers, which may be important in the cichlid evolutionary process. However, playback experiments are required to test the strength of these features in sexual selection. [ABSTRACT FROM AUTHOR]

Body shape is a morphological attribute that frequently changes as organisms adapt to environmental fluctuations and optimize the use of available resources. In fish whose distribution includes estuarine and riverine environments, it is common to observe changes in body shape that are related to maneuverability and speed of movement in response to temporal and spatial variation in water flow. Here, through geometric morphometric and linear morphometric analysis, the intraspecific morphological variation of the cichlids Amphilophus trimaculatus, Astatheros macracanthus, and Mayaheros beani was evaluated to determine if there are repeated patterns of variation in body shape associated with estuarine and riverine environments. The three species showed the same trend of morphological variation; in the estuaries, the specimens were generally deeper and robust, with a long head and short caudal peduncle, while river specimens had shallowed and fusiform bodies with a short head and long caudal peduncle. The magnitude of the changes was not the same in the three species, as M. beani showed greater differentiation, and some morphological measures showed changes in opposite directions between the species. These findings indicate that the environment occupied by the species is an important factor in the differentiation of body shape, probably due to water flow, although other factors may determine the magnitude and direction of change in some morphological traits. [ABSTRACT FROM AUTHOR]

In this study, mitochondrial genomes (mitogenomes) of seven cichlid species (Lamprologus kungweensis, L. meleagris, L. ornatipinnis, Neolamprologus brevis, N. caudopunctatus, N. leleupi, and N. similis) are characterized for the first time. The newly sequenced mitogenomes contained 37 typical genes [13 protein-coding genes (PCGs), two ribosomal RNA genes (rRNAs) and 22 transfer RNA genes (tRNAs)]. The mitogenomes were 16,562 ~ 16,587 bp in length with an A+T composition of 52.1~58.8%. The cichlid mitogenomes had a comparable nucleotide composition, A+T content was higher than the G+C content. The AT-skews of most mitogenomes were inconspicuously positive and the GC-skews were negative, indicating higher occurrences of C than G. Most PCGs started with the conventional start codon, ATN. There was no essential difference in the codon usage patterns of these seven species. Using Ka/Ks, we found the fastest-evolving gene were atp8. But the results of p-distance indicated that the fastest-evolving gene was nad6. Phylogenetic analysis revealed that L. meleagris did not cluster with Lamprologus species, but with species from the genus Neolamprologus. The novel information obtained about these mitogenomes will contribute to elucidating the complex relationships among cichlid species. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Polycyclic aromatic hydrocarbons are present in all environmental matrices. Polycyclic aromatic hydrocarbons-rich wastewater from the oil industry is discharged into natural water bodies. Detritivorous fish shown the effects of pollutants in water. Biomarkers of effect make it possible to demonstrate exposure to xenobiotics such as polycyclic aromatic hydrocarbons. The aim of the present study was to evaluate the hepatic and erythrocyte response in Aequidens metae, a detritivorous fish, exposed to polycyclic aromatic hydrocarbons in terms of morphological, biochemical, and genotoxic changes.METHODS: Juveniles of Aequidens metae were exposed to 50 microgram per gram body weight of beta-naphthoflavone, 100 microgram per gram of naphthalene, 50 microgram per gram of phenanthrene and 10 microgram per gram of benzo[a]pyrene, for 72 hours. Water quality variables, total protein content, 7-ethoxyresorufin-O-deethylase activity, liver histopathological changes and genotoxic alterations in peripheral blood were measured during the assay.FINDING: In polycyclic aromatic hydrocarbons-exposed fish, analysis of liver tissue revealed parenchymal lesions and changes in the number and shape of hepatocyte nuclei. On the other hand, only fish exposed to benzo[a]pyrene shown significant increase in the 7-ethoxyresorufin-O-deethylase activity compared to solvent control. In peripheral blood erythrocytes, increased presence of nuclear abnormalities was higher in fish exposed to phenanthrene, followed by benzo[a]pyrene, beta-naphthoflavone, and naphthalene.CONCLUSIONS: It is concluded that Aequidens metae is a suitable bioindicator for polycyclic aromatic hydrocarbons monitoring in aquatic ecosystems. Phenanthrene reveals for the first time a greater genotoxic effect than benzo[a]pyrene at sublethal concentrations. Juveniles of Aequidens metae exposed to concentrations of polycyclic aromatic hydrocarbons close to those found in the environment showed health-compromising damage.

Antecedentes: La tilapia (Oreochromis niloticus) es de importancia comercial y alimenticia para las familias nicaragüense. Objetivo: Evaluar el crecimiento de tilapia en estanques de liner, aplicando dos tipos de alimento multifuncional que contenían 24% y 14% de proteína. Metodología: Se seleccionaron dos estanques (G1 y G2), cada uno con capacidad de 90 toneladas de agua, en un sistema de producción semiintensiva. Ambos estanques fueron sembrados con una densidad de 13 peces/m², con pesos promedio iniciales de 22.9 g en G1 con fuente de alimento multifuncional de 24% de proteína y 20.2 g en G2 con alimento multifuncional de 14% de proteina. Se realizaron monitoreos biométricos semanales durante 9 semanas, así como un registro de parámetros fisicoquímicos dos veces al día, excepto la turbidez, que se midió a las 12:00 p.m. Resultados: Los resultados indicaron que los parámetros fisicoquímicos se mantuvieron dentro de rangos óptimos a lo largo del cultivo, sin variaciones significativas. Adicionalmente, el análisis de la densidad de microalgas en el estanque reveló que el alimento multifuncional con 24% de proteína no solo favoreció el incremento de biomasa, sino que también mejoró la productividad natural del ecosistema. El crecimiento registrado en el estanque con el alimento de 24% de proteína alcanzó los 135g, en comparación con los 98g en el estanque con alimento de 14% de proteína. Conclusión: Los tratamientos en estudio presentaron un Factor de Conversión Alimentaria de 0.7 al final del cultivo, estos resultados refuerzan la importancia de los contenidos proteicos en el crecimiento de tilapia.

Tourism has increased the contact of tourists with the aquatic environment and is transporting harmful substances such as benzophenone (BP-3) into the water. This is an emerging contaminant present in sunscreens and other cosmetics, which can alter the behavior of fish by acting on the hypothalamus-pituitary-gonad axis. We hypothesized that the use of the water column, feeding, and aggressiveness would be affected by this contaminant. Thirty-six juvenile male Nile tilapia (Oreochromis niloticus) exposed to BP-3 for 1 to 97 hours were analyzed. We compared the time spent at the bottom of the tank, the latency to feed, and the latency to attack a mirror between control and three BP-3 concentrations using an Anova, both parametric and non-parametric followed by post-hoc tests. We observed that the fish spent less time at the bottom of the tank, a normal condition for tilapia, and ate faster, but showed no change in aggressiveness. Effects varied with concentration and duration of exposure. Previous studies have shown similar results with other fish species, suggesting the metabolic cost of BP-3 as a contaminant, but with no significant effect on aggressiveness. Ours is the first study to address the effect of BP-3 on aggressiveness and habitat use of a bottom-dweller and territorial fish also widely used in aquaculture. Protection against ultraviolet radiation is necessary, but the use of BP-3 for this purpose should be considered with caution.

Abstract The increase in the number of Brazilian protected areas has been progressive and, although it is essential for the conservation of biodiversity, it is important to monitor and properly manage these areas, as they present several cases of biological invasions. The Lençóis Maranhenses constitute the peculiar delta of the Americas and are under the consequences of the bioinvasion of tilapias and peacock bass. Collections were carried out in the Lençóis Maranhenses National Park from March/2016 to November/2020, with the aid of gill nets and cast nets. The species were identified with the help of specialized literature and a historical comparison with previous works was carried out. Cytochrome oxidase subunit I was sequenced to confirm identification of non-native species. We recorded the expansion of the occurrence of Oreochromis niloticus, and the first record of the species Oreochromis mossambicus and Cichla monoculus. A total of 31 species belonging to eight orders, eighteen families and twenty-nine genera were identified, indicating a lag in the diversity of species found in relation to previous studies. After 20 years of the first record of invasive fish, there is an expansion of bioinvasion and new cases that indicate a lack of monitoring and containment measures for the species, indicating the fragility of conservation in the area

The modified pharyngeal jaw system of cichlid fishes is widely viewed as a key innovation that substantially facilitated the evolutionary exuberance of this iconic evolutionary radiation. We conduct comparative phylogenetic analyses of integration, disparity, and rate of evolution among feeding-related, skeletal structures in Neotropical cichlids and North American centrarchids, which lack the specialized pharyngeal jaw. Contrasting evolutionary patterns in these two continental radiations, we test a classic decoupling hypothesis. Specifically, we ask whether the modified pharyngeal jaw in cichlids resulted in enhanced evolutionary independence of the oral and pharyngeal jaws, leading to increased diversity of trophic structures. Contrary to this prediction, we find significantly stronger evolutionary integration between the oral and pharyngeal jaws in cichlids compared to centrarchids, although the two groups do not differ in patterns of integration within each jaw system. Further, though we find no significant differences in disparity, centrarchids show faster rates of morphological evolution. Our results suggest that the modified pharyngeal jaw resulted in less evolutionary independence and slower rates of evolution within the feeding system. Thus, we raise the possibility that the cichlid novelty enhances feeding performance, but does not prompt increased morphological diversification within the feeding apparatus, as has long been thought. [ABSTRACT FROM AUTHOR]

The East African Great Lakes are inhabited by impressive radiations of cichlids that display a large variation in morphology, diet, colour pattern, and behaviour and have adapted to a large array of niches. Whilst most of these cichlids are bottom dwellers, a number of species have adapted to a pelagic environment and inhabit open waters. From the Lake Edward system, one pelagic species had been previously described, the zooplanktivorous Haplochromis pappenheimi. Our sampling revealed the Lake Edward system to be inhabited by two more pelagic species that were unknown to science and are formally described here, the zooplanktivorous Haplochromis pelagicus sp. nov. and the insectivorous H. aureus sp. nov. All three species seem mostly restricted to deepwater regions where the depth exceeds six metres in Lake Edward, except for H. pelagicus sp. nov., which also occurs in shallower regions of Lakes Edward and George and of the Kazinga Channel. Sexual dimorphism, mainly in head shape, was discovered in H. pappenheimi and H. pelagicus sp. nov. These differences suggest that females of these species have larger buccal cavities than males, which is most likely linked to female mouth brooding behaviour. [ABSTRACT FROM AUTHOR]

Divergence in body shape is one of the most widespread and repeated patterns of morphological variation in fishes and is associated with habitat specification and swimming mechanics. Such ecological diversification is the first stage of the explosive adaptive radiation of cichlid fishes in the East African Rift Lakes. We use two hybrid crosses of cichlids (Metriaclima sp. × Aulonocara sp. and Labidochromis sp. × Labeotropheus sp., >975 animals total) to determine the genetic basis of body shape diversification that is similar to benthic‐pelagic divergence across fishes. Using a series of both linear and geometric shape measurements, we identified 34 quantitative trait loci (QTL) that underlie various aspects of body shape variation. These QTL are spread throughout the genome, each explaining 3.2–8.6% of phenotypic variation, and are largely modular. Further, QTL are distinct both between these two crosses of Lake Malawi cichlids and compared to previously identified QTL for body shape in fishes such as sticklebacks. We find that body shape is controlled by many genes of small effect. In all, we find that convergent body shape phenotypes commonly observed across fish clades are most likely due to distinct genetic and molecular mechanisms. [ABSTRACT FROM AUTHOR]

Life-history traits (LHT) of Oreochromis niloticus in the Sidi Mohamed Ben Abdellah reservoir (BA reservoir) and Oreochromis aureus in the Nador Channel were studied and compared with those of other populations in the world. Specimens were collected between June 2018 and June 2020. Females of both species were smaller at first sexual maturity than males (O. niloticus: 204 vs. 255 mm, O. aureus: 147 vs. 158 mm). The age of maturity for each species was estimated from seasonal otolith growth marks, based on the von Bertalanffy growth function. The asymptotic length was higher in O. niloticus (males 296 mm and females 339 mm) than in O. aureus (males 171 mm and females 169 mm). Based on a literature survey and the results of this study, the type of ecosystem (reservoir vs. river) influenced growth performance indices (φ and φ′) in both species, with reservoirs leading to a higher asymptotic length in both O. niloticus and O. aureus than rivers. Moroccan populations presented the lowest growth index in the populations assessed. These observations suggest that while both invasive species were able to colonise and adapt to their new environments, this was at the expense of limiting their growth and reducing their size at first sexual maturity. [ABSTRACT FROM AUTHOR]

Because of potentially strong eco-evolutionary interactions with their hosts, parasites may initiate or enhance host diversification. The adaptive radiation of cichlid fish in Lake Victoria provides a good system to study the role of parasites at different stages of host speciation. We analyzed the macroparasite infection of four replicates of sympatric blue and red Pundamilia species pairs that vary in their age and extent of differentiation. Sympatric host species differed in parasite community composition and in the infection levels of some of these parasite taxa. Most infection differences were consistent between sampling years, indicating temporal consistency in parasite-mediated divergent selection between species. Infection differentiation increased linearly with genetic differentiation. However, significant infection differences between sympatric species were only found in the oldest, most strongly differentiated Pundamilia species pair. This is inconsistent with parasite-driven speciation. Next, we identified five distinct species of Cichlidogyrus , a genus of highly specific gill parasites that has radiated elsewhere in Africa. Infection profiles of species of Cichlidogyrus differed between sympatric cichlid species only in the oldest and most differentiated pair, again inconsistent with parasite-mediated speciation. To conclude, parasites may contribute to host differentiation after speciation, but do not initiate host speciation. [ABSTRACT FROM AUTHOR]

Variation in fin shape is one of the most prominent features of morphological diversity among fish. Regulation of fin growth has mainly been studied in zebrafish, and it is not clear whether the molecular mechanisms underlying shape variation are equally diverse or rather conserved across species. In the present study, expression levels of 37 candidate genes were tested for association with fin shape in the cichlid fish Lamprologus tigripictilis. The tested genes included members of a fin shape-associated gene regulatory network identified in a previous study and novel candidates selected within this study. Using both intact and regenerating fin tissue, we tested for expression differences between the elongated and the short regions of the spade-shaped caudal fin and identified 20 genes and transcription factors (including angptl5, cd63, csrp1a, cx43, esco2, gbf1, and rbpj), whose expression patterns were consistent with a role in fin growth. Collated with available gene expression data of two other cichlid species, our study not only highlights several genes that were correlated with fin growth in all three species (e.g., angptl5, cd63, cx43, and mmp9), but also reveals species-specific gene expression and correlation patterns, which indicate considerable divergence in the regulatory mechanisms of fin growth across cichlids. [ABSTRACT FROM AUTHOR]

A new find of the blue tilapia Oreochromis aureus (Steindachner, 1864) from the Volga River, in the area of the Kostroma State District Power Station (57°28′02″ N, 41°11′06″ E), is described. Data on morphology and nucleotide diversity (COI, 16S and 18 loci) for O. aureus are given. It is assumed that the vector of invasion is associated with human activity. There is a high probability of the formation of a large population of blue tilapia in this area. [ABSTRACT FROM AUTHOR]

The speckled peacock bass Cichla temensis is a popular sport and food fish that generates substantial angling tourism and utilitarian harvest within its range. Its popularity and value make this species important for management and a potential aquaculture candidate for both fisheries enhancement and food fish production. However, little is known of optimal physiochemical conditions in natural habitats, which also are important for the development of hatchery protocols for handling, spawning and grow‐out. Speckled peacock bass have been documented to have high sensitivity to extreme temperatures, but the metabolic underpinnings have not been evaluated. In this study, the effects of temperature (25, 30 and 35°C) on the standard metabolic rate (SMR) and lower dissolved oxygen tolerance (LDOT) of juvenile speckled peacock bass (mean ± standard error total length 153 ± 2 mm and wet weight 39.09 ± 1.37 g) were evaluated using intermittent respirometers after an acclimation period of 2 weeks. Speckled peacock bass had the highest SMR at 35°C (345.56 ± 19.89 mgO2 kg−1 h−1), followed by 30°C (208.16 ± 12.45 mgO2 kg−1 h−1) and 25°C (144.09 ± 10.43 mgO2 kg−1 h−1). Correspondingly, the Q10, or rate of increase in aerobic metabolic rate (MO2) relative to 10°C, for 30–35°C was also greater (2.76) than from 25 to 30°C (2.08). Similarly, speckled peacock bass were the most sensitive to hypoxia at the warmest temperature, with an LDOT at pO2 of 90 mmHg (4.13 mg l−1) at 35°C compared to pO2 values of 45 mmHg (2.22 mg l−1) and 30 mmHg (1.61 mg l−1) at 30 and 25°C, respectively. These results indicate that speckled peacock bass are sensitive to temperatures near 35°C, therefore we recommend managing and rearing this species at 25–30°C. [ABSTRACT FROM AUTHOR]

Between March 2015 and September 2016, three species of Cichlidae (Coptodon rendalli, Oreochromis mossambicus and Tilapia sparrmanii) were screened for the presence of stomach monogeneans. Four localities across three provinces of South Africa (Limpopo, Northern Cape and North West) were sampled and a total of five Enterogyrus species were identified, viz. E. cichlidarum, E. coronatus, E. malmbergi, E. mashegoi and E. multispiralis. Finding E. malmbergi from O. mossambicus and T. sparrmanii represents new host and geographic records. Enterogyrus coronatus was reported from C. rendalli and T. sparrmanii from three localities. Both hosts are new host records for the species and show a wide distribution of E. coronatus within South Africa. Tilapia sparrmanii is a new host record for E. cichlidarum, E. mashegoi and E. multispiralis. Enterogyrus mashegoi and E. cichlidarum are reported from new localities. [ABSTRACT FROM AUTHOR]

African cichlids are model systems for evolutionary studies and host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Five locations were sampled in southern Lake Victoria: gill-infecting monogeneans were surveyed from 18 cichlid species belonging to this radiation superflock and two others representing two older and distantly related lineages. We found one species of Gyrodactylidae, Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Dactylogyridae. Four are described herein: Cichlidogyrus pseudodossoui n. sp., Cichlidogyrus nyanza n. sp., Cichlidogyrus furu n. sp., and Cichlidogyrus vetusmolendarius n. sp. Another Cichlidogyrus species is reported but not formally described (low number of specimens, morphological similarity with C. furu n. sp.). Two other species are redescribed: C. bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the others, highlighting the need to re-evaluate the current classification system that considers hook pairs III–VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis, and C. nyanza n. sp. suggest that these are closely related to congeners that infect other haplochromines. Morphological traits indicate that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonised by two cichlid tribes (Haplochromini and Oreochromini).

BACKGROUND AND OBJECTIVES: Polycyclic aromatic hydrocarbons are present in all environmental matrices. Polycyclic aromatic hydrocarbons-rich wastewater from the oil industry is discharged into natural water bodies. Detritivorous fish shown the effects of pollutants in water. Biomarkers of effect make it possible to demonstrate exposure to xenobiotics such as polycyclic aromatic hydrocarbons. The aim of the present study was to evaluate the hepatic and erythrocyte response in Aequidens metae, a detritivorous fish, exposed to polycyclic aromatic hydrocarbons in terms of morphological, biochemical, and genotoxic changes. METHODS: Juveniles of Aequidens metae were exposed to 50 microgram per gram body weight of beta-naphthoflavone, 100 microgram per gram of naphthalene, 50 microgram per gram of phenanthrene and 10 microgram per gram of benzo[a]pyrene, for 72 hours. Water quality variables, total protein content, 7-ethoxyresorufin-O-deethylase activity, liver histopathological changes and genotoxic alterations in peripheral blood were measured during the assay. FINDINGS: In polycyclic aromatic hydrocarbons-exposed fish, analysis of liver tissue revealed parenchymal lesions and changes in the number and shape of hepatocyte nuclei. On the other hand, only fish exposed to benzo[a]pyrene shown significant increase in the 7-ethoxyresorufin-O-deethylase activity compared to solvent control. In peripheral blood erythrocytes, increased presence of nuclear abnormalities was higher in fish exposed to phenanthrene, followed by benzo[a]pyrene, beta-naphthoflavone, and naphthalene. CONCLUSION: It is concluded that Aequidens metae is a suitable bioindicator for polycyclic aromatic hydrocarbons monitoring in aquatic ecosystems. Phenanthrene reveals for the first time a greater genotoxic effect than benzo[a]pyrene at sublethal concentrations. Juveniles of Aequidens metae exposed to concentrations of polycyclic aromatic hydrocarbons close to those found in the environment showed health-compromising damage. [ABSTRACT FROM AUTHOR]

Tourism has increased the contact of tourists with the aquatic environment and is transporting harmful substances such as benzophenone (BP-3) into the water. This is an emerging contaminant present in sunscreens and other cosmetics, which can alter the behavior of fish by acting on the hypothalamus-pituitary-gonad axis. We hypothesized that the use of the water column, feeding, and aggressiveness would be affected by this contaminant. Thirty-six juvenile male Nile tilapia (Oreochromis niloticus) exposed to BP-3 for 1 to 97 hours were analyzed. We compared the time spent at the bottom of the tank, the latency to feed, and the latency to attack a mirror between control and three BP-3 concentrations using an Anova, both parametric and non-parametric followed by post-hoc tests. We observed that the fish spent less time at the bottom of the tank, a normal condition for tilapia, and ate faster, but showed no change in aggressiveness. Effects varied with concentration and duration of exposure. Previous studies have shown similar results with other fish species, suggesting the metabolic cost of BP-3 as a contaminant, but with no significant effect on aggressiveness. Ours is the first study to address the effect of BP-3 on aggressiveness and habitat use of a bottom-dweller and territorial fish also widely used in aquaculture. Protection against ultraviolet radiation is necessary, but the use of BP-3 for this purpose should be considered with caution. [ABSTRACT FROM AUTHOR]

A new species of cichlid fish, Lethrinops atrilabris is described from specimens collected by trawling at a depth of around 90 m off Monkey Bay, southern Lake Malawi. It is assigned to the genus Lethrinops on the basis of its vertical flank barring, lack of enlarged cephalic lateral line canal pores and the form of the lower jaw dental arcade. It can be distinguished from congeneric species by its male breeding dress of contrasting flank barring and dark ventral surface, most strikingly on the lips, throat and chest, its relatively small known maximum size [<75 mm standard length (SL)], large eyes (38%–41% head length), laterally compressed body (depth 2.5–2.7 times max head width) and lower gill raker count (13–14). [ABSTRACT FROM AUTHOR]

A new species of Geophagus sensu stricto is described from the Tapajos River basin, Brazil, elevating the number of species of the genus to 21. The new species is of commercial importance and is known in the aquarist trade as Geophagus 'red head'. The new species is diagnosed using an integrative approach, based on mitochondrial DNA analysis along with morphological evidence. The new species is distinguished from all congeners by the absence of markings on the head, the bar pattern composed by nine vertical bars on the flanks and the presence of distinct longitudinal bands in the caudal fin. Additionally, it shows a genetic distance of at least 2.0% in cytochrome b gene sequences from its closest congeners. Molecular analysis including most genera of Cichlidae from South America corroborates that the new species belongs to the group of Geophagus sensu stricto. [ABSTRACT FROM AUTHOR]

Simple Summary: Morphological variation studies allow us to understand the mechanisms and factors that generate variations in populations, thus allowing the development of conservation plans and sustainable management of species. The "yellow mojarra", Caquetaia kraussii (Perciformes: Cichlidae), is a species native to Colombia and Venezuela that recently has become an essential species in the food security of many Colombian fishing families. Geometric morphometrics (GM) is a tool that quantifies the variation of a shape through multivariate analysis, allowing its graphical and easy visualization. To measure the phenotypic variation of C. kraussii in different localities in "Canal del Dique", Colombia, advanced morphological tools were used to quantify fish shape and evaluate associations between different ecological parameters of the study sites and the morphological differentiation of their populations. Morphological differences between localities were found and the influence of environmental parameters on the geometric shape of C. kraussii was also evidenced. These results demonstrates the efficiency of combined geometrics morphometrics with ecomorphological analysis to evaluate the impact of environmental pressures on fish body shape. Understanding the interspecific morphological variability of Caquetaia kraussii (Perciformes: Cichlidae) between different localities in its distribution range is becoming essential, as this species constitutes a valuable resource for the economy and subsistence of the local human communities where it is endemic in Colombia and Venezuela. In order to develop efficient farming and handling plans for this species, a deep understanding of the factors and mechanisms generating morphological variability is crucial. This study analyzes the morphological variability of C. kraussii by using geometric morphometrics in four localities distributed between the Dique and North channels, which are part of the Bolívar department in Colombia. Likewise, the effect of environmental variables such as temperature (T°), dissolved oxygen (OD) and pH on morphological variability was analyzed using a partial least squares approach. The results show that environmental stress has an influence on ~10% of the body shape of C. kraussii, whereas ~90% of the body shape is not directly influenced by environmental parameters, suggesting an effect from stress related to sexual dimorphism. Similarly, the analyses show shape variation among localities, mainly between populations of lotic environments and those of lentic environments. This morphological disparity seems to be subject to environmental and sexual stresses in the different localities. [ABSTRACT FROM AUTHOR]

This study aims to report the non-native occurrence of Crenicichla semifasciata in the Upper Paraná River in the floodplain region, and the first record of the pughead condition in the species. C. semifasciata was described from the Paraguay River and there are already registers of individuals in the Upper Paraná River basin. The register downstream, in the floodplain region, could be associated with aquarium trade, however, the most likely hypothesis is the anthropological introduction to exploitation in sport fishing. The introduction of C. semifasciata, as well as the discovery of the pugheaded specimen, indicate that humans are most likely interfering with the floodplain region, which is crucial to biological diversity in the Upper Paraná River basin. [ABSTRACT FROM AUTHOR]

Copyright of Acta Natura & Scientia is the property of Semih Kale and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Neotropical cichlids are a group of fish among which there are species with reversed sexual dichromatism, where females have carotenoid-based coloration that males lack. Carotenoid coloration can vary depending on the environment and the distribution of other types of chromatophores in the pigment pattern. The role of thyroid hormones (THs), one of the main signaling molecules regulating fish ontogeny, in the diversity of carotenoid coloration in Neotropical cichlid females remained poorly understood. In this work, using the species Amatitlania nigrofasciata, the effect of elevated TH level on the development of reversed sexual dichromatism was shown. Increases in TH signaling in experimental fish led to heterochrony in the development of the pigment pattern and phenotypic variability with the appearance of variants of carotenoid pigmentation similar to other Neotropical cichlid species. The extent of carotenoid-based ventral coloration of females depended on TH-induced changes in the melanistic pattern. The results obtained testify in favor of the important role of the TH signaling pathway in the diversification of the carotenoid coloration of Neotropical cichlids and provide new perspectives for studying the role of plasticity in the evolutionary adaptation of cichlid fishes. [ABSTRACT FROM AUTHOR]

Males and females of various species spend energy on different activities throughout the day in their natural environment. Thus, the present study aimed to assess whether males and females of A. nyassae differ in learning and preferences through two experiments. Experiment 1 subjected animals to learning by association in a T-maze test. Experiment 2 subjected males and females to a preference test in a T-maze, with each tank arm receiving one of the two following positive stimuli: shelter or food. Experiment 1 found that both sexes were able to learn the association between neutral and positive stimuli. Experiment 2 found that, regardless of sex, the animals frequented more the arm with the presence of shelter. This study demonstrates that males and females of A. nyassae were able to learn the task of object and food association and also preferred to take shelter over eating, even after exposure to stress. [ABSTRACT FROM AUTHOR]

Stripe patterns are a striking example for a repeatedly evolved color pattern. In the African adaptive radiations of cichlid fishes, stripes evolved several times independently. Previously, it has been suggested that regulatory evolution of a single gene, agouti‐related‐peptide 2 (agrp2), explains the evolutionary lability of this trait. Here, using a comparative transcriptomic approach, we performed comparisons between (adult) striped and nonstriped cichlid fishes of representatives of Lake Victoria and the two major clades of Lake Malawi (mbuna and non‐mbuna lineage). We identify agrp2 to be differentially expressed across all pairwise comparisons, reaffirming its association with stripe pattern divergence. We therefore also provide evidence that agrp2 is associated with the loss of the nonstereotypic oblique stripe of Mylochromis mola. Complementary ontogenetic data give insights into the development of stripe patterns as well as vertical bar patterns that both develop postembryonically. Lastly, using the Lake Victoria species pair Haplochromis sauvagei and Pundamilia nyererei, we investigated the differences between melanic and non‐melanic regions to identify additional genes that contribute to the formation of stripes. Expression differences—that most importantly also do not include agrp2—are surprisingly small. This suggests, at least in this species pair, that the stripe phenotype might be caused by a combination of more subtle transcriptomic differences or cellular changes without transcriptional correlates. In summary, our comprehensive analysis highlights the ontogenetic and adult transcriptomic differences between cichlids with different color patterns and serves as a basis for further investigation of the mechanistic underpinnings of their diversification. Highlights: A single gene, agouti‐related‐peptide 2 (agrp2), shows robust gene expression differences between African cichlid fish species that repeatedly evolved similar stripe patterns.Expression differences of agrp2 do not only associate with stereotypic patterns in cichlids, but also with the oblique stripe patterns found in some cichlids of Lake Malawi.Horizontal stripe patterns form postembryonically and, in most species, much later than vertical bar patterns.Spatial gene expression variation between pigmented and non‐pigmented regions of Lake Victoria cichlid bar and stripe patterns is subtle. [ABSTRACT FROM AUTHOR]

Peacock basses (genus Cichla) are Amazonian piscivorous fish that have been widely introduced into freshwater systems and caused great ecological impacts. Our goal was to assess the worldwide distribution of Cichla ocellaris and C. kelberi to delineate their niche and predict the most suitable areas for their invasion using data available in the scientific literature. We combined ecological niche models to identify hotspots of environmental suitability and invasion risk worldwide, in addition to niche similarity analysis in the geographic space, principal component analysis in the environmental space, and bias metric to assess niche changes between native and non-native ranges. We found 373 records (88 native and 285 non-native populations) for the occurrence of C. kelberi and C. ocellaris in several ecoregions around the world. Native populations were restricted to Amazonian and Tocantins-Araguaia ecoregions. Suitable areas for both species were concentrated within the tropical climatic zone. Amid the top 10 ecoregions more suitable for their occurrence there are four in Africa, one in Asia and also one in Brazil. The Upper Parana ecoregion deserves special highlight due to its prevalence in the number of non-native records and also of suitable areas for new invasions. There was a great increase in the Extent of Occurrence of non-native occurrences compared to native records. We found a moderate niche overlap in the geographical space and a high overlap in the environmental space between native and non-native ranges for both species, suggesting niche conservatism, but with some dissimilarity, higher for C. ocellaris. [ABSTRACT FROM AUTHOR]

C. kraussii is an endemic fish species from Colombia and Venezuela and represents a valuable food resource for local human communities. Due to its economic importance, the management and captive breeding of this species are of special interest. However, the anatomical similarities between sexes have been a problem for visual identification. It is also important to indicate that C. kraussii has cryptic morphological behavior between sexes, a topic that has been one of the main problems for the implementation of management plans. The following research studied individuals from three different localities along the Canal del Dique, Bolívar Department in Colombia, in which the body shape of C. kraussii was analyzed using geometric morphometric analysis. The analyses detected the presence of intralocality sexual dimorphism in two of the three localities analyzed, showing a low morphological variability among males, presenting conserved body shape, as well as a greater morphological disparity among females. This sexual shape dimorphism may be associated with the environmental variation among different locations. These results suggest the presence of two evolutionary forces acting asymmetrically between the sexes of C. kraussii, with males mostly subject to sexual selection pressure, while females are mainly subject to environmental pressures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gill monogeneans on Neotropical cichlid fish were studied. • Species of Gussevia , Trinidactylus , and Scadicleithrum were identified. • The high diversity of cichlid monogeneans was revealed. • Divergent lineages of Sciedicleithrum from South America and Mexico were inferred. • Host switch and duplication were the main coevolutionary events for monogeneans. Host-parasite coevolution is one of the main topics of the evolutionary biology of host-parasite associations. The majority of monogeneans parasitizing fish exhibit a high degree of host specificity. As a result, their evolutionary history might be intertwined with that of their fish hosts. The Cichlidae represent a diverse group of secondary freshwater fish with disjunctive distribution. Host-specific dactylogyrid monogeneans commonly parasitize cichlid fish. Their high diversity is associated with the main areas of cichlid distribution, i.e., Neotropical America and Africa. Nevertheless, the parasite fauna of cichlids from Neotropical America is still underexplored. A total of 31 cichlid species were examined for the presence of monogeneans, with 20 of them being parasitized. On these cichlids, 30 monogeneans belonging to the genera Gussevia , Trinidactylus , and Scadicleithrum were identified, 17 of them potentially representing new species for science. Phylogenetic analyses revealed three monophyletic groups of Neotropic cichlid monogeneans. Genus Gussevia was monophyletic, while Sciadicleithrum resulted polyphyletic. Sciedicleithrum from South America and Sciadicleithrum from Mexico represented two divergent lineages. The plesiomorphic Neotropical cichlid host group for dactylogyrid monogeneans was Cichlini, from which the representatives of other Neotropical cichlid tribes were colonised. Cophylogenetic analyses revealed a statistically significant cophylogenetic signal in the investigated host-parasite system, with host switch and duplication representing the main coevolutionary events for monogeneans parasitizing Neotropical cichlids. This scenario is in accordance with previous studies focussed on dactylogyridean monogeneans parasitizing freshwater fish in Europe and Africa. [ABSTRACT FROM AUTHOR]

Many species‐rich ecological communities emerge from adaptive radiation events. Yet the effects of adaptive radiation on community assembly remain poorly understood. Here, we explore the well‐documented radiations of African cichlid fishes and their interactions with the flatworm gill parasites Cichlidogyrus spp., including 10,529 reported infections and 477 different host–parasite combinations collected through a survey of peer‐reviewed literature. We assess how evolutionary, ecological, and morphological parameters determine host–parasite meta‐communities affected by adaptive radiation events through network metrics, host repertoire measures, and network link prediction. The hosts' evolutionary history mostly determined host repertoires of the parasites. Ecological and evolutionary parameters predicted host–parasite interactions. Generally, ecological opportunity and fitting have shaped cichlid‐Cichlidogyrus meta‐communities suggesting an invasive potential for hosts used in aquaculture. Meta‐communities affected by adaptive radiations are increasingly specialised with higher environmental stability. These trends should be verified across other systems to infer generalities in the evolution of species‐rich host–parasite networks. [ABSTRACT FROM AUTHOR]

Conflict solving strategies can prevent fights from escalating and reduce the costs of aggressive encounters. Having the capacity to efficiently assess an opponent's fighting abilities before fully committing to a fight is a useful social skill. Here, we conducted two experiments to investigate how a colony living, cichlid species, Neolamprologus caudopunctatus , changes its aggressive behaviour when faced with familiar vs unfamiliar opponents. First, we staged size matched, same-sex, dyadic resource contests and found that fights were always of low-intensity with neither familiarity nor sex influencing how quickly the conflict ended. Second, we explored the dual defence of mated territorial pairs together defending their territory boundaries against other pairs, either familiar or unfamiliar ones, and discovered that fights between two pairs were more vigorous, and that unfamiliar neighbouring pairs were attacked significantly more often than familiar pairs. We also observed that dark bars sometimes appeared on the sides of contestant's bodies, and that these bars were far more common in winners than in losers, suggesting that these might be visual signals of dominance. However, conflicts where contestants displayed bars were of longer duration than those without. Taken together, our results further advance our understanding of territoriality and conflict resolution strategies and set the stage for future studies focusing on how animals manage to co-exist in closely aggregated breeding territories and to form colonies. [ABSTRACT FROM AUTHOR]

The risk of a newly discovered non-native fish species in Florida (USA): Cichlasoma dimerus ([Heckel, 1840]; Family: Cichlidae) is assessed. Its tolerance to cold temperatures was experimentally evaluated and information on its biology and ecology was synthesized. In the cold-temperature tolerance experiment, temperature was lowered from 24 °C by increments of 1 °C per hour, mimicking a typical cold weather front. Fish lost equilibrium at a mean temperature of 7.8 °C and died at 4.7 °C. Those values are lower than most other non-native fishes from the state that have been experimentally evaluated, and it appears C. dimerus is the most cold-tolerant cichlid established in Florida. The combination of cold-temperature tolerance and other biological/ecological factors (e.g., adult size, reproduction and parental care, diet, habitat, and other behaviors) along with the geographic range and habitat diversity of specimens vouchered in museums, indicate C. dimerus may be able to invade many freshwater ecosystems in the state, including environmentally sensitive freshwater springs. [ABSTRACT FROM AUTHOR]

The Nile Tilapia, Oreochromis niloticus, is a freshwater cichlid indigenous to the tropical and subtropical parts of the eastern and western Africa and is being cultured in the Lake Malawi catchment on the Tanzanian side. Historically, the Nile Tilapia has been successful in dispersing once it has been introduced into a catchment area. The probability of the Nile Tilapia successfully colonizing Lake Malawi is enhanced by many of its life history attributes including its fast growth rate, large size relative to native Oreochromis spp., and its diverse repertoire of feeding options. Where introduced, Nile Tilapia has had devastating impacts through competition or hybridization with native congenerics. We contend that the Nile Tilapia is a significant threat to the native fishes of Lake Malawi. With Lake Malawi harboring more species of fishes than any other freshwater lake in the world, a loss of species diversity due to the introduction of Nile Tilapia would be catastrophic for this unique system. Native fishes that in recent years provided 70% of the animal protein consumed in the country would be threatened by the colonization of the Nile Tilapia. We are convinced that should the Nile Tilapia become established in Lake Malawi it would (1) Cause the extirpation/extinction of native fishes, (2) Hybridize with endemic Oreochromis spp., and (3) Damage the livelihoods of existing artisanal fishermen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cichlidogyrus spp. from most East African cichlids are monophyletic. • Host switching followed by duplications is the most frequent coevolutionary event. • Strict specialist species of Cichlidogyrus possess primitive character states. Cichlidogyrus (including Scutogyrus) is the most speciose dactylogyridean monogenean genus known from African and Levantine cichlid fishes (Cichlidae). While its taxonomy is well established, little is known about the phylogenetic relationships and evolutionary history of this ectoparasite, especially from hosts belonging to one of the most impressive vertebrate radiations, the cichlid fishes from the East African Great Lakes and surrounding hydrological systems. Phylogenetic inference based on DNA sequences of the nuclear 18S, internal transcribed spacer 1 and 28S rDNA genes revealed that Cichlidogyrus parasitizing mainly West African cichlid tribes is paraphyletic with respect to species parasitizing hosts belonging to the East African cichlid radiation, which constitute a well-supported monophylum. Members of Cichlidogyrus from tylochromine and oreochromine hosts that colonised Lake Tanganyika only recently, cluster with their non-Lake Tanganyika relatives, indicating that they colonised Lake Tanganyika with their current host species, and did not jump over from any of the many cichlid species already present in the lake. The diversification of Cichlidogyrus in Lake Tanganyika seems to be driven by failure to diverge in old lineages of cichlids, cospeciation in more recently evolved ones, and host switching followed by parasite duplication at the level of the various host tribes. Evaluation of host specificity and structural evolution of haptoral and reproductive organs in Lake Tanganyika Cichlidogyrus revealed that strict specialist species together with larval hook size represent the ancestral state of haptor configuration, suggesting that members of Cichlidogyrus in this system evolved from a very simple form to a more complex one similarly to their West African congeners. Generalist species among Cichlidogyrus with a sclerotized vagina parasitizing ancient Lake Tanganyika lineages seem to have developed a different hook configuration, most probably to ensure successful colonisation of new, phylogenetically unrelated hosts. [ABSTRACT FROM AUTHOR]

Abstract Background Teleosts display a spectacular diversity of craniofacial adaptations that often mediates ecological specializations. A considerable amount of research has revealed molecular players underlying skeletal craniofacial morphologies, but less is known about soft craniofacial phenotypes. Here we focus on an example of lip hypertrophy in the benthivorous Lake Tangnayika cichlid, Gnathochromis permaxillaris, considered to be a morphological adaptation to extract invertebrates out of the uppermost layer of mud bottom. We investigate the molecular and regulatory basis of lip hypertrophy in G. permaxillaris using a comparative transcriptomic approach. Results We identified a gene regulatory network involved in tissue overgrowth and cellular hypertrophy, potentially associated with the formation of a locally restricted hypertrophic lip in a teleost fish species. Of particular interest were the increased expression level of apoda and fhl2, as well as reduced expression of cyp1a, gimap8, lama5 and rasal3, in the hypertrophic lip region which have been implicated in lip formation in other vertebrates. Among the predicted upstream transcription factors, we found reduced expression of foxp1 in the hypertrophic lip region, which is known to act as repressor of cell growth and proliferation, and its function has been associated with hypertrophy of upper lip in human. Conclusion Our results provide a genetic foundation for future studies of molecular players shaping soft and exaggerated, but locally restricted, craniofacial morphological changes in fish and perhaps across vertebrates. In the future, we advocate integrating gene regulatory networks of various craniofacial phenotypes to understand how they collectively govern trophic and behavioural adaptations.

Molecular phylogenetic evidence clearly resolves the African cichlid fish genus Ctenochromis, as defined by Greenwood (1979), as paraphyletic. Here, we redefine the genus Ctenochromis and assign Ctenochromis horei, a member of the Tropheini from Lake Tanganyika, to a new genus Shuja gen. nov. We restrict Ctenochromis to Ctenochromis pectoralis and Ctenochromis scatebra sp. nov., both of which are endemic to the Pangani River catchment in northern Tanzania, and are resolved as sister taxa in a phylogenetic analysis using genome-wide data. Ctenochromis pectoralis is the type species of the genus and described from specimens collected near Korogwe, Tanzania. The species was declared extinct in a 2016 IUCN Red List Assessment. We confirm the continued presence of a population of C. pectoralis within the Ruvu tributary linking Lake Jipe to Nyumba ya Mungu Reservoir. The new taxon Ctenochromis scatebra sp. nov. is described from Chemka Springs, and recognised on the basis of differences from C. pectoralis in tooth and jaw morphology.

High‐throughput DNA sequencing technologies make it possible now to sequence entire genomes relatively easily. Complete genomic information obtained by whole‐genome resequencing (WGS) can aid in identifying and delineating species even if they are extremely young, cryptic, or morphologically difficult to discern and closely related. Yet, for taxonomic or conservation biology purposes, WGS can remain cost‐prohibitive, too time‐consuming, and often constitute a "data overkill." Rapid and reliable identification of species (and populations) that is also cost‐effective is made possible by species‐specific markers that can be discovered by WGS. Based on WGS data, we designed a PCR restriction fragment length polymorphism (PCR‐RFLP) assay for 19 Neotropical Midas cichlid populations (Amphilophus cf. citrinellus), that includes all 13 described species of this species complex. Our work illustrates that identification of species and populations (i.e., fish from different lakes) can be greatly improved by designing genetic markers using available "high resolution" genomic information. Yet, our work also shows that even in the best‐case scenario, when whole‐genome resequencing information is available, unequivocal assignments remain challenging when species or populations diverged very recently, or gene flow persists. In summary, we provide a comprehensive workflow on how to design RFPL markers based on genome resequencing data, how to test and evaluate their reliability, and discuss the benefits and pitfalls of our approach. [ABSTRACT FROM AUTHOR]

South American peacock basses (genus Cichla) have been widely introduced within and outside the Neotropical region due to their importance to fisheries, despite threats to the native fish fauna. We performed a literature review on the worldwide distribution of valid Cichla species by focusing on records of species richness and populations in their native and non‐native ranges. We tested for an effect of area, the number of large dams, human population density and gross domestic product as drivers of the distribution of peacock basses across the Freshwater Ecoregions of the World (FEOWs). A total of 544 studies led to 1,289 records of nine species. Their distributions within their native range (19 native FEOWs) were narrower than their distributions in their non‐native range (23 non‐native FEOWs), which encompass tropical and subtropical ecoregions of the Americas, Africa, Southeast Asia and the Pacific islands. Several of these FEOWs harboured more than one species, usually C. ocellaris and C. piquiti. Ecoregion areas were positively associated with species richness and population records in native FEOWs, whereas the number of reservoirs was positively related to the records of non‐native populations. These patterns provide further evidence of the role played by reservoirs as the main pathway for the introduction of peacock basses; thus, special attention should be given to the continuous monitoring of the spread of these invaders across watersheds in invaded ecoregions. Considering their broad distribution and the potential for peacock basses to thrive in human‐modified systems, severe damage to the native fish fauna is predicted. [ABSTRACT FROM AUTHOR]

Cichlid fishes are an important component of the African freshwater ecosystem and the evolution of this group has captured the interest of ichthyologists for many decades. The distribution of cichlid fishes in both Africa and South America, and the apparent reciprocal monophyly of the cichlids in the two areas, has led to differences in opinion as to whether their modern distribution reflects a dispersal event from Africa to South America or was the result of a vicariant event–the break-up of the two continental masses in the mid-Cretaceous. 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; however, the fossil record indicates a younger, Cenozoic, age for the family. The known fossil taxa in Africa often are difficult to assign to extant tribes which creates inaccuracies when they are used to date lineages within Cichlidae. The difficulty of assigning fossil cichlids to modern lineages is caused by most of these lineages being recognized based on DNA or soft-tissue characters, which are generally not preserved in fossils. This hampers our understanding of the early history of the family. Despite this, new African cichlid fossils that have been described in the past two decades and a new technique to determine relationships of these fossils are beginning to elucidate the early history of the family in Africa. Here the Palaeogene (Eocene and Oligocene) cichlids of Africa are reviewed and a new taxon from the Oligocene of Somalia, Somalichromis hadrocephalus gen. et sp. nov. is described.

BackgroundThe past decade has witnessed remarkable progress towards resolution of the Tree of Life. However, despite the increased use of genomic scale datasets, some phylogenetic relationships remain difficult to resolve. Here we employ anchored phylogenomics to capture 107 nuclear loci in 29 species of acanthomorph teleost fishes, with 25 of these species sampled from the recently delimited clade Ovalentaria. Previous studies employing multilocus nuclear exon datasets have not been able to resolve the nodes at the base of the Ovalentaria tree with confidence. Here we test whether a phylogenomic approach will provide better support for these nodes, and if not, why this may be.ResultsAfter using a novel method to account for paralogous loci, we estimated phylogenies with maximum likelihood and species tree methods using DNA sequence alignments of over 80,000 base pairs. Several key relationships within Ovalentaria are well resolved, including 1) the sister taxon relationship between Cichlidae and Pholidichthys, 2) a clade containing blennies, grammas, clingfishes, and jawfishes, and 3) monophyly of Atherinomorpha (topminnows, flyingfishes, and silversides). However, many nodes in the phylogeny associated with the early diversification of Ovalentaria are poorly resolved in several analyses. Through the use of rarefaction curves we show that limited phylogenetic resolution among the earliest nodes in the Ovalentaria phylogeny does not appear to be due to a deficiency of data, as average global node support ceases to increase when only 1/3rd of the sampled loci are used in analyses. Instead this lack of resolution may be driven by model misspecification as a Bayesian mixed model analysis of the amino acid dataset provided good support for parts of the base of the Ovalentaria tree.ConclusionsAlthough it does not appear that the limited phylogenetic resolution among the earliest nodes in the Ovalentaria phylogeny is due to a deficiency of data, it may be that both stochastic and systematic error resulting from model misspecification play a role in the poor resolution at the base of the Ovalentaria tree as a Bayesian approach was able to resolve some of the deeper nodes, where the other methods failed.

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A small assemblage of 22 otoliths was identified from the historical collection of Bluntschli and Peyer gathered in 1912 on the Itaya riverbank at Iquitos, Peru (Amazonia), from the Pebas Formation. The Pebas Mega-Wetland System in western Amazonia during the Miocene represented a unique, albeit short-lived, biotope characterized by a pronounced endemic evolution with gigantism in some vertebrate groups (e.g., turtles, crocodylians). Thus far, fishes have mainly been recorded based on isolated skeletal remains and teeth. Here, we describe the first well-preserved otolith assemblage from the Pebas Formation. This otolith assemblage adds a new facet to the fauna by complementing the skeletal bony fish data, primarily with species of the Sciaenidae and, to a lesser extent, Ariidae and Cichlidae. The sciaenids and ariids indicate that migration must have occurred between the marginal marine environments to the north and the Pebas Wetland System. The otoliths also indicate the likelihood of endemic developments of adapted marine immigrants to the Pebas Wetland System, some of which have become extinct (Pogonias, Umbrina), while others now represent typical South American freshwater fish groups (Plagioscion). Six new species are described based on otoliths, one in the Cichlidae—Cichlasoma bluntschlii n. sp., one in the Ariidae—Cantarius ohei n. sp., and four in the Sciaenidae—Pebasciaena amazoniensis n. gen. et n. sp., Plagioscion peyeri n. sp., Pogonias tetragonus n. sp. and Umbrina pachaula n. sp. [ABSTRACT FROM AUTHOR]