Cichlid Research Articles

Heavy metals analysis of S. schall and O. niloticus fish species sold at Otuocha Market, Anambra State, Nigeria

The potentials of heavy metal pollution in natural environments have necessitated the need to determine the presence of heavy metal pollutants in the surface waters and possible bioaccumulation in the inhabiting fish species and other aquatic organisms. This study thus aimed to determine the heavy metal species that occur outside their recommended ranges in the test fish species and two Cichlid fish species namely, Synodontis schall and Oreochromis niloticus were selected for the analysis. Water samples were taken to assess the concentrations of these heavy metals in the river while tissues and organs of the test fish samples were extracted for further analysis to determine the cumulative tendencies of these metals in the organisms. All the heavy metals (Cd, Zn, Mn, Cu, Pb) were detected in the fish organs except copper (Cu) which was not detected in the fillet/tissue. The metals occurred in the order; Pb > Zn > Cd > Cu > Mn in both fish species. The gill emerged as the organ with the highest concentration of heavy metal with a value of 100.92ppm of lead in Synodontis schall and 111.34 ppm in Oreochromis niloticus. The high concentrations of Zinc and Lead found in the fish organs were compared with the habitat and discovered that the concentrations were high compared to the lower levels found in the river water. Although Zn occurred at very high concentrations, they were still below the threshold recommended by WHO/FAO. However, Cadmium and Lead exceeded their permissible limits, Lead occurred in outrageous amounts while other metals tested (Mn, Zn, Cu) fell within acceptable ranges. Nonetheless, care should be taken and environmental laws and policies guiding the use and discharge of harmful substances put in place to check the influx and accumulation of these toxicants which pose as threat to man. Metal pollution results in abnormal physiological function of the body cells when they exceed these limits and so guidelines on the use of related products and industrial discharge of effluents should be adhered to and penalty measures taken out on defaulters.

Acoustic innovations in courtship sounds generated by hybridization in cichlid fish

Abstract 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.

Cellular profiling of a recently-evolved social behavior in cichlid fishes

Social behaviors are diverse in nature, but it is unclear how conserved genes, brain regions, and cell populations generate this diversity. Here we investigate bower-building, a recently-evolved social behavior in cichlid fishes. We use single nucleus RNA-sequencing in 38 individuals to show signatures of recent behavior in specific neuronal populations, and building-associated rebalancing of neuronal proportions in the putative homolog of the hippocampal formation. Using comparative genomics across 27 species, we trace bower-associated genome evolution to a subpopulation of glia lining the dorsal telencephalon. We show evidence that building-associated neural activity and a departure from quiescence in this glial subpopulation together regulate hippocampal-like neuronal rebalancing. Our work links behavior-associated genomic variation to specific brain cell types and their functions, and suggests a social behavior has evolved through changes in glia.

Phenotypic rate and state are decoupled in response to river-to-lake transitions in cichlid fishes.

Geographic access to isolated ecosystems is an important catalyst of adaptive radiation. Cichlid fishes repeatedly colonized rift, crater, and volcanic lakes from surrounding rivers. We test the "lake effect" on the phenotypic rate and state across 253 cichlid species. The rate of evolution was consistently higher (~10-fold) in lakes, and consistent across different dimensions of the phenotype. Rate shifts tended to occur coincident with or immediately following river-to-lake transitions, generally resulting in 2- to 5-fold faster rates than in the founding riverine lineage. By contrast, river- and lake-dwelling cichlids exhibit considerable overlap in phenotypes, generally with less disparity in lakes, but often different evolutionary optima. Taken together, these results suggest that lake radiations rapidly expand into niches largely already represented by ancestral riverine lineages, albeit in different frequencies. Lakes may provide ecological opportunity via ecological release (e.g., from predators/competitors) but need not be coupled with access to novel ecological niches.

Catch composition and species diversity during dredging operations of Mediterranean coastal lagoon, Lake Manzala, Egypt

Lake Manzala, the largest Egyptian coastal lake, is one of the most valuable fish sources in Egypt, which contributes about 14% to the total annual Egyptian fisheries production. However, given that Lake Manzala suffers from major environmental and fisheries problems, an ambitious national project for the dredging, purification, and development of this lake was established in 2017. Hence, this study was conducted to assess seasonal diversity and to provide an inventory of fish species at Lake Manzala during dredging operations. Five seasonal surveys were conducted during the period from 2019 to 2021. By using different fishing gears and methods operating in the lake, a total of 7774 fish and crustaceans—belonging to 29 fish species and three crustacean species that clump into 21 families—were collected from Lake Manzala. During the study period, the family Cichlidae showed the highest occurrence of about 70%. The marine-brackish species recorded the highest aquatic environment (milieu) diversity with 34.4% of the collected species, but only 12.5% of the freshwater species. Six of the collected fish species were recorded of Indo-pacific origin, as Lissepsian migrant species. In this study, the diversity index (H) was calculated, ranging between 1.13 and 1.77. As indicated by the seasonal variation of the diversity index, the highest diversity index of Lake Manzala was evident in autumn 2019 and spring 2021 at 1.700 and 1.365, respectively. The governmental dredging and cleaning operations in the lake have a relative impact on the species composition in this area. Further studies are recommended after the completion of these operations to confirm the impact of dredging on species composition alteration.

Species Diversity of Freshwater Fish in Lake Toba using Shanon Wiener

The diversity of fish in Lake Toba is a natural resource that can increase the fulfillment of the protein needs of the people living around Lake Toba. This research is to find out: (1) the classification of fish found in Lake Toba; (2) the diversity of fish in Lake Toba. Fish found in Lake Toba consist of goldfish (Cyprinus carpio), red devil cichlid fish (Amphilophus labiatus), blue phancax fish (Aplocheilus panchax), Batak fish (Neolissochilus sp), Ikaan Rasbora Tobana (Rasbora tobana), selur fish. Maninjau (Osteochilus vittatus), Mystacoleucus Padangensis Fish (Cyprinidae), Tilapia Mossambica Fish (Tilapia Mosammabica), and Channa Striata Fish (Channa Striata). The diversity index of freshwater fish species in Lake Toba shows a moderate level of diversity, namely H' = 1.831.

The cichlid pharyngeal jaw novelty enhances evolutionary integration in the feeding apparatus.

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.

Myxozoan Ceratomyxids Infecting the Gallbladder of Amazonian Ornamental Cichlid Fish: Description of Ellipsomyxa santarenensis n. sp. and Report of Ceratomyxa amazonensis in a New Host

Although most Myxozoa species of the genera Ceratomyxa and Ellipsomyxa have been described in marine hosts worldwide, an increasing diversity has been reported infecting South American freshwater fish, mainly in Amazonian waters. The present study deals with two species of myxozoan ceratomyxids parasitizing the gallbladder of Amazonian ornamental cichlids fish: Ceratomyxa amazonensis is identified from a new host—Geophagus altifrons; while Ellipsomyxa santarenensis n. sp. is described infecting Satanoperca jurupari. Morphological (light microscopy and transmission electron microscopy), molecular (small ribosomal subunit DNA—SSU-rDNA sequencing) and phylogenetic analyses were used to characterize both species. Ceratomyxa amazonensis showed a prevalence of 64.2%, with plasmodia showing a vermiform shape and motility. For E. santarenensis n. sp., the prevalence was 33.3%. Ultrastructural analysis revealed that the vermiform C. amazonensis plasmodia were composed of an outer cytoplasmic region and a large vacuole occupying the inner area. In E. santarenensis n. sp., cytoplasmic expansions were observed in pseudoplasmodia originating pseudopodia. SSU rDNA sequencing-based genetic distance analysis revealed a very small difference between C. amazonensis, parasite of G. altifrons, and C. amazonensis, parasite of S. discus—host of the original description, thus showing that they are the same species occurring in a new host. For Ellipsomyxa santarenensis n. sp., molecular data revealed a difference of 1.6% for Ellipsomyxa amazonensis and Ellipsomyxa paraensis. The phylogenetic analysis revealed the grouping of E. santarenensis n. sp. together with the other freshwater Ellipsomyxa species of the Amazonian region, and associated with the morphological data, it was possible to identify it as a new taxon within the genus Ellipsomyxa.

Testing trade‐offs in amphibian metamorphic traits: Swimming performance and selection across metamorphic stages in the aquatic frog Xenopus laevis

Abstract As frogs undergo metamorphosis from tadpole to adult, they may be susceptible to decreases in locomotor performance and survival during stages in which the tail and limbs are both present. Because these alternative axial and appendicular propulsive systems might interfere with each other, performance might be better when only one or the other system predominates. This framework, termed the ‘adaptive peak hypothesis’ emerged from studies of generalist anuran taxa with biphasic life histories in which aquatic larvae transition to terrestrial adults. However, it is not clear that such patterns apply to taxa with different patterns of ontogenetic environmental transitions. We evaluated the relationship between morphology, locomotor performance and survival versus predators across metamorphic stages of a fully aquatic frog, the pipid Xenopus laevis. We measured escape performance from individuals of four developmental stages spanning possession of just a tail, the presence of both tail and legs and resorption of the tail, and then conducted selection trials in which equal numbers of individuals of all stages were exposed to an aquatic predator (cichlid fish). After collecting survivors from these trials, we calculated linear and nonlinear selection gradients for a suite of morphological traits. Unlike generalist frogs, we found that both locomotor performance and survival increased across metamorphic stages of X. laevis. Linear selection gradients favoured tadpoles with longer hindlimbs, longer and narrower bodies, and shorter tails—patterns that generally parallel trends during metamorphic growth. Nonlinear selection showed that longer hindlimbs were favoured as body length increased and the positive effect of forelimb length was reduced as tail length increased. The relationship between hindlimb and body length aligns with expected changes in growth postmetamorphosis where postmetamorphic individuals are expected to have greater survival. However, longer forelimbs are generally associated with decreased locomotor performance, suggesting that alternative mechanisms of selection may be acting on the forelimbs of Xenopus through development. Overall, our results indicate that the generality of the adaptive peak framework, as applied to amphibian metamorphosis, can be impacted by specifics of life history patterns across species. Read the free Plain Language Summary for this article on the Journal blog.

Single fathers sacrifice their broods and re-mate quickly in a socially monogamous cichlid.

When one of two parents disappears in the midst of caring for offspring, the remaining parent is left with several options. They can either (1) desert the brood, (2) continue caring on their own and reject propositions from new potential partners, or (3) continue caring but remain receptive to re-mating opportunities. The presence of a brood may increase re-mating success of single parents, either because brood care is perceived as a signal of partner quality, or because prospective mates perceive the brood as potential energy source. In this field experiment, we used the socially monogamous, biparental cichlid fish Variabilichromis moorii to examine the re-mating strategy of males with or without dependent offspring after the loss of their female partner. Partner vacancies were filled quickly by new females, and these females engaged in high levels of affiliative behavior with the males. The new females engaged in territorial defense, but focused primarily against intruding conspecifics, likely as a means to repel rivals. The males, in turn, took over the majority of territorial defense against intruding heterospecifics. Interestingly, males that still had offspring from their previous partnerships did not show aggression toward their new female partners, even when those females were infanticidal and cannibalizing the males' current offspring. Overall, our experiment shows that single fathers of a biparental species will re-mate quickly even at the detriment to their current offspring.

EFFECTS OF LEAD ACETATE ON RESPIRATORY BEATS AND OPERCULUM ACTIVITIES OF SNAKEHEAD FISH, CHANNA PUNCTATUS

Channa punctatus, a species of freshwater fish, was subjected to an experiment to measure the effects of lead acetate on its morphology, respiratory rate, and operculum activity. The fish in the experiment were dosed with lead acetate, which might have entered their bodies through their gills, skin, or digestive systems. Lead acetate was shown to have accumulated on the gills, operculum, morphology, and respiratory rate of the cichlid fish Channa punctatus. Fishes are particularly vulnerable to the accumulation of heavy metals in fresh water since they are the top consumer in aquatic systems. Fish consumption may have an effect on humans, especially in regions where fish is a staple meal. Keyboard: Lead Acetate, Behavioral changes, Operculum movement, Channa punctatus.

Egg-mediated maternal effects in a cooperatively breeding cichlid fish

Mothers can influence offspring phenotype through egg-mediated maternal effects, which can be influenced by cues mothers obtain from their environment during offspring production. Developing embryos use these components but have mechanisms to alter maternal signals. Here we aimed to understand the role of mothers and embryos in how maternal effects might shape offspring social phenotype. In the cooperatively breeding fish Neolamprologus pulcher different social phenotypes develop in large and small social groups differing in predation risk and social complexity. We manipulated the maternal social environment of N. pulcher females during egg laying by allocating them either to a small or a large social group. We compared egg mass and clutch size and the concentration of corticosteroid metabolites between social environments, and between fertilized and unfertilized eggs to investigate how embryos deal with maternal signalling. Mothers in small groups produced larger clutches but neither laid smaller eggs nor bestowed eggs differently with corticosteroids. Fertilized eggs scored lower on a principal component representing three corticosteroid metabolites, namely 11-deoxycortisol, cortisone, and 11-deoxycorticosterone. We did not detect egg-mediated maternal effects induced by the maternal social environment. We discuss that divergent social phenotypes induced by different group sizes may be triggered by own offspring experience.

Evolution of MHC IIB Diversity Across Cichlid Fish Radiations.

The genes of the major histocompatibility complex (MHC) are among the most polymorphic genes in vertebrates, and crucial for their adaptive immune response. These genes frequently show inconsistencies between allelic genealogies and species phylogenies. This phenomenon is thought to be the result of parasite-mediated balancing selection maintaining ancient alleles through speciation events (trans-species polymorphism, TSP). However, allele similarities may also arise from post-speciation mechanisms, such as convergence or introgression. Here, we investigated the evolution of MHC class IIB diversity in the cichlid fish radiations across Africa and the Neotropics by a comprehensive review of available MHC IIB DNA sequence information. We explored what mechanism explains the MHC allele similarities found among cichlid radiations. Our results showed extensive allele similarity among cichlid fish across continents, likely due to TSP. Functionality at MHC was also shared among species of the different continents. The maintenance of MHC alleles for long evolutionary times and their shared functionality may imply that certain MHC variants are essential in immune adaptation, even in species that diverged millions of years ago and occupy different environments.

Molecular Identification of Several Morphologically Distinct Flowerhorn Fish (Family) Using Mitochondrial <i>COI</i> Gene Marker

Flowerhorn fish has been known as a breed of fish produced by artificial hybridization between several cichlid fish. Other ornamental cichlid fish generally known to be crossed to make flowerhorn variant includes Amphilophus citrinelus, Amphilophus labiatus, Vieja melanurus, and Amphilophus trimaculatus. Our study identified a variety of flowerhorn samples with distinct morphotypes, dubbed as Cencu (LH1CC), Kamfa (LH2KF), Thai Silk (LH3TS), Kirin (LH4KR), Parrot (LH5PR), and Vieja (LH6VJ) using mtDNA COI-based DNA barcoding. Molecular analysis and phylogenetics showed that all sample had 0% genetic divergence and conspecific with A. trimaculatus sequence. Hence, we concluded that despite having varied morphotypes, all flowerhorn samples were identified as A. trimaculatus and were a variation of flowerhorn from A. trimaculatus lineage. The findings should be used as a precaution as the fish is identified as an invasive species.

Social deprivation in maternal mouthbrooders Tropheus sp. “Caramba” (Teleostei: Cichlidae) decreases the success rate of reproduction and survival rate of fish fry

Early offspring separation from mothers causes social deprivation. Mouthbrooding, when eggs and fry are incubated in the buccal cavity of the parent, is one of the reproductive strategies in fish. The mother is the incubating parent in African lake cichlids from the genus Tropheus. Many of these are produced in captivity and some producers use artificial incubators in which eggs are incubated separately from the mother. We hypothesized that this practice may dramatically modify the reproduction rate of fish individuals produced by the method of artificial incubation. The long-term experiment focused on Tropheus sp. “Caramba” had been carried out for 10 years when maternally incubated and separated individuals were compared. We found a negative effect of artificial egg and offspring incubation out of the mother’s buccal cavity. The deprived females laid the same number of eggs as maternally incubated females, but most eggs were lost during the incubation. Moreover, the reproduction frequency was significantly lower in deprived females in comparison with those maternally incubated. This study should be perceived as preliminary. For this reason and with respect to welfare principles, we strongly recommend similarly designed experiments focused on other potentially sensitive fish mouthbrooders. Once the syndrome would be confirmed, we recommend avoiding artificial incubation of mouthbrooding fish in general.

SCIENCE BEHIND THE COLOR CHANGES IN TILAPIA DURING STRESS

Tilapia is the common name applied to three genera of fish in the family Cichlidae. the genera include Oreochromis, Sarotherodon and Tilapia. Tilapia has become the third most important fish in aquaculture after carp and salmon. The nature’s aim in imparting versatile colours to the fishes is to facilitate their survival and as a mode of communication. Colouration in fishes are highly correlated to their behaviour and habitat as morphological patterns always indicate the physiological functions. Some fishes may change its colour due to environmental conditions. Due to the growth of Tilapia production in aquaculture field, indicates how tilapia is important for world’s total production and economy.

Variation in parasite infection between replicates of speciation in Lake Victoria cichlid fish.

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.

Urotensin-I suppresses the hypothalamo-hypophyseal-ovarian axis in the Mozambique tilapia, Oreochromis mossambicus

Urotensin-I (UI) is a peptide belonging to the corticotropin-releasing hormone family, produced in the urophysis of teleosts. This investigation was undertaken to examine the effect of UI on the hypothalamo-hypophyseal-ovarian axis in the Mozambique tilapia, a cichlid fish. In the first experiment, administration of UI (2 μg/100 μL saline) for 22 days caused a significant reduction in the number of follicles at stages I, II, III (previtellogenic), IV (vitellogenic), and V (preovulatory), concomitant with a significant increase in the percent atresia of follicles at stages II, III, and IV than in controls. In the pituitary, gonadotropin-releasing hormone (GnRH) - positive fibres were detected in the proximal pars distalis (PPD) in both controls and UI-treated fish; however, there was a significant reduction in the intensity and percent area of GnRH-immunoreactive fibres in fish treated with UI compared with controls. The serum luteinizing hormone (LH) level was significantly lower, whereas a significant rise in the serum level of cortisol was noticed in UI-treated fish compared with controls. In the second experiment, treatment with a low dose of UI (10 mM) did not affect the number of ACTH-secreting cells in vitro, but the number of these cells was significantly higher in high-dose UI (50 mM)-treated pituitaries compared to controls. Together, the present investigation reveals for the first time that the treatment of UI affects the follicular development process through the downregulation of the GnRH-LH axis and activation of the pituitary-interrenal pathway in teleosts.

Genetic basis of ecologically relevant body shape variation among four genera of cichlid fishes.

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.

A kiss of deep homology: partial convergence in the genomic basis of hypertrophied lips in cichlid fish and human cleft lip.

The genomic loci generating both adaptive and maladaptive variation could be surprisingly predictable in deeply homologous vertebrate structures like lips. Variation in highly conserved vertebrate traits such as jaws and teeth in organisms as evolutionarily disparate as teleost fishes and mammals are known to be structured by the same genes. Likewise, hypertrophied lips that have evolved repeatedly in Neotropical and African cichlid fish lineages could share unexpectedly similar genetic bases themselves and even provide surprising insight into the loci underlying human craniofacial anomalies. To isolate the genomic regions underlying adaptive divergence in hypertrophied lips, we first employed genome wide associations (GWA) in several species of African cichlids from Lake Malawi. Then, we tested if these GWA regions were shared through hybridization with another Lake Malawi cichlid lineage that has evolved hypertrophied lips seemingly in parallel. Overall, introgression among hypertrophied lip lineages appeared limited. Among our Malawi GWA regions, one contained the gene kcnj16 that has been implicated in the convergently evolved hypertrophied lips in Central American Midas cichlids that diverged from the Malawi radiation over 50 million years ago. The Malawi hypertrophied lip GWA regions also contained several additional genes that cause human lip-associated birth defects. Cichlid fishes are becoming prominent examples of replicated genomic architecture underlying trait convergence and are increasingly providing insight into human craniofacial anomalies such as cleft lip.