World Cichlids Research Articles

Tol2 transposon-mediated transgenesis in the Midas cichlid (Amphilophus citrinellus) \u2014 towards understanding gene function and regulatory evolution in an ecological model system for rapid phenotypic diversification

BackgroundThe Midas cichlid species complex (Amphilophus spp.) is widely known among evolutionary biologists as a model system for sympatric speciation and adaptive phenotypic divergence within extremely short periods of time (a few hundred generations). The repeated parallel evolution of adaptive phenotypes in this radiation, combined with their near genetic identity, makes them an excellent model for studying phenotypic diversification. While many ecological and evolutionary studies have been performed on Midas cichlids, the molecular basis of specific phenotypes, particularly adaptations, and their underlying coding and cis-regulatory changes have not yet been studied thoroughly.ResultsFor the first time in any New World cichlid, we use Tol2 transposon-mediated transgenesis in the Midas cichlid (Amphilophus citrinellus). By adapting existing microinjection protocols, we established an effective protocol for transgenesis in Midas cichlids. Embryos were injected with a Tol2 plasmid construct that drives enhanced green fluorescent protein (eGFP) expression under the control of the ubiquitin promoter. The transgene was successfully integrated into the germline, driving strong ubiquitous expression of eGFP in the first transgenic Midas cichlid line. Additionally, we show transient expression of two further transgenic constructs, ubiquitin::tdTomato and mitfa::eGFP. Transgenesis in Midas cichlids will facilitate further investigation of the genetic basis of species-specific traits, many of which are adaptations.ConclusionTransgenesis is a versatile tool not only for studying regulatory elements such as promoters and enhancers, but also for testing gene function through overexpression of allelic gene variants. As such, it is an important first step in establishing the Midas cichlid as a powerful model for studying adaptive coding and non-coding changes in an ecological and evolutionary context.

Evaluation of Proposed Speckled Peacock Bass Cichla temensis Introduction to Puerto Rico

AbstractSpeckled Peacock Bass Cichla temensis are being considered for introduction into Puerto Rico to provide sportfishing opportunities and biological control for invasive New World cichlids. The proposed introduction was evaluated by following the American Fisheries Society's recommended seven‐step approach to introducing nonnative fish. This paper documents the evaluation process, which included a rapid risk screening approach using the Fish Invasiveness Screening Kit (FISK) version 2 and a series of controlled experiments on prey selection, agonistic behavior, and competition. The overall FISK score was 6 with a certainty factor of 0.84, placing the introduction in the medium‐risk category (0–18) for invasiveness. Many of the attributes elevating this species to the medium‐risk designation were the same attributes desired during species selection, including generalist feeding behavior and large body size, which are required for predation on New World cichlids. In controlled experiments, Speckled Peacock Bass consumed all cichlid species offered, suggesting that they may have potential as a biological control agent, although some selectivity in species and size was observed. Speckled Peacock Bass showed aggression toward conspecifics and other species in a mesocosm environment, but aggression generally decreased with time. There was no evidence of negative effects on Largemouth Bass Micropterus salmoides in terms of growth or condition via aggression or competition in controlled small‐pond experiments. Although some downstream movement from receiving reservoirs would be possible, downstream habitats are unsuitable for establishment of this species. The greatest risk may be unauthorized movement by anglers to other reservoirs where this species is not desired. It is the conclusion of this evaluation that Speckled Peacock Bass will consume New World cichlids and that the risks of introduction are acceptably low. Thus, introduction may proceed on a limited scale with proper scientific evaluation and public outreach directed at reducing unauthorized translocation by anglers.Received October 12, 2016; accepted June 19, 2017 Published online August 31, 2017

The complete mitochondrial DNA of the bay snook, Petenia splendida, a native Mexican cichlid.

The mitogenome of the tenguayaca, Petenia splendida (GenBank accession number KJ914664) has a total length of 16,518 bp, and the arrangement consist of 15 protein-coding genes, 2 ribosomal RNA (rRNA) genes and 22 transfer RNA (tRNA) genes. Gene order was equal to the mitogenomes of other new world cichlids.

Social status and GnRH soma size in female convict cichlids (Amatitlania nigrofasciatus)

Gonadotropin-releasing hormone (GnRH) neurons in the preoptic area (POA) of the hypothalamus play a key role in regulating reproductive function. These neurons in turn are modulated by environmental influences, including the social environment. In both the Old World cichlid Astatotilapia burtoni and the New World cichlid Amatitlania nigrofasciatus, the size of the soma of GnRH expressing neurons in the POA varies with social status in males and breeding state in females. Dominant males have larger GnRH-releasing cells than subordinate males, and spawning females have larger GnRH-releasing cells than brooding females. A. nigrofasciatus is monogamous and both sexes engage in similar levels of aggression and territorial defense. Here we test whether female A. nigrofasciatus display GnRH-releasing cell plasticity as a function of dominant status. We find that GnRH-releasing neuron soma sizes are larger in dominant females and that this difference is independent of differences in gonado-somatic index in A. nigrofasciatus.

Social status, breeding state, and GnRH soma size in convict cichlids (Cryptoheros nigrofasciatus)

Gonadotropin-releasing hormone (GnRH) expressing neurons in the preoptic area (POA) of the hypothalamus plays a key role in regulating reproductive function through the control of gonadotropin release. Several studies have illustrated the importance of the social environment in modulating the size of GnRH expressing neurons. In the African cichlid fish Astatotilapia burtoni, the size of the soma of GnRH expressing neurons in the POA varies with social status in males, and with breeding state in females. Territorial males have larger GnRH+ cells than non-territorial males, while brooder females have smaller GnRH+ cells than control females. The lek-like breeding system of A. burtoni is, however, only one type of social system within the diverse assemblage of cichlids. To gain a better understanding of GnRH neuronal plasticity in response to the changes in the social environment, we tested whether similar effects occur in the monogamous New World cichlid, the convict cichlid (Cryptoheros nigrofasciatus), a model species for the study of social behaviour. Our results indicate that, indeed GnRH expressing neuron soma size, and not cell number, varies with both male territorial status, and manipulations of female breeding state in this monogamous, biparental, New World cichlid.

A new cichlid Tremembichthys garciae (Actinopterygii, Perciformes) from the Eocene-Oligocene of eastern Brazil

The Aiuruoca Basin is located in the Mantiqueira Range and Alto Rio Grande Plateau, southern Minas Gerais State, Brazil. It includes two formations: Entre-Corregos, lacustrine facies, and Pinheirinho, alluvial fan facies. The specimen described here comes from the shales of the Entre-Corregos Formation, dated as Eocene-Oligocene. The phylogenetic analysis to establish its position within the Cichlidae was based on a matrix with 53 taxa (including two fossil taxa) and 91 characters. The fossil specimen preserved as part and counterpart, is assigned to a new cichlid species, Tremembichthys garciae sp. nov., as sister group of T. pauloensis in the Cichlasomatinae. The position of Tremembichthys within Cichlasomatinae is supported by infraorbitals with laminar expansion, the articulating process of the premaxilla moderately developed, and 13-14 pectoral-fin rays. The Neotropical cichlids resulted monophyletic and sister group of the Old World cichlids. Extant members of the family Cichlidae live mostly in lentic freshwater bodies, corroborating the lacustrine paleoenvironment assigned to this formation.

Phenotypic plasticity: its role in trophic radiation and explosive speciation in cichlids (Teleostei: Cichlidae)

Abstract Phenotypic plasticity is the capacity of an organism's phenotype to vary in different environments. Although diet-induced phenotypic plasticity has been documented in New World cichlids, it has been hypothesised that this type of plasticity would be limited in certain Old World cichlids, because of the morphological constraints on the jaw imposed by mouth-brooding. This hypothesis was experimentally tested by determining the effect of different diets on the head and jaw morphology of split broods of several species of haplochromine cichlids from Lake Malaŵi, Africa, and two substrate-spawning cichlids, one from the Old World, Tilapia mariae (Boulenger), and one from the New World, Herichthys cyanoguttatum (Baird and Girard). Different feeding regimes resulted in differences in head morphologies in both New and Old World cichlid species. Although Old World mouth-brooding haplochromine cichlids exhibited phenotypic plasticity, the magnitude of head-shape plasticity observed was greater in the New World substrate-spawning cichlid, H. cyanoguttatum . The Old World tilapiine cichlid, T. mariae , did not exhibit phenotypic plasticity of head morphology. Experiments with modified foods demonstrated that the observed changes were unrelated to dietary nutrition, but were a result of differing feeding modes. Phenotypic plasticity might have contributed to the extensive trophic radiation and subsequent explosive speciation observed in Old World haplochromine cichlids. The existence of phenotypic plasticity has implications for morphology-based species descriptions as well.

Getting into Shape: An Empirical Comparison of Traditional Truss-Based Morphometric Methods with a Newer Geometric Method Applied to New World Cichlids

Body shape is a difficult, but important, trait to quantify. Researchers have traditionally used multivariate analysis of several linear measures ('trusses') across the body form to quantify shape. Newer geometric morphometric methods claim to better estimate shape because they analyze the geometry among the locations of all landmarks simultaneously rather than the linear distances between pairs of landmarks. We tested this claim by comparing the results of several traditional morphometric analyses against a newer geometric analysis involving thin-plate splines (TPS), all applied to a common data set of morphologically variable new world cichlids Amphilophus citrinellus and A. zaliosus. The TPS method yielded slightly stronger evidence of morphological differences among forms, although traditional methods also distinguished the two species. Perhaps our most important result was the idiosyncratic interpretation of shape variation among the traditional truss-based methods, whereas the generation of deformation grids using the TPS approach yielded clear and visually interpretable figures. Our results indicate that geometric morphometrics can be a more effective way to analyze and interpret body form, but also that traditional methods can be relied upon to provide statistical evidence of shape differences, although not necessarily accurate information about the nature of variation in shape.

Functional groups in the social behavior of a cichlid fish, the Oscar, Astronotus ocellatus

Dummy conspecifics were presented to isolated adults of the cichlid fish Astronotus ocellatus to investigate the functional organization of cichlid social behavior. Body size and 15 dummy-elicited activities were recorded during 15 min sessions and analyzed by principal components analysis (PCA) to reveal their temporal organization. Five principal components explained almost 80% of the variation in dummy-elicited behavior, and these five factors define functional groups for 1. (a) investigation, 2. (b) attack, 3. (c) nesting, 4. (d) boldness, 5. (e)distress. Nest-oriented and attack modal action patterns are not mutually inhibitory during this time frame, and biting does not appear to function exclusively during an attack on a conspecific. Comparison with previous studies of New and Old World cichlids suggests evolutionary conservation of the functional organization of social behavior.

PHENOTYPIC PLASTICITY AND HETEROCHRONY IN CICHLASOMA MANAGUENSE (PISCES, CICHLIDAE) AND THEIR IMPLICATIONS FOR SPECIATION IN CICHLID FISHES.

Cichlid fishes in African rift lakes have undergone rapid speciation, resulting in "species flocks" with more than 300 endemic species in some of the lakes. Most researchers assume that there is little phenotypic variation in cichlid fishes. I report here extensive phenotypic plasticity in a Neotropical cichlid species. I examined the influence of diet on trophic morphology during ontogeny in Cichlasoma managuense. Two groups of full siblings were fed two different diets for eight months after the onset of feeding; thereafter both groups were fed a common diet. Phenotypes that differed significantly at 8.5 months converged almost completely at 16.5 months. If feeding on two different diets is continued after 8.5 months, the phenotypes remain distinct. Differences in diet and possibly in feeding mode are believed to have caused these phenotypic changes. Phenotypic plasticity is described in terms of a qualitative model of heterochrony in which phenotypic change in morphology is explained as retardation of the normal developmental rate. If phenotypic expression of morphology is equally plastic in African cichlid species as it may be in the American cichlids, as exemplified by C. managuense, then taxonomic, ecological, and evolutionary analyses of "species flocks" may be in need of revision. However, Old World cichlids may be less phenotypically plastic than New World cichlids, and this may contribute to the observed differences in speciation rate and degree of endemism.

A Quantitative Study of Long-Term Courtship: II. a Comparative Study of the Dynamics of Courtship in Two New World Cichlid Fishes

i. The courtship behavior of two sympatric species of New World cichlid fish was quantitatively studied. The two species were Cichlasoma citrinellum (Gunther) and C. zaliosum Barlow. The species are closely related. 2. Data recording was based on heterosexual, homospecific dyads. Ten event categories, representing cichlid courtship behaviors, were recorded for each sex. 3. Both species showed long-term courtship behavior, the minimum time to spawning after first contact being 52 hrs. Data were recorded three times a day for each pair throughout the courtship period. 4. Four measures based on information theory were used to describe overall changes in behavior with the pair. These were H1, the first order diversity; D1, the first order redundancy (repetition); H2, the second order diversity; and D2, the second order redundancy (divergence from independence). 5. Courtship in these species has three distinct phases that can be characterized quantitatively by their patterns of behavioral diversity. There is an early phase of high activity, high first order diversity, and low first order redundancy. This appears to be the time of pair formation. The second, intermediate phase, is a period of relatively low activity and intermediate behavioral diversity and redundancy. This is the interval after pair formation, but prior to attachment to a spawning site. The third phase is characterized by high activity, primarily by the female, with low diversity and high redundancy. This phase is primarily one of spawning-site preparation and synchronization for the release of gametes. 6. The changes in the overall organization of behavior within the pair were primarily the result of frequency of occurrence (first order). There were no apparent overall changes in the level of dependency between events during courtship (second order). 7. Similar analysis of a species showing short-term courtship should reveal greater importance of second order effects due to reliance on releasers and chaining of events between the sexes. 8. The two species differ primarily in the frequency with which they performed various courtship behaviors. C. zaliosum did more agonistic behaviors such as Bite, Lateral, Frontal and Yield; C. citrinellum performed more behaviors typical of later stages of courtship, such as Quiver and Nip Off. 9. The frequencies with which the behaviors followed each other differed in the two species. 10. The species were least similar in their courtship behavior during the earliest stages of courtship, and showed the greatest resemblance during the parental period. II. Heterospecific pairs resembled C. citrinellum more in their overall behavior than they did C. zaliosum, but this may have been an artifact of the abnormal size ratios within those pairs. 12. The differences in behavior seem due mainly to a lower threshold of aggression in C. zaliosum, while C. citrinellum has a lower threshold for sexual behavior. 13. The differences in courtship are sufficient to explain the reproductive isolation of the two species, but the mechanism is effective only when a choice of mates from both species is available.

Genetic Variation and Speciation in New World Cichlids

Genetic Variation and Speciation in New World Cichlids

Sufficient Conditions for Multiple Niche Polymorphism

Sufficient Conditions for Multiple Niche Polymorphism