Cichlasoma Meeki Research Articles

Susceptibility of selected tropical non-tilapine ornamental cichlids to Tilapia tilapinevirus following experimental infection

The emergence and spread of transboundary aquatic animal diseases have been frequently associated with international trade of live aquatic animals. Tilapia is one of the most traded aquatic animals and the recent global spread of Tilapia tilapinevirus, also known as tilapia lake virus (TiLV), is speculated to be due to transboundary movement of infected fish. Further, extensive trade of ornamental cichlids can be a major threat to the spread of TiLV. However, there is little information about susceptibility of ornamental fishes, especially cichlids, to this virus. In this background, the present study evaluated the susceptibility of three ornamental cichlids (angelfish, firemouth cichlid and parrotfish) and two non-cichlids (three spot gourami and goldfish) vis-à-vis Nile tilapia following experimental infection with TiLV through intraperitoneal injection. The study carried out quantification of viral load using real-time PCR, histopathology and isolation of the virus in permissive cell line developed previously from Oreochromis niloticus heart (OnH). Experimental infection resulted in the successful reproduction of the disease in tilapia with typical clinical signs. In angelfish, 40% mortality was observed and the TiLV copy number/100 ng RNA was determined to be 2.49 × 106, 1.52 × 106 and 2.64 × 104 in the target tissues, namely liver, spleen and brain, respectively at 4 days post-infection (dpi). In addition, TiLV could be detected in the target tissues till end of the experimental period of 24 days. Although no clinical signs or mortality were observed in firemouth cichlid, but TiLV copies were detected in the target organs with significant increase in the viral load up to 12 dpi. Histopathological examination of liver tissue of the experimentally infected fishes revealed typical syncytial cells only in tilapia whereas necrosis of hepatocytes was observed in tilapia, angelfish and firemouth cichlid. Besides, TiLV could be isolated from target tissues of both angelfish and firemouth cichlid at 8 dpi, using OnH cell line. On the other hand, in parrotfish, three spot gourami and goldfish, the virus copy number in the target tissues showed a decline from 1 dpi and no evidence of virus replication could be noticed in the cell line studies. Hence, these three ornamental fishes were considered resistant to experimental infection with TiLV. The findings of this study indicated the existence of wide host-range of TiLV in non-tilapine ornamental fishes including angelfish and firemouth cichlid, and the potential role of these fishes in the epidemiology of TiLV disease.

Afferent and efferent connections of the nucleus posterior tuberis in the firemouth cichlid, Thorichthys meeki

The nucleus posterior tuberis (NPT) in teleost fishes, also called posterior tuberal nucleus, is situated in the posterior tuberculum of the diencephalon. It is fused across the midline and densely packed with small cells, but little is known about its connections. In this study, the afferent and efferent connections of the NPT were examined by means of tracer applications of the carbocyanine dye DiI in the firemouth cichlid, Thorichthys meeki. Retrogradely labeled cell bodies were found in the corpus mamillare and nucleus periventricularis of the inferior lobe; and anterogradely labeled terminal fibers were detected in the medial zone of the dorsal telencephalon, medial part of the nucleus lateralis tuberis, dorsal posterior thalamic nucleus, torus lateralis, medial part of the nucleus diffusus of the inferior lobe, and tectum opticum. All these connections show an ipsilateral tendency. The NPT is apparently a significant relay nucleus in the diencephalon of T. meeki, and possibly involved in a variety of feedback circuits. It seems also to be part of a tecto-hypothalamo-telencephalic pathway in cichlids.

Characterization and phylogenetic analysis of the complete mitochondrial genome of the firemouth cichlid, Thorichthys meeki (Perciformes: Cichlidae)

Here, we report information on the complete mitochondrial genome of the firemouth cichlid, Thorichthys meeki (Brind 1918). Illumina HiSeq genome sequencing produced the assembly of a circular mitogenome of 16,527 base pairs (bp) from T. meeki consisting of 46.8% GC nucleotides, 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and a putative control region as shown in the typical teleost gene composition. The gene order of the T. meeki mitogenome was identical to that of other cichlid species. A maximum likelihood phylogenetic tree based on mitochondrial PCGs showed a close relationship of T. meeki with Thorichthys aureus (Gunther 1862) within Heroini tribe.

Hydrogeomorphological controls on reach‐scale distributions of cichlid nest sites in a small neotropical river

AbstractThe Cichlidae are among the most diversified families of fish in the Neotropics and represent an important component of aquatic biodiversity. Understanding cichlid nest‐site selection is important for assemblages facing uncertain futures due to species invasions and environmental change. This information could be used to predict how inter‐ and intraspecific competition for reproductive space may affect populations with changing community dynamics or to identify areas as targets for conservation. We investigated which hydrogeomorphological factors correlated to preferred nest sites of four native cichlid species in the Bladen River, Belize. We recorded the locations of nest sites and collected habitat data through the study reach, including flow velocity, depth, sediment type, fish cover type richness and distance to the bank. Nest locations and physical habitat data were used to construct spatially explicit habitat models using boosted regression trees (BRTs). The models provided statistically significant evidence that physical habitat variables influence the distribution of the nest sites. We found that all species except Archocentrus spilurus were associated with substrate, specifically sand. Thorichthys meeki was also associated with lower water velocities, whereas Cichlasoma salvini was influenced by all five variables. Vieja maculicauda and Archocentrus spilurus were both influenced by flow velocity, distance to bank and depth, although A. spilurus preferred deeper, slightly faster locations about the same distance to the bank. This study suggests that the spatial distribution of nest sites within this cichlid community is significantly different than random and is at least partially governed by physical controls.

Calretinin immunoreactivity in the inferior lobe of the hypothalamus and associated nuclei of the firemouth cichlid, Thorichthys meeki

The distribution of the calcium-binding protein calretinin (CR) was examined by an immunohistochemical method using specific antibodies. CR is involved in the visual system, and the inferior lobe of the hypothalamus represents a multisensory integration center in cichlids. The focus of the present study was to analyze the distribution of CR immunoreactivity in a cichlid fish, the firemouth cichlid, Thorichthys meeki, for the hypothalamic inferior lobe and for the torus lateralis, nucleus glomerulosus, nucleus posterior tuberis, and corpus mamillare as associated nuclei of the hypothalamus. CR-immunoreactive (CR-ir) cell bodies were visualized in the lateral and medial part of the diffuse nucleus of the inferior lobe, ventral portion of the central nucleus of the inferior lobe, torus lateralis, nucleus glomerulosus, and nucleus posterior tuberis. CR-ir fibers could be detected in the dorsal portion of the central nucleus of the inferior lobe and corpus mamillare. The strongest labeling of CR-ir neuropil was observed in the lateral part of the diffuse nucleus of the inferior lobe, outer zone of the periventricular nucleus of the inferior lobe, torus lateralis, nucleus glomerulosus, and nucleus posterior tuberis. CR is abundantly present in the inferior lobe of the hypothalamus and associated nuclei. The role of CR in highly active processes in the inferior lobe of cichlids will be discussed.

Mycobacterial Infection in Ornamental Fishes Farmed in Low Saline Waters of Tiruvallur District, India

Gokulraj, A.; Praveenraj, J.; Gnanadesikan, R., and Arumugam, U., 2019. Mycobacterial infection in ornamental fishes farmed in low saline waters of Tiruvallur District, India. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 134–137. Coconut Creek (Florida), ISSN 0749-0208.The present study reports the detection of Mycobacterium sp. infection in the ornamental fish, Carassius auratus (Gold fish) and two exotic cichlid fishes, Andinoacara rivulatus (Green terror cichlid) and Thorichthys meeki (Fire mouth cichlid) cultured in the low saline waters (5 ppt) of Tiruvallur district. The infected gold fish demonstrated symptoms of skin ulceration, frayed fins, pale gills, disorientation in swimming, ascites and nodules in the liver, whereas the cichlid fishes possessed severe emaciation, skeletal deformity, blackening, weakness and ulceration. The pathogen was isolated in Middlebrook 7H9 broth as typical pink colonies characteristic of Mycobacterium sp. PCR sequencing of the HSP gene was done for molecular confirmation, and the sequences generated were submitted in the GenBank under the accession numbers MK424614, MK424615 and MK424616. Histopathological observation of the organs of the infected fishes revealed granuloma, neutrophil infiltration and vacuolisation in heart, liver and brain. Histopathological changes typical of Mycobacterium sp. viz., lamellar disorientation, and neutrophil infiltrations in the heart, inflammation and congestion in the liver, granuloma in the kidney were documented in infected cichlids. The detection and confirmation of mycobacteriosis in the ornamental fishes cultured in low saline waters of Tamil Nadu is the first report and alert the fish handlers to undertake precautionary measures to prevent the transmission of mycobacterium infection from fish to fish handlers.

GONADAL HISTOPATHOLOGY OF FISH FROM LA PÓLVORA URBAN LAGOON IN THE GRIJALVA BASIN, MEXICO

Studies on environmental pollution in Mexican freshwater ecosystems by means of fish histopathology are extremely scarce. In that view, this research analyzed the gonad histopathology of four teleost fish species from a hyper-eutrophicated fragmented urban lagoon, in order to determine possible harmful effects of water pollutants on their reproductive fitness. Gonads were processed by histological conventional techniques. The gonadal alterations detected in both, the clupeid Dorosoma petenense and the cichlid Thorichthys meeki expose the need to clarify the connection of these alterations to the presence of specific pollutants.

Investigating the behavioral significance of color pattern in a cichlid fish: firemouths Thorichthys meeki respond differently to color-manipulated video and dummy conspecifics

Red coloration is a conspicuous feature of many visual signals and can function to attract or deter its viewers. Among fishes, red is associated with specialized nuptial, territorial and aposematic (warning) displays. Both sexes of the firemouth cichlid fish Thorichthys meeki develop red ventral coloration at sexual maturity, along with temporally variable black (melanic) elements. Isolated adult firemouth cichlids sequentially presented paired dummy and paired video conspecifics, both with and without red ventral coloration. Subjects interacted more with red-containing stimuli, but with a significant interaction: dummy presentations revealed a strong, positive red bias that video presentations did not. In addition, the melanic color pattern displayed by subjects at the initiation of each trial had a significant effect on subject responsiveness. These results reveal the potential for between-subject differences and experimental design parameters to interact critically in the study of animal color patterns.

Los cíclidos (Pisces: Pereiformes) de la Laguna de Términos y sus afluentes

Of the 283 cichlids collected between 1970 and 1973 in and around Laguna de Terminos, Campeche, Mexico, nine species (25% of the total cichlid fauna of Mcxico) have presently been identified. Identification is based on meristic and morphologic characteristics and on color patterns. The hydrologic basin of the Rio Usumacinta is one of the richest in cichlid populations which retain the primitive characteristics of tbe family: Petenia splendida, Cichlasoma meeki, C. aurcum, and C. pearsei. Cichlasoma fenestratum is curyhaline but restricted to tbe rivers and streams. On the other hand, C. urophthalmus appears to be better adapted to the marine conditions wbich occur along the coast of the Isla del Carmen Lagoon. It is also found athough less frequently, in fresh water, an indication tbat it can tolerate a wide range of chlorinity.

On endocytosis of foreign ferritin and occurrence of phagolysosomes in fish heart endothelial cells

In the present study the ultrastructure and function of the endothelial cells enveloping the muscle trabeculae in heart in two teleosts, platyfish and firemouth cichlid, are described and discussed. These cells displayed a structure making them able to take up large amounts of foreign ferritin particles from the blood stream. The ferritin particles were assembled into huge phagolysosomes. Large amounts of Prussian blue were precipitated throughout these lysosomes when treated with acid ferrohexacyanide solution. The occurrence of Prussian blue precipitations in the control heart endothelial cells after Schmorl’s solution, suggests that these cells normally contain undigestible material, a finding which strengthens the view that this tissue is involved in blood clearance in the present species. In conclusion, these heart endothelial cells seem able to perform a very efficient blood clearance of scavenger and foreign macromolecules and particles in the present species.

Histology of melanic flank and opercular color pattern elements in the firemouth cichlid, Thorichthys meeki

Dark melanic color pattern elements, such as bars, stripes, and spots, are common in the skin of fishes, and result from the differential distribution and activity of melanin-containing chromatophores (melanophores). We determined the histological basis of two melanic color pattern elements in the integument of the Firemouth Cichlid, Thorichthys meeki. Vertical bars on the flanks were formed by three layers of dermal melanophores, whereas opercular spots were formed by four layers (two lateral and two medial) in the integument surrounding the opercular bones. Pretreatment of opercular tissue with potassium and sodium salts effectively concentrated or dispersed intracellular melanosomes. Regional differences in epidermal structure, scale distribution, and connective tissues were also identified.

DNA damage in cichlids from an oil production facility in Guatemala

This study focused on several wetlands in Laguna del Tigre National Park (Guatemala) as part of Conservation International's Rapid Assessment Program. Sediment and water samples were collected from a laguna near Xan field, Guatemala's largest oil facility, and three other sites for determination of levels of polycyclic aromatic hydrocarbons (PAHs). Cichlid fish (Thorichthys meeki and Vieja synspila) were collected for determination of DNA strand breakage (by gel electrophoresis), chromosomal breakage (flow cytometry), and fin erosion. For T. meeki from Xan field, chromosomal breakage and strand breakage was greater than in at least two of the three reference sites. For V. synspila, chromosomal breakage and strand breakage were greater in Xan than one of the two reference sites. Fin erosion was observed only at the Xan laguna. Genetic biomarker effects and fin erosion, along with patterns of aqueous PAH concentrations, indicate that fish are affected by anthropogenic contaminants. PAHs were elevated at some reference sites, but environmental forensic analysis suggested a pyrogenic or diagenic origin. It is possible that oil field brines injected into the ground water caused fin erosion and genotoxicity in fish at Xan field, and it is also possible that pyrogenic PAHs influence levels of DNA damage in reference sites. These analyses represent one of the first efforts to examine genotoxicity in native Mesoamerican cichlids.

Carbohydrates in rod and cone light absorbing segments in the firemouth cichlid Thorichthys meeki retina

Carbohydrates in photoreceptor segments in the retina of the firemouth cichlid Thorichthys meeki are described and compared. The present periodic acid-Schiff (PAS) and lectin results revealed the occurrence of neutral carbohydrates, composed mainly of glycosamine and mannose and glucose, in the light absorbing segments in rods and cones in this species. Unlike in mammals, the retina in this teleost seems to be poor in galactose and galactose-galactosamine units in the light absorbing segments.

Uptake of Foreign Ferritin in Heart of Firemouth Cichlid (Cichlidae: Teleostei)

The ultrastructure of the endothelium in the heart of the firemouth cichlid (Thorichthys meeki) and its capability and capacity to take up foreign ferritin are described. The entire wall in atrium and ventricle was spongy and composed of muscle trabeculae, covered by endothelial cells which were about 4-6-μm thick in atrium and flat in ventricle. These cells contained a number of moderately electron-dense bodies (MDBs, diameter 2 μm and less), clathrin-coated vesicles, and tubules of agranular endoplasmatic reticulum. Numerous yellow-brown granules, width 2 μm and less, occurred in the endocardial endothelium covering the cardiac muscle trabeculae in ferritin-injected firemouth cichlid 8 hr postinjection; much Prussian blue precipitated within these granules when treated with acid ferrocyanide. When the time between the injection and sacrifice was extended to 24 hr, the granules and Prussian blue precipitations in the corresponding endocardial endothelium displayed a width of 3 μm and more. The endocardial endothelium facing the cardiac main lumen or covering the valves and walls of the atrio-ventriclar or ventriculo-bulbar apertures nearly lacks such granules and precipitations as well as MDB, clathrin-coated vesicles and tubules of agranular endoplasmic reticulum, suggesting that the endothelium at these sites is not endocytic. Lipofuscinlike pigments were demonstrated by the Schmorl's technique in the endocardial endothelium covering the heart muscle trabeculae in firemouth cichlid. Together these findings suggest that the endocardial endothelium cover on the muscle trabeculae in heart wall in firemouth cichlid is highly specialized to play important roles in the uptake of scavenger molecules and foreign particles. Such an uptake may be very efficient as this cell layer comes in contact with nearly the entire blood volume throughout the spongy heart wall in this type of teleosts.

Ontogenetic Color Change in the Firemouth Cichlid, Thorichthys meeki

Color pattern changes in fishes can vary from nearly instantaneous changes to long term, developmental (ontogenetic) changes. Species-typical patterns of ontogenetic color change (OCC) can provide insight regarding the behavior, ecology, and evolution of a taxon. Observations performed on laboratory-reared Firemouth Cichlids, Thorichthys meeki, from hatching to age 205 days, revealed 16 dynamic color pattern elements. Color pattern changes were correlated with age, but a significantly better correlation was found with body size. Ontogenetic color change in the Firemouth Cichlid featured the expression of some transitory color pattern elements not found in adults, and several elements and their sequence of expression were similar to those previously described for other cichlid species.

Structural and Histochemical Studies on the Teleostean Bulbus Arteriosus

The structure and histochemical properties of the bulbus arteriosus in two species from an evolutionary old teleost family, Characidae, and in three modern teleosts, family Cichlidae, are described. The bulbar wall was composed of an outer layer, a middle layer and a strongly folded inner layer covered by a thick, granule-rich endothelial cell layer towards the lumen. One of the cichlid species (Thorichthys meeki) was injected intraperitoneally with horse ferritin; the endothelial cell layer of the heart atrium and ventricle displayed high ability to endocytose ferritin particles from the blood stream, but the corresponding layer in the bulbus arteriosus displayed no such uptake. This finding suggests that the bulbar endothelial cell layer plays no scavenger or immunological blood cleansing roles in this species. The bulbar endothelial cell granules were strongly coloured by periodic acid-Schiff (PAS) in the present cichlids, but weakly coloured by PAS in the present characids. These cell layers were uncoloured by alkaline carmine in ethanol in both cichlids and characids. The negative carmine test combined with a positive PAS test for the bulbar endothelial cell layer in the present cichlids indicates that these cells contain only small amounts of polysaccharides. The weak PAS-colouring for the bulbar endothelial cell layer in characids indicates a very low content of sugars in these cells. These findings together with the fact that this cell layer in the present cichlids and characids was nearly uncoloured when treated with orcein, Heidenhain's Azan or Schmorl's solutions for elastic materials suggest that the bulbar endothelial granules do not play any role in the blood cleansing or in the rebuilding or maintenance of the ground substance or elastic material in the bulbar wall. Probably, the granules in the bulbar endothelial cell layer in the present species contain mainly proteins, connected to some PAS-positive polysaccharides to enhance their solubility.

Histochemical study on the intestine goblet cells in cichlid and poecilid species (Teleostei)

Histochemical properties of intestine goblet cells in firemouth cichlid, zebra mbuna, freshwater angelfish and platyfish are described. Goblet cells occurred regularly in the epithelial cell layer throughout the entire intestine, they were strongly coloured by alcian blue at pH 2.5. This colour got gradually weaker when the pH was reduced, but still after alcian blue at pH 0.2 these cells displayed a distinct blue colour. When the goblet cells were treated with periodic acid-Schiff (PAS), they displayed a strong purple-magenta colour. The findings that a number of goblet cells displayed various colours between blue and purple-magenta when acidic alcian blue was followed by PAS, and between blue and red-brown when acidic alcian blue was followed by neutral red, may reflect different ages or stages of development and differentiation for these cells. However, such results may also suggest a true cellular heterogeneity in the present population of goblet cells, reflecting that the intestine mucus layer has a number of roles in teleosts like lubrication, protection, immunological defence, digestion and absorption. In the ferritin injected specimens of firemouth cichlid and platyfish, a number of macrophage-like cells in intestine wall displayed Prussian blue precipitations in tissue treated with acid ferrocyanide, suggesting that these cells play a cleansing role in the intestinal wall. No ferritin uptake was seen in the intestine goblet cells and eosinophilic granule cells.

Differences in reproductive seasonality of the Central American cichlidCichlasoma urophthalmusfrom three ‘cenotes’ (sinkholes)

Summary A total of 966 cichlids, Cichlasoma urophthalmus, was sampled from three karstic water bodies (cenotes) in the Yucatan Peninsula. Sex ratio was not different from 1. Specimens with ripe eggs were found during the dry and rainy seasons in the inland cenote and during the dry, rainy, and north winds seasons in the two wetland cenotes. With respect to relative fecundity, data show the C. urophthalmus inland population as two- to three-fold greater (53.1 ± 27.7) than the wetland populations (15.7 ± 5.1 and 18.2 ± 3.1). This is attributable to the different breeding strategies of C. urophthalmus populations inhabiting these two types of cenotes. In particular, the ichthyofauna from the two wetlands showed not only higher species richness (17 and 16 species) but also a higher number of potential predators (nine and eight species) as compared to the inland cenote (six species; two potential predators). It is hypothesized that C. urophthalmus adjusts its clutch size and extends its breeding periods as a response to riskier sites as compared to more secure ones; a higher competition for breeding sites and to increased fishing mortality.

Spatial distribution of cichlids in Tzendales River, Biosphere Reserve Montes Azules, Chiapas, Mexico

Located within Mexico’s Montes Azules Biosphere Reserve, the Tzendales River is part of the Usumacinta River Basin, which supports the largest diversity of cichlid fishes in Middle America. We evaluated temporal and spatial variation of species richness and distribution of cichlids in the Tzendales River; we collected 14 species with nine native and five endemic. The species with greatest relative abundances and broadest spatial distributions were Vieja intermedia and Amphilophus nourissati; and the rarest and most spatially restricted species were Thorichthys meeki and Parachromis friedrichsthalii. Environmental characteristics varied seasonally although fish assemblages and distributions were relatively stable over time. Based on habitat use patterns, three species associations were observed: (1) Amphilophus nourissati, Petenia splendida, Vieja argentea, V. bifasciata, V. intermedia, V. pearsei, V. synspila and V. ufermanni; (2) ‘Cichlasoma’ salvini and Parachromis friedrichsthalii; and (3) Thorichthys helleri and Thorichthys meeki. Two rheophilic species, Theraps lentiginosus and Theraps irregularis, had low habitat overlap with all of the other cichlid species. Canonical correspondence analysis showed that the depth, current speed and quantity of rocks in the substrate defined the spatial distribution of species in dry season. Cichlids of the Tzendales River appear to partition habitat in a manner that reduces resource competition.

Maintaining a Competitive Edge: Dominance Hierarchies, Food Competition and Strategies To Secure Food in Green Anoles (Anolis carolinensis) and Firemouth Cichlids (Thorichthys meeki)

We explored whether the opportunity to learn about the arrival of food, a scarce resource, might facilitate subordinates’ food-stealing attempts―and dominants’ strategies to prevent stealing―in two species, namely green anole lizards (Anolis carolinensis) and firemouth cichlid fish (Thorichthys meeki). Following establishment of a dominance hierarchy, each group was randomly assigned to one of two treatment conditions, either a learning treatment in which a signal preceded the appearance of food, or a control treatment in which both signal and food appeared at randomly determined times. Dominants and subordinates of both species learned to anticipate food arrival using learned cues, which in turn changed their social dynamic. In anoles, learning enabled subordinates to steal food more effectively, and both dominants and subordinates to capture it more quickly. Alternatively, learning enabled dominant cichlids to protect their food more successfully by mounting a more aggressive defense. These results suggest that learning could play an important role in the competition for a scarce resource amongst many animals that form dominance hierarchies.