Cichlids

Current knowledge on fate and effect of agricultural pesticides comes is mainly from temperate ecosystems. More studies are needed in tropical systems in order to assess contamination risks to nontarget endemic tropical species from the extensive use of pesticides e.g. in banana and pineapple plantations. In this study, acute laboratory toxicity tests with organophosphate pesticides ethoprophos and chlorpyrifos were conducted on two Costa Rican species, cladoceran Daphnia ambigua and fish Parachromis dovii. Tests showed that chlorpyrifos was more toxic than ethoprophos to D. ambigua and P. dovii and that D. ambigua was also more sensitive than P. dovii to both pesticides. Additionally, bioassays were performed by exposing D. magna and P. dovii to contaminated water collected from the field. Chemical analyses of field water revealed that fungicides were generally the most frequent pesticide group found, followed by insecticides/nematicides and herbicides. The bioassays and values obt...

The mode of action of honey bee pollen (HBP) was investigated in Nile tilapia (Oreochromis niloticus) challenged with Aeromonas hydrophila. Thus, fish with an average weight of 29 ± 3 g were divided into four groups, and fed with HBP-free diet (control), and 1%, 2.5% and 4% (w/v) HBP incorporated into basal diet for 10, 20 and 30 days. Immunological, hematological, biochemical and growth parameters were measured, and sub-groups of fish were challenged with A. hydrophila via intraperitoneal injection. HBP significantly increased the growth performance parameters [body weight, length, average daily gain (ADG), specific growth rate (SGR), and feed efficiency ratio (FER)] and immunological (phagocytic activity, serum bactericidal activity and nitroblue tetrazolium assay (NBT)), hematological (hematocrit (Hct), leucocrit (Lct), the numbers of neutrophils, monocytes and lymphocytes) and biochemical parameters (serum total protein, albumin and globulin ratios). Furthermore, all treated fis...

The current study investigated the levels of multi pesticide residues in the highly consumed types of Nile fish in Egypt: tilapia and cat fish. A total of 50 Nile tilapia (Oreochromis niloticus) and 50 African catfish (Clarias gariepinus) were collected from two areas in Assiut city, where most industries are situated and where agricultural activities and raising of farm animals are the main activities. In the first area, Elwasta, there is an electrical power station, and the second area, Mankbad, there is a cement factory. Fish samples were analyzed by High Resolution Gas Chromatography/Mass Spectrometry. Average pesticide residue concentrations±SE in muscle of tilapia and catfish (n = 10 pooled samples with five fish each) were determined. The results indicated the presence of different types of organophosphorous (OPs), organochlorine (OC), polychlorinated biphenyles (PCBs), hexachlorobenzene (HCB) and trifluralin pesticides in Elwasta and Mankbad in varying degrees. Diazenon was ...

Copper oxide nanoparticles (nCuO) are widely used in boat antifouling paints and are released into the environment, potentially inducing toxicity to aquatic organisms. The present study aimed to understand the effects of nCuO and dissolved copper (Cu) on two ornamental Amazon fish species: dwarf cichlid (Apistogramma agassizii) and cardinal tetra (Paracheirodon axelrodi). Fish were exposed to 50% of the LC for nCuO (dwarf cichlid 58.31μgL and cardinal tetra 69.6μgL) and Cu (dwarf cichlid 20μgL and cardinal tetra 22.9μgL) for 24, 48, 72 and 96h. Following exposure, aerobic metabolic rate (ṀO), gill osmoregulatory physiology and mitochondrial function, oxidative stress markers, and morphological damage were evaluated. Our results revealed species specificity in metabolic stress responses. An increase of ṀO was noted in cardinal tetra exposed to Cu, but not nCuO, whereas ṀO in dwarf cichlid showed little change with either treatment. In contrast, mitochondria from dwarf cichlid exhibit...

Edwardsiella ictaluri was consistently isolated from the spleens, livers, and head kidneys of diseased Nile tilapia Oreochromis niloticus from a farm experiencing mortality events in several culture ponds. We describe the first published outbreak of E. ictaluri–induced edwardsiellosis in Nile tilapia. Pure cultures of the isolated bacteria were characterized both biochemically and molecularly. Biochemical analysis was performed using the API-20E and RapID One systems, and antimicrobial susceptibility was determined by the broth microdilution method. Molecular analysis involved sequencing of the 16S rRNA gene, species-specific real-time polymerase chain reaction (PCR), and PCR-mediated genomic fingerprinting (rep-PCR). Pairwise sequence analysis of the 16S rRNA gene identified the case isolates to be a 100% match to E. ictaluri cultured from channel catfish in the southeastern United States. However, rep-PCR analysis identified the case isolates to be genetically different from representative strains isolated from disease outbreaks in cultured channel catfish in Mississippi. Infectivity challenges (intraperitoneal injection and immersion) demonstrated that a representative E. ictaluri strain isolated from tilapia was pathogenic to naïve tilapia, reproducing clinical signs and mortality, thereby establishing Koch's postulates.Received August 30, 2011; accepted January 30, 2012

This is an epistemological research, concerning knowledge processes. The choice of African Cichlids as a subject has been stimulated mainly by the fact that these fishes are targeted by remarkably different observers: fishermen, ecologists, biologists, geneticists, evolutionists wirh different approaches, hobbyists and aquarists - beginners and experts. The great epistemological interest of this crowd of observers lies not only in the comparison of different knowing processes applied to the same object, but also in their multiple and complex reciprocal interactions...

The aim of present study was determination effects of dietary administration of C. militaris spent mushroom substrate (SMS) on mucosal and serum immune parameters, disease resistance, and growth performance of Nile tilapia (Oreochromis niloticus). Two hundred twenty five fish of similar weight (37.28 ± 0.10 g) were assigned to the following diets [0 (T1- Control), 5 (T2), 10 (T3), 20 (T4) and 40 g kg(-1) (T5) SMS]. After 60 days of feeding trial, growth performance, skin mucus lysozyme and peroxidase activities as well as serum innate immune were measured. In addition, survival rate and innate immune responses were calculated after challenge test (15 days) against Streptococcus agalactiae. The results revealed that regardless of inclusion levels, feeding Nile tilapia with SMS supplemented diets significantly increased skin mucus lysozyme and peroxidase activities as well as serum immune parameters (SL, ACH50, PI, RB, and RB) compared control group (P < 0.05). The highest incremen...

Androgen and estrogen metabolism were examined in the period of steroid sensitivity during sex differentiation in mono-sex populations of Oreochromis niloticus. Fry (XX, XY, and YY genotypes) were maintained at 28 degrees and were sampled at 8, 10, 11, and 13 days postfertilization. Subsamples (n = 2-4) of pooled fry from each maternally distinct family were homogenized and incubated with either [(3)H]androstenedione or [(3)H]estradiol. Metabolites present in organic extracts were identified by thin-layer chromatography, microchemical reactions, and recrystallization to constant specific activity. Androstenedione was metabolized into at least seven readily identifiable compounds by all genotypes. In the XY genotype, 5beta-androstane-3alpha,17beta-diol synthesis decreased rapidly from 8 to 13 days postfertilization, with a concomitant increase in testosterone synthesis. Testosterone synthesis did not increase in the XX genotype. Testosterone synthesis in the YY genotype was intermediate to that of the XY and XX genotypes. Estrogens were not synthesized by any genotype. We hypothesize that 5beta-reduction (or further hydroxylation) is a mechanism important in regulating testosterone production and subsequent sex differentiation. Results of incubations with estradiol show an age-dependent increase in metabolism which did not vary among genotypes. Metabolites synthesized included estrone and up to five unidentified compounds.

Microcystins (MCs) have been reported to induce oxidative stress in aquatic organisms including fish. The effect of acute exposure to toxic cyanobacterial material containing MCs on antioxidant enzymes and lipid peroxidation has been studied in liver, kidney and gills of tilapia fish (Oreochromis niloticus). Fish were orally exposed to a single dose of cyanobacterial cells containing 120 μg/fish MC-LR and sacrificed at 24 and 72 h. The activities of glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD) and catalase (CAT) enzymes in the studied organs decreased in general 24 and 72 h after the dose application, although elevation of CAT and GR was found in liver at 72 h post exposure in comparison to 24 h values. In contrast, the lipid peroxidation level increased significantly in all the studied organs with the liver (3.6-fold) proving to be the most affected. Protein oxidation was also increased 1.5-fold in the liver. However, recovery in these parameters was observed in liver 72 h after exposure. The results show that an acute dose of MCs does not induce an adaptative response of the antioxidant enzymes, as a sub-chronic exposure to MCs in tilapia fish does, but a general decrease in them with an initial recovery of the oxidative damage after 72 h, expressed as enhancement of CAT and GR activities and a reduction of LPO and protein oxidation in comparison to 24 h values.

Deltamethrin, a synthetic pyrethroid contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The purpose of this study was to evaluate LC50 values of deltamethrin on Nile tilapia (Oreochromis niloticus L.) fingerlings and investigate histopathological responses of fish exposed to deltamethrin. The 48 h LC50 value for Nile tilapia fingerlings was estimated as 4.85 μg/L using static test system. In addition, behavioral changes at each deltamethrin concentration were observed closely. All fish, exposed to 5 μg/L deltamethrin revealed severe morphological alterations in the gills and liver. In the gills hyperemia, fusion of secondary lamellae and telangiectasis were observed; whereas hydropic degenerations in liver were observed in all examined fish. The results are significant for reporting acute deltamethrin toxicity in terms of behavioral and histopathological changes: Deltamethrin is highly toxic to fingerlings. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 614–620, 2006.

High temperature treatments induce germ cell loss in gonads of vertebrate animals, including fish. It could be a reliable source for induction of sterility if the treatments led to a permanent loss of germ cells. Here we report that heat treatment at 37°C for 45-60days caused a complete loss of germ cells in female Nile tilapia, Oreochromis niloticus, and that sterility was achieved in fish at all stages of their life cycle. Unlike previous observations, germ cells did not repopulate even after returning them to the water at control conditions suggesting permanent depletion of germ cells. Gonadal somatic cells immunopositive for 3β-hydroxysteroid dehydrogenase (3β-HSD) were clustered at one end of the germ cell depleted gonads close to the blood vessel. Serum level of testosterone, 11-ketotestosterone, and 17β-estradiol was significantly decreased in sterile fish compared to control. Body weight of sterile fish was higher than control fish at the end of experiment. Our observations ...

The objective of the present thesis was to determine the taxonomic status of the members of the genus Herichthys in northeastern Mexico, as well as to establish their evolutionary, zoogeographic and phylogenetic relationships. Biological material was obtained during collecting trips to the water bodies that make up the historical distribution range of the Cichlidae family north of the Punta del Morro. The material was fixed in formaline and deposited in the “Colección Ictiológica de la Facultad de Ciencias Biológicas de la UANL”. Tissue samples of pectoral or pelvic fins were obtained and DNA was extracted. The mitochondrial gene cytochrome oxidase I (Cox1) was amplified via polymerase chain reaction (PCR) at the “Museo Nacional de Ciencias Naturales” of Madrid, Spain. A genetic data base was obtained. The database was supplemented with data from genebank. A Bayes phylogenetic tree was inferred and the genetic divergence (Dp = distances without correction) among the different lineages was estimated. Biometrics was taken from 374 Herichthys specimens. The integrated database was subjected to Principal Component Analysis, Discriminant Analysis and Similarity Based Hierarchical Clustering. Morphometric analysis showed a highly significant association between the groups analyzed and predictive characters that discriminate between lineages. Nonetheless, a high degree of overlap was observed for the individual diagnostic characters in most measurements, which do not allow discrimination between some of the lineages without the use of predictive canonical functions, making taxonomic categorization based on morphometric analysisis difficult. Morphometric results were validated by low levels of interspecific genetic divergence, allowing inference of high levels of phenotypic plasticity in the group; and the existence of divergent intraspecific geological forms. Based on the above, a theory of dispersion, isolation, introgressive hybridization, reticulation and sympatric speciation was made for the group by combining the results with the available information on the palaeo hydrology of the region, as well as paleo volcanic and climatic events. The taxonomic status of the species within the genus Herichthys was clarified, a new genus and four new species were described, and a taxonomic proposal was developed based on existing species concepts, under the International Code of Zoological Nomenclature in its 1999 edition.

Objective. This investigation aimed to study the presence of Streptococcus spp. in tilapia (Oreochromis niloticus) from fish farm located in Sullana-Piura, Peru. Materials and methods. 150 fish with clinical signs of streptococcal disease were sampled, and the bacterium isolation was performed on blood agar, correlated to histopathological lesions description and molecular confirmation by real-time PCR. Results. The necropsy revealed exophthalmia, hyphema, congestion and/or haemorrhagic meninges, ascites, splenomegaly, hepatomegaly and diffuse haemorrhagic zones throughout the body. 102 isolated positives (54 tilapias) to Streptococcus spp. were identified in the microbiological analysis (prevalence of 26%), the brain was the organ with the highest percentage of this bacteria (34.31%), and 19 isolates were beta-haemolytic (18.63%) with prevalence of 10.12%. Fish beta-haemolytic streptococci presented epicarditis, perisplenitis and chronic meningitis, panophthalmitis, coagulative necrosis of skeletal muscle and granulomas formation. In the confirmatory test by real-time PCR, any positive tilapia to S. iniae was obtained. The results were analysed using a stochastic simulation of beta distribution using @Risk program uncertainty, reporting an average prevalence of 0.66% in sick tilapias. Conclusions. The analysed fishes were positive to bacteria of the genus Streptococcus, which confirms its presence in the fish farm. However, 19 isolates were beta-haemolytic, and the presence of S. iniae was not positive to the limit prevalence of 2.7% in real-time PCR.

Cichlid fishes are classic examples of adaptive radiation because of their putative tendency to explosively diversify after invading novel environments. To examine whether ecological opportunity increased diversification (speciation minus extinction) early in a species-rich cichlid radiation, we determined if Heroine cichlids experienced a burst of diversification following their invasion of Central America. We first reconstructed the Heroine phylogeny and determined the basal node to use as the root of Central American Heroine diversification. We then examined the influence of incomplete taxon sampling on this group's diversification patterns. First, we added missing species randomly to the phylogeny and assessed deviations from a constant rate of lineage accumulation. Using a range of species numbers, we failed to recover significant deviations from a pure-birth process and found little support for an early burst of diversification. Then, we examined patterns of lineage accumu...