Species or population? Systematic status of Vieja coatlicue (Teleostei: Cichlidae)

Pacific and Atlantic-slope rivers of the Isthmus of Tehuantepec in Mexico contain two cichlid species of the genus Vieja relevant to the current study, V. zonata and V. coatlicue, respectively. The Atlantic-slope species was initially considered a population of uncertain taxonomic status and recently described as a distinct species based on three putatively diagnostic morphological characters. The objective of this study was to combine new and existing genetic data, along with reanalysis of morphological characters, to test the distinctiveness of V. coatlicue. Little genetic variability and no geographic structuring were recovered. Additionally, putatively diagnostic morphological character states were present across both species, failing to separate the forms. The synthesis of molecular and morphological data supports the recognition of V. coatlicue as a junior synonym of V. zonata.(AU)

Dos especies del género Vieja se encuentran distribuidas a lo largo Istmo de Tehuantepec en México; V. zonata se distribuye en los ríos de la vertiente del Pacífico y V. coatlicue en los ríos de la vertiente del Atlántico. La especie que se distribuye en la vertiente del Atlántico era considerada como una población de estado taxonómico incierto, pero recientemente fue descrita como nueva especie en base a tres caracteres morfológicos diagnósticos. El objetivo de este estudio fue utilizar datos moleculares nuevos con datos moleculares previamente publicados en combinación con una reanálisis de los caracteres morfológicos para testear la validez taxonómica de la especie V. coatlicue. Nuestros análisis moleculares no recobran estructura geográfica y además muestran baja variabilidad genética. Además, los tres caracteres morfológicos diagnósticos se encontraron presentes en individuos de ambas especies, nuestro trabajo sugiere que estos caracteres morfológicos diagnósticos no proven información que permita separar a las formas que se distribuyen en la vertiente del Pacífico y la vertiente del Atlántico. Nuestra síntesis de datos moleculares y morfológicos provee evidencia para reconocer a V. coatlicue como una sinónima mas reciente de V. zonata.(AU)

Unusual effect of chemical communication on social aggression in juvenile cichlid fish Cichlasoma paranaense (Cichliformes: Cichlidae)

Some fish species are socially organized and show a social rank order which is achieved through aggressive interactions. After hierarchy is settled, such species communicate their ranks through several sensorial cues; this communication is adaptive because it reduces detrimental effects from physical contests. Cichlid fish are socially organized and signal their social ranks through visual, acoustic and chemical communication. The response to signaling may vary according to the species and environment; the knowledge of different species is fundamental to understand the evolutionary forces upon their social communication. We tested the effect of chemical signaling on social groups of juvenile cichlid Cichlasoma paranaense by renewing the water in the aquarium, a procedure that washes away chemical information and increases aggressive interactions in other cichlid species. Two treatments were designed: 50% and 0% water renewal. Aggressive interactions were video-recorded immediately before water renewal, 1min, 1h, 2h, and 24h after water renewal. The treatment with the water renewal did not increase aggressive interactions within the group. The 50% water renewal apparently reduced aggressive interactions in this species, indicating an interspecific difference on the aggressive response to chemical variation in the social environment.(AU)

Algumas espécies de peixes são organizadas socialmente e apresentam uma ordem de rank social que é alcançada por meio de interações agressivas. Após o estabelecimento da hierarquia, essas espécies comunicam seu rank por diversas pistas sensoriais, essa comunicação é adaptativa, pois reduz os efeitos prejudiciais das lutas físicas. Peixes ciclídeos são socialmente organizados e sinalizam o rank social por comunicação visual, acústica e química. A resposta à sinalização pode variar de acordo com a espécie e o ambiente; o conhecimento sobre diferentes espécies é necessário para entender as forças evolutivas sobre sua comunicação social. Nós testamos o efeito da sinalização química em grupos sociais de juvenis do ciclídeo Cichlasoma paranaense por meio da renovação de água do aquário, um procedimento que dilui informações químicas e aumenta a interação agressiva em outras espécies de ciclídeos. Dois tratamentos foram realizados: 50% e 0% de renovação da água. A interação agressiva foi registrada imediatamente antes da renovação da água, 1min, 1h, 2h e 24h após a renovação da água. O tratamento com renovação não aumenta as interações agressivas dentro do grupo. A renovação de 50% da água do aquário aparentemente diminui as interações agressivas nessa espécie, indicando uma diferença interespecífica na resposta agressiva a variação química no ambiente social.(AU)

Temperature affects the hypoxia tolerance of neotropical Cichlid Geophagus brasiliensis

Oxygen and temperature are the most limiting factors in aquatic environments. Several species are exposed to variations of these factors in water because of physical, chemical and biological processes. The objective of this study was to evaluate the metabolic profile and the tolerance to the hypoxia of Geophagus brasiliensis exposed to changes in temperature and oxygen availability. The fish were exposed to 20 and 90% of oxygen saturation combined with different temperatures (20°, 24° and 28° C) for 8 h. Hepatic and muscular glycogen, as well as the activities of lactate dehydrogenase (LDH), malate dehydrogenase (MDH), citrate synthase (CS) and their ratios were evaluated. Both glycogen and MDH activity showed a significant difference in the liver. While CS showed increased activity only in the heart. The increase in LDH activity in the white muscle shows the importance of the anaerobic pathway as energy source in this tissue. The MDH / LDH ratio increased in all tissues, while CS / LDH increased in the liver and decreased in the heart. Based on the results of the present study it may be concluded that this species used the anaerobic metabolism as the main strategy for hypoxia tolerance.(AU)

O oxigênio e a temperatura são os fatores mais limitantes em ambientes aquáticos. Várias espécies são expostas a variações destes fatores na água como resultado de processos físicos, químicos e biológicos. O estudo objetivou avaliar o perfil metabólico e a tolerância à hipóxia de Geophagus brasiliensis expostos a alterações na temperatura e disponibilidade de oxigênio. Os peixes foram expostos a 20% e 90% de saturação de oxigênio combinadas com diferentes temperaturas (20 ° C, 24 ° C e 28 ° C) durante 8h. Foram avaliados o glicogénio hepático e muscular, assim como as atividades das enzimas lactato desidrogenase (LDH), malato desidrogenase (MDH), citrato sintase (CS) e suas razões. Tanto o glicogênio quanto a atividade da MDH apresentaram diferença significativa no fígado. Enquanto a CS apresentou aumento de sua atividade apenas no coração. O aumento da atividade LDH no músculo branco mostra a importância da via anaeróbia como fonte de energia neste tecido. A razão MDH/LDH aumentou em todos os tecidos, enquanto CS/LDH apresentou aumento no fígado e diminuição no coração. Os resultados obtidos permitem concluir que esta espécie utilizou o metabolismo anaeróbio como principal estratégia de tolerância à hipóxia.(AU)

Water temperature affects aggressive interactions in a Neotropical cichlid fish

Changes in water temperature may affect the aggressive behavior of aquatic organisms, such as fish, either by changing some physiological mechanisms or by increasing the probability of encounters between individuals as a result of variation in their swimming activity. In our study, we evaluated the influence of increasing and decreasing temperature on the aggressive behavior of the Neotropical cichlid fish Cichlasoma paranaense. Firstly, we tested the critical thermal maximum (CTMax) tolerated by this species. Then, we tested the effect of decreasing or increasing the water temperature in 6o C (starting at 27° C) on the aggressive interactions of fish under isolation or housed in groups. We found a CTMax value of 39° C for C. paranaense. We also observe that a 6° C decrease in water temperature lowers swimming activity and aggressive interactions in both isolated and group-housed fish, as expected. On the other hand, the increase in temperature had no effect on the fish's aggressive behavior, neither for isolated nor for grouped fish. We concluded that C. paranaense shows high tolerance to elevated temperatures and, in turn, it does not affect aggressive behavior. Nevertheless, we cannot dismiss possible effects of elevated temperatures on aggressive interactions over longer periods.(AU)

Mudanças na temperatura da água podem afetar o comportamento agressivo de organismos aquáticos, como peixes, seja alterando alguns mecanismos fisiológicos ou aumentando a probabilidade de encontros entre os indivíduos como um resultado da variação na sua atividade natatória. Em nosso estudo, nós avaliamos a influência do aumento e da diminuição da temperatura sobre o comportamento agressivo do peixe ciclídeo neotropical Cichlasoma paranaense. Primeiramente, nós testamos a temperatura crítica máxima (CTMax) tolerada por essa espécie. Depois disso, nós testamos o efeito de reduzir ou aumentar a temperatura da água em 6° C (a partir de 27° C) sobre as interações agressivas de peixes sob isolamento ou alojados em grupos. Nós encontramos um valor de CTMax de 39° C para C. paranaense. Nós também observamos que uma redução de 6° C na temperatura da água diminui a atividade natatória e as interações agressivas tanto em peixes isolados quanto agrupados, como esperado. Por outro lado, o aumento na temperatura não teve efeito no comportamento agressivo dos peixes nem isolados, nem agrupados. Nós concluímos que C. paranaense apresenta alta tolerância a temperaturas elevadas, e que isso, por sua vez, não afeta o comportamento agressivo. No entanto, nós não podemos descartar possíveis efeitos de temperaturas elevadas sobre interações agressivas durante longos períodos.(AU)

First record of pughead deformity in Cichla kelberi (Teleostei: Cichlidae), an invasive species in an estuarine system in south-eastern Brazil.

The first record of pughead deformity in a Neotropical freshwater fish not raised in captivity is provided, based on an adult male of Cichla kelberi introduced into an estuary of Rio de Janeiro State, south-eastern Brazil. A general biological characterization of the specimen is provided and aspects of its aberrant anatomy are described. Environmental and biological factors that may cause pughead deformity in fishes are discussed.

Redescription of Pseudotropheus livingstonii and Pseudotropheus elegans from Lake Malawi, Africa.

Pseudotropheus livingstonii and P. elegans are two sand-dwelling cichlid species that belong to the so-called mbuna, a group of predominantly rock-dwelling haplochromines of Lake Malawi. The identity of these two species has confused taxonomists for almost a century until a recent rediscovery of representatives of P. elegans close to its type locality. New diagnoses for both species are provided.

Prevention of cytogenetic, histochemical and biochemical alterations in Oreochromis niloticus by dietary supplement of sorbent materials.

The current study was conducted to evaluate the ability of Egyptian bentonite (EB) and montmorillonite (EM) for the prevention of genotoxicity, histochemical and biochemical changes induced by aflatoxin B(1) (AFB(1)) using the micronucleus (MN) assay, chromosomal aberrations and DNA fragmentation analysis in Tilapia fish. Six groups of fish were treated for 3 weeks and included the control group, AFB(1)-treated group and the groups treated with EB or EM alone or in combination with AFB(1). At the end of experiment period, blood samples were collected for MN, testosterone and biochemical assays. Chromosomal aberrations were determined in kidney tissues, DNA fragmentation test was determined in liver and testis, whereas histochemical study was carried out on liver, testis and gills. The results indicated that a significant decrease in total protein, albumin, globulin, testosterone and DNA content in liver, gills and testis accompanied with a significant increase in number of micronucleated erythrocytes (MnRBCs), total chromosomal aberrations in kidney and DNA fragmentation in testis and liver of fish received AFB(1) alone. Fish treated with EB or EM alone were comparable to the control regarding the biochemical parameters except testosterone in EB-treated group which was significantly decreased. Both clays did not induce any significant differences in number of MnRBCs, chromosomal aberrations in the kidney, DNA fragmentation in testis, but not in liver of EB-treated group. The combined treatment with AFB(1) and EB or EM succeeded to improve all the tested parameters towards the control values although it did not normalize them. Moreover, the improvement was pronounced in the group received EM plus AFB(1). It could be concluded that EB and EM have the ability to tightly bind AFB(1) in the gastrointestinal tract of fish resulting in decreasing its bioavailability. Moreover, the two tested clays were safe and can be used as potential aflatoxin binders in animal feed.