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The enemy release hypothesis (ERH) posits that invasive species are released from their natural enemies in their invasive range, which promotes their successful invasion. In this study, we tested the ERH in a population of the convict cichlid Amatitlania nigrofasciata, an invasive species in Mexico. The ERH predicts that the convict cichlid: (a) is not infected by specialist helminth parasites in the invasive range; (b) has lower infection parameter values, as measured through richness, prevalence, abundance and diversity of helminths, than a native species—the redside cichlid Cichlasoma istlanum; and (c) is not affected in its condition factor by the abundance of helminths it carries. The convict cichlid was infected by two (33%) specialist helminths relative to the six specialist helminths that infect the cichlid in its native range. The convict cichlid had lower helminth richness and diversity than the redside cichlid. However, the prevalence and abundance of the parasite species varied between the host fish. While the prevalence and abundance of the nematode Rhabdochona kidderi was higher in the redside cichlid, the prevalence and abundance of the trematode Uvulifer sp. was higher in the convict cichlid. The condition factor in both host fish was not correlated with helminth abundance. Our results do not agree with the prediction that the convict cichlid is completely released from specialist parasites, nor with the prediction that this invasive species has lower infection parameter values than the native redside cichlid. However, our results agree with the prediction that the abundance of parasite helminths do not affect the cichlid's condition factor. More studies are necessary to determine the advantages that the convict cichlid could have in the invasive range when it is infected with a low richness and diversity of helminths. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate the effects of methanolic extract of nettle (Urtica dioica) on growth, reproduction, biochemical and immunological parameters of female convict cichlid (Amatitlania nigrofasciata). For this purpose, 54 fish were distributed in 3 treatments included: without supplementation (control), 0.1 g (NE0.1), and 0.5 g (NE0.5) nettle extract per kilogram feed over 56 days. The highest final weight (4.2 ± 0.1 g), weight gain (2.8 ± 0.1 g), and specific growth rate (2.0 ± 0.0% day−1) were recorded in NE0.1 group. Higher and lower feed conversion ratio were obtained in control and NE0.1 treatments, respectively. Hepatosomatic and viscerosomatic indices in NE0.1 treatment were significantly lower compared with control treatment. Fish fed NE0.1 showed significantly lower glucose (55.2 ± 6.5 mg g−1), cholesterol (28.4 ± 3.3 mg g−1), and triglyceride (211.5 ± 39.0 mg g−1) levels. Total protein (36.3 ± 3.4 mg g−1) and albumin (2.7 ± 0.1 mg g−1) showed a marked increase in NE0.1 treatment. Same trend was observed in C3, C4, and IgM concentrations. NE0.1 showed the highest number of eggs per female (183.7 ± 10.2), hatching rate (97 ± 0.7%), and larval survival rate at 3 days post hatch (86.3 ± 0.6%) compared with the other treatments. These findings indicated that 0.1 g methanolic extract of nettle kg feed−1 could enhance growth, improve metabolic, and immune function of convict cichlid. Moreover, this study confirmed that appropriate dose of nettle can positively promote reproductive performance which makes it as a valuable and cost-effective herb in aquaculture industry. [ABSTRACT FROM AUTHOR]

In this study, growth performance, body composition, digestive enzymes activity, mucosal and immunological parameters, cultivable bacterial populations, and stress resistance were investigated in juvenile convict cichlid fish (Amatitlania nigrofasciata) that received a dietary supplement containing 0 (control), 5 × 106 (LC1), 5 × 107 (LC2), and 5 × 108 CFU g−1 diet (LC3) Lacticaseibacillus casei PB-LC39. Two hundred and forty fish (2.44 ± 0.04 g) were assigned to twelve experimental aquariums and feed ad libitum three times a day for 8 weeks. After final sampling, final body weight, percentage of weight gain (WG %), specific growth rate (SGR), food conversion ratio (FCR), and protein content of whole‐body composition were significantly higher (P < 0.05) in fish fed LC1 diet than other treatments. Total protease, amylase, and lipase activities were also significantly higher (P < 0.05) in fish fed LC1 diet than other groups. Total protein from serum and mucus, lysozyme activity, total immunoglobulin (Ig), and serum globulin were significantly increased (P < 0.05) in fish fed LC1 diet compared with other groups. Moreover, total counts of lactic acid bacteria (LAB) in fish gut were significantly higher (P < 0.05) by different levels of L. casei PB-LC39 than the control group. Recovery rates of fish fed the probiotic cells, after an air-dive test, was significantly increased (P < 0.05) compared with the control group. Therefore, the results showed that L. casei PB-LC39 resulted in improving growth, health status, and stress resistance of fish during the rearing of juvenile convict cichlid fish. [ABSTRACT FROM AUTHOR]

Cerebral lateralization, the partitioning of functions into a certain hemisphere of the brain, is ubiquitous among vertebrates. Evidence suggests that the cognitive processing of a stimulus is performed with a specific hemisphere depending in part upon the emotional valence of the stimulus (i.e. whether it is appetitive or aversive). Recent work has implicated a predominance of right-hemisphere processing for aversive stimuli. In fish with laterally placed eyes, the preference to view an object with a specific eye has been used as a proxy for assessing cerebral lateralization. The habenula, one of the most well-known examples of an asymmetrical neural structure, has been linked to behavioural asymmetry in some fish species. Here, we exposed convict cichlid fish ( Amatitlania nigrofasciata) to both a social and non-social lateralization task and assessed behavioural lateralization in either the presence or absence of an aversive stimulus, damage-induced alarm cues. We also assessed whether behavioural asymmetry in these tests was related to asymmetry of the habenular nuclei. We found that when alarm cues were present, fish showed increased left-eye (and by proxy, right hemisphere) preference for stimulus viewing. In addition, females, but not males, showed stronger eye preferences when alarm cues were present. We did not find a relationship between behavioural lateralization and habenular lateralization. Our results conflict with previous reports of concordance between behavioural and habenular lateralization in this fish species. However, our results do provide support for the hypothesis of increased right-hemisphere use when an organism is exposed to aversive stimuli. [ABSTRACT FROM AUTHOR]

Female convict cichlids ( Amatitlania siquia) exhibit bright orange ventral coloration that males lack. The behavioral implications of this color are poorly understood, particularly in naturally occurring populations where female coloration could play a role in the expression of territorial nest-guarding behaviors. In this field experiment, monogamous breeding pairs of convict cichlids were presented with 3D printed model conspecific intruders of three body sizes (small, medium, and large) exhibiting three orange patch sizes (large, small, or none) to observe how territorial aggression varied as a function of intruder size and female coloration. Individuals occupying breeding pairs that were defending hatched offspring were significantly more aggressive toward intruders with small and large amounts of orange than toward models lacking orange, indicating that color is an important context-dependent elicitor of aggression in this species. Males were significantly more aggressive toward the intruder than females, and male aggression was strongly influenced by their size relative to the intruder. When males were smaller than the intruder, they performed significantly more aggressive acts than when they were the same size or larger than the intruder; this trend persisted across three putative populations in Lake Xiloa, Nicaragua. A potential explanation for these findings is that the orange color functions as a signal of individual quality or breeding readiness and that breeding pairs increase aggression to repel intruders that pose the greatest threat to pair bond and nest maintenance. Significance statement: One or both sexes of many animal species possess brightly colored features that might communicate information about overall heath or reproductive status. In convict cichlid fish, males and females establish pair bonds and jointly defend their nest and offspring. Single females exhibit striking orange coloration that males and breeding females lack. Our field-based experiment provided evidence that more colorful females, which likely pose a threat to pair bond stability and nest maintenance, incite more aggression from breeding pairs than drab females. Our study suggests that color provides salient information about, perhaps, female quality or readiness to breed in natural populations, and adds to a growing body of research that seeks to understand the varied roles that colorful ornaments play in animal communication. [ABSTRACT FROM AUTHOR]

The signaling function of carotenoid-based orange ventral coloration expressed by female convict cichlids ( A. siquia) is still largely unknown. This field study examined the relationship between breeding female A. siquia orange coloration and predation stress, territorial competition, and offspring developmental stage. Female orange coloration decreased significantly with increased behavioral interactions with predators and heterospecific competitors, and the presence of wrigglers, fry, or juveniles was significantly associated with a lack of orange coloration. Multiple alternative explanations for these observations are discussed, including body carotenoid re-allocation and variation in environmental characteristics. [ABSTRACT FROM AUTHOR]

The convict cichlid, Amatitlania siquia, is a serially monogamous, bi-parental cichlid species native to Costa Rican rivers. Numerous field studies conducted in the Rio Cabuyo (Lomas Barbudal, Costa Rica) have provided a wealth of information regarding the behavioral ecology of this species. Recently a cichlid species that was previously not found in the Rio Cabuyo was identified as Hypsophrys nematopus. This influx of this non-native species provides an interesting ability to study the interactions of this potentially invasive species and to monitor the changes made by the native cichlid species. Over the course of several field seasons, I investigated the interactions between the native convict cichlid and the non-native cichlid. I surveyed the distribution of breeding pairs of both species and conducted behavioral tests to examine the interactions between the native and non-native species. I found an overall decline breeding pairs of both species over the course of the study. I found that both species were more aggressive to conspecific intruders and that female convict cichlids were aggressive to juveniles but males were not. These results provide important information concerning how native species interact with non-native species. It appears that the A. siquia population may experience a change in its reproductive behaviors due to the influx of H. nematopus. [ABSTRACT FROM AUTHOR]

The neotropical convict cichlid fish ( Amatitlania siquia) is an important model species for the study of animal behaviour. It is therefore surprising that no genetic markers are available for this species. Here, we have optimised four polymorphic microsatellite loci for use with this fish, where each locus comprises between 9 and 28 alleles. We demonstrate how these markers can be used to genotype fry (young) and for the analyses of genetic structure and prevalence of interfamilial mixing within biparental broods of wild convict cichlids. These microsatellites will facilitate future research, hitherto not possible, on the molecular, behavioural and evolutionary ecology of the convict cichlid and possibly other closely related species. [ABSTRACT FROM AUTHOR]

Parental investment theory states that parents should contribute more to older offspring. Differences between the sexes also influence how each parent contributes to offspring in biparental species. Here, we examined a naturally occurring population of biparental convict cichlids in Costa Rica to determine how each parent cared for offspring during two distinct offspring development stages. Consistent with the predictions of the reproductive value hypothesis, we hypothesized that the levels of parental contribution would be relative to the value that each parent places on a brood. We predicted that female parents would contribute more than male parents because female convict cichlids have lower future reproductive success than males. Additionally, we predicted that both parents should contribute more to older offspring, either due to the young's increased susceptibility to predation (i.e., the vulnerability hypothesis) or because of the longer period of time parents have been interacting with older offspring (i.e., feedback hypotheses). This increase in investment by males should coincide with a change in the coordination of care between parents. Detailed observations of parental pairs in their natural habitat supported these predictions. Females contributed more to broods than males and were relatively unaffected by offspring age while males spent significantly more time with older, free-swimming fry. Additionally, males tended to leave younger offspring more than females did, and were more likely to do so consecutively with younger offspring. This suggests that the coordination of duties between parents changes as parental investment changes. Overall, these data support both the reproductive value and the vulnerability hypotheses, but not necessarily the feedback hypothesis. [ABSTRACT FROM AUTHOR]

Results of study of the effect of presence of model predator on parental care in convict cichlid Amatitlania nigrofasciata are presented. Main differences in parental functions of male and female in the family group and their transformation in the case of a potential threat for the clutch and litter are considered. The dynamics of parental behavior throughout the period of parental care and the effect of the predator's presence on this dynamics are analyzed. It is shown that predator's presence exerts a complex transforming effect on the entire structure of parental behavior in the family group of the convict cichlid. Male behavior is distinguished by highest lability in the period after passing of juveniles to free swimming. [ABSTRACT FROM AUTHOR]

Fight theory predicts that asymmetries between contestants can be used to predict the winners and losers in fights. Using the monogamous convict cichlid ( Amatitlania nigrofasciata), we examined whether being in a pair bond has an advantage in defeating a single same-sex individual. We hypothesize that the male and female members of a pair bond would defeat a same-sex single intruder because it is beneficial to form a pair bond prior to competing for mutual resources, such as a breeding site. To test our hypotheses, we allowed paired males to engage in contests with single males with and without the interaction of their mate. In addition, we allowed paired females to engage in contests with single females with and without the interaction of their mate. Our results indicate that the paired male gained no advantage in being paired; however, paired females seem to have an advantage over single females because they typically defeated them. To reduce the influence of the other pair member on the fight, we restrained one member and allowed the other pair member to confront the same-sex individual. The paired male was frequently defeated while the paired female typically won. These results suggest that forming a pair bond gives females, but not males an advantage in fights with same-sex competitors. [ABSTRACT FROM AUTHOR]

Convict cichlids ( Archocentrus nigrofasciatus) form pair bonds, are serially monogamous, and give biparental care to their offspring. Males and females may individually establish a breeding site before courtship, or they may form a pair and then obtain a breeding site together. Such sites are important resources for convict cichlids, and their availability often limits reproduction. Here, we examined if variation in breeding-site availability affected pair bonding between males and females and aggressive behaviors between bonded pairs. Groups of three males and three females were placed in large aquaria and randomly assigned to the following treatments: (1) the fish were provided with two breeding sites; (2) the fish were provided with two breeding sites throughout the experiment, one of which was later removed; (3) the fish were provided with one breeding site initially, and a second was later added; (4) the fish were provided with no breeding sites throughout the experiment. We found that pair bonds rarely formed when no breeding sites were provided; however, pair-bond formation was not limited by breeding-site number when at least one breeding site was available. In addition, there were no differences in aggression by paired individuals after breeding site manipulation, perhaps indicating that changes in the subsequent availability of breeding sites after pair formation did not influence a pair’s aggression. [ABSTRACT FROM AUTHOR]

Ethanol and three beverage alcohols were examined for their effects on the aggressive responses of the convict cichlid. At an ethanol concentration that gave negligible effects on the basal level of these responses, rum was observed to depress aggression. As its concentration of acetaldehyde was significantly higher than that of the other beverage alcohols, we assessed the effects of acetyldehyde on the aggressive responses, as well as the locomotor activity of the fish. At 4mg/l, acetaldehyde completely inhibited aggressive responses, without affecting locomotor activity. It is likely, however, that acetaldehyde does not explain the entire inhibitory effect of rum on the aggressive responses of the cichlid. [ABSTRACT FROM AUTHOR]