Male Cichlids Research Articles

Androgen receptor deficiency is associated with reduced aromatase expression in the ventromedial hypothalamus of male cichlids.

Social behaviors are regulated by sex steroid hormones, such as androgens and estrogens. However, the specific molecular and neural processes modulated by steroid hormones to generate social behaviors remain to be elucidated. We investigated whether some actions of androgen signaling in the control of social behavior may occur through the regulation of estradiol synthesis in the highly social cichlid fish, Astatotilapia burtoni. Specifically, we examined the expression of cyp19a1, a brain-specific aromatase, in the brains of male A. burtoni lacking a functional ARα gene (ar1), which was recently found to be necessary for aggression in this species. We found that cyp19a1 expression is higher in wild-type males compared to ar1 mutant males in the anterior tuberal nucleus (ATn), the putative fish homolog of the mammalian ventromedial hypothalamus, a brain region that is critical for aggression across taxa. Using insitu hybridization chain reaction, we determined that cyp19a1+ cells coexpress ar1 throughout the brain, including in the ATn. We speculate that ARα may modulate cyp19a1 expression in the ATn to govern aggression in A. burtoni. These studies provide novel insights into the hormonal mechanisms of social behavior in teleosts and lay a foundation for future functional studies.

Endocrine and neuroendocrine regulation of social status in cichlid fishes

Position in a dominance hierarchy profoundly impacts group members' survival, health, and reproductive success. Thus, understanding the mechanisms that regulate or are associated with an individuals' social position is important. Across taxa, various endocrine and neuroendocrine signaling systems are implicated in the control of social rank. Cichlid fishes, with their often-limited resources of food, shelter, and mates that leads to competition, have provided important insights on the proximate and ultimate mechanisms related to establishment and maintenance of dominance hierarchies. Here we review the existing information on the relationships between endocrine (e.g., circulating hormones, gonadal and other tissue measures) and neuroendocrine (e.g., central neuropeptides, biogenic amines, steroids) systems and dominant and subordinate social rank in male cichlids. Much of the current literature is focused on only a few representative cichlids, particularly the African Astatotilapia burtoni, and several other African and Neotropical species. Many hormonal regulators show distinct differences at multiple biological levels between dominant and subordinate males, but generalizations are complicated by variations in experimental paradigms, methodological approaches, and in the reproductive and parental care strategies of the study species. Future studies that capitalize on the diversity of hierarchical structures among cichlids should provide insights towards better understanding the endocrine and neuroendocrine mechanisms contributing to social rank. Further, examination of this topic in cichlids will help reveal the selective pressures driving the evolution of endocrine-related phenotypic traits that may facilitate an individual's ability to acquire and maintain a specific social rank to improve survival and reproductive success.

Male dominance status regulates odor-evoked processing in the forebrain of a cichlid fish

The ability to identify odors in the environment is crucial for survival and reproduction. However, whether olfactory processing in higher-order brain centers is influenced by an animal’s physiological condition is unknown. We used in vivo neuron and local field potential (LFP) recordings from the ventral telencephalon of dominant and subordinate male cichlids to test the hypothesis that response properties of olfactory neurons differ with social status. Dominant males had a high percentage of neurons that responded to several odor types, suggesting broad tuning or differential sensitivity when males are reproductively active and defending a territory. A greater percentage of neurons in dominant males also responded to sex- and food-related odors, while a greater percentage of neurons in subordinate males responded to complex odors collected from behaving dominant males, possibly as a mechanism to mediate social suppression and allow subordinates to identify opportunities to rise in rank. Odor-evoked LFP spectral densities, indicative of synaptic inputs, were also 2–3-fold greater in dominant males, demonstrating status-dependent differences in processing possibly linking olfactory and other neural inputs to goal-directed behaviors. For the first time we reveal social and reproductive-state plasticity in olfactory processing neurons in the vertebrate forebrain that are associated with status-specific lifestyles.

Chemical communication in cichlids: A mini-review

The family Cichlidae is well-known for pair-formation, parental care, territoriality, elaborate courtship and social organization. Do cichlids use chemical communication to mediate any of these behaviours? Early studies suggest that parent cichlids can discriminate between conspecific and heterospecific wrigglers (but not eggs) using olfactory cues. Some species are able to discriminate between their own brood and other conspecific broods based on olfaction. The young recognise conspecific adults (although not necessarily their parents) through the odorants they release. In both scenarios, protection of the young from predation is the likely selective force. Some male cichlids use urinary pheromones during courtship and spawning to attract females and induce ovulation. Females – in their turn – may base their mate-choice in part on assessment of those self-same pheromones. The same pheromonal system may be involved in establishing and maintaining the social hierarchies in lek-breeding cichlids. Individual recognition is also mediated by chemical communication. Finally, there is ample behavioural evidence that cichlids – like ostariophysan fish – release alarm cues that alert conspecifics to predation danger. Although the effects of these cues may be similar (e.g., increased shelter use, tighter schooling), they are different substances which remain to be identified. Cichlids, then, use chemical communication associated with many different behaviours. However, given the diversity of cichlids, little is known about the mechanisms of chemical communication or the chemical identity of the cues involved. The aim of this mini-review is to persuade those working with cichlids to consider the involvement of chemical communication, and those working in chemical communication to consider using cichlids.

The diversity of male nuptial coloration leads to species diversity in Lake Victoria cichlids

The amazing coloration shown by diverse cichlid fish not only fascinates aquarium keepers, but also receives great attention from biologists interested in speciation because of its recently-revealed role in their adaptive radiation in an African lake. We review the important role of coloration in the speciation and adaptive evolution of Lake Victoria cichlids, which have experienced adaptive radiation during a very short evolutionary period. Mature male cichlids display their colors during mate choice. The color of their skin reflects light, and the reflected light forms a color signal that is received by the visual system of females. The adaptive divergence of visual perceptions shapes and diverges colorations, to match the adapted visual perceptions. The divergence of visual perception and coloration indicates that the divergence of color signals causes reproductive isolation between species, and this process leads to speciation. Differences in color signals among coexisting species act to maintain reproductive isolation by preventing hybridization. Thus, the diversity of coloration has caused speciation and has maintained species diversity in Lake Victoria cichlids.

Sounds produced by the cichlid fish Metriaclima zebra allow reliable estimation of size and provide information on individual identity

Sounds produced by male cichlids Metriaclima zebra during aggressive interactions were recorded to conduct a detailed analysis and to search for potential individual acoustic signatures. Fish from two different size groups (small and large individuals) were analysed. The two groups were significantly different for all acoustic variables considered; six of seven features demonstrated a significant interindividual variability and most of them were correlated with the size of the emitter. A cross-validated and permuted discriminant function analysis (pDFA) separated the two groups and correctly classified around 50% of the sounds to the correct individuals. Acoustic features that best distinguished among males were the instantaneous frequency of sounds and the modulation of pulse amplitude. These results suggest that acoustic signals could bear information about individual identity. The long-term stability of this signature is likely to be weak since the signature of a growing individual may change over time.

Subordinate male cichlids retain reproductive competence during social suppression

Subordinate males, which are excluded from reproduction often save energy by reducing their investment in sperm production. However, if their position in a dominance hierarchy changes suddenly they should also rapidly attain fertilization capability. Here, we asked how social suppression and ascension to dominance influences sperm quality, spermatogenesis and reproductive competence in the cichlid Astatotilapia burtoni, where reproduction is tightly coupled to social status. Dominant territorial (T) males are reproductively active while subordinate non-territorial (NT) males are suppressed, but given the opportunity, NT males will perform dominance behaviours within minutes and attain T male testes size within days. Using the thymidine analogue 5-bromo-2-deoxyuridine (BrdU) to label germ cell proliferation, we found that the spermatogenic cycle takes approximately 11-12 days, and social status had no effect on proliferation, suggesting that spermatogenesis continues during reproductive suppression. Although sperm velocity did not differ among social states, NT males had reduced sperm motility. Remarkably, males ascending in status showed sperm motility equivalent to T males within 24 h. Males also successfully reproduced within hours of social opportunity, despite four to five weeks of suppression and reduced testis size. Our data suggest that NT males maintain reproductive potential during suppression possibly as a strategy to rapidly improve reproductive fitness upon social opportunity.

Aggression in closely related Malawi cichlids varies inversely with habitat complexity

Within the past 2 million years, the cichlids of Lake Malawi have diversified into well over 500 species resulting in one of the worlds largest lacustrine fish radiations. As a result, many of the habitats within the lake support a high diversity of species. In these highly species rich communities, male cichlids must acquire and defend a territory to successfully reproduce. Within the rock-dwelling cichlids of Lake Malawi (mbuna), this has resulted in the formation of polyspecific leks on the heterogeneous rocky benthos. Aggression is fairly common in these leks and has been tied not only to individual reproduction but to the larger phenomenon of community assembly and the maintenance of biological diversity. In this study, I examined the patterns of aggressive acts of four species within the mbuna genus Maylandia at two locations in the southern Lake Malawi. The number of aggressive acts of two sympatric species was examined at each location. At each site, one species defends territories over bedrock and the other over cobble. The number of aggressive acts across the four species was compared. The influence of habitat type on male aggression was examined and the targets of male aggression were identified to evaluate several hypotheses concerning the evolution of male aggression. The results show that aggression quantitatively varied among species, was largely directed towards heterospecifics, and was strongly influenced by habitat type. The aggressive behavior of one sympatric species pair, Maylandia benetos and Maylandia zebra, was observed under controlled laboratory conditions. Laboratory results support field observations: the bedrock associated species performed more aggressive acts and aggressive acts were directed equally at con- and heterospecifics. The results of this study suggest that habitat complexity plays a larger role in shaping aggressive behavior than other suggested factors such as competition for resources.

Courtship and agonistic sounds by the cichlid fishPseudotropheus zebra

Courtship and agonistic interactions in an African cichlid species present a richer diversity of acoustic stimuli than previously reported. Male cichlids, including those from the genus Pseudotropheus (P.), produce low frequency short pulsed sounds during courtship. Sounds emitted by P. zebra males in the early stages of courtship (during quiver) were found to be significantly longer and with a higher number of pulses than sounds produced in later stages. During agonistic intrasexual quiver displays, males produced significantly longer sounds with more pulses than females. Also, male sounds had a shorter duration and pulse period in courtship than in male-male interactions. Taken together, these results show that the acoustic repertoire of this species is larger than what was previously known and emphasize the importance of further research exploiting the role of acoustic stimuli in intra- and interspecific communication in African cichlids.

The effect of substrate availability on behavioural and physiological indicators of welfare in the African cichlid (Oreochromis mossambicus)

AbstractMale African cichlids (Oreochromis mossambicus) establish territories on the substrate upon which spawning pits are dug, thus attracting females. The substrate, therefore, plays a very significant role in its lifecycle. The effects of substrate access on behaviour and physiology in captivity were assessed. Mixed-sex, all-male and all-female groups were observed for five days, with and without substrate. Social patterns, behaviour directed towards the substrate, locomotor activity and spatial behaviour were recorded, and haematocrit, plasma cortisol and glucose levels were measured. Substrate inclusion saw a significant increase in behavioural diversity, sexual behaviour of dominant males in mixed groups, pit digging and territoriality whereas a lack of substrate was characterised by increased chafing and inactivity. Vacuum-pit digging was also observed. Frequency of aggression did not differ significantly and female behaviour was not affected by the presence of substrate. For both sexes, no differences in cortisol and glucose levels were found between the two treatments, but haematocrit increased with substrate. The key role played by substrate in territorial males is consistent with the behavioural and physiological data reported. In the absence of substrate, decreased territorial behaviour is contrasted with similar levels of aggression, cortisol and glucose; all of which are suggestive of a stress-related context. Moreover, the exhibition of vacuum activities is a signal that behavioural needs are not being met and may be some form of coping mechanism. These findings, taken in conjunction with the variations in behavioural diversity and inactivity, suggest that the welfare of male cichlids may be adversely affected by the absence of substrate.

Social interactions tune aggression and stress responsiveness in a territorial cichlid fish ( Archocentrus nigrofasciatus)

We examined the relative influences of pre-fight housing condition, contest intensity, and contest outcome in modulating post-fight stress hormone concentrations in territorial male convict cichlids ( Archocentrus nigrofasciatus). Individuals were housed either in isolation or in semi-natural communal tanks. Pairs of male cichlids that differed considerably in body mass were selected from the same housing regime. Pre-fight water-borne cortisol levels were obtained before allowing the dyad to interact until contest resolution, after which time post-fight cortisol levels were obtained from the winner and loser. There were no outcome-related differences in post-fight cortisol concentrations following escalated or non-escalated contests, a result that held true for both housing regimes. Pre-fight cortisol levels were significantly higher than post-fight cortisol levels, suggesting that initial confinement in a beaker for the water-borne hormone samples was a stressor, but that the animals acclimated quickly to confinement. Fights involving previously isolated participants were significantly more intense than those involving group-housed animals, which we explain as being a function of established relationships between social isolation, heightened acute cortisol responsiveness, and the expression of excessive aggressive behavior. Only group-housed losers demonstrated the ability to modulate aggression or hypothalamic–pituitary–interrenal (HPI) activity in a graded fashion to acute increases in cortisol or changes in contest intensity, respectively. We discuss a variety of factors that could disrupt the ability of isolates to appropriately modulate interactions between social behavior and the HPI axis, and we examine a number of functional hypotheses underlying the sensitivity of group-housed losers to changes in contest dynamics.

Egg mimicry and allopaternal care: two mate-attracting tactics by which nesting striped darter ( Etheostoma virgatum ) males enhance reproductive success

In a variety of fish species with paternal care of offspring, females prefer to spawn in nests that already contain eggs. This female preference has been hypothesized to explain egg thievery in male sticklebacks, allopaternal care of eggs in minnows, and the evolution of egg-mimicking body features in male cichlids and darters. Here we employ microsatellite-based parentage analyses to evaluate the reproductive success of striped darter (Etheostoma virgatum) males that appear to utilize two of these functionally related tactics to entice females to spawn in their nests. In an isolated population (Clear Creek, Ky.), we observed that breeding males develop conspicuous white spots on their pectoral fins. If these spots are egg mimics, as we suspect, then this represents the fourth independent evolutionary origin of egg mimicry documented to date in darters, the first based on pigmentation (as opposed to physical structures), and the first in which the egg mimics vary greatly in number among males. From direct counts of microsatellite genotypes in clutches of embryos, at least 3.8 females contributed to the progeny within a typical nest, and females tended to spawn preferentially with males that were larger and displayed more egg-mimic spots. In another population (Hurricane Creek, Tenn.) without egg mimics, the multi-locus genetic data document that allopaternal care is common, especially among the smallest males who sometimes tend nests containing their own as well as an earlier sire's offspring. Thus, these foster males had adopted egg-containing nests and then successfully spawned with subsequent females. Overall, the genetic data on paternity and maternity, in conjunction with field observations, suggest that egg mimicry and allopaternal care are two mate-attracting reproductive tactics employed by striped darter males to exploit female preferences for spawning in nests with 'eggs'.

Escalated fighting despite predictors of conflict outcome: solving the paradox in a South American cichlid fish

Several studies have found behavioural differences between the interactions of opponents, early in a conflict. These differences consistently predict which individual will be the winner. Surprisingly, opponents appear not to use this information: they continue fighting and even proceed to highly damaging escalation. We attempted to resolve this paradox in a series of experiments on interactions between male cichlids. First, the cost of fighting and escalating in terms of energy expenditure (oxygen consumption: gill movements) and injuries was high. Second, previous social experience was important but could not explain the occurrence of predictors of conflict outcome. Third, a less artificial conflict set-up, in which territory ownership was asymmetrical and opponents were allowed to see each other before the conflict, resulted in shorter interactions with reduced escalation phases. This suggests that the occurrence of predictors of conflict outcome and the subsequent lack of response of the opponents is the result of unnatural, highly symmetrical designs, as used in many studies. We propose the following mechanism. Prospective winners postpone escalation as much as possible because of the high cost involved. At the same time, prospective losers continue the fight because they lack alternatives. We tested this ‘desperado hypothesis’ in a fourth experiment, in which losers were offered alternative options. These conflicts were shorter and both predictors of outcome and escalated fighting were absent.

Tactic for bower acquisition by male cichlids,Cyathopharynx furcifer, in Lake Tanganyika

A tactic for bower acquisition by male cichlids,Cyathopharynx furcifer, was studied in Lake Tanganyika. Males held crater-shaped bowers of sand within their territories, which were located adjacent to each other. Females visited bowers to spawn eggs, subsequently brooding the eggs in their mouths. Some individuals held territories without bowers near those of males with bowers. Although only the males with bowers succeeded in reproduction, they were apparently exhausted by bower maintenance and reproduction, and often deserted their bowers. These were soon occupied by males which had held nearby territories without bowers, such males then engaging in reproductive activity. Although the construction of new bowers by males was observed, such was unsuccessful, probably because too much energy was required and/or the optimal space for bowers was limited. Direct aggression by males without bowers against bower-holding males to deprive the bowers was not observed, possibly due to the high costs of such competition. Therefore, waiting for bower desertion by other males may be the best bower acquisition tactic for males without bowers.

Aggressiveness as a function of external stimulation

The attack readiness of a male cichlid, as measured by the rate of attacks directed at small blinded test fish, falls to a very low level if the animal is isolated from adult conspecifics for several weeks. It recovers again within a few days after repeated exposure to adult conspecifics. This readiness to attack could also be restored by repeated presentation of fish dummies, resembling a territorial conspecific male, over a period of 10 successive days. After being raised by this procedure, the attack readiness returned to its prestimulatory level with a half time of 7 days. Theoretical implications and the ecological significance of this long term process are discussed.

Influence of the Stimuli Provided by the Male Cichlid Fish, Tilapia macrocephala, on the Spawning Frequency of the Female

Previous articleNext article No AccessInfluence of the Stimuli Provided by the Male Cichlid Fish, Tilapia macrocephala, on the Spawning Frequency of the FemaleLester R. AronsonLester R. Aronson Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 18, Number 4Oct., 1945 Article DOIhttps://doi.org/10.1086/physzool.18.4.30151902 Views: 2Total views on this site Citations: 19Citations are reported from Crossref Journal History This article was published in Physiological Zoology (1928-1998), which is continued by Physiological and Biochemical Zoology (1999-present). PDF download Crossref reports the following articles citing this article:Matthew McConnell Frontiers in Cichlid Research: A History of Scientific Advancement, (Sep 2021): 13–78.https://doi.org/10.1007/978-94-024-2080-7_2K. Coward, N.R. Bromage Spawning periodicity, fecundity and egg size in laboratory-held stocks of a substrate-spawning tilapiine, Tilapia zillii (Gervais), Aquaculture 171, no.3-43-4 (Feb 1999): 251–267.https://doi.org/10.1016/S0044-8486(98)00498-0K. Coward, N. R. Bromage Influence of Conspecific Contact Upon Blood Sex Steroid Levels and the Dynamics of Ovarian Development in Female Red-Bellied Tilapia, Tilapia zillii, Journal of Applied Aquaculture 9, no.11 (Jan 1999): 23–34.https://doi.org/10.1300/J028v09n01_02Ann L. Kyle, N.E. Stacey, R.E. Peter, R. Billard Elevations in gonadotrophin concentrations and milt volumes as a result of spawning behavior in the goldfish, General and Comparative Endocrinology 57, no.11 (Jan 1985): 10–22.https://doi.org/10.1016/0016-6480(85)90195-9Natasha B. Fraley, Russell D. Fernald Social Control of Developmental Rate in the African Cichlid, Haplochromis burtoni, Zeitschrift für Tierpsychologie 60, no.11 (Apr 2010): 66–82.https://doi.org/10.1111/j.1439-0310.1982.tb01077.xHarold I. Silverman Effects of different levels of sensory contact upon reproductive activity of adult male and female Sarotherodon (Tilapia) mossambicus (Peters); Pisces: Cichlidae, Animal Behaviour 26 (Nov 1978): 1081–1090.https://doi.org/10.1016/0003-3472(78)90097-0Harold I. Silverman The effects of visual social stimulation upon age at first spawning in the mouth-brooding cichlid fish Sarotherodon (Tilapia) mossambicus (Peters), Animal Behaviour 26 (Nov 1978): 1120–1125.https://doi.org/10.1016/0003-3472(78)90101-XA. M. Timms Intraspecific communication in goldfish, Journal of Fish Biology 7, no.33 (May 1975): 377–389.https://doi.org/10.1111/j.1095-8649.1975.tb04612.xAndrew K. Chien Reproductive behaviour of the angelfish Pterophyllum scalare (Pisces: Cichilidae) II. Influence of male stimuli upon the spawning rate of females, Animal Behaviour 21, no.33 (Aug 1973): 457–463.https://doi.org/10.1016/S0003-3472(73)80005-3Gerard P. Baerends The Ethological Analysis Of Fish Behavior, (Jan 1971): 279–370.https://doi.org/10.1016/S1546-5098(08)60150-8Dietrich Ohm Die Entwicklung des Kommentkampfverhaltens bei Jungcichliden Ein ethologischer Vergleich zwischen Aequidens latifrons und Ae. portalegrensis1, Zeitschrift für Tierpsychologie 21, no.33 (Apr 2010): 308–325.https://doi.org/10.1111/j.1439-0310.1964.tb01197.xWILLIAM C. YOUNG The Hormones and Behavior, (Jan 1964): 203–251.https://doi.org/10.1016/B978-0-12-395548-7.50011-8Martin Dambach Vergleichende Untersuchungen über das Schwarmverhalten von Tilapia-Jungfischen (Cichlidae, Teleostei), Zeitschrift für Tierpsychologie 20, no.33 (Apr 2010): 267–296.https://doi.org/10.1111/j.1439-0310.1963.tb01154.xHans M. Peters Eizahl, Eigewicht und Gelegeentwicklung in der GattungTilapia (Cichlidae, Teleostei), Internationale Revue der gesamten Hydrobiologie und Hydrographie 48, no.44 (Jan 1963): 547–576.https://doi.org/10.1002/iroh.19630480403ROSEMARY H. LOWE McCONNELL BREEDING BEHAVIOUR PATTERNS AND ECOLOGICAL DIFFERENCES BETWEEN TILAPIA SPECIES AND THEIR SIGNIFICANCE FOR EVOLUTION WITHIN THE GENUS TILAPIA (PISCES: CICHLIDAE), Proceedings of the Zoological Society of London 132, no.11 (Oct 2009): 1–30.https://doi.org/10.1111/j.1469-7998.1959.tb05510.xG.P. BAERENDS BEHAVIOR: THE ETHOLOGICAL ANALYSIS OF FISH BEHAVIOR, (Jan 1957): 229–269.https://doi.org/10.1016/B978-1-4832-2763-4.50010-9L.R. ARONSON REPRODUCTIVE AND PARENTAL BEHAVIOR, (Jan 1957): 271–304.https://doi.org/10.1016/B978-1-4832-2763-4.50011-0Rosemary H. Lowe (McConnell) The Fecundity of Tilapia Species, The East African Agricultural Journal 21, no.11 (Dec 2015): 45–52.https://doi.org/10.1080/03670074.1955.11665004LESTER R. ARONSON SECTION OF BIOLOGY: PROBLEMS IN THE BEHAVIOR AND PHYSIOLOGY OF A SPECIES OF AFRICAN MOUTHBREEDING FISH*, Transactions of the New York Academy of Sciences 11, no.2 Series II2 Series II (Apr 2012): 33–42.https://doi.org/10.1111/j.2164-0947.1948.tb00956.x