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• Pair-bonded convict cichlids express synchronized cortisol levels. • A stressor in the form of prolonged pair separation can effectively disrupt cortisol synchrony. • A disruption in cortisol synchrony does not lead to an immediate increase in intrapair aggression but may accompany pair-dissolution. Endocrine synchronization is a biological process often associated with social bonding. The mechanisms that mediate this process have been well studied in many vertebrate clades with evolved complex social behaviors. However, studies focusing on such processes in the less neurologically complex teleost clade are surprisingly lacking. In this study, we investigated the hypothesis that mated pairs of convict cichlids (Amatitlania nigrofasciata) perform cortisol synchronization and that the disruption of this might accompany pair-bond instability. Mated pairs were subjected to both behavioral and non-invasive waterborne hormonal assays to better understand the biological complexity of endocrine synchrony and its role in pair-bonding. Baseline cortisol assays indicated a positive correlation between male and female cortisol levels. Individuals that were subjected to a prolonged separation from their mate exhibited a negative correlation in cortisol synchrony after being reunited with their mate. Cortisol synchrony was disrupted, but pairs did not show a significant variance of intrapair aggression after initial pair reunion. However, more than half of the pairs that received the stressor exhibited significantly higher levels of intrapair aggression than their time matched controls approximately 1–7 days following this reunion, indicating pair-dissolution. Concurrently, pairs who underwent the stressor but maintained their bonds did not display an increase in intrapair aggression and also re-synchronized their cortisol levels. Not only does this study provide crucial insights in regard to the role of cortisol synchrony in serially monogamous systems, but it also suggests that the mechanisms that mediate the synchronization of endocrine through the formation of social bonds are more evolutionarily conserved than originally thought. [ABSTRACT FROM AUTHOR]

Parental aggression can be a costly behaviour and flexible based upon context. While defence of offspring from potential predators has been well studied in the convict cichlid, it is unclear why parents are aggressive towards other parental pairs who are not likely to be offspring predators. In this experiment we explore the aggressive behaviour of pairs towards parental pairs and nonparental individuals using experimental presentations in the field. We found that parental pairs showed more aggressive displays towards other parental pairs than towards nonparental individuals. Bites did not differ between treatments, but there was a sex difference in bites, with males preferring to bite males and females showing no preference. As a higher level of display was observed both in the presence and absence of fry, we also examined the pair response to fry alone. Focal pairs were more aggressive to stimulus fry that were larger than their own fry, indicating that the larger stimulus fry represented a risk to the focal pair, as predicted by previous findings on brood mixing. We conclude that pair aggression towards parental pairs is a means to prevent brood mixing, and the greater aggression shown towards parental pairs suggests that the risk to parental pairs of brood mixing is greater than that of fry predation by nonparental fish. • We studied context-dependent decisions of biparental defence in convict cichlids. • Parents were more aggressive to other parental pairs than to nonparental adults. • Parents were also more aggressive to fry that were larger than their own. • Pair aggression towards parental pairs appears to be a means to prevent brood mixing. • Parents appear more threatened by brood mixing than by potential fry predation. [ABSTRACT FROM AUTHOR]

Early life experience may have lifelong influences on an individual's behaviour in ways that are either adaptive or maladaptive depending in part on whether these early experiences accurately foreshadowed conditions in later life. Stress coping style is one example of a suite of behaviours, or personality traits, that may be influenced by early exposure to stressful stimuli. Here we examine the effect of developmental stress exposure on behavioural syndromes in adult convict cichlids, Amatitlania nigrofasciata. We found that early life stress did not exert significant effects on personality traits in adulthood at the individual level, but that this stress exposure prevented the formation of an exploration–boldness syndrome that was present in the unstressed population. These results suggest that an exploration–boldness syndrome is present in this species in the absence of stress-related environmental constraints. However, greater plasticity may be selected for in response to early life cues that reflect high predator pressure. • Juvenile stress disrupted formation of an exploration–boldness behavioural syndrome. • Fish with prior stress exposure tended to display proactive coping behaviours. • Early stress exposure may result in higher baseline cortisol levels. • Early life constraints can cause lasting phenotypic change. • Natural constraints may lead to an exploration–boldness behavioural syndrome. [ABSTRACT FROM AUTHOR]

Positive differential allocation predicts that females will increase their parental investment when mated to high-quality males due to the benefits that these males provide to offspring. Differential allocation predicts trade-offs between current and future reproduction, but investment trade-offs can also occur within a breeding event for species that provide parental care. However, differential allocation studies that have examined investment in both gametic effort and parental care remain rare and have only been conducted in birds. Fish may have more conservative investment strategies due to the large effect that current reproductive investment has on future reproductive potential. We examined gametic effort and parental care in the convict cichlid, Amatitlania siquia , a biparental fish, in response to male size, a proxy for quality. We randomly mated females to either large or small males and measured fecundity and parental behaviour of both parents. Females mated to large males did not increase their fecundity, but did provide more parental care to offspring during the larval stage, which is when male desertion in natural populations is most likely. Male size did not predict the amount of paternal care provided to offspring during the larval stage. Female condition at the end of the breeding event was negatively associated with higher fecundity and level of maternal care provided. The observed pattern of maternal investment suggests that females limit costs to future reproduction by limiting their increased investment to only one component of their reproductive effort. The increase in maternal investment during the larval stage may also serve to stabilize the pair bond and ensure continued male care, which ultimately increases the reproductive success of both parents. These results highlight important taxonomic and parental care pattern differences and broaden our understanding of the factors that influence differential allocation in diverse taxa. Highlights • We examined maternal investment in response to mate quality in a biparental fish. • Female convict cichlids did not increase their fecundity for large males. • However, females provided more parental care to the offspring of large males. • Fecundity and maternal care were both negatively associated with female condition. • Increased maternal care may stabilize the pair bond and ensure male care. [ABSTRACT FROM AUTHOR]

How an organism deals with stressors is an integral component of survival. Recent research has shown that differences in a well-studied personality axis in fish, the shy–bold axis, relate to stress-coping behaviours. Bold fish tend to cope in a proactive manner (e.g. fighting) while shy fish cope more reactively (e.g. freezing). Because bold fish behave in a more risk-prone manner, it is likely that they encounter more stressors on average than shy fish. Greater exposure to stressful conditions may result in bold fish being less behaviourally sensitive to stressors (i.e. stress resilience). To investigate the idea of stress exposure leading to resilience, we examined whether fish personality (i.e. more bold or shy) affected anxiety-related behaviour in an open field task after fish had been exposed to a net-chasing stressor. We investigated open field behaviour in the presence and absence of a stressor (i.e. damage-induced alarm cues) to determine whether bolder fish would cope differently with a stressor than shy fish after recent stress exposure of a different type. Furthermore, we examined whether asymmetry in the habenula, an asymmetrical nucleus related to behavioural responses to stress and anxiety, is related to behaviour in the presence of stressors. We found no relationship between habenular asymmetry and behaviour in the open field. Net chasing increased activity in the open field for both sexes. We found an interaction between stress exposure and freezing behaviour in females but not in males. When females were not net-chased, shyer females showed a decrease in freezing behaviour when exposed to alarm cues, whereas bolder females showed no change in behaviour. When females were net-chased, there was no difference in freezing behaviour between bolder and shyer fish. We suggest that different parental care roles in this species lead to differential perceptions of the threat of stress between the sexes. [ABSTRACT FROM AUTHOR]

Previous breeding experience affects parental care, yet in biparental species it is unclear how the inexperience of only one parent influences parental dynamics and division of labour. Using the biparental convict cichlid, Amatitlania siquia , I assessed how female breeding experience affects male and female parental behaviour. Females that either had bred (experienced) or were virgins (inexperienced) were paired with experienced males. Inexperienced females were less likely to form pairs and took longer to spawn. Female experience also affected parental division of labour between direct offspring care and territory defence. Female behaviour was compared in the presence and absence of their male partners. When males were present, all females divided their time similarly: more time was spent in direct care. When male mates were removed, experienced females divided their time equally between territory defence and direct care, while inexperienced females continued to spend more time in direct care. Males paired to inexperienced females divided their time equally between territory defence and direct care, while males paired to experienced females spent more time in defence. Males were also more aggressive towards experienced females. Overall, experienced females tended to adopt the male-typical role of defence, which probably caused the increased intrapair conflict in these pairs. This aggression helps explain why both experienced and inexperienced females showed similar role choices in the presence of their male partner and supports previous claims that male aggression helps maintain the division of labour in this species. Female inexperience potentially presents a trade-off for males: males paired to inexperienced females engaged in less intrapair conflict, but showed less division of labour between parental roles than is typical and were less likely to pair and spawn. The effect of female experience on division of labour, parental dynamics and pair bonding success probably influences other factors such as mate choice, effectiveness of parental care and overall fitness. [ABSTRACT FROM AUTHOR]

Many monogamous animals engage in a period of pair bonding prior to their ultimate mate choice (reproduction). One hypothesis about the function of this behaviour is that it allows individuals to continuously assess the quality of their partner as well as other potential mates. I tested this hypothesis in the convict cichlid, Amatitlania nigrofasciata, by providing males and females with a choice between their partner and a novel individual of the opposite sex at various time points after formation of a pair bond. Sex differences were observed in patterns of behaviour, with females significantly more likely to spend time with their partner than with another male, while males generally spent more time with a novel female than with their partner. The time spent in a pair bond affected this pattern, however, with both sexes showing a decreased time-based partner preference as the time in a pair bond increased. After forming a pair bond, males were largely aggressive towards novel females, treating them as territorial intruders, while pair-bonded females generally ignored novel males. Neither sex appeared to actively court potential mates apart from their partner. In a second experiment, I attempted to alter this pattern by presenting pair-bonded individuals with novel potential mates of relatively higher quality (larger size) than their partner. When given a ‘better option’, neither females nor males showed a preference for their partner over a large novel mate. All males continued to treat novel females as territorial intruders, while a subset of females shifted their preference from their partner to a larger novel male. These results support the hypothesis that the role of pair bonding may differ between the sexes in this species, functioning as a prolonged period of mate assessment in females, but not in males. [ABSTRACT FROM AUTHOR]

The convict cichlid Amatitlania nigrofasciata is a monogamous, biparental teleost species. Convict cichlids form pairs to provide parental care and share in territory defence. In order for pairs to be successful there must be coordination of behaviour between the sexes. Although pair dynamics have been studied in the laboratory, few field experiments have investigated male and female responses to mate removal. We examined how convict cichlids modulate their parental defence behaviour in response to mate removal at Lomas Barbudal Biological Reserve, Costa Rica. We presented convict cichlid pairs with a conspecific intruder and observed the parental defence behaviour of both individuals. One member of the pair was then removed and the remaining individual was presented with the intruder. Both males and females significantly increased aggression towards the intruder after the removal of the mate; however, males were able to fully compensate for the loss of the female, whereas females were not. These results suggest that both male and female convict cichlids may modulate their behaviour in response to changing stimuli. [ABSTRACT FROM AUTHOR]

Males and females of many species engage in agonistic encounters. However, differing selection pressures on each sex are predicted to result in sex differences in aggressive behaviour during contests. Comparing male and female intrasexual contests can yield intriguing differences, shedding light on the forces shaping the use of particular aggressive tactics. We investigated whether fundamental gender-related differences in aggression, not explained by current parental role, are present in convict cichlids, Amatitlania nigrofasciata. Intrasexual agonistic encounters between isolated males and between isolated females not previously paired to a breeding partner were staged. Using this approach we first tested for behavioural differences between the sexes. Second, using a novel startle technique aimed at probing motivation to fight, we tested for gender-related differences in aggressive motivation. Third, we examined whether size, rather than gender, plays a role in determining the tactics used during contests. In addressing these aims we found: (1) females used more frontal display and biting, and spent more time in close proximity to their opponent, whereas males used more lateral display and tail beating than females during agonistic encounters; (2) there was no difference in the response of male or female convict cichlids to a startling stimulus aimed at probing motivation to fight; and (3) the addition of focal weight and length as possible covariates had no significant effect on the analyses. Possible causal and functional reasons for these gender-related differences in fight tactics are discussed. [Copyright &y& Elsevier]

Cerebral lateralization, the preferential use of one hemisphere of the brain to perform certain cognitive functions, is a widespread and evolutionarily ancient adaptation. Lateralization appears to enhance cognitive capacity, yet substantial individual variation in the strength cerebral lateralization is apparent in all species studied so far. It is puzzling that cerebral lateralization, a seemingly advantageous trait, has not been driven to fixation. It has been suggested that variation in lateralization may be linked to individual variation in behaviour, which itself may be subject to disruptive selection. We examined the relation between cerebral lateralization and individual variation in boldness in the convict cichlid, Archocentrus nigrofasciatus. We show that convict cichlids that are more strongly lateralized when exploring a familiar environment, but not a novel one, are quicker to emerge from a shelter in a test for boldness. The possibility that cerebral lateralization is linked to life history strategy is discussed. [Copyright &y& Elsevier]

We studied parental care behaviour in a field population of convict cichlids, Amatitlania siquia, a fish with biparental care of its free-swimming young (fry). We simulated catastrophic brood loss by removing all of the young from 26 broods of various ages. We recorded parental defence behaviour for 5min preremoval and three consecutive 5min postremoval intervals. We then returned all of the young and recorded 5min of parent–offspring reunion behaviour. Following brood loss, both parents defended the empty territory and searched for missing young. Females spent more time in the empty territory and performed more attacks in defence of the empty territory than did males. Females searched and defended a significantly larger area than males did. During the 15min fry-absent period, males increasingly spent more time away, whereas females maintained a constant level of investment in searching the brood area. Four of 26 males (15%) engaged in courtship with a new female within 15min of brood loss. Attacks to repel potential predators from the brood area declined in frequency over the 15min fry-absent period in both sexes. Standard length (age) of young was positively correlated with parental investment for females but not males. Number of young was positively correlated with parental investment for males but not for females. We conclude that post-brood-loss behaviours are search and recovery tactics that contribute to parental inclusive fitness in the event of incomplete brood predation. [Copyright &y& Elsevier]

The causes and consequences of territory size have attracted considerable attention, but there has been relatively little research on optimal territory shape. We manipulated the shape of food patches, independent of patch area (square, 13.6×13.6cm; rectangular, 46.5×4.0cm; elongated, 93.0×2.0cm), presented to small, medium and large convict cichlids, Archocentrus nigrofasciatus, in groups of varying size (three, six, 12 fish). We used a 3×3 factorial design to test the predictions that the defence and monopolization of a food patch would decrease as both patch perimeter and group size increased. As predicted, with increasing patch perimeter, the ability of the large (dominant) fish to defend the patch decreased, as reflected by a decrease in the frequency of aggression and the proportion of the aggression by the dominant. Similarly, intruder success typically increased with increasing patch perimeter, as reflected by an increase in the proportion of intruders in the patch and the duration that an intruder remained in the patch. Group size also had the predicted effect on most response variables; in general, defender success decreased and intruder success increased as group size increased. Furthermore, the effects of increasing the patch perimeter and group size on measures of defensibility were largely additive. [Copyright &y& Elsevier]