Mate choice in female convict cichlids (<Emphasis Type="Italic">Amatitlania nigrofasciata</Emphasis>) and the relationship between male size and dominance

We examined how male size and fighting ability influence a female’s mate assessment process and her eventual mate choice in the monogamous convict cichlid, Amatitlania nigrofasciata. Females always chose the larger of two males when they were allowed to see a larger male next to a smaller one and when a larger male defeated a smaller one in a fight. They did not differentiate between large and small males when they did not see the two males together nor did they choose a dominant over a subordinate male when both were the same size. We suggest that females select on the basis of male size because it is a better predictor of both direct and indirect benefits (i.e., future competitive interactions and foraging ability) than dominance behavior only. Despite selecting one male over the other early in the courtship period, females continued to visit both males until spawning. Our evidence suggests that this assessment behavior more closely resembles a bet-hedging tactic rather than the female’s indecision as to which male will be her mate.     

Predator–prey relationships in a Mediterranean vertebrate system: Bonelli’s eagles,rabbits and partridges

How predators impact on prey population dynamics is still an unsolved issue for most wild predator–prey communities. When considering vertebrates, important concerns constrain a comprehensive understanding of the functioning of predator–prey relationships worldwide; e.g. studies simultaneously quantifying ‘functional’ and ‘numerical responses’ (i.e., the ‘total response’) are rare. The functional, the numerical, and the resulting total response (i.e., how the predator per capita intake, the population of predators and the total of prey eaten by the total predators vary with prey densities) are fundamental as they reveal the predator’s ability to regulate prey population dynamics. Here, we used a multi-spatio-temporal scale approach to simultaneously explore the functional and numerical responses of a territorial predator (Bonelli’s eagle Hieraaetus fasciatus) to its two main prey species (the rabbit Oryctolagus cuniculus and the red-legged partridge Alectoris rufa) during the breeding period in a Mediterranean system of south Spain. Bonelli’s eagle responded functionally, but not numerically, to rabbit/partridge density changes. Type II, non-regulatory, functional responses (typical of specialist predators) offered the best fitting models for both prey. In the absence of a numerical response, Bonelli’s eagle role as a regulating factor of rabbit and partridge populations seems to be weak in our study area. Simple (prey density-dependent) functional response models may well describe the short-term variation in a territorial predator’s consumption rate in complex ecosystems.     

The cost of parental care inHaplochromis ‘argens’ (Cichlidae)

Synopsis The cost of parental care in the maternal, mouthbrooding cichlid,Haplochromis ‘argens’ was measured in terms of parental survival, fecundity and breeding frequency. In comparison with non-parental females, those that mouthbrooded eggs for a period of 16 days took 33 % longer to respawn. Parental females also grew more slowly between spawnings, and this may affect their future fecundity. These costs were attributed to the cessation of feeding by parental females while mouthbrooding and/or the hormonal inhibition of oogenesis.     

How Similar is the Coordination of Parental Roles Among Different Pairs? An Examination of a Monogamous Fish

Although most studies on biparental care assume that parents cooperate in raising offspring, few studies have documented how parents coordinate their activities. Using the biparental convict cichlid (Archocentrus nigrofasciatum) we compared the parental behavior of both single (‘widowed’) parents and individuals within pairs during the 5 d when the offspring were in the relatively uniform and stationary wriggler stage. In particular, we were interested in the consistency of day‐to‐day parental activities among single individuals and among individuals within pairs. Single parents showed differences in most parental activities that were consistent from one day to the next. This day‐to‐day consistency remained after an intruder was added and / or the mate was present. Thus, although the social context changed (i.e., presence or absence of mate, presence or absence of an intruder), an individual's consistency remained. The male and female within pairs were significantly correlated in the time spent on most parental activities across experimental pairs. Thus, while individuals within pairs were unique in their performance of a parental activity, paired males and females managed a high degree of correlation (i.e., coordination). In general, pairs were homogeneous in the degree to which males and females were correlated across different parental activities.     

Activity of Sphaerotheca breviceps tadpoles in response to chemical cues of the predaceous tadpoles Hoplobatrachus tigerinus

Tadpoles of Sphaerotheca breviceps raised in the laboratory from the egg stage, and hence lacking prior experience of a predator or its odors, were tested to examine their responses to a predator’s (tadpoles of Hoplobatrachus tigerinus) water-borne chemical cues. The stimulus solution was obtained following 24 h of rearing tadpoles of H. tigerinus (one tadpole per 200 mL water) that were not fed during this period. Upon exposure to the stimulus solution the activity of S. breviceps tadpoles decreased by about 90% within 5 min. Their resting period increased significantly over baseline activity, whereas the swimming period, distance traversed, and swimming spurts declined. However, whenever a test tadpole moved, its swimming velocity was high in response to stimulus solution. The antipredatory responses declined with increase in time of storage of the stimulus solution, indicating decay of the predator’s chemical cues. The findings suggest that (1) antipredator defense strategies of S. breviceps do not require prior experience of predators, (2) the predator’s chemical cues are labile in nature, and (3) the response of prey tadpoles to such cues is similar to reported behavior of anuran tadpoles in response to real predators and alarm cues.     

Kinship,Family, and Gender Effects in the Ultimatum Game

Kinship and reciprocity are two main predictors of altruism. The ultimatum game has been used to study altruism in many small-scale societies. We used the ultimatum game to examine effects of individuals’ family and kin relations on altruistic behavior in a kin-based horticultural community in rural Dominica. Results show sex-specific effects of kin on ultimatum game play. Average coefficient of relatedness to the village was negatively associated with women’s ultimatum game proposals and had little effect on men’s proposals. Number of brothers in the village was positively associated with men’s ultimatum game proposals and negatively associated with women’s proposals. Similarly, presence of father in the village was associated with higher proposals by men and lower proposals by women. We interpret the effect of brothers on men’s proposals as a consequence of local competition among brothers. We speculate that daughter-biased parental care in this community creates a sense of entitlement among women with brothers, which may explain the inverse relation between number of brothers and women’s ultimatum game proposals. The pattern of results may be consistent with how matrifocality affects cultural models of fairness differently along gender and family lines.     

Does Parental Fin Digging Improve Feeding Opportunities for Offspring in the Convict Cichlid?

The function of the fin digging behaviour in increasing food availability for the offspring was analysed in the convict cichlid, Cichlasoma (Archocentrus) nigrofasciatum. Consistent individual differences in the frequency of fin digging were found in the parental fish. Examination of the gastrointestinal tract of young revealed that higher frequency of parental fin digging was associated with higher consumption of large and more profitable prey (Diptera larvae), which inhabited deep horizons of the bottom substrate and possibly were difficult to access without parental assistance. Thus, parental fin digging was initially associated with a significant increase of the offspring growth rate. However, at later brood intervals, when parental care ceased, the young of the high-digging parents were characterised by a poorer consumption of small larvae that were most accessible for them without parental aid and represented an increasingly more important component of their ration than large larvae. Offspring of the low-digging parents, on the other hand, presumably as a result of their individual experience, showed a considerably better consumption of small larvae, increasing their growth rate. As a consequence, prior parental fin digging did not affect the offspring body size after independence. Thus, there exist pronounced individual differences and alternative parental styles in the convict cichlid.     

Polymorphic microsatellite loci optimised for studies on the convict cichlid fish (<Emphasis Type="Italic">Amatitlania siquia</Emphasis>)

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.     

Antipredator Behaviour and Suppressed Aggression by Convict Cichlids in response to Injury-released Chemical Cues of Conspecifics but not to those of an Allopatric Heterospecific

In aquatic environments, chemical cues serve as an important source of information for the detection of predation risk. Here, we investigate the response of convict cichlids, Cichlasoma nigrofasciatum, to injury-released chemical cues. We exposed pairs of juvenile convict cichlids first to dechlorinated tap water (control), then later to one of two test stimuli: 1. chemical cues from injured convict cichlids; or 2. chemical cues from injured mosquito fish, Gambusia affinis. Gambusia are allopatric and phylogenetically unrelated to convict cichlids. Gambusia skin was used to control for a general response to injured fish. In response to conspecific cues, convict cichlids significantly increased time spent near the bottom of test aquaria and time under a shelter object. In response to Gambusia skin, convict cichlids tended to increase time spent near the tank bottom but did not increase use of the shelter object. There was a trade-off between antipredator and agonistic behaviours. In response to convict cichlid cues, there was a significant reduction in the frequency of approaches and bites. Gambusia skin extract had no significant effect on aggressive behaviour. These data suggest a species-specific antipredator response to conspecific alarm pheromones in a New World cichlid fish and demonstrate a trade-off between predator avoidance and intraspecific aggression. Further, the presence of an alarm response in this model species sets the stage for the use of chemical cues as a research tool to manipulate predation risk in studies of the interaction between predation risk and reproductive behaviour.     

Effect of Mate Removal on Current and Subsequent Parental Care in the Convict Cichlid (Pisces: Cichlidae)

In most biparental, substrate-brooding species of cichlid fishes, female and male roles differ. Females are usually more involved in direct care of the young while males spend more time away patrolling the territory. This study tested the flexibility of these sex roles with removal experiments in the convict cichlid, Cichlasoma nigrofasciatum. When males were removed, female fanning activity increased. When females were removed, males spent more time fanning and less time away from the brood. Other behavioural variables (frequency of digging, mouthing, foraging and retrieving) were not affected. Being alone or paired during a first breeding episode did not affect parental behaviour during a subsequent episode in which all fish were paired. Observations were carried out during the day and at night, and nocturnal fanning of fry is reported here for the first time. Female role appears less flexible than male role, as befits the more direct care normally given by females.     

Adjusting parental investment to changing environmental conditions: the effect of food ration on parental behaviour of the convict cichlid, Cichlasoma nigrofasciatum

Animals that care for their offspring may vary the amount of care provided for a particular brood in relation to environmental conditions. Food availablity is one factor that may affect the costs and benefits associated with parental investment. The convict cichlid, Cichlasoma nigrofasciatum, is a small, substrate-spawning cichlid from Central America. Both male and female provide parental care for eggs and fry. Paris were kept at one of three ration levels, high, medium or low. Time spent in parental fanning by females was positively related to ration. Males spent less time fanning than females and their parental behaviour varied considerably between individuals. Males on the high ration spent slightly more time fanning than those on the lower rations. The number of eggs produced per spawning and the post-spawning weight of both males and females were significantly and positively related to ration. Foraging frequency of both males and females was inversely related to ration. There was no significant effect of ration on the frequency of mouthing eggs and young or on intra-pair aggression. Eggs of low-ration fish hatched earlier than those of medium- and high-ration fish but there was no significant difference in the number of days that the young survived. These results suggest that the allocation of time and effort between parental and maintenance activities differs in relation to food supply. Parents may provide more care for the large brood produced when food is plentiful but place more emphasis on their own survival when food is short and broods are small.     

Life history of the nonnative convict cichlid <Emphasis Type="Italic">Amatitlania nigrofasciata</Emphasis> in the Haebaru Reservoir on Okinawa-jima Island,Japan

Life history parameters associated with reproductive biology, age, and growth of the convict cichlid (also known as the zebra cichlid) Amatitlania nigrofasciata, which was introduced into the Haebaru Reservoir on Okinawa-jima Island, were estimated using 437 specimens that ranged from 13.7 to 82.9 mm standard length (SL). Lengths of females at first maturity (SL) and 50% maturity (L ₅₀) were estimated to be 32.2 and 37.3 mm SL, respectively. The spawning period continued throughout the year, with a peak spawning cycle from March to May 2006–2007. Observations of postovulatory follicles and tertiary yolk stage oocytes indicate that convict cichlids spawn multiple times within a year. Female cichlids that hatched during the peak spawning seasons matured after October of the same year. Batch fecundity of females (32.2–61.2 mm SL) ranged from 65 to 345 (mean ± SD = 155 ± 63). Opaque zones along the outer margins of otoliths formed annually. The maximum age of male and female cichlids was 3 years. The von Bertalanffy growth formulae (VBGF) were expressed as L_t = 57.4( 1 - e ^{- 0.78( t + 0.91 )} ) {{\hbox{L}}_{\rm{t}}}{ = 57}{.4}\left( {1 - {e^{ - 0.78\left( {t + 0.91} \right)}}} \right) for females and L_t = 69.5( 1 - e ^{- 1.07( t + 0.24 )} ) {{\hbox{L}}_{\rm{t}}}{ = 69}{.5}\left( {1 - {e^{ - 1.07\left( {t + 0.24} \right)}}} \right) for males. Males grew larger than females beginning from the first year. Certain life history characteristics, such as year-round spawning and early maturation, probably contributed to the successful establishment of the convict cichlid, and this species in particular is thought to adapt and become established quickly upon introduction to freshwater systems on Okinawa-jima Island.     

Sex differences in biparental care as offspring develop: a field study of convict cichlids (<Emphasis Type="Italic">Amatitlania siquia</Emphasis>)

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.     

Native fish, <Emphasis Type="Italic">Cichlasoma istlanum</Emphasis>, hide for longer,move and eat less in the presence of a non-native fish, <Emphasis Type="Italic">Amatitlania nigrofasciata</Emphasis>

Introduction of non-native species is a problem worldwide. Local populations of the Mexican mojarra, Cichlasoma istlanum, have been hypothesized to be negatively affected by the introduction of the convict fish, Amatitlania nigrofasciata. The Mexican mojarra is a cichlid fish native to the Balsas-River Basin. As a first approach to understand the behavioral effect of the convict fish on Mexican mojarra, we experimentally studied the behavioral responses of the latter when exposed to the former. Thus, we recorded refuge use, swimming activity and feeding rate of Mexican mojarra in the presence of a convict fish, a conspecific, and alone. Mexican mojarra used refuges for longer, swum for shorter and ate less in the presence of convict fish than with conspecifics or alone. Because prolonged use of refuge habitat may deprive Mexican mojarra of opportunities to feed, grow, and reproduce, we hypothesize that convict fish can negatively affect the fitness of the former where the two species co-occur.     

Chemical defence by mono-prenyl hydroquinone in a freshwater ciliate, <Emphasis Type="Italic">Spirostomum ambiguum</Emphasis>

Several species of ciliates produce and accumulate low molecular weight toxic compounds in specialised membrane-bound ejectable organelles: extrusomes. These compounds can be used in predator–prey interaction for killing prey as well as for chemical defence. Here, we describe the isolation and characterisation of 2-(3-methylbut-2-enyl)benzene-1,4-diol(mono-prenyl hydroquinone), the extrusomal defensive toxin of the freshwater heterotrich ciliate Spirostomum ambiguum. The toxin was purified at homogeneity by RP-HPLC, and its structural characterisation was carried out through NMR and MS measurements. In vivo experiments involving S. ambiguum and Climacostomum virens in predator–prey interaction, and the analysis of cytotoxic activity of mono-prenyl hydroquinone on a panel of free-living freshwater ciliates, indicated that the toxin is very effective in S. ambiguum’s chemical defence.     

Aphid infestation promotes survival of a seed predator: observations and experiments on a tritrophic community module

We investigated whether aphid presence and abundance influence the survival of an endophagous pre-dispersal seed predator of the same host plant. We studied a terrestrial community module consisting of one plant (Laburnum anagyroides) and four insect species/groups (an aphid, Aphis cytisorum, a pre-dispersal seed predator bruchid, Bruchidius villosus, aphid-attending ant species, and parasitoids of the bruchid). Two complementary investigations were carried out in parallel: (a) a plant-aphid-ant complex was experimentally manipulated by excluding aphids, ants, or both for 5 years to assess their impacts on the seed predator’s survival and parasitism rate; and (b) different aphid infestation levels on randomly selected infructescences were correlated with plant traits, nutrient allocation pattern, and variables of seed predator’s survival, such as the number of eggs laid and adults emerged influenced by parasitoid activity, for 7 years. We found that ants did not affect bruchid oviposition negatively, but egg-parasitism was significantly decreased by their presence. Plant traits, such as the number of seeds and seed mass, as well as seed predator performance were negatively affected by heavy aphid infestation. Seed predator -infested seeds had no effect on the mass of remaining seeds in the pods. This study suggests that aphids were nevertheless promoting bruchid abundance and survival, depending on their infestation rate.     

Repeated Copulation in the Wood-feeding Cockroach <Emphasis Type="Italic">Cryptocercus punctulatus</Emphasis> Does Not Influence Number or Development of Offspring

Wood-feeding cockroaches in the genus Crytocercus live in biparental family groups in the interior of rotten logs and are considered socially monogamous. They typically produce a single brood of altricial offspring, with parental care then lasting until the death of adults 2 or 3 years later. Field and laboratory evidence suggests that copulation occurs repeatedly in C. punctulatus, with sexual activity occurring during non-fertile periods. We carried out a long-term field study to explore the significance of repeated copulation in C. punctulatus. The presence of a male positively affected the onset of female reproduction, but neither the male’s physical presence nor his ability to mate influenced the number or early development of nymphs. Sperm are viable in the spermathecae for at least 3 years. We conclude that it is unlikely that male-derived material benefits have driven the evolution of repeated copulation in C. punctulatus. Accumulating evidence suggests that prior to oviposition, repeated copulation may be rooted in sperm competition, but after the eggs are laid it may secure the continued paternal contribution of the male social partner.     

Simple order of prey preference technique for modelling the predator functional response

The predator functional response to several prey types and densities may be conceptualized as a multi-dimensional version of the one-dimensional Holling functional-response curves; however, this empirical approach requires inordinate amounts of data to develop and test. A simulation method of modelling this functional response is to consider the behavior of a predator faced with the choice of several prey types. In this model, when all prey are available the predator’s selection will depend on the absolute abundance of the most-preferred prey type, irrespective of the abundances of the less-preferred prey types. Consequently, the predator will consume only the most-preferred prey types while that type is available in sufficient numbers. When abundance of the most-preferred type declines below a certain level, the predator will begin to include in its diet the second-most-preferred prey type along with the most-preferred prey type. This order-of-preference technique holds up well when the model is compared to population data fromOligonychus pratensis (Acarina: Tetranychidae)/Neoseiulus fallacis (Acarina: Phytoseiidae), and is consistent with optimal foraging theory. Implementation is simple, and the data requirements are reduced to determining the predator’s order of preference and normalizing the nutritional values of the prey types to a single type.     

Social Reversal of Sex‐Biased Aggression and Dominance in a Biparental Cichlid Fish (Julidochromis marlieri)

In biparental species, aggression, dominance, and parental care are typically sexually dimorphic. While behavioral dimorphism is often strongly linked to gonadal sex, the environment—either social or ecological—may also influence sex‐biased behavior. In the biparental cichlid fish Julidochromis marlieri, the typical social environment for breeding pairs consists of large females paired with smaller males. While both sexes are capable of providing territory defense and parental care, the larger female provides the majority of defense for the pair, while the smaller male remains in the nest guarding their offspring. We examine the contributions of sex and relative mate size to these sex‐biased behaviors in monogamous J. marlieri pairs. Both female‐larger and male‐larger pairs were formed in the laboratory and were observed for territorial aggression (against conspecifics and heterospecifics), dominance, and parental care. In female‐larger pairs, territorial aggression and intra‐pair dominance were female‐biased, while in male‐larger pairs this bias was reversed. For both pairing types, the presence of an intruder amplified sex differences in territorial aggression, with the larger fish always attacking with greater frequency than its mate. Though less robust, there was evidence for plasticity of sex‐bias for some egg care related behaviors in the inverse direction. Our study suggests that relative mate size strongly influences the sex bias of aggression and dominance in J. marlieri and that this aspect of the social environment can override the influence of gonadal sex on an individual's behavior. The remarkable plasticity of this species makes Julidochromis an exciting model that could be used to address the relationship between proximate and ultimate mechanisms of behavioral plasticity.     

Reliance on trial and error signal derivation by <Emphasis Type="Italic">Portia africana</Emphasis>, an araneophagic jumping spider from East Africa

All species from the jumping spider (Salticidae) genus Portia appear to be predators that specialize at preying on other spiders by invading webs and, through aggressive mimicry, gaining dynamic fine control over the resident spider’s behavior. From previous research, there is evidence that P. fimbriata, P. labiata and P. schultzi derive signals by trial and error. Here, we demonstrate that P. africana is another species that uses a trial and error, or generate and test, algorithm when deriving the aggressive-mimicry signals that will be appropriate in different predator–prey encounters. We discuss the implications of these new findings and the findings from previous work in order to understand the selection factors that drive the evolution of flexibility in aggressive-mimicry strategies.