No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Male Siamese fighting fish use gill flaring as the first display towards territorial intruders
Abstract
The Siamese fighting fish (Betta splendens) is well known as an aggressive fish with unique spawning and parental care behavior. During reproduction, male fish construct a bubble nest, court females, protect the brood, and defend the territory through aggressive displays. Aggression in male Siamese fighting fish has long been the subject of investigation; however, the kinematics of aggression during contests have been largely overlooked. Here we investigated how nest-holding, male Siamese fighting fish use two different types of displays, gill flaring and fin spreading, towards intruders during various reproductive phases; before (BB) and after bubble nest building, and after spawning (AS), and hatching (AH). Males were more aggressive towards male than female intruders and the level of aggression changed significantly between reproductive phases. Gill flaring, the more energetically costly display, was the dominant initial display towards male and female intruders in BB, AS, AH phases. However, defending males switched to fin spreading after prolonged exposure to intruders. The results suggest that Siamese fighting fish use gill flaring as an acute response in order to defend their territory; this response may be replaced by fin spreading as a chronic response, probably to reduce the energetic costs during the contest.
... Such strategic decisions by B. splendens, whether for wining or minimizing costs, involve a welldocumented, stereotyped and easily identifiable behavioural repertoire [29,30]. This includes frontal displays with extended gill-covers and lateral displays with spread fins for signalling size, biting and tail-beating attacks for inflicting physical injury, and retreats for avoiding attack or signalling submission [23][24][25][26][27][28][29][30][31]. Even though evidence is rare, these behaviours have been noted to exhibit chronological organisation during contests and individual variation due to underlying personality-trait aggressiveness [31,32]. ...
... This includes frontal displays with extended gill-covers and lateral displays with spread fins for signalling size, biting and tail-beating attacks for inflicting physical injury, and retreats for avoiding attack or signalling submission [23][24][25][26][27][28][29][30][31]. Even though evidence is rare, these behaviours have been noted to exhibit chronological organisation during contests and individual variation due to underlying personality-trait aggressiveness [31,32]. In addition, the behaviours can be adjusted to assessments of RHP and the perceived value of defended territory, which can vary in quality with noise disturbances and 'subjectively' with the construction of bubble-nests [23][24][25]. ...
... (b) The contribution of consistent predictors, such as trait aggressiveness, resource value factors and morphological measures, varied across sequential outputs, and progressive effects by preceding behaviour were identified. (c) Motivation was also adjusted by resource value, morphology and behavioural information, but was also progressively affected by own energetic state [all models were statistically significant at P < 0.001] aggressive intent for resolving contests without escalation [15,31,35]. This has been previously observed in B. splendens, but is also common in other vertebrates and in invertebrates, such as horses and fiddler crabs [27,36,37]. ...
Background
Animals use contests to attain resources and employ strategic decisions to minimise contest costs. These decisions are defined by behavioural response to resource value and competitive ability, but remain poorly understood. This is because the two factors are typically studied separately. Also, their study relies on overgeneralised assumptions that (i) strategies are fixed, (ii) modulated by the motivation or drive to fight and (iii) used to manage costs proportional to the timing of the loser’s retreat. To address these problems, we adopt an integrative sequential analysis that incorporates competitive ability and resource value factors, to characterise territorial contest decisions in male Siamese fighting fish (Betta splendens).
Results
Individuals exhibited a chronological organisation of behaviour, engaging opponents first with frontal display, then switching to lateral display before deciding to attack, and reserved retreats for later stages. Using asymmetries in retreats as a proxy for outcome, the likelihood of winning was found to be mostly dependent on display. However, resource and contest conditions affected initiation latency, display, attack and retreat, suggesting that strategic decisions influence all behaviour. Overall, sequential behaviour varied consistently with individual aggressiveness and resource-value factors, and increasingly with information on competitive ability collected during the contest. This enabled shifts in tactics, such as disadvantaged individuals responding first with aggression and later with submission. Motivation to continue fighting, after interruption by startle, was also adjusted to information gathered during the contest and progressively with energetic state. Two clusters of correlated behaviours were identified, cost-mitigation (display and retreat) and escalation (initiation and attack), but changes in motivation were associated only with cost mitigation.
Conclusions
Our findings contrast dominant assumptions that strategic decisions are fixed, controlled by motivational state and sufficiently described by outcome-dependent measures. We instead demonstrate that strategic decisions are complex, comprising functional changes in assessment, information use and motivational effects, which are not always inter-dependent.
... This response could be substituted by fin spreading as a subsequent response, reducing the contestant's energetic costs. 46 Many studies have focused on its distinctive opercular pattern. [46][47][48] Aggression in fighting fish is influenced by a variety of factors, including body length 49 and the personality trait of boldness. ...
... 46 Many studies have focused on its distinctive opercular pattern. [46][47][48] Aggression in fighting fish is influenced by a variety of factors, including body length 49 and the personality trait of boldness. 50 Males with blue fins were more aggressive in one study, with longer lateral displays occurring more frequently. ...
The fighting fish Betta splendens is a freshwater species from Thailand and other Southeast Asian countries. This fish has been domesticated for 1000 years and bred for fighting, various colours, body size and fin types for 600 years. It is one of the most important fish species cultured for the world ornamental fish market. This fish is easy to culture, highly fecund and displays great morphological diversity. Its biology has been studied for over 100 years. Recently, its compact genome and transcriptomes have been sequenced. Genome editing with CRISPR/cas9 has been applied to knock out genes in this fish. Its diverse phenotypes, including colours, colour patterns, fin types, and aggressive behaviour, are complementary to those of other model animals. Therefore, this fish could be the next important model organism for studying phenotypic variation and aggressive behaviour. In this paper, we synthesized knowledge about its aquaculture, biology, genetics, genomic tools, phenotypes and novel insights on phenotypic variation, sex determination and aggression. We hope that the information described in this paper will facilitate genetic studies on phenotypic variations in aquaculture and aggressive behaviour in other species, including humans.
... Domesticated B. splendens males exhibit large flowing fins making them popular in the aquarium trade with notable commercial value (Venkatasubramanian et al. 2018). They also display unique social/reproductive behaviors rendering them as popular models in behavioral ecology and ecotoxicology (Forsatkar et al. 2014;Forsatkar et al. 2017a;Venkatasubramanian et al. 2018). In particular, opercular display and fin spreading are characteristic behaviors when males confront intruders (Forsatkar et al. 2017a). ...
... They also display unique social/reproductive behaviors rendering them as popular models in behavioral ecology and ecotoxicology (Forsatkar et al. 2014;Forsatkar et al. 2017a;Venkatasubramanian et al. 2018). In particular, opercular display and fin spreading are characteristic behaviors when males confront intruders (Forsatkar et al. 2017a). This species has become a classic model organism in studies of the effects of endocrine disrupting chemicals (EDCs). ...
Siamese fighting fish (Betta splendens) has been extensively exploited in the behavioral and physiological toxicology studies of drugs. Tacrolimus is an immunosuppressant drug largely used in liver and renal transplantations. Here we found that a 7-day exposure of male B. splendens to concentrations of 0.05 and 0.1 µg/mL Prograf® (tacrolimus) caused alterations in aggression and immunity indexes. Tacrolimus exposed fish presented lower opercular display in a mirror test which is indicative of reduced aggression. In addition, serum levels of lysozyme, IgM, alternative complement, and bactericidal activity of subjects exposed to 0.1 µg/mL tacrolimus were lower than those from the control treatment. These results showed the behavioral impairment and immunotoxic impacts of tacrolimus in a model of aquatic toxicology. The results suggest fishes provide a possible model for better understanding of the drug action in vertebrates, and possible consequences for the environment via its effects on non-target organisms in an ecotoxicology context.
... The opercular flare, in particular, compounds this condition as it prevents water (an already poor source of DO) from effectively passing over gills and forces an individual into a self-imposed hypoxic state (Abrahams et al., 2005). Owing to their costly nature, the opercular flare is only used as an acute response to other males and is swiftly swapped for less costly behaviours, such as fin flaring, against persistent intruders (Forsatkar et al., 2016). As such, the duration of opercular and dorsal-fin flaring relates to an individual's condition and can subsequently be used to indicate the winner of an interaction (Simpson, 1968;Evans, 1985;Abrahams et al., 2005). ...
... The female is led to the nest by the male which will perform lateral displays to the female and then return to the nest in a zig-zag manner, regularly halting (Miller, 1964;Miller & Jearld, 1983). During courtship displays, males use the same behaviours as in territory defence, however, the frequency and intensity of these behaviours are altered, with males rarely biting (Simpson, 1968;Robertson & Sale, 1975;Forsatkar et al., 2016). Both chemical and visual cues are assessed during courtship, with female pheromones eliciting nesting behaviour in male T. trichopterus (Cheal & Davis, 1974). ...
... The opercular flare signifies the intensity of the male to attract the female (Goddard & Mathis 1997). This type of aggressive behaviour is also displayed by other anabantoid fish to compete between males for female attraction and deter intruders from their territory (Forsatkar et al. 2016). The act of flaring is taxing to their physiology, as it prevents water from passing through gills making the fish experience a hypoxic state (Abrahams et al. 2005;Castro et al. 2006). ...
The giant gourami (Osphronemus goramy Lacepede, 1801), a popular aquaculture species in Southeast Asia, exhibits unique cooperative biparental care behaviour. To support captive breeding efforts, this study aimed to visually document the reproductive activity of giant gourami, elucidate each stage in detail, and provide insights into the distinct parenting roles of males and females. Underwater cameras were used to observe a breeding pair of gourami in a pond for five days, conducted three times with different pairs during different spawning periods. The male and female contributions to nest building were quantitatively analysed using the T-test, while their parental care involvement was qualitatively assessed and statistically analysed using the Mann-Whitney U test. The results revealed three main phases of giant gourami reproduction: pre-spawning (including adaptation, nest building, and courtship), spawning and fertilisation, and post-spawning with parental care. Our observation confirmed the biparental tendency, with males being more involved in pre-spawning activities and females taking on a prominent role in post-spawning care. In conclusion, males focused on mating preparations and courtship, while females invested more in parental care.
... In addition to the causes discussed earlier, energetics could also play a role in the observed aggression patterns. Engaging in physical combat is energetically costly and may divert resources away from reproduction and paternal care (Qvarnström 1997, Forsatkar et al. 2016. It is possible that males rely on female mate choice to reduce the number of potential competitors thereby conserving energy. ...
Assortative or disassortative aggression – when individuals display more aggression towards conspecifics with similar or different phenotypic characteristics – can either maintain polymorphisms or facilitate gene flow between populations depending on which direction the aggression is aimed. Deciphering which factors elicit or prevent aggression is crucial to improving our knowledge of the origin and maintenance of reproductive barriers and subsequent speciation. The Peruvian mimic poison frog, Ranitomeya imitator, is a monogamous and territorial species that has evolved into four distinct color-pattern morphs in a mimetic radiation. Here we use historical landscape genetic data and competition trials between male individuals sourced from different populations and color-pattern morphs to show that the level of aggression between individuals is not associated with color morph or body size but rather with source population. Individuals spent more time in combat with individuals from their own deme (genetically homogeneous population), irrespective of color morph or size. These findings indicate that genotypic similarity is correlated with increased aggression in R. imitator, though the mechanism by which R. imitator males identify conspecifics as territorial threats remains unclear. As body size and color morph were not significantly associated with aggression levels, this study emphasizes the necessity of further research to identify whether other phenotypic traits are influencing territorial behavior between male frogs, and if these factors play a role in increasing gene flow, or conversely, the formation of reproductive barriers between populations.
... The higher predation risk of tumor-bearing hydras could be ascribed to both visual and chemical cues, since the fish species used here is able to exploit both, at least in sexual selection and competition contexts (Forsatkar et al., 2017;Ingersoll et al., 1976;Romano et al., 2017). However, given that this fish is mostly a visually hunting predator (Bando, 1991; da Silva Souza et al., 2020) and from our observations during the experiments, we favor the first hypothesis, i.e. that they detect and capture preferentially bigger (tumorous) preys. ...
Tumors form as a result of abnormal and uncontrolled proliferation of cells within a multicellular organism, which can lead to cancer. Although this phenomenon exists in all metazoans, most research has focused on malignancies in humans and domestic animals. Thus, the evolutionary ecology of host-tumor interactions and their consequences for ecosystem functioning is a virtually untouched area of research.
To address these scientific questions, the biological model used in this thesis is a freshwater cnidarian, the brown hydra hydra oligactis, some of whose laboratory lines harbor tumors with notable specificities. In addition to the fact that the benign/malignant status of these tumors is not clear, they are capable of vertical transmission, during asexual reproduction of their host by budding. Furthermore, tumorous hydras have an increased number of tentacles compared to healthy hydras.
This thesis is organized in 5 sections, an introduction with two synthesis articles, three chapters presenting the research done and a general discussion. The first synthesis deals with the comparison between benign and malignant tumors, the second one deals with the costs of anticancer defenses in host organisms.
Our research on H. oligactis first described spontaneous tumors within several wild-type lineages (Chapter 1). This work shows that brown hydra tumors always appear to be of germline origin.
Moreover, we show that the presence of a bacterial species of the order Chlamydiales, could play a role in the initiation and/or maintenance of these tumor processes.
We then studied (chapter 2) the impact of the tumor-bacterial transmissible complex (i.e. tumor cells and bacteria) on the life history traits of the hydra host. This work shows that polyps derived from tumorous parents, prior to becoming tumoral themselves, intensify their sexual and asexual reproductive e�orts. Moreover, these tumorous polyps subsequently have a reduced survival compared to healthy ones. The adaptive nature of these life history trait changes, for the host and/or for the transmissible tumor cells, is discussed. This chapter also focuses on the origin of the increased number of tentacles in tumor polyps. By transplanting di�erent tumors into hydras of varying genetic background, we showed that polyps developing supernumerary tentacles after transplantation were always those that had received tumor tissue from hydras lines harboring transmissible tumors, and already associated with the appearance of supernumerary tentacles in their original host. Rather than a compensatory response initiated by the host, the growth of supernumerary tentacles in some tumor-bearing hydras would therefore be induced by transmissible
tumor cells.
Finally, in order to improve our understanding of the ecological consequences of host-tumor interactions on ecosystem functioning, we experimentally explored (Chapter 3) the relationships that tumor-bearing hydras have with other animal species living in aquatic environments. We demonstrated that, compared to healthy hydras, tumorous ones had an increased risk of predation by fish, a higher rate of colonization by commensal ciliates, and their ability to capture prey was superior due to their increased number of tentacles.
Taken together, this work argues for a better consideration of tumor processes in evolutionary ecology, both in terms of the ecological and evolutionary trajectory of host species and the consequences of these interactions on ecosystem functioning.
... Displays of the focal animals included the opening of the opercula and other aggression elements, suggesting that indeed video images were being perceived as meaningful. Similar results were obtained by Neri (2019), with males orienting towards a video playback of a conspecific and opening the opercula, the first element to be displayed in a fight (Forsatkar et al. 2016). Interestingly, in the Neri (2019) study some fish showed only a weak response to the video playback, corroborating our findings that video images produced more variable results than live stimuli. ...
The physiological mechanisms underlying variation in aggression in fish remain poorly understood. One possibly confounding variable is the lack of standardization in the type of stimuli used to elicit aggression. The presentation of controlled stimuli in videos, a.k.a. video playback, can provide better control of the fight components. However, this technique has produced conflicting results in animal behaviour studies and needs to be carefully validated. For this, a similar response to the video and an equivalent live stimulus needs to be demonstrated. Further, different physiological responses may be triggered by live and video stimuli and it is important to demonstrate that video images elicit appropriate physiological reactions. Here, the behavioural and endocrine response of male Siamese fighting fish Betta splendens to a matched for size conspecific fighting behind a one-way mirror, presented live or through video playback, was compared. The video playback and live stimulus elicited a strong and similar aggressive response by the focal fish, with a fight structure that started with stereotypical threat displays and progressed to overt attacks. Post-fight plasma levels of the androgen 11-ketotestosterone were elevated as compared to controls, regardless of the type of stimuli. Cortisol also increased in response to the video images, as previously described for live fights in this species. These results show that the interactive component of a fight, and its resolution, are not needed to trigger an endocrine response to aggression in this species. The study also demonstrates for the first time in a fish a robust endocrine response to video stimuli and supports the use of this technique for researching aggressive behaviour in B. splendens.
... The genus Betta or popularly known as fighting fish is one of the most popular ornamental and commercially important fish group in Asia and worldwide (Thongprajukaew et al. 2011). They are aggressive and territorial, especially when spawning and incubating eggs (Alton et al. 2013;Forsatkar et al. 2017;Goldstein 2015). This group contains fishes that are generally small in size and have a round body shape (Alderton 2012). ...
Species of the genus Betta are very similar morphologically which could lead to inaccuracy in taxonomic identification. Therefore, morphological data should also be complemented with other approaches such as genetics to validate the taxonomic status of member species. The objective of this study was to validate the taxonomic status of the genus Betta from Aceh waters using morphometric and genetic data. Sampling was conducted from January to September 2020 at 12 locations within Aceh province. Based on initial assessment identification of morphology, there were four presumed species of Betta in Aceh waters, namely; Betta rubra, Betta dennisyongi, Betta splendens, Betta imbellis. A total of 50 samples from each presumed species were assessed for traditional and truss morphometric analysis, while 5 specimens were randomly selected from each morphospecies for genetic analysis based on the cytochrome oxidase subunit I (COI) gene. The traditional morphometric data divided the four Betta species into two group with B. rubra and B. dennisyongi in same group (group I), while B. splendens and B. imbellis in different group (group II). While, the truss morphometric data divided the four Betta species into three groups with B. rubra and B. dennisyongi in group 1, B. splendens in group 2, while B. imbellis form the other group. The head depth of the fishes was an important characteristic to distinguish members of the four species. In parallel, the genetic analysis supported the occurrence of four valid species with intraspecific values of 0.0–1.59% and interspecific values ranging from 3.3 to 24.7%, the same clustering relationship as in the morphometric data. While B. rubra, B. splendens, and B. imbellis sequences are already available in GenBank, this study reports the first record of B. dennisyongi COI sequences.
... The higher predation risk of tumor-bearing hydras could be ascribed to both visual and chemical cues, since the fish species used here is able to exploit both, at least in sexual selection and competition contexts (Forsatkar et al., 2017;Ingersoll et al., 1976;Romano et al., 2017). However, given that this fish is mostly a visually hunting predator (Bando, 1991;da Silva Souza et al., 2020) and from our observations during the experiments, we favor the first hypothesis, i.e. that they detect and capture preferentially bigger (tumorous) preys. ...
While it is often assumed that oncogenic processes in metazoans can influence species interactions, empirical evidence is lacking. Here, we use the cnidarian Hydra oligactis to experimentally explore the consequences of tumor associated phenotypic alterations for its predation ability, relationship with commensal ciliates and vulnerability to predators. Unexpectedly, hydra's predation ability was higher in tumorous polyps compared to non-tumorous ones. Commensal ciliates colonized preferentially tumorous hydras than non-tumorous ones, and had a higher replication rate on the former. Finally, in a choice experiment, tumorous hydras were preferentially eaten by a fish predator. This study, for the first time, provides evidence that neoplastic growth has the potential, through effect(s) on host phenotype, to alter biotic interactions within ecosystems and should thus be taken into account by ecologists.
... Males are territorial and defend an area where they build nests of bubbles by covering a gulp of air with mucus in their mouth (Cain & Baenninger, 1980;Goldstein, 1975). This is a very costly behavior, and males defend their nests with high aggression (Forsatkar et al., 2016). The males' nests of bubbles attract females' attention, and females approach the males' area to be courted and breed. ...
Individual differences in behavior are observed in the variety of ways animals respond to environmental challenges, interact in a social group, take risks to access a resource, and so forth. In the present study, we investigated the behavioral reactions of male and female Siamese fighting fish (Betta splendens) in different contexts and how they affect female mate choice. A total of 100 females and 50 males were classified according to boldness, sociability, and aggression, and then female mate choice was observed based on male profile and body color. Our results showed sex-related differences in Siamese fighting fish behavioral profiles: Males exhibited a higher correlation with aggression and females with boldness. Both male and female behavioral profile affected female mate choice. Females preferred bold red and nonaggressive red males. Sex-related differences in behavioral profiles may reflect ecological differences between male and female Siamese fighting fish. Female mate choice could be related to behavioral profiles that indicate better parental care, as male features may influence parental care decisions and the development of offspring behavioral profiles. (PsycInfo Database Record (c) 2021 APA, all rights reserved).
... Video-taping and counting the aggressive displays also enable researchers to identify the winner, the loser and provide rankings. Some behaviours may be species-and sexspecific; in male B. splendens, gill flaring is the initial aggressive display towards both males and females but after prolonged exposure to intruders, there is a switch to fin-spreading (Forsatkar et al., 2016). ...
Fishes show remarkably diverse aggressive behaviour. Aggression is expressed to secure resources; adjusting aggression levels according to context is key to avoid negative consequences for fitness and survival. Nonetheless, despite its importance, the physiological basis of aggression in fishes is still poorly understood. Several reports suggest hormonal modulation of aggression, particularly by androgens, but contradictory studies have been published. Studies exploring the role of chemical communication in aggressive behaviour are also scant, and the pheromones involved remain to be unequivocally characterized. This is surprising as chemical communication is the most ancient form of information exchange and plays a variety of other roles in fishes. Furthermore, the study of chemical communication and aggression is relevant at the evolutionary, ecological and economic levels. A few pioneering studies support the hypothesis that aggressive behaviour, at least in some teleosts, is modulated by “dominance pheromones” that reflect the social status of the sender, but there is little information on the identity of the compounds involved. This review aims to provide a global view of aggressive behaviour in fishes and its underlying physiological mechanisms including the involvement of chemical communication, and discusses the potential use of dominance pheromones to improve fish welfare. Methodological considerations and future research directions are also outlined.
... Sebagai contoh, ikan Artedius harringtoni jantan memiliki membran branchiostegal berwarna cerah yang bertujuan menarik perhatian lawan jenis (Ragland dan Fischer, 1987). Ikan Betta splendens memiliki kemampuan melebarkan membran branchiostegal beserta tulang operculum untuk menghasilkan tampilan antagonistik (Farina et al., 2015;Forsatkar et al., 2017). Pada ikan laut dalam seperti Argyropelecus hemigymnus dan Maurolicus muelleri, membran branchiostegal memiliki kemampuan menghasilkan cahaya untuk menarik perhatian mangsa (Cavallaro et al., 2004). ...
Penelitian ini bertujuan untuk mengkaji perbedaan anatomi insang ikan keureling (Tor tambroides), ikan mas (Cyprinus carpio) dan ikan nila (Oreochromis niloticus). Tahapan penelitian ini meliputi persiapan ikan uji, preparasi anatomi insang, dokumentasi, identifikasi dan analisis. Jumlah sampel yang digunakan untuk masing masing jenis ikan adalah sebanyak lima ekor dengan kisaran bobot antara 500-1000 g dan kisaran panjang antara 28 sampai 40 cm. Pengamatan dilakukan secara morfologi dan morfometrik. Data morfometrik pada bagian arcus branchialis yang diamati meliputi rasio panjang arcus branchialis dengan panjang total, pada bagian filamen branchialis meliputi rata-rata jumlah filamen branchialis per arcus branchialis, rata-rata kerapatan filamen branchialis (filamen/cm), dan rasio panjang filamen branchialis dengan panjang arcus branchialis, sedangkan pada bagian branchiospinalis meliputi rata-rata jumlah branchiospinalis per arcus branchialis dan kerapatan branchiospinalis. Hasil penelitian menunjukkan bahwa secara morfologi, perbedaan anatomi insang ikan keureling, ikan mas dan ikan nila terletak pada bentuk membran branchiostegal dan branchiospinalis. Perbedaan morfometrik antar ketiga jenis ikan terlihat pada berat insang relatif, rasio panjang arcus branchialis, rata-rata kerapatan branchiospinalis, rata-rata jumlah filamen branchialis, rata-rata kerapatan filamen branchialis dan rata-rata jumlah branchiospinalis. Ikan mas memiliki nilai berat insang relatif yang lebih besar dibandingkan dengan ikan nila dan ikan keureling yaitu masing masing sebesar 3,73 ± 0,43%, 2,82 ± 0,64% dan 1,92 ± 0,55%. Ikan nila memiliki bentuk dan ukuran insang yang lebih berkembang dalam mendukung kinerja sistem respirasi dibandingkan ikan mas dan ikan keureling. Kata-kata kunci: arcus branchialis; filamen branchialis; branchiospinalis; membran branchiostegal ABSTRACT This study aims to describe the anatomical differences in the gills of the thai mahseer's (Tor tambroides), carp (Cyprinus carpio) and tilapia (Oreochromis niloticus). The stages of this study include the preparation of test fish, preparation of gill, documentation, identification, and analysis. This study used five fish for each type of fish with total weight ranged from 500-1000 g and length 28 to 40 cm. Analysis of each gill section was carried out morphology and morphometric. Morphometric data on the arcus branchialis section observed included the ratio of branchial arcus length to total length, on the part of the branchial filament
... Consequently, the most frequently reported modality for discrimination is vocalizations, which have the practical benefit of being relatively easy to manipulate via playbacks in controlled experiments. However, many species depend on olfactory cues (Wyatt 2014) and/or visual displays (e.g., Forsatkar et al. 2017;Ramos and Peters 2018) when vocal advertisement is lacking. ...
According to the dear enemy phenomenon, territory owners decrease costs of ownership by decreasing aggression toward neighbors once territory boundaries have been established. To maintain this cooperation, when territorial neighbors are caught in the act of “cheating” by failing to respect territory boundaries, they should be “challenged” via increased aggression. Most studies examining this prediction tested neighbor recognition through playback of advertisement calls. We tested whether territorial terrestrial salamanders, Plethodon serratus, would identify cheating neighbors via chemical or visual cues. In separate experiments, focal residents were exposed to either territorial substrate markings from another salamander or to a mirror (simulating a territorial neighbor) on one side of their territory for several days. During subsequent testing, the chemical or visual (mirror) cues were presented at either the trained location (cooperating) or on the opposite (cheating) side. Either olfactory or visual cues alone were sufficient for discrimination of cheating/cooperating neighbors, with cheating neighbors receiving the most aggressive displays and chemosensory sampling behavior from focal residents. Aggressive displays were particularly high in trials with visual cues, which likely indicated a more immediate threat. Moreover, responses to the visual threat may have been more escalated because the “neighbor” did not back down following threat posturing from the focal resident. Qualitatively, focal residents attempted to physically interact with the mirror images even in cooperating neighbor treatments. Therefore, in accordance with the dear enemy hypothesis, cheating neighbors elicited a higher level of threat displays than cooperating neighbors, but even cooperating neighbors could sometimes be challenged at the territory border.
Significance statement
For territorial neighbors, cooperating by respecting territorial boundaries can reduce the cost of ownership by reducing aggressive interactions between neighbors. Cooperating neighbors (“dear enemies”) remain in their own territories, whereas cheating neighbors travel beyond their territory boundaries. Evolutionarily, cooperation can be maintained if neighbors that “cheat” must pay a cost. Thus, location of individuals (detected via advertisement signals) is predicted to influence aggressive behavior by adjacent neighbors. We demonstrated that territorial southern red-backed salamanders responded with a higher level of aggressive displays to cheating neighbors whose presence was detected via either chemical (substrate markings) or visual (mirror) displays. In mirror trials, focal residents paced back and forth with their mirror images, exhibiting short bursts of threat posturing and tapping the image with their snouts, which is consistent with behavior toward other salamanders. Therefore, cooperation between neighbors can be maintained via increased aggression toward cheaters.
... In the Siamese fighting fish (Betta splendens), for example, opercula displays serve as an acute response to a territory intrusion, while fin spreading is a chronic response, probably due to the lower energetic costs of such displays (Forsatkar, Nematollahi, & Brown, 2017). The intensity of opercula displays is a good predictor for the outcome of subsequent fights, indicating that they are honest signals for the signaller's RHP (Evans, 1985). ...
Aggressive interactions are ubiquitous among animals. They are either directed towards heterospecifics, like predators or competitors, or conspecifics. During intraspecific encounters, aggression often serves to establish hierarchies within the social group. Thus, in order to understand the mechanisms mediating social organization, it is important to comprehend the escalation and avoidance of aggressive behaviour.
Overt aggressive interactions are costly not only in terms of increased risk of injury or death, but also due to opportunity costs and energy expenditure. In order to reduce these costs, animals are expected to communicate their strength and aggressive motivation prior to fights. For this purpose, they use different means of communication in various sensory modalities, that is visual, acoustic, chemical, mechanosensory and electric cues. These different modalities can convey different or similar information, underlining the importance of understanding the multimodal communication of aggression.
Thus far, most studies on signalling during aggressive encounters have focussed on visual or acoustic cues, most likely as these are the two modalities predominantly used by humans. However, depending on the species’ ecology, visual or acoustic cues might play a minor role for many species. Especially in aquatic systems, visual communication is often hampered due to high levels of turbidity or limited light conditions. Here, alternative modalities such as chemical, mechanical or electrical cues are expected to play a prominent role.
In this review, I provide an overview of different modalities used during aggressive communication in aquatic organisms. I highlight the importance of studying the role of multimodal communication during aggressive encounters in general and discuss the importance of understanding aquatic communication in the light of conservation and animal welfare issues.
... Although the practice of purchasing individuals from local shops is widely adopted for research on B. splendens (e.g. Forsatkar et al. 2017;Arnott et al. 2016;Eisenreich and Szalda-Petree 2015;Romano et al. 2017), we hope to rectify its limitations in further studies by relying exclusively on institutional breeding facilities and it is further hoped that the latter practice will come to dominate the field in the near future. ...
We currently have limited knowledge about complex visual representations in teleosts. For the specific case of Siamese fighting fish (Betta splendens), we do not know whether they can represent much more than mere colour or size. In this study, we assess their visual capabilities using increasingly complex stimulus manipulations akin to those adopted in human psychophysical studies of higher-level perceptual processes, such as face recognition. Our findings demonstrate a surprisingly sophisticated degree of perceptual representation. Consistent with previous work in established teleost models like zebrafish (Danio rerio), we find that fighting fish can integrate different features (e.g. shape and motion) for visually guided behaviour; this integration process, however, operates in a more holistic fashion in the fighting fish. More specifically, their analysis of complex spatiotemporal patterns is primarily global rather than local, meaning that individual stimulus elements must cohere into an organized percept for effective behavioural drive. The configural nature of this perceptual process is reminiscent of how mammals represent socially relevant signals, notwithstanding the lack of cortical structures that are widely recognized to play a critical role in higher cognitive processes. Our results indicate that mammalian-centric accounts of social cognition present serious conceptual limitations, and in so doing they highlight the importance of understanding complex perceptual function from a general ethological perspective.
... Male Siamese fighting fish (Betta splendens) are popular as ornamental aquarium fish around the world (Froese and Pauly 2017), whereas females are usually sold in bulk at low price, with some being kept by producers for breeding purposes (Monvises et al. 2009). Fin shape and body color are the main criteria used by culturists when choosing male fish for stocking aquaria, but the aggressive and territorial nature of the males means that they are usually held separately from each other (Forsatkar et al. 2017;Monvises et al. 2009). Therefore, improving the physical environment in an aquarium could serve the well-being of captive fish. ...
The effects of five aquarium backgrounds (transparent, white, red, blue, and black) on growth, feed utilization, digestive enzyme activities, skin coloration, muscle parameters, and carcass composition were investigated in solid red male Siamese fighting fish (Betta splendens). The fish (1.13 ± 0.01 g initial body weight) were distributed individually into glass aquaria (3.5 cm width × 8 cm length × 20 cm height) varying in color backgrounds (n = 15 per treatment). They were fed a commercial floating diet for small ornamental fish (35% crude protein) twice daily (0800 and 1700 h), and all measurements of fish were examined at the end of 8 weeks. The growth performance (specific growth rate = 0.97% body weight day⁻¹) and feed utilization (feed conversion ratio = 1.60 g feed g gain⁻¹ and protein efficiency ratio = 1.83 g gain g protein⁻¹) of the fish reared on blue background were superior relative to the other treatments, followed by red background as next best (0.86% body weight day⁻¹, 1.50 g feed g gain⁻¹, and 1.71 g gain g protein⁻¹, respectively). There were no significant differences in specific activities of digestive enzymes (pepsin, trypsin, chymotrypsin, lipase, and amylase) between the fish reared on blue and transparent backgrounds (P > 0.05), but significantly increased ratio of amylase to trypsin was observed in the blue treatment. Skin coloration (in terms of lightness and redness), muscle RNA concentration, and muscle RNA/protein ratio did not differ in the fish reared on blue background, while muscle actin/myosin ratio and carcass lipid increased, relative to the control with transparent background. Findings from the current study indicate that the blue-based aquarium background is appropriate for rearing male Siamese fighting fish.
... Previous studies have illustrated that the intensity of the aggression of the host males is impacted by the sex of the intruder (Forsatkar et al 2017). In general, our results show that the degree of male Siamese fighting fish responses to intrusions varies after instantaneous visual exposure to social environments representing different context and status of the competitive resource (female fish) with the modest territorial aggression occurred when previous possession (escorting) of the resource is perceived. ...
There has been a growing trend towards examining interactions in the context of communication networks consisting of many individuals rather than isolated pairs of signaling animals. An important question in state-dependent behavior is how multiple influences on state are integrated to determine current behavior. The goal of the following study was to investigate whether the availability of female, both in terms of density and accessibility, affects male-male interactions in male Siamese fighting fish, Betta splendens. For this purpose, direct male-male fighting trials were performed considering 12 different scenarios. The findings indicated that it is the physical isolation and/or presence of an escorting male in the community, not female density, which modifies male-male interactions. These results suggest that the resource holding power (RHP) in a specimen can be innately recognized by other opponents in bettas.
Occasionally, in science, models are used to stimulate other systems rather than to perform surrogative reasoning. More specifically, in what is called surrogative stimulation, a model is used to stimulate a focal system in order to learn how it would respond to the system represented by the model. This article proposes a methodological reconstruction of the surrogative stimulation strategy and addresses the so-called model evaluation problem in relation to it. It is argued that in order to be adequate for surrogative stimulation, the model must provide stimuli that are similar to those provided by the target system, and a tentative definition of ‘stimulus similarity’ is offered. It is also argued that whether the model and the target system are similar in this sense is a question that depends not only on the context and interests of the modeller, but more crucially on facts about how the focal system works. Representative examples are taken from ethorobotics and social robotics, but the analysis made here is not intended to be applicable only to these areas of research. While much remains to be learned about this emerging use of models, the analysis undertaken here aims to offer a preliminary methodological reconstruction that may be useful for future studies.
Assortative or disassortative aggression – when individuals display more aggression towards conspecifics with similar or different phenotypic characteristics – can either maintain polymorphisms or facilitate gene flow between populations depending on which direction the aggression is aimed. Deciphering which factors elicit or prevent aggression is crucial to improving our knowledge of the origin and maintenance of reproductive barriers and subsequent speciation. The Peruvian mimic poison frog, Ranitomeya imitator , is a monogamous and territorial species that has evolved into four distinct color-pattern morphs in a mimetic radiation. Here we use historical landscape genetic data and competition trials between male individuals sourced from different populations and color-pattern morphs to show that the level of aggression between individuals is not associated with color morph or body size but rather with source population. Individuals spent more time in combat with individuals from their own deme (genetically homogeneous population), irrespective of color morph or size. These findings indicate that genotypic similarity is correlated with increased aggression in R. imitator , though the mechanism by which R. imitator males identify conspecifics as territorial threats remains unclear. As body size and color morph were not significantly associated with aggression levels, this study emphasizes the necessity of further research to identify whether other phenotypic traits are influencing territorial behavior between male frogs, and if these factors play a role in increasing gene flow, or conversely, the formation of reproductive barriers between populations.
The smallest water volume that humanely supports Siamese fighting fish (Betta splendens) during local transportation was determined. Mature male Siamese fighting fish (1.46 ± 0.01 body weight, n = 90) were individually packed in transparent bags containing different water volumes (40, 60, 80, 100, 120, and 140 mL) that gave a 1: 3 ratio of water to air. The packaging procedures followed the Thai Post Office’s standard. The fish were domestically transported to five different destinations and returned. The total duration of transit was approximately 48 h. On arrival back at the laboratory, the specimens were immediately harvested, and water quality, survival, morphometric changes, digestive enzyme activities, skin coloration, muscle quality, and whole-body composition were determined. The results were compared with a group (n = 15) that was not transported. Water pH, temperature, dissolved oxygen, alkalinity, and ammonia were significantly affected by water volume (P < 0.05). Survival and weight loss variation indicated against using water volumes of 40 or 60 mL (P < 0.05), although weight and length characteristics were similar to other treatments (P > 0.05). Fish transported in 80 and 100 mL of water showed similar characteristics for skin coloration and muscle quality (P > 0.05) but no difference in whole-body composition was observed between the two treatments compared to the control (P > 0.05). The findings of our study indicated that the minimal water volume that B. splendens tolerated well during transportation was 80 mL. This study can be used as a guide for local overland shipping of male Siamese fighting fish.
The mechanisms of action of hormones regulating aggression in fish remain poorly understood. One possibly confounding variable is the lack of standardization in the type of stimuli used to elicit aggression. The presentation of controlled stimuli in videos, a.k.a. video playback, can provide better control of the fight components. However, this technique has produced conflicting results in animal behaviour studies and needs to be carefully validated. Here, the response of male Betta splendens to a matched for size conspecific fighting behind a one-way mirror presented live or through video playback was compared. Despite their non-interactive nature, both stimuli elicited a strong aggressive response by focal fish, which started with stereotypical threat displays and progressed to overt attacks. Overall, the frequency and duration of aggressive behaviours and swimming activity were similar towards live and video stimuli. Post-fight plasma levels of the androgen 11-ketotestosterone were elevated as compared to controls, regardless of the type of stimuli. Cortisol also increased in response to the video images, as previously described for interactive live fights in this species. The study shows for the first time in a fish a robust endocrine response to video stimuli and supports the use of this technique for researching aggressive behaviour in B. splendens.
17α-Ethynylestradiol (EE2) is a synthetic hormone that has become a widespread problem in the aquatic environments. The immunomodulatory effects of EE2 in fish have attracted much attention in recent years; however, little is known about its immunotoxicological impacts. This study was conducted to investigate the immune function of female Siamese fighting fish exposed to an environmental concentration of EE2, 10 ng/L. Aggressive reproductive behavior in this species often results in injuries to females after spawning, and thus they are a good candidate in immunotoxic actions of EE2. Fish were exposed to EE2 for 15 days and then distributed for breeding. Immune function, pathogen resistance, and survival rate were assessed after spawning. Immune responses including serum concentrations of IgM, lysozyme, complement, and bactericidal activity were lower in EE2-exposed females than the control fish. Also, EE2-exposed females showed higher mortality rate regardless of whether they were challenged with the bacterium. These results suggest that EE2 suppressed immune responses of spawned female fighting fish, thereby reducing its potential to resist against opportunistic pathogens.
Siamese fighting fish, Betta splendens, have been extensively studied due to their aggression and stereotypical displays. Many studies have focused on their characteristic opercular flaring, while the less aggressive and less energetically costly lateral display have been comparatively understudied. Many factors have been shown to influence aggression in Bettas, notably body length and the personality trait of boldness, however, the role that colour plays in determining an individuals aggressiveness is much less clear. The role of colour has only been briefly studied, and based on human interpretations of colour, i.e. limited to what the receivers eyes and sensory systems actually can process and discriminate, with results suggesting blue males are more aggressive than red males. Using male-male interactions, measuring opercular flaring and lateral display we found that colour and personality do play a role in determining the degree of aggressiveness in Betta splendens. Blue-finned males were more aggressive, performing longer lateral displays more frequently. Blue fins are a phenotype observed in wild type males and is likely selected for to allow visual cues to travel through the murky water they inhabit. Body mass was positively correlated with lateral display frequency, and opercular flare frequency and duration. Finally, neophobic individuals, individuals that were less willing to approach a novel object, were more aggressive, performing significantly more lateral displays. This indicates that personality may impact fighting strategy, with males either choosing to end conflicts quickly with more aggressive displays or to outlast their opponent with less energetically costly displays.
Fish models are increasingly used in a wide variety of experimental contexts and their adoption is growing globally. This chapter reviews the evidence for sentience and cognitive abilities in fishes to highlight the growing empirical evidence of the mental capacities of fish. The definition of sentience is presented along with the scientific data pertinent to understanding what fishes are capable of, as well as higher order cognitive abilities such as numerical skills and the capacity for learning and memory. Being able to experience positive and negative welfare states such as pain, fear, and stress is highly debated for fishes; thus this chapter reviews the evidence for and arguments against conscious perception of pain and fear. If suffering and sentience are accepted in fishes, this has ethical implications for the way in which we use fish in scientific studies.
The evolution of signals has mainly been considered in the context of an emitter-receiver dyadic interaction. However, communication usually occurs in the presence of individuals (an audience) that are not directly involved in the communication interaction, and it is more realistic to assume that signal evolution occurs in a network. Several types of information could be available to an audience, and, therefore, the presence of an audience could have effects on the behavior of the communicating animals and on signal evolution. We investigated whether the presence of an audience of conspecifics affected intrasexual aggressive communication in male fighting fish. We found that if the audience was a female, males increased the intensity of conspicuous displays that can be used in communication with both males and females and decreased highly aggressive displays that are solely directed to males. If the audience was a male of similar size, there was no significant change in the way in which males displayed. These results suggest that the presence of an audience could be one reason that many long-range and conspicuous signals are often shaped to transmit information to both males and females.
Siamese fighting fish Betta splendens in Thailand inhabit shallow water amongst dense emergent vegetation near the margin of rice paddy fields. Nesting water was low in dissolved oxygen, pH, salinity but high in free carbon dioxide and temperature. This fish aggregated with a mean population density of 1·7 fish m-2 and an equal adult sex ratio. Males were heavier, longer and wider than females. The size of their bubble nest is in proportion to their weight and length.
The Siamese fighting fish, of which Betta splendens is representative, is gaining popularity as judged by increasing export values and demands for novel types worldwide, especially the ornamental ones. However, relatively little is known about the bettas scientifically. In this review we cover what is known about the desired morphology and pigments, genetics, aquaculture, diseases and feeds involved in breeding bettas. We also propose breeding the bettas for domestic enjoyment and export by exploiting current knowledge of gene technology and molecular developmental biology in addition to the use hitherto of only classical genetics. Other aspects of fish culture such as feeds, disease prevention and water quality should also be scientifically studied and improved upon. Because of dwindling and worsening habitats in Thailand, more studies on biodiversity and work towards species conservation of the wild types are needed.
Aggressive conflicts between males are often resolved by means of multiple ritualized agonistic displays without damaging escalation. Apparently, in such cases by using those displays opponents exchange important motivational and physical information on which they base a decision to stay or leave the interaction. In the Siamese fighting fish, the time spent spreading the dorsal fin and erecting the gill coverts predicts who will be the winner or loser of the interaction. Two experiments were carried out to study whether display performance might be costly. First, oxygen consumption was measured during mirror-image stimulation. This experiment showed that oxygen consumption was positively correlated with gill cover erection and dorsal fin spread. In the second experiment, a fight between two opponents was simulated and the oxygen consumption of the expected winner and loser was compared. Metabolic rates were not different between winners and losers before and during the fight, but winners showed higher oxygen consumption in the night after the fight. These results are in accordance with costs of display performance and with long-lasting physiological consequences of winning or losing a fight. Aggr. Behav. 32:1–7, 2006. © 2006 Wiley-Liss, Inc.
Threat display in male Siamese fighting fish was studied with respect to two types of water condition: water in which a conspecific had previously performed threat display and water in which conspecifics had been wounded during a pair encounter. No effects were found for either type of water condition when compared with control groups studied in normal water. Differences were noted, however, between the three types of agonistic stimulation used to release threat display: mirror presentation produced a larger amount of display than a conspecific placed behind a glass partition, which in turn elicited more threat than an opponent in an actual fight. Air gulping was correlated with the various threat components measured and appears to be an integral part of agonistic behaviour in this species.
Investigations of communication networks in animals have focused primarily on determining whether animals extract information from peripheral contests (eavesdropping) or respond to the presence of bystanders (audience effect). The possibility that an animal's response to being watched might be context dependent, however, has been explored in far less detail. This study investigated the influence of two contexts, exposure to audiences of different sexes and presence or absence of a nest, on the aggressive behavior of interacting male Siamese fighting fish, Betta splendens. Males interacted in the presence (male, female) or absence of an audience in three different nest conditions (0, 1, or 2 nests). Audience sex and territorial status influenced aggressive behavior in the interacting males, but a strong audience × nest interaction also was uncovered. Males were more aggressive when neither male had a nest and a male audience was present than when a female or no audience was present. Males also were more aggressive when only one male had a nest and a male audience was present than when a female or no audience was present. When both males had nests and a male audience was present, however, males were less aggressive than when only one male or neither male had a nest. In sum, aggressive behavior was influenced by the interaction between audience and nest; neither nest nor audience alone was sufficient to explain the results. Male Siamese fighting fish alter their behavior based on both external cues, the sex of the audience, and internal cues, reproductive state and resource possession. Our results emphasize the importance of considering aspects of an animal's environment when examining audience effects and communication networks in general. Copyright 2005.
A preference for the left-eye use during aggressive interactions has been widely reported in the literature, even though in some cases the direction of lateralization varies among individuals within populations. Laterality of aggression in male Siamese fighting fish has been described in a number of studies, yet very little is known about lateralization of aggression during reproduction and/or parental care in fish. Here, we aimed to investigate the relationship between the different reproductive phases and lateralization in eye use during aggressive interactions in males of Siamese fighting fish. Lateralization in eye use is influenced during the early reproductive state, before and after the bubble nest construction stages. We found that nest-holding males preferentially used the right eye before and after bubble nest construction independent of the sex of the intruder. During the later reproductive phases, aggressiveness increased whereby the direction of lateralization rather than the degree was influenced supporting the hypothesis that reproductive state influences behavioral consistency in Siamese fighting fish.
The increasing presence of aquatic contami-nants, such as the pharmaceutical fluoxetine, has raised concerns over potentially disrupting effects on several aspects of fish reproduction. However, the effects of flu-oxetine on reproductive and paternal behavior in fish remain understudied, particularly at environmentally rele-vant concentrations. In the current study, we therefore tested the hypothesis that waterborne fluoxetine at an environmentally relevant concentration (540 ng/l), disrupts specific reproductive and paternal behaviors in male Sia-mese fighting fish at distinct reproductive phases. A pre-post test design was adopted to investigate specific behavioral responses at the individual fish level in response to male conspecific intruders at two different distances from the nest across four distinct reproductive phases (before bubblenest construction, following bubblenest construction, after spawning and after hatching of the lar-vae). In the control specimens, the measured behaviours were not different between the spawning times and among the interactions in either distance to nest at the different reproduction phases. Our results indicate that fluoxetine specifically disrupts characteristic paternal territorial aggression behaviour only after spawning and hatching of the larvae, while male behaviour in previous reproductive phases is unaffected by fluoxetine exposure. Results of comparison between males at 1st spawning and specimens exposed to fluoxetine at 2nd spawning showed that the first reaction of the nest-holding males to the intruders, duration of fin spreading, number of bites, and 90° turn, and the frequency of sweeps were different between the spawning times after spawning or hatching of embryos. However, interaction of spawning time and reproduction phase was significant on biting behaviour. These results demonstrate that fluoxetine exposure at environmental concentrations negatively affects territorial defense behaviour in fighting fish during parental care after larval hatching, which may have possible implications on reproductive success and population dynamics.
Consistent individual differences in behavior suggest that individuals respond in a predictable and repeatable manner in a specific situation while differing from other individuals. Male Siamese fighting fish exhibit consistent individual differences in decision‐making strategies when they encounter a receptive female and a rival male simultaneously. However, whether these differences are altered by recent experience is unknown. We examined the influence of repeated aggressive encounters on behavioral consistency and decision‐making. Males were presented with paired female–male dummies prior to any aggressive experiences to obtain a baseline measure. Next, males either won or lost three consecutive contests against rivals and then received the paired female–male dummies after each of these encounters. Overall levels of highly aggressive behaviors were affected by contest outcome, while levels of female‐directed were not. Not surprisingly, winning a fight led to an increase in male‐directed bites, an overtly aggressive behavior that only occurs after fights have escalated. Fighting a male before encountering the dummies caused males to perform more tail beats to the dummy male, perhaps as a result of increased motivation. Males exhibited similar levels of repeatability and used the same strategies when faced with conflicting stimuli regardless of fighting experience. Thus, while winning or losing a fight impacts overall aggression, it does not influence behavioral consistency. This study demonstrates that consistent individual differences and decision‐making strategies may be resistant to recent aggressive experiences, even over a period of days.
Communication in the natural environment often involves more than a simple sender-receiver dyad because signals may be detected by more than one individual (i.e. communication occurs in networks). The presence of individuals other than those involved in the signalling interaction has been shown to change signallers' behaviour. Previous experiments have shown that intra-sexual communication of male fighting fish (Betta splendens) is affected by the presence of a female but not by a male conspecific. However the experimental design did not allow the effect of the sex of the audience to be compared. We used an experimental design that allowed direct investigation of the effect of the sex of an audience on male-male fighting fish interactions. Our results show that the sex of a conspecific audience influences male-male aggressive displays. When a male audience was present subjects attempted significantly more bites and spent less time near the opponent than with a female audience. The results of this experiment support the view that the presence and sex of an audience is important in determining how individuals should display during an interaction.
Summary This study examines differences in é ghting strategies between small and large male crayé sh, Orconectes rusticus . Due to allometric growth of claws, é ghting weapons are of dispropor- tionate size in large crayé sh compared to those in smaller individuals. Presumably, such dif- ferences in the prominence of claws are reè ected in differences in the likelihood of injuries, and we thus explored é ghting in size-matched pairs of small or large crayé sh and assessed as- sociated strategies in situations of conè ict. Although é ghting reached the highest intensities in a similar proportion of instances in small and large pairs, differences in é ghting strate- gies were evident. Small crayé sh escalated more rapidly, é ghts were settled more quickly, and were resolved overall at lower intensities. This may be explained by lower risks of in- jury compared to encounters among larger males due to proportionally smaller claws. Larger males thus appear to spend considerably more time in assessing their opponent' s é ghting ability before each escalation event.
We staged contests between convict cichlids (Cichlasoma nigrofasciatum) that were matched for size and gender to test the influence of prior information and resource value on the duration and structure of fights. The contestants were separated before the contest by either clear or opaque dividers to allow or prevent visual assessment, respectively. Contests were shorter in the ''clear'' than in the ''opaque'' treatment, suggesting that visual assessment occurred. The duration of lateral display, a noncontact display, was shorter in the clear than in the opaque treatment, but the treatments did not differ significantly in the duration of three contact displays (biting, mouth wrestling, and circling). These results are consistent with the hypothesis that lateral display provides primarily visual information, probably about body size, whereas the other behavior patterns provide primarily nonvisual information, probably about strength. Second contests between the same pair of fish were shorter than first contests, suggesting that the information acquired during the first contest made it easier to resolve the second. After the subordinate fish from the second contest was given access to a mate, it fought more persistently so that third contests were longer than second contests. Our results support the predictions of the sequential assessment model.
Many fish, including the fighting fish Betta splendens, perform a display in which the opercula are extended away from the head and gills. Previous work has shown that opercular display rates by male B. splendens decrease under conditions of reduced dissolved oxygen (hypoxia). We tested the hypothesis that the ability to maintain opercular display rates under hypoxic conditions is related to body condition in male B. splendens. We also tested the hypothesis that females would show a greater preference for males performing this display under hypoxic conditions, when the display should be a more reliable indicator of male phenotypic quality. We found no evidence to support either hypothesis. Male opercular display rate in hypoxic conditions was unrelated to natural or experimentally induced variation in body condition. Female B. splendens showed no differential preference for the opercular display, assessed through the use of computer animated male stimuli, in either acute or chronic hypoxia. We conclude that the presence of an air-breathing organ in this species makes the opercular display an unreliable signal of male quality as measured by body condition.
1. Dominance/subordinance is a relationship between two individuals in which one defers to the other in contest situations. Each such relationship represents an adaptive compromise for each individual in which the benefits and costs of giving in or not giving in are compared. Familiar associates in groups or neighbours on nearby territories may develop relatively stable dominant‐subordinate relationships based on individual recognition. Although the aggressive aspects of dominance are usually emphasized, the less conspicuous actions of the subordinate individual are actually more important in maintaining a stable relationship.
2. In evolutionary terms, dominance essentially equals priority of access to resources in short supply. Usually the subordinate, who would probably lose in combat anyway, is better off to bide its time until better able to compete at another time or another place. Both individuals save time, energy, and the risk of injury by recognizing and abiding by an established dominant‐subordinate relationship.
3. Dominance can be either absolute or predictably reversible in different locations or at different times. Of the various forms of dominance behaviour, rank hierarchies and territoriality represent the two extremes of absolute and relative dominance, respectively. A dominance hierarchy is the sum total of the adaptive compromises made between individuals in an aggregation or organized group. Many animals seem to be capable of both absolute and relative dominance, and within species‐specific limits the balance may shift toward one or the other. High density, or a decrease in available resources, favours a shift from relative to absolute dominance. Some species may exhibit both simultaneously. Social mammals may have intra‐group hierarchies and reciprocal territoriality between groups, while the males of lek species may exhibit ‘polarized territoriality’ by defending small individual territories, with the most dominant males holding the central territories where most of the mating takes place.
4. Territoriality is a form of space‐related dominance. Most biologists agree that its most important function is to provide the territory holder with an assured supply of critical resources. Territoriality is selected for only when the individual's genetic fitness is increased because its increased access to resources outweighs the time, energy, and injury costs of territorial behaviour.
5. Territoriality was first defined narrowly as an area from which conspecifics are excluded by overt defence or advertisement. The definition has been variously expanded to include all more or less exclusive areas without regard to possible defence, and finally to include all areas in which the owner is dominant. I define territory as a fixed portion of an individual's or group's range in which it has priority of access to one or more critical resources over others who have priority elsewhere or at another time. This priority of access must be achieved through social interaction.
6. My definition excludes dominance over individual space and moving resources, and includes areas of exclusive use maintained by mutual avoidance. It differs from most other definitions in its explicit recognition of time as a territorial parameter and its rejection of exclusivity and overt defence as necessary components of territorial behaviour. There is an indivisible continuum of degrees of trespass onto territories, and functionally it is priority of access to resources that is important rather than exclusive occupancy.
7. There is a similarly indivisible continuum in the intensity of behaviour needed to achieve priority of access to resources. Deciding whether or not an exclusive area is defended leads to the pointless exercise of trying to decide which cues indicating the owner's presence are conspicuous enough to merit being called defence. Concentrating on overt defence emphasizes the aggressive aspects of territorial behaviour rather than the equally or more important submissive aspects such as passive avoidance.
Courtship displays should be exaggerated enough to attract mates and yet tempered so as not to deter them. We tested this hypothesis in the fighting fish Betta splendens by studying courtship displays and body size and their relationships with male parental quality and female fecundity, as well as the effects of display behavior and body size on mate choice decisions and spawning success. Because of their high degree of parental investment, males are expected to be discriminating in their choice of mates. Males who displayed more frequently built larger nests, a measure of parental quality, but larger males did not. When females were paired with males with high display rates, however, the pair had fewer eggs in their nest, even when accounting for female body mass. In a mate choice test using computer-generated male stimuli that differed only in display behavior, females showed no preferences for displaying males vs. non-displaying males, or for males with higher display rates vs. lower display rates. In similar tests in which the computer-generated males differed only in size, females preferred larger males, but also preferred males that differed with respect to body size (negative assortative mating). Males preferred computer-generated females that performed courtship displays over non-displaying females, but showed no preferences for female body size. Neither a female's body size nor her display behavior was a significant predictor of her fecundity as estimated by the number of eggs released during spawning. Thus, our results suggest that female B. splendens must balance male parental quality (nest size) with the risk of potentially disruptive or dangerous behavior during spawning, and that females may minimize these risks through negative size-assortative mating. Female display behavior, while unrelated to fecundity in our study, may attract males because it indicates reproductive readiness or serves a species-recognition function.
The display of 24 individual male Siamese fighting fish to an unresponsive stimulus conspecific was measured, and the fish were then placed together in pairs. For 11 of the 12 pairs, the outcome of the aggressive interaction which ensued was predicted by the gill cover erection durations obtained in the pre-fight isolate tests. The implications of this result for theories of display function are discussed.
We examined the effect of prior winning and losing experiences on the initiating and responding strategies of contestants in contests between individuals of Rivulus marmoratus (Cyprinodontidae). Each contestant was given a penultimate and a recent fighting experience approximately 48 and 24 h prior to the dyadic contests, respectively, through randomly selected procedures. Winning and losing experience appeared to influence different types of fighting behaviours. Losing experiences decreased the probability of an individual initiating a confrontation and thus increased its tendency to retreat immediately when challenged. Winning experiences did not affect the probability of initiation, but significantly increased the likelihood of an individual initiating with attacks that effectively deterred its opponents. A substantial proportion (59/153) of individuals retreated immediately when challenged and reduced the number of fights available for examining experience effects on responding strategies at later stages of a contest. None the less, winning experiences consistently increased the likelihood of an individual retaliating by attacking its opponent at various stages of a contest, and eventually increased its probability of escalating a confrontation into physical fights. However, the effects of losing experiences on these responding strategies were undetectable. Recent experiences significantly affected all fighting behaviours examined, but penultimate experiences significantly affected only the tendency to initiate a confrontation with attacks and the likelihood of escalation. These results indicated that prior experiences had the longest lasting effect on the potentially most costly fighting behaviour. Prior experiences influenced the outcome of nonescalated contests as well as the probability of escalation, but did not significantly affect the outcome of escalated contests. These results are consistent with the hypothesis that prior experiences modify the information that an individual has about its fighting ability but do not alter its actual fighting ability and that actual fighting ability becomes the more important influence on outcomes of escalated contests.
Aggressive signalling interactions contain information that could be used by individuals other than those directly involved in the interaction. We investigated whether the relative information contained in such signalling interactions is used by others in a laboratory setting. Male fighting fish (subjects) were allowed to see three treatments, without themselves being seen. In the control treatment subjects saw two males that were not interacting. In the real interaction treatment the subjects saw two males interacting. In the apparent interaction treatment the two males could appear to the subject to be interacting but were actually interacting with males hidden from the subject's view. After observing a treatment the subject was allowed to interact visually with the two male ‘opponents’ in turn. In both interaction treatments the outcome of the interaction observed by the subject (i.e. whether the opponent won or lost) significantly affected the subject's aggressive response to the opponent, but more strongly in apparent interactions. Subjects responded to opponents that had apparently won with shorter latencies, more time spent near and displaying, more tail beats and attempted bites. No absolute measures of opponents were significantly related to the subjects' responses. Our results suggest that the level of aggression seen by eavesdroppers in interactions affects how they gather and use information.
Arginine vasotocin (AVT) and isotocin (IT) are fish nonapeptides synthesized in separate hypothalamic neurons from where they are transported to the neurohypophysis for storage and release into circulation. AVT is known to modulate aggression, courtship and parental care or social communication in many species, including fish, amphibians and birds. In this paper we examined a link between the level of AVT and IT in the brain and particular reproductive behavior in males of three-spined stickleback (Gasterosteus aculeatus). AVT and IT levels in whole brain of males of three-spined stickleback vary depending on specific breeding behavior of the individuals and their social status. These studies have shown the highest AVT levels in aggressive males that took care of the eggs. Brain AVT concentrations are also increased in nuptial colored subordinate males that fight to change their social status. On the other hand, IT is significantly higher in aggressive dominant males that defend their territory. IT may be also involved in courtship in three-spined stickleback. These findings highlight the importance of determination of "free", bioavailable neuropeptides' level in behavioral studies.
The role of past investment in parental-care behaviour has often been controversial. Some researchers have argued that organisms basing present investment on past investment are committing the 'Concorde fallacy'. Others have incorporated life history theory to suggest that investing according to past investment is one component of investing according to expected future reproductive success: a parent can use past investment as well as other information, such as brood size, to make its optimal parental-investment decisions. Although parental-investment research is still in its infancy, the incorporation of life history theory suggests that the Concorde fallacy is a misleading concept.
Individuals must often decide among a range of behavioral responses in a given situation and individuals will likely vary from one another in the choices they make. A rarely explored example of this is when both a male and a female are present simultaneously and a male must decide to fight or court. Consistent individual differences have been found in decision-making in Siamese fighting fish; however, dummies were used to explore this question and it is possible that individuals respond differently in this situation when faced with live stimuli as a result of feedback. Therefore, this study investigated whether males behave similarly to dummy and live stimuli by exposing them to male and female conspecifics both simultaneously and separately. Subjects were tested first with dummies and then in the same situations using live conspecifics. It was hypothesized that males would respond in the same manner to both the dummy and live fish. The results indicated that individuals behaved similarly to the dummy fish and the live fish in corresponding conditions. In addition, repeatability levels suggest that individuals behaved similarly across trials of a given treatment type while differing from one another in their responses. This study demonstrates that males are consistent in their responses even when receiving feedback from conspecifics and supports the continued use of dummy stimuli as an effective tool.
This study investigated how parental care increases with offspring age by examining the level of male aggressiveness toward potential intruders during egg guarding in a natural population of Siamese fighting fish (Betta splendens Regan). The degree of aggressiveness was measured at two reproductive phases in response to three types of intruders: male, female and females that have laid eggs. The nest-holding males became more aggressive after their eggs hatched than after the eggs were laid. Nest-holding males displayed gill cover erection, biting, tail beating and attacking at the highest rate towards male intruders, intermediate towards female intruders and the least aggressive towards females, which have laid eggs.
Behavioural syndromes are correlations between behaviours in different functional contexts. Behavioural syndromes are attracting the attention of evolutionary biologists because they mean that different behaviours might not be free to evolve independently of one another. In a landmark study, Huntingford (1976) showed that individual stickleback which were bold toward predators were also aggressive toward conspecifics and active in an unfamiliar environment. Here, I revisited the activity-aggression-boldness syndrome in stickleback and tested the hypothesis that correlations between behaviours might act as evolutionary constraints. I measured a suite of behaviours on wild-caught individuals and their offspring from two different populations and calculated heritabilities and genetic correlations between the different behaviours. I found that these behaviours were phenotypically and genetically correlated in one population but not another. On average, boldness and aggression were negatively related to each other across the populations. These results suggest that behavioural syndromes don't always act as evolutionary constraints.
This study investigated the effects of nesting status and the presence of an audience on 11-ketotestosterone (11KT) levels in male Siamese fighting fish, Betta splendens. Prior studies have demonstrated that both nesting status, an indicator of territory-holding power and reproductive state, and the sex of a conspecific audience lead to differences in male behavior during aggressive encounters. Since behavioral changes have already been demonstrated, we chose to investigate whether 11KT levels were also influenced by nesting status and audience presence as 11KT both stimulates, and is stimulated by, reproductive and aggressive behaviors in male teleosts. Male 11KT levels were measured from water samples taken from containers holding fish both before and after interaction. Males interacted under three treatment conditions: no audience, female audience, and male audience. Within these treatments were two nest paradigms: both males had nests or neither male had a nest. 11KT levels varied depending on nesting status and audience type. In general, 11KT levels were lower in interacting males when a female audience was present or when males had nests. Overall, 11KT showed increases or decreases as aggression increased or decreased, as shown by already established behavioral findings [see Dzieweczynski T.L., Green T.M., Earley R.L., Rowland W.J., 2005. Audience effect is context dependent in Siamese fighting fish, Betta splendens. Behav. Ecol. 16, 1025-1030; Doutrelant, C., McGregor, P.K., Oliveira, R.F., 2001. Effect of an audience on intrasexual communication in male Siamese fighting fish (Betta splendens). Behav. Ecol. 12, 283-286.]. Our results suggest that 11KT levels are influenced by reproductive status, as indicated by nest ownership, and audience presence and are most likely modulated by territorial behavior and social environment.
We examined the influence of sex, line, i.e., broods from different parents, and previous fight experience on the aggressiveness of the Siamese fighting fish Betta splendens in intrasexual competition. The innate aggressiveness of the fish against their mirror images was measured on the day prior to the direct fight with other individuals, and it was found to be influenced by the line type but not by the sex. In the direct fight with other individuals, the males invested more effort in the fight than the females. In addition, the individuals of a particular line that exhibited a lower innate aggressiveness spent less time in the direct fight and were often losers when compared with those of other lines. After the direct fight with other individuals, the aggressiveness of the fish against their mirror images was remarkably influenced by the outcome of the direct fight, i.e., the winners exhibited more aggressive behavior, whereas the losers exhibited a lesser degree of aggressive behavior. This influence of the previous fight experience on subsequent aggressiveness was the greatest in the individuals of the line that have exhibited the lowest innate aggressiveness. However, the positive effect of the winning experience or the negative effect of the losing experience on subsequent aggressiveness decreased following several days after the previous fight increased.
Change in reproductive behavior of fighting fish, Betta splendens by fluoxetine exposure
- M N Forsatkar
Forsatkar MN (2012) Change in reproductive behavior of fighting
fish, Betta splendens by fluoxetine exposure. Master's thesis,
University of Tehran. (in Persian)