Astatotilapia burtoni | |
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Two males dispute a territorial boundary. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cichliformes |
Family: | Cichlidae |
Genus: | Astatotilapia |
Species: | A. burtoni |
Binomial name | |
Astatotilapia burtoni (Günther, 1894) | |
Synonyms | |
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Astatotilapia burtoni is a species of fish in the family Cichlidae.
It is found in Lake Tanganyika and its surrounding waterways, [2] including parts of Burundi, Rwanda, Tanzania, and Zambia.
Its natural habitats are rivers, intermittent rivers, swamps, freshwater lakes, freshwater marshes, intermittent freshwater marshes, and inland deltas.
Astatotilapia burtoni has been used as a model organism to study the behaviors and physical systems of cichlids, including their development and embryogenesis. [3] Moreover, the phylogenetic position of this particular species makes it an ideal model system for comparative genomic research. A. burtoni belongs under the haplochromines, which is the lineage of cichlids with the most species, and has been discovered to be a sister group to both the Lake Victoria region superflock (which has about 600 species) and the species flock of Lake Malawi (which has about 1,000 species). [4]
The males of the Astatotilapia burtoni come in two phenotypes that are reversible. The males can readily switch between being territorial and non-territorial based on the social environment they are in: dominant, territorial males possess bright coloration, aggressive behavior while defending territory, and an active role in sexually reproducing with the females; subordinate and non-territorial males possess coloration similar that of the females, lack initiative to pursue female counterparts, and are reproductively suppressed due to regressed gonads. [5] The transitions between different social roles cause several changes in the brain and reproductive system, such that the social transformation affects them both behaviorally and physically. [6]
To expand on reversibility, if a territorial male is placed with an individual that is significantly larger in size, it will then rapidly socially transform into the non-territorial type. This change can be detected by the behavior and alternate coloration that follows. The change in reproductive competence, however, occurs about three weeks after the formerly territorial male loses its territory to the larger fish. [7] In regards to the other social transition, when a non-territorial male becomes the territorial type, it will almost immediately exhibit aggressive behavior and an eyebar, [8] while the physiological changes will follow in about one week. [7]
Several studies have been done in order to pinpoint the biological basis on which this reversal occurs, and they suggest that the stress hormone cortisol may have a direct role in social status, because cortisol may change the biological priorities of the cichlid's system. [9] Under chronic stress, the animal may experience reproductive regression (as shown in the territorial's male shift to the non-territorial type) as a result of the body's efforts to combat the stressor, as opposed to using the metabolic energy for long-term goals like reproduction. [10] Moreover, studies have also shown that the male cichlid's social phenotype directly influences the hormone levels of testosterone and 11-ketotestosterone. Plasma concentrations of these androgens in both the territorial males and non-territorial males were measured and assessed, and it was found that the territorial males have drastically higher plasma concentrations of both hormones. [11]
The cichlid males' behavior of shifting between dominant and subordinate states as a result of the social environment can also be related to females in their vicinity, for females may alternate between reproductive states as well, but independently of social conditions. Females use a complex integration of cues in order to make their mate preferences, which may be from genetic factors, learned behaviors, or hormone levels. They can socially transform between a gravid reproductive state, which is egg-bearing, and a non-gravid reproductive state, and it was shown in a study that the mating preferences of the female highly depended on the reproductive state in which the female was in. Gravid female cichlids will prefer to spend time with the dominant male type instead of the subordinate male type, whereas the non-gravid females do not have a preference for either one. This may be explained by the fact that because for spawning to occur, the gravid females must be courted by the dominant males, suggesting that gravid females' preference for dominant males is a behavioral priming mechanism. [12]
Astatotilapia burtoni, like Oreochromis mossambicus , is a lekking species, so the dominant males will have male displays of courtship in order to attract and lure females that are passing by. Studies have revealed that a male's dorsal fin's color plays a crucial role in attracting females, and that the neural activity in the ventral telencephalon area of the brain is correlated with female preference for males with more vibrant dorsal fins. [13] The behavior starts with the male attempting to catch the female's attention by displaying his side to the female while quivering his body. The males then increase urination rates towards gravid females, which send unidentified pheromones to stimulate ovulation. [14] [15] The male will then try to lead the female back to a spawning site, and if she follows and thus is ready to spawn she will peck at egg-shaped spots on the male's anal fin as he quivers again. The female will then lay her eggs, collect them in her mouth, then peck at the egg spots on the male. The male releases sperm and fertilizes the eggs in the female's mouth. This pecking and fertilizing behavior repeats until the female is done laying eggs. [16]
Once the females are enticed and enter the male's territory to spawn, after spawning, the females will rear the young in their mouths, a behavior called mouthbrooding. [17] After about two weeks of incubation have passed, the females will release their young. However, exposure to excess noise during maternal mouthbrooding can cause cannibalization or premature release of the brood. [18] Following brood release, after several more weeks have passed, the female cichlids will have recovered physiologically enough to be able to spawn again. [6]
Maternal mouthbrooding is recognized to affect hormones and reproductive cycles for the female cichlids, but the effects as a result of neural processing and food deprivation are not known. A study particularly focused on this subject matter examined the effects that maternal mouthbrooding may have on a wide variety of physiological practices, in order to see if they are consequences of food deprivation, and indeed it was found that many of the changes (not all) are explained by food deprivation. [19]
Many animals use multimodal communication, having multiple sensory modalities at their disposal for reproductive interactions, and the Astatotilapia burtoni has been used as a model to study the production of the wide variety sexual signal types. A. burtoni incorporate multiple sensory systems, including chemosensory, visual, acoustic, to be able to socially interact in their complex manner. [6]
East African cichlids, in general, are especially known for their vibrantly colored bodies and the role that coloration plays in courting and mating, but the A. burtoni is known to be phenotypically distinct in its use of a completely different form of sensory communication: acoustic communication. Sounds and the corresponding behaviors of the male sex of these particular African cichlids have been studied while observing the female mate preference, and behavioral experiments demonstrated that acoustic information does indeed play a significant role in sexual reproduction. This reliance on non-visual sensory information in order to coordinate complex social behaviors indicates that acoustic signaling is important for the A. burtoni. This suggests that there are internal cues in these cichlid fish that can significantly change the way in which the fish respond to auditory signals because the physiological state of the fish can directly affect the perception of the auditory signals. Thus, more efforts have been made to understand how the females perform sexual selection by closely examining the signaling systems and how they relate to the neural processing in the fish to result in such behaviors. [6]
A particular study showed that dominant males will issue auditory signals in order to court females, and that these courtship sounds are similar to those that they themselves could perceive. The study found that the broadband sounds that the dominant males produced were associated with body quivers, suggesting that the sounds were produced intentionally for courting and not a by-product of the quivers, as not all the quivers were accompanied by sounds. The data also suggested that auditory perception of A. burtoni changes in accordance with the reproductive cycle of the fish. This may be potentially due to levels of circulating hormones. [6] Intra- and inter-sexual social communications in males can also be affected by underwater noise exposure. [20] Noise exposure was even found to change when and how males produced courtship behaviors, such as producing mating calls by quivering inside their spawning shelters instead of near a female. This behavioral change likely decreases the chance of females hearing male mating calls.
Cichlids are fish from the family Cichlidae in the order Cichliformes. Traditionally Cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Argentina during the Early Eocene epoch, about 48.6 million years ago; however, molecular clock estimates have placed the family's origin as far back as 67 million years ago, during the late Cretaceous period. The closest living relative of cichlids is probably the convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. This family is large, diverse, and widely dispersed. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.
Mouthbrooding, also known as oral incubation and buccal incubation, is the care given by some groups of animals to their offspring by holding them in the mouth of the parent for extended periods of time. Although mouthbrooding is performed by a variety of different animals, such as the Darwin's frog, fish are by far the most diverse mouthbrooders. Mouthbrooding has evolved independently in several different families of fish.
In evolutionary biology, sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap so that they occur together at least in some places. If these organisms are closely related, such a distribution may be the result of sympatric speciation. Etymologically, sympatry is derived from Greek συν (sun-) 'together' and πατρίς (patrís) 'fatherland'. The term was coined by Edward Bagnall Poulton in 1904, who explains the derivation.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and released from GnRH neurons within the hypothalamus. The peptide belongs to gonadotropin-releasing hormone family. It constitutes the initial step in the hypothalamic–pituitary–gonadal axis.
In the zoological field of ethology, a dominance hierarchy is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is sometimes called an alpha, and a submissive lower-ranking individual is called a beta. Different types of interactions can result in dominance depending on the species, including ritualized displays of aggression or direct physical violence. In social living groups, members are likely to compete for access to limited resources and mating opportunities. Rather than fighting each time they meet, individuals of the same sex establish a relative rank, with higher-ranking individuals often gaining more access to resources and mates. Based on repetitive interactions, a social order is created that is subject to change each time a dominant animal is challenged by a subordinate one.
Mbuna is the common name for a large group of African cichlids from Lake Malawi, and are members of the haplochromine family. The name mbuna means "rockfish" in the language of the Tonga people of Malawi. As the name implies, most mbuna are cichlids that live among the piles of rocks and along the rocky shores of Lake Malawi, as opposed to the utaka, cichlids that live in the open water or on sandy shores or soft substrates. Some species of mbuna are highly sexually dimorphic, although many are not. Almost all of the cichlid species of Lake Malawi, including mbuna and non mbuna such as the utaka, are believed to have descended from one or a very few species that became isolated in the lake. With rising water levels, new habitats could be colonized and the many isolated rocky outcrops allowed new mbuna species to form. Their striking colors, intriguing behavioral characteristics, and relative hardiness make them very popular despite their unique demands for the home aquarist.
Thalassoma bifasciatum, the bluehead, bluehead wrasse or blue-headed wrasse, is a species of marine ray-finned fish, a wrasse from the family Labridae. It is native to the coral reefs of the tropical waters of the western Atlantic Ocean. Individuals are small and rarely live longer than two years. They form large schools over the reef and are important cleaner fish in the reefs they inhabit.
Tropheus moorii is a species of cichlid endemic to Lake Tanganyika in Africa. Over 40 different color morphs of this species are dispersed throughout the lake, ranging from dark green to flame red and yellow. They mostly feed on filamentous algae on the rocky shallows they inhabit. T. moorii is a maternal mouthbrooder, so eggs are fertilized and young are carried in the mouth of the female while they hatch and develop.
In biology, a pair bond is the strong affinity that develops in some species between a mating pair, often leading to the production and rearing of young and potentially a lifelong bond. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary biology circles. The term often implies either a lifelong socially monogamous relationship or a stage of mating interaction in socially monogamous species. It is sometimes used in reference to human relationships.
The Nile tilapia is a species of tilapia, a cichlid fish native to parts of Africa and the Levant, particularly Israel and Lebanon. Numerous introduced populations exist outside its natural range. It is also commercially known as mango fish, nilotica, or boulti.
Reproductive synchrony is a term used in evolutionary biology and behavioral ecology. Reproductive synchrony—sometimes termed "ovulatory synchrony"—may manifest itself as "breeding seasonality". Where females undergo regular menstruation, "menstrual synchrony" is another possible term.
Vasotocin is an oligopeptide homologous to oxytocin and vasopressin found in all non-mammalian vertebrates and possibly in mammals during the fetal stage of development. Arginine vasotocin (AVT), a hormone produced by neurosecretory cells within the posterior pituitary gland (neurohypophysis) of the brain, is a major endocrine regulator of water balance and osmotic homoeostasis and is involved in social and sexual behavior in non-mammalian vertebrates. In mammals, it appears to have biological properties similar to those of oxytocin and vasopressin. It has been found to have effects on the regulation of REM sleep. Evidence for the existence of endogenous vasotocin in mammals is limited and no mammalian gene encoding vasotocin has been confirmed.
The haplochromine cichlids are a tribe of cichlids in subfamily Pseudocrenilabrinae called Haplochromini. This group includes the type genus (Haplochromis) plus a number of closely related genera such as Aulonocara, Astatotilapia, and Chilotilapia. They are endemic to eastern, southern and northern Africa, except for Astatotilapia flaviijosephi in the Middle East. A common name in a scientific context is East African cichlids – while they are not restricted to that region, they are the dominant Cichlidae there. This tribe was extensively studied by Ethelwynn Trewavas, who made major reviews in 1935 and 1989, at the beginning and at the end of her career in ichthyology. Even today, numerous new species are being described each year.
The Mozambique tilapia is an oreochromine cichlid fish native to southeastern Africa. Dull colored, the Mozambique tilapia often lives up to a decade in its native habitats. It is a popular fish for aquaculture. Due to human introductions, it is now found in many tropical and subtropical habitats around the globe, where it can become an invasive species because of its robust nature. These same features make it a good species for aquaculture because it readily adapts to new situations. It is known as black tilapia in Colombia and as blue kurper in South Africa.
Neolamprologus pulcher is a species of cichlid endemic to Lake Tanganyika where it prefers locations with plenty of sedimentation. The common names for N. pulcher include daffodil cichlid, fairy cichlid, princess of Zambia and lyretail cichlid. This species can reach a length of 10 centimetres (3.9 in) TL. It can also be found in the aquarium trade.
Russell D. Fernald is an American neuroscientist/neuroethologist, currently on the Biology faculty at Stanford University. Fernald is known for his interdisciplinary work based on fieldwork and subsequent neuroethological analysis of an African cichlid fish that he has shown to be a useful and novel model organism. His research spans several domains: 1) in the visual system including the discovery of rod photoreceptor stem cells, circadian renewal of photoreceptor opsins and mechanisms of crystalline lens focus ; 2) In social control of reproductive behavior: social regulation of reproduction via gonadotropin releasing hormones through specific brain circuitry; 3) Cognitive skills that have evolved to regulate social status.
Ritualized aggression or ritualized fighting is when animals use a range of behaviours as posture or warning but without engaging in serious aggression or fighting, which would be expensive in terms of energy and the risk of injury. Ritualized aggression involves a graded series of behaviours or displays that include threatening gestures and occasionally posturing physical actions such as inhibited (non-injurious) bites.
Vertebrate maternal behavior is a form of parental care that is specifically given to young animals by their mother in order to ensure the survival of the young. Parental care is a form of altruism, which means that the behaviors involved often require a sacrifice that could put their own survival at risk. This encompasses behaviors that aid in the evolutionary success of the offspring and parental investment, which is a measure of expenditure exerted by the parent in an attempt to provide evolutionary benefits to the offspring. Therefore, it is a measure of the benefits versus costs of engaging in the parental behaviors. Behaviors commonly exhibited by the maternal parent include feeding, either by lactating or gathering food, grooming young, and keeping the young warm. Another important aspect of parental care is whether the care is provided to the offspring by each parent in a relatively equal manner, or whether it is provided predominantly or entirely by one parent. There are several species that exhibit biparental care, where behaviors and/or investment in the offspring is divided equally amongst the parents. This parenting strategy is common in birds. However, even in species who exhibit biparental care, the maternal role is essential since the females are responsible for the incubation and/or delivery of the young.