| 1. |
- Amcoff, Mirjam, et al.
(author)
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A test of sensory exploitation in the swordtail characin (Corynopoma riisei) based on colour matchingbetween female prey and a male ornament
- 2014
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 97:3, s. 247-254
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Journal article (peer-reviewed)abstract
- The sensory exploitation hypothesis states that pre-existing biases in female sensory systems may generate strong selection on male signals to match such biases. As environmental conditions differ between populations, sexual preferences resulting from natural selection are expected to vary as well. The swordtail characin (Corynopoma riisei) is a species in which males carry a flag-like ornament growing from the operculum that has been proposed to function as a prey mimic to attract females. Here, we investigated if female plasticity in feeding preferences is associated with plasticity in preference for an artificial male ornament in this species. Females were trained for 10 days by offering them differently coloured food items and were then tested for changes in preferences for differently coloured artificial male ornaments according to foraging experience. We found a rapid and pronounced change in female preference for the colouration of the artificial ornament according to food training. Thus our results support the possibility that sensory exploitation may act as a driving force for female preferences for male ornaments in this species.
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| 2. |
- Amcoff, Mirjam, et al.
(author)
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Courtship signalling with a labile bilateral signal : males show their best side
- 2009
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In: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 63:12, s. 1717-1725
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Journal article (peer-reviewed)abstract
- Asymmetries in courtship signals can result from both developmental instability during ontogeny and from temporary or permanent damage following mating, fighting, or interactions with predators. These two types of asymmetries, which can be divided into fluctuating asymmetry (FA) and damage asymmetry (DA), have both been suggested to play an important role in mate choice as potential honest indicators of phenotypic and/or genetic quality, while at the same time, DA may affect ornament asymmetry in a random manner. Interestingly, despite the massive research effort that has been devoted to the study of asymmetry during the past decades, very little is known about how an individual's behaviour relates to asymmetry. Here, we measure and characterise asymmetry in morphological courtship signals in Corynopoma riisei, a fish where males carry elaborate paddle-like appendices on each side of the body that they display in front of females during courtship. Moreover, we investigate whether male courtship display, employing this bilateral morphological trait, reflects trait asymmetry. Finally, we assess whether males respond to phenotypic manipulations of DA with corresponding changes in courtship behaviour. We show that male display behaviour is asymmetric in a manner that reflects asymmetry of their morphological courtship trait and that male display behaviour responds to manipulations of asymmetry of these paddles. Our results thus suggest that males preferentially use their best side and, hence, that males respond adaptively to temporary changes in signal trait asymmetry.
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| 3. |
- Amcoff, Mirjam, et al.
(author)
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Does female feeding motivation affect the response to a food-mimicking male ornament in the swordtail characin Corynopoma riisei?
- 2013
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In: Journal of Fish Biology. - : Wiley. - 0022-1112 .- 1095-8649. ; 83:2, s. 343-354
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Journal article (peer-reviewed)abstract
- Female response to various aspects of male trait morphology and the effect of female feeding motivation were investigated in the swordtail characin Corynopoma riisei, a species where males are equipped with a flag-like food-mimicking ornament that grows from the operculum. Unfed females responded more strongly to the male ornament and showed a stronger preference for larger ornaments than did fed females. Females were shown not to discriminate between artificial male ornaments of either undamaged or damaged shape.
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| 4. |
- Amcoff, Mirjam, et al.
(author)
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Evolution of egg dummies in Tanganyikan cichlid fishes : the roles of parental care and sexual selection
- 2013
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In: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 26:11, s. 2369-2382
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Research review (peer-reviewed)abstract
- Sexual selection has been suggested to be an important driver of speciation in cichlid fishes of the Great Lakes of Africa, and the presence of male egg dummies is proposed to have played a key role. Here, we investigate how mouthbrooding and egg dummies have evolved in Tanganyikan cichlids, the lineage which seeded the other African radiations, with a special emphasis on the egg dummies. Using modern phylogenetic comparative analyses and a phylogeny including 86% of the 200 described species, we provide formal evidence demonstrating correlated evolution between mouthbrooding and egg dummies in Tanganyikan cichlids. These results concur with existing evidence, suggesting that egg dummies have evolved through sensory exploitation. We also demonstrate that there is a strong evolutionary correlation between the presence of egg dummies and both pre- and post-copulatory sexual selection. Moreover, egg dummy evolution was contingent on the intensity of pre- and post-copulatory sexual selection in Tanganyikan cichlids. In sum, our results provide evidence supporting the hypothesis of egg dummies evolving through sensory exploitation and highlight the role of sexual selection in favouring the evolution and maintenance of this trait.
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| 5. |
- Amcoff, Mirjam, 1983-
(author)
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Fishing for Females : Sensory Exploitation in the Swordtail Characin
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Mate choice plays an important role in sexual selection and speciation. The evolution of mate choice is intriguing in cases where choosy individuals gain little except for genetic material from the mate and where the trait used as a criterion for the choice is costly to its bearer. The sensory exploitation hypothesis is an interesting idea that applies to such cases because it suggests that sexual preferences may arise as side-effects of preferences that are under selection in other contexts. The role of mate choice in speciation is strong but is debated because the reasons for population divergence in mate preferences and sexual traits are sometimes hard to explain. Also in this context sensory exploitation offers a potential explanation in that a link between natural and sexual selection may result in divergence in sexual selection whenever populations differ in natural selection.In this thesis, I test several aspects of this hypothesis in a species of fish, the swordtail characin (Corynopoma riisei). In this species males display a flag-like ornament that grows from the operculum. Because females respond to this ornament by biting at it, it has been proposed to act as a food-mimic. By manipulating female food type and quantity, and testing the resulting female preference for the male ornament, I find support for the theory that the preference has evolved through sensory exploitation and that females indeed appear to relate the ornament to a food item. Furthermore, I show that sensory exploitation can lead to morphological divergence among natural populations in this species. Apart from the flag-ornament, other courtship signals are also investigated. The results show that the relative importance of different signals may vary depending on receiver motivation. This suggests that various aspects of both male courtship signals and the conditions during which they are being signalled should be considered to gain a full understanding of mate choice and its role in sexual selection and speciation.
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| 6. |
- Amcoff, Mirjam, et al.
(author)
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Male Courtship Pheromones Affect Female Behaviour in the Swordtail Characin ( Corynopoma riisei)
- 2014
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In: Ethology. - : Wiley. - 0179-1613 .- 1439-0310. ; 120:5, s. 463-470
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Journal article (peer-reviewed)abstract
- Pheromones constitute an important cue used by both males and females during courtship. Here, we investigate the effect of male pheromones on female behaviour in the swordtail characin (Corynopoma riisei), a species of fish where males have a caudal pheromone gland which has been suggested to affect female behaviour during courtship. We subjected female C.riisei to male courtship pheromones and investigated the effect on both female behaviour and brain serotonergic activity levels compared to a control group. While no difference in serotonergic activity was found, the pheromone-treated females showed lower stress levels compared to the control group. Furthermore, pheromone-treated females increased locomotor activity over time, while a decrease in locomotor activity was observed in the control group. These results suggest that the male courtship pheromones may serve to reduce female stress and increase female activity, possibly to aid males in gaining access to females and facilitating sperm transfer.
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| 7. |
- Amcoff, Mirjam, et al.
(author)
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Multiple male sexual signals and female responsiveness in the swordtail characin, Corynopoma riisei
- 2015
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In: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 98:7, s. 1731-1740
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Journal article (peer-reviewed)abstract
- In the courtship process, multiple signals are often used between the signaller and the receiver. Here we describe female response to multiple male visual morphological and behavioural signals in the swordtail characin, Corynopoma riisei. The swordtail characin is a species in which males display several morphological ornaments as well as a rich courtship repertoire. Our results show that high courtship intensity was associated with an increased female response towards the male ornament, increased number of mating attempts and a reduction in female aggression. The morphological aspects investigated here did not seem to correlate with female response. This may indicate that, when both behaviour and morphology are considered simultaneously, courtship behaviour may have priority over morphological cues in this species.
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| 8. |
- Amcoff, Mirjam, et al.
(author)
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Sensory exploitation and plasticity in female mate choice in the swordtail characin
- 2013
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In: Animal Behaviour. - : Elsevier BV. - 0003-3472 .- 1095-8282. ; 85:5, s. 891-898
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Journal article (peer-reviewed)abstract
- Despite extensive research in the field of sexual selection, the evolutionary origin and maintenance of preferences for sexual ornaments are still debated. Recent studies have pointed out that plasticity in mate choice might be more common than previously thought, but little is still known about the factors that affect such plasticity. The swordtail characin, Corynopoma riisei, is a tropical fish species in which males use a food-mimicking ornament to attract females. We tested whether ecological factors, more specifically prior foraging experience, can affect female preference for male ornaments. For this, we habituated females on a diet consisting of either red-coloured food or standard-coloured green food items and then we tested whether female preferences for artificially red-coloured male ornaments matched their previous foraging experience. We found a strong effect of food treatment: females trained on red food showed a stronger response to males with red-coloured ornaments than females trained on green food. Our results show that ecological variation can generate divergence of female preferences for male ornaments and that the response in preference to environmental change can be rapid if the bias is partly learnt.
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| 9. |
- Boussard, Annika, et al.
(author)
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Brain size does not predict learning strategies in a serial reversal learning test
- 2020
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:15
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Journal article (peer-reviewed)abstract
- Reversal learning assays are commonly used across a wide range of taxa to investigate associative learning and behavioural flexibility. In serial reversal learning, the reward contingency in a binary discrimination is reversed multiple times. Performance during serial reversal learning varies greatly at the interspecific level, as some animals adopt a rule-based strategy that enables them to switch quickly between reward contingencies. A larger relative brain size, generating enhanced learning ability and increased behavioural flexibility, has been proposed to be an important factor underlying this variation. Here, we experimentally tested this hypothesis at the intraspecific level. We used guppies (Poecilia reticulata) artificially selected for small and large relative brain size, with matching differences in neuron number, in a serial reversal learning assay. We tested 96 individuals over 10 serial reversals and found that learning performance and memory were predicted by brain size, whereas differences in efficient learning strategies were not. We conclude that variation in brain size and neuron number is important for variation in learning performance and memory, but these differences are not great enough to cause the larger differences in efficient learning strategies observed at higher taxonomic levels.
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| 10. |
- Boussard, Annika, et al.
(author)
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The link between relative brain size and cognitive ageing in female guppies (Poecilia reticulata) artificially selected for variation in brain size
- 2021
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In: Experimental Gerontology. - : Elsevier BV. - 0531-5565 .- 1873-6815. ; 146
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Journal article (peer-reviewed)abstract
- Cognitive ageing is the general process when certain mental skills gradually deteriorate with age. Across species, there is a pattern of a slower brain structure degradation rate in large-brained species. Hence, having a larger brain might buffer the impact of cognitive ageing and positively affect survival at older age. However, few studies have investigated the link between relative brain size and cognitive ageing at the intraspecific level. In particular, experimental data on how brain size affects brain function also into higher age is largely missing. We used 288 female guppies (Poecilia reticulata), artificially selected for large and small relative brain size, to investigate variation in colour discrimination and behavioural flexibility, at 4-6, 12 and 24 months of age. These ages are particularly interesting since they cover the life span from sexual maturation until maximal life length under natural conditions. We found no evidence for a slower cognitive ageing rate in large-brained females in neither initial colour discrimination nor reversal learning. Behavioural flexibility was predicted by large relative brain size in the youngest group, but the effect of brain size disappeared with increasing age. This result suggests that cognitive ageing rate is faster in large-brained female guppies, potentially due to the faster ageing and shorter lifespan in the large-brained selection lines. It also means that cognition levels align across different brain sizes with older age. We conclude that there are cognitive consequences of ageing that vary with relative brain size in advanced learning abilities, whereas fundamental aspects of learning can be maintained throughout the ecologically relevant life span.
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