Biology subjects

Solomon-Lane, T. K.

Publications and source records attributed to Solomon-Lane, T. K..

6 recordsLinked to original sources

bioRxiv2025

Background color matching influences sexual behavior, growth, and mortality rate in an African cichlid fish

Phenotypic plasticity allows organisms to adapt to changing environments within their lifetimes. The cost of plastic adaptations may constrain the persistence of plasticity over evolutionary time. One potential cost is the possibility that phenotypic adjustment to specific environments can cause correlated responses that are not necessarily adaptive. Males in the African cichlid Astatotilapia burtoni are blue or yellow, and males are able adjust their body coloration to the color of the background, presumably to increase crypsis. To test whether background color influences fitness-related traits, we raised mix-sex groups of juvenile A. burtoni to adulthood in yellow or blue tanks. We found that fish in blue tanks were darker and more bluish, whereas fish reared in yellow tanks were paler and more yellow in body coloration. Males, but not females, from blue tanks showed earlier sexual maturation than those held in yellow tanks. However, across the duration of the experiment, there was a higher frequency of females mouthbrooding in groups housed in yellow tanks than those that were housed in blue tanks. In addition, fish in blue tanks exhibited reduced growth rate but higher survivorship relative to their yellow-reared counterparts. Our data suggests that background color affects important fitness-related traits in a color polymorphic cichlid, which may influence the evolution of phenotypic plasticity.

animal behavior and cognition↗

bioRxiv2024

Early Life Behavior Phenotypes and Cortisol Responses to Common Lab Stressors in a Cichlid Fish

The stress response is highly conserved across species, and increased glucocorticoid release (cortisol in fishes) is a key element. In the highly social cichlid fish, Burtons Mouthbrooder (Astatotilapia burtoni), stress axis activity is associated with juvenile social behavior and status, and it mediates early-life social effects, yet little is known about early-life stress physiology. We measured water-borne cortisol, a non-invasive method, in juveniles less than 1-week old. We first tested whether juveniles habituate to the beaker confinement necessary for sample collection. Repeated exposure to a beaker did not affect cortisol compared to handled and unhandled controls. In a separate cohort, we next measured behavior in an open field exploration and social cue investigation, followed by a test of whether common lab stressors elevated cortisol. Controls were undisturbed in a collection beaker (90 min). For the stressor treatments, we collected three sequential samples (30 min each) to try and quantify stress response peak and recovery; however, we found no effect of time. Stressors included handling, brief net confinement, and brief gentle movement. These stressors led to a significant increase in cortisol, with the highest levels resulting from confinement. The behavior tests revealed a bold-shy axis across both tests, describing the behavior of most individuals. A distinct group of socially-motivated juveniles showed a dramatic switch, staying in the territory during the open field but leaving to investigate the social cue. We found no associations between behavior and cortisol response. This work provides insight into early-life behavior and stress axis development and function. HighlightsO_LIAstatotilapia burtoni under 1-week old did not habituate to beaker confinement C_LIO_LIYoung juveniles displayed bold/shy or socially-motivated behavior phenotypes C_LIO_LICortisol increased in response to lab stressors: handling, confinement, and movement C_LIO_LIIndividual variation in cortisol establishes an expected hormone range for this age C_LIO_LIJuvenile cortisol did not correlate with behavior or differ by behavior phenotype C_LI

physiology↗

bioRxiv2023

Multiple behavioral mechanisms shape social behavioral development in a highly social cichlid fish

Early-life social experiences shape adult phenotype, yet the underlying behavioural mechanisms remain poorly understood. We manipulated early-life social experience in the highly social African cichlid fish Astatotilapia burtoni to investigate the effects on behaviour and neuroendocrine stress axis function. Juveniles experienced different numbers of early-life social partners in stable pairs (1 partner), stable groups (6 fish; 5 partners), and socialized pairs (a novel fish was exchanged every 5 days; 5 partners). Treatments differed in group size (groups vs. pairs) and stability (stable vs. socialized). We then measured behaviour in multiple contexts and collected water-borne cortisol. We found effects of treatment on behaviour across all assays: open field exploration, social cue investigation, dominant behaviour, and subordinate behaviour. Cortisol did not differ across treatments. Principal components (PC) analysis revealed robust co- variation of behaviour across contexts, including with cortisol, to form behavioural syndromes sensitive to early-life social experience. PC1 (25.1%) differed by numbers of social partners: juveniles with more social partners were more active during the social cue investigation, spent less time in the territory, and were more interactive as dominants. Differences in PC5 (8.5%) were based on stability: socialized pairs were more dominant, spent less time in and around the territory, were more socially investigative, and had lower cortisol than stable groups or pairs. Behaviour observations in the home tanks provided further insights into the behavioural mechanisms underlying these effects. These results contribute to our understanding of how early- life social experiences are accrued and exert strong, lasting effects on adult phenotype.

animal behavior and cognition↗

bioRxiv2018

A simple egg marking method for polygynous fishes

Fitness is the ultimate measure of organismal function; however, technical challenges can limit researchers ability to quantify fitness. We developed a simple and inexpensive method of marking eggs inside of the ovary of a nesting fish, the bluebanded goby (Lythrypnus dalli), in order to quantify female reproductive success. Multiple females in a harem of L. dalli can lay eggs inside of the males nest within a short period of time, making the timing of egg laying or developmental stage of the eggs insufficient to identify which female laid which clutch of eggs. After injecting small volumes of food coloring into the ovaries, each females eggs can be identified throughout development by the color of the yolk. We make preliminary observations about the efficacy of different colors (red, yellow, green, blue) for use in L. dalli, including effects on female survival, social behavior, and the enzyme immunoassays used to quantify hormones. While rigorous validations should be conducted for each species and experimental context, this method of marking eggs has the potential to be broadly useful for directly estimating fitness in species with external fertilization, as well as research in reproductive biology, development, behavioral ecology, and evolution.

physiology↗

bioRxiv2018

A tagging method for very small fish

Identifying individuals over time and across contexts is essential in many scientific fields. There are a variety of well-established methods for uniquely marking individuals (e.g., visible implant elastomer, barcodes, paint). However, for some species, life history stages, and/or experiments, existing methods are not sufficient. Here, we describe procedures for how two tagging methods - a tattoo ink injection method and a fishing line piercing method - can be used with the youngest, smallest juveniles of the African cichlid fish, Astatotilapia burtoni, which are too small for the methods used with adults. With the tattoo method, we injected tattoo ink into the dorsal muscle. Different colors and injection locations can be used to distinguish among individuals over a period of weeks (up to 4 weeks, average 2.5-3 weeks under our conditions). Because fish this young and small are sensitive to handling and injection, we also include physiological data showing fish recover well from anesthetization and tagging. With the piercing method, very thin fishing line is threaded through the dorsal muscle and tied into a barbell or loop. Unique colors and patterns can be used to distinguish among individuals over a period of months. Because a physical tag might impede normal movement in a very small fish, we also include data from an open field exploration test showing similar behavior between tagged and control (non-tagged) juveniles. We expect these effective and inexpensive methods to be useful for a variety of small species and will facilitate early-life, developmental, and longitudinal research.

animal behavior and cognition↗

bioRxiv2018

Early-life social environment alters juvenile behavior and neuroendocrine function in a highly social cichlid fish

Early-life experiences can shape adult behavior, with consequences for fitness and health, yet fundamental questions remain unanswered about how early-life social experiences are translated into variation in brain and behavior. The African cichlid fish Astatotilapia burtoni, a model system in social neuroscience, is well known for its highly plastic social phenotypes in adulthood. Here, we rear juveniles in either social groups or pairs to investigate the effects of early-life social environments on behavior and neuroendocrine gene expression. We find that both juvenile behavior and neuroendocrine function are sensitive to early-life effects. Behavior robustly co-varies across multiple contexts (open field, social cue investigation, and dominance behavior assays) to form a behavioral syndrome, with pair-reared juveniles towards the end of syndrome that is less active and socially interactive. Pair-reared juveniles also submit more readily as subordinates. In a separate cohort, we measured whole brain expression of stress and sex hormone genes. Expression of glucocorticoid receptor (GR) 1a was elevated in group-reared juveniles, supporting a highly-conserved role for the stress axis mediating early-life effects. The effect of rearing environment on androgen receptor (AR) and estrogen receptor (ER) expression was mediated by treatment duration (1 vs. 5 weeks). Finally, expression of corticotropin-releasing factor (CRF) and GR2 decreased significantly over time. Rearing environment also caused striking differences in gene co-expression, such that expression was tightly integrated in pair-reared juveniles, but not group-reared or isolates. Together, this research demonstrates the important developmental origins of behavioral phenotypes and identifies potential behavioral and neuroendocrine mechanisms.

neuroscience↗