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Department of Zoology



The role of thyroid hormone in the plastic development of pigmentation patterns

Supervisor: Dr Emília Santos


Phenotypic plasticity - the ability of a given genotype to express different phenotypes when exposed to different environments – is thought to facilitate adaptation to novel and fluctuating environments. Yet, we do not fully understand the hormonal and developmental mechanisms by which the same genotype develops into distinct phenotypic states. Here, we will uncover the hormonal and developmental mechanisms underlying the plastic development of pigmentation patterns using cichlid fish as a model system.

Pigmentation pattern development in cichlids is highly plastic and is influenced by an individual’s social environment, with dominant individuals developing conspicuous pigmentation patterns earlier in ontogeny. Preliminary data suggests that thyroid hormone (TH) controls differences in pigment cell differentiation and migration that could lead to these distinct adult colour patterns. To test this hypothesis, we will: 1) measure and manipulate TH levels throughout pigmentation development to determine its role in plastic trait development; 2) perform comparative transcriptomics experiments (RNAseq) to identify the genes responding to hormonal manipulations, and; 3) perform gene expression studies (using in situ Hybridisation Chain Reaction), for key pigment cell markers and candidate genes identified in aim 2, to uncover the cellular mechanisms by which TH controls the plastic development of pigmentation patterns.


Clark, B. et al. (2023) ‘Developmental plasticity and variability in the formation of egg-spots, a pigmentation ornament in the cichlid Astatotilapia calliptera’. bioRxiv, p. 2023.04.06.535385. Available at:

McMenamin, S.K. et al. (2014) ‘Thyroid hormone–dependent adult pigment cell lineage and pattern in zebrafish’, Science, 345(6202), pp. 1358–1361. Available at:

Prazdnikov, D.V. and Shkil, F.N. (2023) ‘Thyroid hormones in development of coloration of two species of Neotropical cichlids’, Journal of Experimental Biology, p. jeb.245710. Available at:

Salis, P. et al. (2021) ‘Thyroid hormones regulate the formation and environmental plasticity of white bars in clownfishes’, Proceedings of the National Academy of Sciences, 118(23), p. e2101634118. Available at: