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Laterality, reproduction and parental care : an investigation in fish

McLean, Stephanie Eilidh


Stephanie Eilidh McLean


Lesley J. Morrell

James Gilbert

Isabella Capellini


Cerebral lateralisation or ‘laterality’, the partitioning of different cognitive functions in specific brain hemispheres, is a selectively advantageous trait that can enhance cognition. The selective advantages of exhibiting laterality are hypothesised to be the primary selective force driving its widespread evolution in both vertebrate and invertebrate taxa. However, substantial variation persists within this trait, particularly between the sexes. The underlying drivers of this variation are poorly understood, with social behaviours, especially those tightly associated with fitness, having received little consideration in this regard. In this thesis, I explored the relationship between cerebral lateralisation at the behavioural level, and
reproduction and reproductive social behaviours, specifically parental care.

In the first section of this thesis (chapters 2 - 4), I investigated whether variation in laterality, particularly between the sexes, is associated with reproduction and the performance of reproductive behaviours. In chapter 2, I provide evidence that in a live bearing species (guppies, Poecilia reticulata) there is variation in the pattern of laterality exhibited between the sexes, whereby individual males are consistent in the expression of laterality across three different behavioural contexts, while females are not, and instead exhibit substantial within individual variation.
In chapter 3, I showed that in a uniparental species (threespine stickleback, Gasterosteus aculeatus), variation in laterality both between the sexes and within a single sex was attributed to reproduction and variation in individuals experience of performing reproductive behaviours respectively. Males, the caring sex, were more strongly lateralised than the non-caring sex (females) during reproduction, and laterality was reduced outside of the breeding season in males. Additionally, males with experience of mating and performing parental care behaviours were more strongly lateralised than males absent in this experience.

In chapter 4, I explored whether laterality and its associated costs and benefits vary in different social contexts, while reproductive and performing parental care and in a nonreproductive non-social state, in a biparental substrate brooding cichlid fish, Telmatochromis temporalis. While I demonstrate no variation in laterality in a reproductive and nonreproductive state, I identified a cost of exhibiting laterality, poorer performance in a task requiring communication and cooperation between the left and right brain hemispheres, that is consistent regardless of sex or social context.

In the latter section of this thesis (chapters 5 and 6), I assessed laterality in a fitness related reproductive social behaviour, parental care. Specifically, I explored whether parental care behaviours are lateralised in T. temporalis (chapter 5) and whether any biases in such behaviours are flexible when the selective pressures thought to select for laterality are altered (chapter 6). I provide the first evidence that parental care behaviours, specifically brood defence behaviour and visual hemisphere use during care, are lateralised in fish (chapter 5), and report that lateral biases in parental care behaviours may be flexible under differing selective pressures, here social and predation pressures, that result from experimental removal of the female biparental parent (chapter 6).

Together, my findings suggest that reproduction and reproductive behaviours, particularly parental care, represent key but previously unidentified drivers of variation in laterality both within a sex and between the sexes. These findings provide new insights that help further our understanding of how variation in cerebral lateralisation evolved and why it may be maintained.


McLean, S. E. (2021). Laterality, reproduction and parental care : an investigation in fish. (Thesis). University of Hull. Retrieved from

Thesis Type Thesis
Deposit Date May 24, 2022
Publicly Available Date Feb 24, 2023
Keywords Biological sciences
Public URL
Additional Information Department of Biological & Marine Science, The University of Hull
Award Date Aug 1, 2021


Thesis (6.2 Mb)

Copyright Statement
© 2021 McLean, Stephanie Eilidh. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.

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