Nonapeptide cell size differs between male morphs of the West African cichlid, Pelvicachromis pulcher

Reddon, AR ORCID: 0000-0002-3193-0388, Wylie, DR ORCID: 0000-0003-0782-1146 and Hurd, PL ORCID: 0000-0002-4389-0846 (2025) Nonapeptide cell size differs between male morphs of the West African cichlid, Pelvicachromis pulcher. Journal of Fish Biology. ISSN 0022-1112

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Abstract

Alternative male morphs are found in many species of fishes. These morphs often differ in suites of social behaviours, such as aggression and territoriality, associated with alternative reproductive tactics. Such consistent morph-typical behavioural profiles suggest common differences in underlying neuroendocrine mechanisms. The nonapeptide hormones oxytocin and vasotocin are linked to a wide range of behaviours, including aggression, mating behaviour and social attraction. These behaviours often differ between male morphs, suggesting that nonapeptides may mediate behavioural variation between morphs. We compared two morphs of a West African cichlid, Pelvicachromis pulcher, to test for differences in nonapeptide neuronal phenotypes. P. pulcher exhibit at least four distinct male colour morphs, of which the red and yellow morphs are the most common and have the best-described social and reproductive behaviours. Red males tend towards breeding as harem holders, whereas yellow males breed monogamously or act as satellite males on the territories of red males. Here, we examine nonapeptide-producing neurons in the preoptic area of the hypothalamus in the red and yellow morphs. We found that the more aggressive polygynous red morph has larger parvocellular oxytocin and vasotocin-producing neurons, as well as larger gigantocellular oxytocin neurons, compared to the yellow morph. We did not find any association between the number of oxytocin or vasotocin cells and male morph. Our results suggest that the production of oxytocin and vasotocin in the preoptic area may play a role in determining morph-typical behaviour among P. pulcher males.

Item Type:	Article
Uncontrolled Keywords:	0602 Ecology; 0608 Zoology; 0704 Fisheries Sciences; Fisheries; 3005 Fisheries sciences; 3103 Ecology; 3109 Zoology
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QH Natural history > QH301 Biology S Agriculture > SH Aquaculture. Fisheries. Angling
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Wiley on behalf of The Fisheries Society of the British Isles
Date of acceptance:	17 November 2025
Date of first compliant Open Access:	28 November 2025
Date Deposited:	28 Nov 2025 11:14
Last Modified:	28 Nov 2025 11:14
DOI or ID number:	10.1111/jfb.70306
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27643

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