Sex-specific hormone signatures in four fish species with divergent reproductive strategies
- 1Marine Evolutionary Biology, Zoological Institute, Christian-Albrechts-Universität Kiel , ,
Abstract
Introduction: Steroid hormones regulate diverse biological processes, including development, immunity and reproduction. Because biological sex, pregnancy, parental care, and mate competition are closely associated in most established model organisms, it remains unclear whether endocrine differences between males and females are primarily linked to gametic sex or to the reproductive roles performed by each sex. Syngnathid fish, the pipefishes, seadragons, and seahorses, provide a powerful system for disentangling these effects, because males, rather than females, carry the developing embryos. Species further differ in sexual selection and in the extent of paternal investment, ranging from externally attached eggs to incubation with an enclosed brood pouch.
Methods: This study provides baseline hormonal profiles of key steroid and peptide hormones in three syngnathid species across the unique evolutionary parental care gradient of male pregnancy ( Nerophis ophidion, Syngnathus typhle, Hippocampus abdominalis ). We additionally included the female-pregnant livebearing fish Heterandria formosa as a comparative reference for a conventional separation of reproductive roles.
Results: Sex-specific endocrine profiles broadly followed sexual selection differentials: species with stronger sexual heteromorphism, i.e., more extreme reproductive roles ( N. ophidion ), exhibiting stronger endocrine sexual heteromorphism. In contrast, species with higher parental care investment ( H. abdominalis, H. formosa ) show reduced endocrine differentiation between the sexes. The intermediate species S. typhle, which combines sex-role reversal with a moderately complex brood pouch, displayed tissue-specific patterns, with hormonal dimorphism retained primarily in the gonads.
Discussion: By incorporating a cross-species comparative framework with both sex-role reversed and a conventional viviparous species, we can begin to understand which hormonal functions are conserved versus derived, and whether endocrine profiles are primarily aligned with biological sex or reproductive role, such as mate competition and parental care, thereby revealing how endocrine constraints and plasticity contribute to reproductive evolution.
Related
- Ovarian Anti-Müllerian Hormone Expression in Hyperprolific Sows: Associations with Reproductive Stage and Parity, with Elevated Expression in the Corpus Luteum During the Luteal Stage.
- Association of Sex Hormone-Binding Globulin with Glycated Hemoglobin and Multidimensional Biomarker Structure in Reproductive-Age Women: An Analysis Based on NHANES 2021--2023
- Structures of methanogenic schizorhodopsins reveal divergent strategies for proton transport and thermal adaptation
- Species-specific gene programs define divergent antiviral responses in Marburg virus reservoir bats and humans
- Divergent processing strategies for auditory sequence recognition in humans and zebra finches (Taeniopygia guttata)
BibTeX
@article{pappert2026sexspecific,
title = {{Sex-specific hormone signatures in four fish species with divergent reproductive strategies}},
author = {Freya Adele Pappert and Olivia Roth},
journal = {Frontiers in endocrinology},
year = {2026},
month = oct,
doi = {10.3389/fendo.2026.1923972},
url = {https://europepmc.org/article/PMC/PMC13672188},
note = {CC BY},
}
RIS
TY - JOUR
TI - Sex-specific hormone signatures in four fish species with divergent reproductive strategies
AU - Freya Adele Pappert
AU - Olivia Roth
PY - 2026
DA - 2026/10/02
JO - Frontiers in endocrinology
DO - 10.3389/fendo.2026.1923972
UR - https://europepmc.org/article/PMC/PMC13672188
AB - Introduction: Steroid hormones regulate diverse biological processes, including development, immunity and reproduction. Because biological sex, pregnancy, parental care, and mate competition are closely associated in most established model organisms, it remains unclear whether endocrine differences between males and females are primarily linked to gametic sex or to the reproductive roles performed by each sex. Syngnathid fish, the pipefishes, seadragons, and seahorses, provide a powerful system for disentangling these effects, because males, rather than females, carry the developing embryos. Species further differ in sexual selection and in the extent of paternal investment, ranging from externally attached eggs to incubation with an enclosed brood pouch. Methods: This study provides baseline hormonal profiles of key steroid and peptide hormones in three syngnathid species across the unique evolutionary parental care gradient of male pregnancy ( Nerophis ophidion, Syngnathus typhle, Hippocampus abdominalis ). We additionally included the female-pregnant livebearing fish Heterandria formosa as a comparative reference for a conventional separation of reproductive roles. Results: Sex-specific endocrine profiles broadly followed sexual selection differentials: species with stronger sexual heteromorphism, i.e., more extreme reproductive roles ( N. ophidion ), exhibiting stronger endocrine sexual heteromorphism. In contrast, species with higher parental care investment ( H. abdominalis, H. formosa ) show reduced endocrine differentiation between the sexes. The intermediate species S. typhle, which combines sex-role reversal with a moderately complex brood pouch, displayed tissue-specific patterns, with hormonal dimorphism retained primarily in the gonads. Discussion: By incorporating a cross-species comparative framework with both sex-role reversed and a conventional viviparous species, we can begin to understand which hormonal functions are conserved versus derived, and whether endocrine profiles are primarily aligned with biological sex or reproductive role, such as mate competition and parental care, thereby revealing how endocrine constraints and plasticity contribute to reproductive evolution.
SN - 1664-2392
ER -