title: Social dominance and reproductive differentiation mediated by dopaminergic signaling in a queenless ant.
abstract: In social Hymenoptera with no morphological caste, a dominant female becomes an egg layer, whereas subordinates become sterile helpers. The physiological mechanism that links dominance rank and fecundity is an essential part of the emergence of sterile females, which reflects the primitive phase of eusociality. Recent studies suggest that brain biogenic amines are correlated with the ranks in dominance hierarchy. However, the actual causality between aminergic systems and phenotype (i.e. fecundity and aggressiveness) is largely unknown due to the pleiotropic functions of amines (e.g. age-dependent polyethism) and the scarcity of manipulation experiments. To clarify the causality among dominance ranks, amine levels and phenotypes, we examined the dynamics of the aminergic system during the ontogeny of dominance hierarchy in the queenless ant Diacamma sp., which undergoes rapid physiological differentiation based on dominance interactions. Brain dopamine levels differed between dominants and subordinates at day 7 after eclosion, although they did not differ at day 1, reflecting fecundity but not aggressiveness. Topical applications of dopamine to the subordinate workers induced oocyte growth but did not induce aggressiveness, suggesting the gonadotropic effect of dopamine. Additionally, dopamine receptor transcripts (dopr1 and dopr2) were elevated in the gaster fat body of dominant females, suggesting that the fat body is a potential target of neurohormonal dopamine. Based on this evidence, we suggest that brain dopamine levels are elevated in dominants as a result of hierarchy formation, and differences in dopamine levels cause the reproductive differentiation, probably via stimulation of the fat body.
authors: Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Tokyo 3-8-1, Japan Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan okayasukazu@gmail.com.
authors: Yasukazu
authors: Y
authors: Okada
authors: Department of Bioresource Science, Tamagawa University, Machida, Tokyo 194-8610, Japan.
authors: Ken
authors: K
authors: Sasaki
authors: Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan Department of Hygiene and Public Health, Tokyo Women's Medical University, Shinjuku-ku, Tokyo 162-8666, Japan.
authors: Satoshi
authors: S
authors: Miyazaki
authors: Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Hiroyuki
authors: H
authors: Shimoji
authors: Department of Subtropical Agro-Environmental Sciences, Faculty of Agriculture, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan.
authors: Kazuki
authors: K
authors: Tsuji
authors: Laboratory of Ecological Genetics, Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan.
authors: Toru
authors: T
authors: Miura
mesh_terms: D000367:Age Factors; D000818:Animals; D001000:Ants / Q000502:physiology*; D001921:Brain / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D005216:Fat Body / Q000378:metabolism; D005260:Female; D005298:Fertility; D018507:Gene Expression Regulation, Developmental; D009655:Octopamine / Q000494:pharmacology; D009866:Oogenesis; D011954:Receptors, Dopamine / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D012930:Social Dominance
chemical_list: D011954:Receptors, Dopamine; D009655:Octopamine; D004298:Dopamine
keywords: Biogenic amine; Diacamma; Ponerine ant; Primitively eusocial; Reproductive dominance