PhD position

 Plastic sex allocation in hermaphrodites and beyond:
oxytocin and social interactions across annelids’ sexual
systems
Applica(on deadline: May 5th, 2025
Applica(ons to: mariacristinalorenzi@gmail.com virginie.canoine@univie.ac.at
We are looking for a highly motivated and competent candidate for a 3-year PhD thesis at the
Laboratoire d’Ethologie Expérimentale et Comparée - LEEC, Sorbonne Paris Nord University
(Villetaneuse Campus, France) and at the Department of Behavioral & Cognitive Biology - BeCogBio,
Vienna University (Austria) to study the role of oxytocin/oxytocin-like peptides in modulating social
interactions and reproductive output in annelids with different sexual systems.
Background: Our understanding of the adaptive value of social behaviour, here defined in the
broad sense of interactions between conspecifics, has a solid theoretical background; yet
research on the mechanisms of social behaviour has proven challenging (Hofmann et al., 2014).
Evidence has been accumulating in the last decades that Oxytocin (OT) or OT-like peptides
play an important regulatory role in physiological and behavioural processes associated with
social interactions, including cooperation, pair formation, parental care, etc. Typically, OT/OT-
like peptides promote tolerance and bonding across vertebrate taxa, from mammals and birds
to fish and amphibians (Donaldson & Young, 2008; Froemke & Young, 2021; Grinevich et al.,
2021; Carter, 2022). Yet, OT-like peptides are evolutionarily well conserved - they appeared
at least 700 million years ago – and have been detected in invertebrates (Donaldson & Young,
2008; Odekunle & Elphick 2020), where scanty evidence shows they play a role in egg-laying
(Garrison et al., 2012; Oumi et al., 1996). Therefore, OT-like peptides are a candidate
mechanism for investigating the hormonal control of social and reproductive behaviours in
invertebrates.
Study models: Marine annelid worms of the genus Ophryotrocha include species which exhibit
a striking diversity in sexual systems: some species are simultaneous hermaphrodites, others
are sequential hermaphrodites, yet others have separate sexes; however, all species need a
partner to reproduce (i.e., hermaphrodites do not self). The hermaphroditic species have a
plastic sex allocation which they vary with the social context, that is, they adjust their resource
investment into a more female-biased or male-biased allocation depending on mating
opportunity (typically, they exhibit a relatively more female-biased allocation with low mating
opportunity - such as in pair - and move to a relatively more male-biased allocation with higher
mating opportunity, e.g., Scharer 2009; Santi et al., 2018). These allocation adjustments are
also expressed into striking changes in the quality of their social interactions, which vary from
pair bonding and sophisticated form of cooperation (reciprocity in egg exchange, Picchi et al.,
2018) to overt aggression and competition (e.g., Lorenzi et al., 2006; Santi et al., 2018).
Research question: The candidate will investigate the role of OT/OT-like peptides on social
interactions and reproductive outcomes in three species of the genus Ophryotrocha with
different sexual systems (O. diadema, O. puerilis and O. labronica, which are simultaneous
hermaphrodites, sequential hermaphrodites and separate-sexes, respectively) and will quantify
OT and OT-like peptides and other potential candidate hormones using state-of-the-art
methods. These data will offer valuable information on the role(s) of OT-like peptides in
mediating social interactions in invertebrates and along the evolutionary transition from
hermaphroditism to separate sexes, that is, along a gradient of increasingly important
behavioural, physiological and hormonal sexual specialization.
Candidate: We are seeking a creative and motivated candidate with a Master in ethology,
behavioural sciences or a related field, with experience in behavioural observations and animal
experimentation and good statistical bases (preferably using R). The candidate should have
very good English communication skills (min. B2); proficiency in French is not required.
Supervision: Joint supervision by Prof. Maria-Cristina Lorenzi (Laboratoire d’Ethologie
Expérimentale et Comparée - LEEC, Sorbonne Paris Nord University, Campus Villetaneuse,
France) and Dr. Virginie Canoine (Department of Behavioral & Cognitive Biology -
BeCogBio, Vienna University, Austria).
The successful candidate will perform behavioural experiments at the LEEC, USPN (located
at Villetaneuse, France) and hormone quantification at the BeCogBio (Vienna University,
Austria).
The LEEC is a laboratory investigating different questions on social behaviour across different
animal models. The LEEC worm lab hosts Ophryotrocha worm species with different sexual
systems: simultaneous and sequential hermaphrodites and separate sexes. Being almost
microscopic but easy to handle, these worms are ideal model systems for the study of the effects
of the social environment on sex allocation.
The BeCogBio focuses on behavioural and cognitive traits from the multiple perspectives of
mechanism, function, development and evolutionary history. This international and
interdisciplinary research centre studies the endocrine and genetic control of behaviour, the
influence of ecological and environmental factors on behavioural phenotypes under controlled
lab- and ecologically valid field conditions.
Application procedure: Applicants should send their 1) CV; 2) motivation letter; 3)
recommendation letters by referees; and 4) a written project (no more than 4 pages, including
references) in a single PDF file, to mariacristinalorenzi@gmail.com and
virginie.canoine@univie.ac.at by 05/05/2025 (applications beyond 05/05/2025 may be
considered until the position is filled).
The chosen candidate will then apply with his/her project to the Ecole Doctorale Galilée
(Université Sorbonne Paris Nord, Villetaneuse, France) for the funding of a 3-year contract.
Candidates should be willing to come in person for the interview by the Ecole Doctorale on
early June 2025 (date not fixed yet). The thesis will start in September 2025.
References:
• Carter, C. S. (2022). Oxytocin and love: myths, metaphors and mysteries. Comprehensive Psychoneuroendocrinology, 9, 100107.
• Donaldson, Z. R., & Young, L. J. (2008). Oxytocin, vasopressin, and the neurogeneIcs of sociality. Science, 322, 900-904.
• Froemke, R. C. & Young, L. J. (2021). Oxytocin, Neural PlasIcity, and Social Behavior. In B. Roska & H. Y. Zoghbi (Eds.), Annual Review of
Neuroscience, 44, 359-381.
• Garrison, J. L., Macosko, E. Z., Bernstein, S., Pokala, N., Albrecht, D. R., & Bargmann, C. I. (2012). Oxytocin/vasopressin-related pepIdes
have an ancient role in reproducIve behavior. Science, 338, 540-543.
• Grinevich, V. & Neumann, I. D. (2021). Brain oxytocin: how puzzle stones from animal studies translate into psychiatry. Molecular
Psychiatry, 26, 265-279.
• Hofmann, H. A., Beery, A. K., Blumstein, D. T., Couzin, I. D., Earley, R. L., Hayes, L. D., Hurd, P. L., Lacey, E. A., Phelps, S. M., Solomon, N.
G. and Taborsky, M., Young, L. J. & Rubenstein, D. R. (2014). An evoluIonary framework for studying mechanisms of social
behavior. Trends in Ecology & EvoluBon, 29, 581-589.
• Lorenzi, M.C., Schleicherová, D., Sella, G. (2006). Life history and sex allocaIon in the simultaneously hermaphrodiIc polychaete worm
Ophryotrocha diadema: the role of sperm compeIIon. IntegraBve and ComparaBve Biology, 46, 381-389.
• Odekunle, E.A., Elphick, M.R. (2020). ComparaIve and evoluIonary physiology of asopressin/ Oxytocin-type neuropepIde signaling in
invertebrates. FronBers in Endocrinology, 11, 225.
• Oumi, T., Ukena, K., Matsushima, O., Ikeda, T., Fujita, T., Minakata, H., & Nomoto, K. (1996). Annetocin, an annelid oxytocin-related
pepIde, induces egg-laying behavior in the earthworm, Eisenia foeBda. Journal of Experimental Zoology, 276, 151-156.
• Picchi, L., Cabanes, G., Ricci-Bonot, C. & Lorenzi, M.C. (2018). QuanItaIve matching of clutch size in reciprocaIng hermaphrodiIc worms.
Current Biology, 28, 3254-3259.e3.
• SanI, M., Picchi, L., Lorenzi, M.C. (2018). Dynamic modulaIon of reproducIve strategies in a simultaneous hermaphrodite and the
preference for the male role. Animal Behaviour, 146, 87-96.
• Schärer, L. (2009). Tests of sex allocaIon theory in simultaneously hermaphrodiIc animals. EvoluBon, 63, 1377-1405.