DOI: 10.5281/zenodo.17140214
title: Early-life social environment shapes sex allocation in a sex-changing worm

description: This dataset was collected to investigate sex allocation plasticity in juvenile Ophryotrocha puerilis worms in response to social cues. Age- and size-matched juveniles were exposed to different social environments (isolation, pairs, triplets, and groups with multiple adults) over a 60-day period. Data includes the timing (day) of sex change and individual body size measurements (segment count) at the time of sex change.
description: Sexual plasticity allows individuals to maximize fitness by adjusting sex allocation in response to environmental cues. Sequential hermaphroditism, or sex change, is expected to evolve when the reproductive value (i.e., expected future reproductive success) of one sex increases disproportionately with body size. While socially mediated sex change is well documented in adults, little is known about how juveniles respond to social cues during development. Here, we investigated sex allocation plasticity in size- and age-matched juveniles of the marine annelid Ophryotrocha puerilis exposed to four social environments: isolation, exposure to adults, and size-matched pairs and triplets. Isolated juveniles changed sex early, whereas nearly all juveniles exposed to adults deferred sex change, suggesting that the presence of adults modulates the timing of sex change. Juveniles in pairs and triplets consistently formed mating pairs, with one individual changing sex to female early, supporting what we term the matchmaking hypothesis, which proposes that juveniles use conspecific cues to adjust their developmental trajectories and resulting sex allocation. We discuss the adaptive value of early-life social sensitivity and the potential for sex role preferences in juveniles. This study highlights how social environments shape developmental trajectories in sequential hermaphrodites, beginning earlier in life than previously recognized.
description: Description of Variables

1) Experimental Setup & Identification

unique_ID – Unique identifier assigned to each individual worm.

bowl.no – Identifier for the bowl where the worm was housed (numerical for each treatment)

bowl.id – Unique bowl ID for each bowl (individuals in a bowl share the same bowl.id)

replicate – Name of the observer taking measurements 

treatment – Social environment the individual was assigned to (1Isolated, Pair, Triplets, or Groups).

exp.day - Number of days since the experiment started (0-60) 

2) Sex Change & Body Size Measurements

body.size.focal –

i. Number of body segments of all experimental worms on day 0 (start of experiment)

ii. Number of body segments on the day of sex change (of worms that changed sex)  

presence.of.eggs – Indicates whether eggs were observed (yes = presence of oocytes; no = no oocytes)

moment.sex.change – exp.day when sex change occurred (a single event; 1 = day of sex change; 0 = no sex change) 

partner.size.pairs (L1 Pair) – Body size of the L1 (small juvenile in manuscipt) when the L2 ('large juveniles' in manuscript) in pairs changed sex.

partner.size (L2 Triplets) – Body size of the L2 (intermediate juvenile in manuscript) when the L3  ('large juveniles' in manuscript) in tripletschanged sex.

partner.size (L1 Triplets) – Body size of the L1 (small juvenile in manuscript) when the L3 ('large juveniles' in manuscript) in triplets changed sex.