DOI: 10.5061/dryad.z8w9ghxqv
title: The external rumen of dung beetles: Complex interactions between larvae and their ontogenetic environments shape growth and life history

description: Organisms are not just passive recipients of environmental pressures but
 are able to shape the environment they experience. However, the mechanisms
 and the evolutionary implications of such niche construction remain poorly
 understood. Larvae of the gazelle dung beetle (Digitonthophagus gazella)
 extensively modify their environment and benefit from microbial symbionts
 to digest their cellulose-rich diet. These modifications are so extensive
 that previous research suggests that dung beetle larvae establish an
 “external rumen”, where behavioral adaptations promote beneficial
 symbionts that enhance nutrient availability in the developmental
 environment. However, the mechanisms underlying these environmental
 modifications and their impact on species differences remain unclear. To
 investigate the external rumen hypothesis, we study the impact of larval
 environmental modifications on adult life-history traits in the dung
 beetle Digitonthophagus gazella. We did this by transplanting eggs into
 modified and unmodified environments, whilst excluding maternally derived
 microbes. Additionally, we include a heterospecific (Onthophagus binodis)
 manipulated environment to investigate the evolution of species-specific
 effects. Counter to expectations, we find larval modifications by
 conspecifics did not confer a benefit to D. gazella in any aspect
 measured. However, surprisingly, focal from heterospecific treatments
 emerged significantly quicker. Additionally, we highlight the primary
 condition of the developmental environment as an essential factor in
 determining fitness benefits compared to any additive environmental
 effects. Our research adds to the growing literature on
 organism-environment interactions and demonstrates that the relationship
 between dung beetle larvae and their developmental environment is complex
 and is not consistent with the presence of a simple external rumen.
description: # The external rumen of dung beetles: Complex interactions between larvae
 and their ontogenetic environments shape growth and life history Dataset
 DOI: [10.5061/dryad.z8w9ghxqv](10.5061/dryad.z8w9ghxqv) ## Description of
 the data and file structure **ExRuDB1.csv** Development data for
 individuals who made it past 7 days. Empty cells represent that the data
 was not determined. * **Block**: * Block 1 = 8/29/2024 - 10/19/2024 *
 Block 2 = 9/13/2024 - 10/31/2024 * Block 3 = 09/22/2024 - 11/16/2024 *
 Dates include breeding container and brood ball collection *
 **Treatment**: * 8-UB = Unmodified Control incubated for 8 days * 1-UB =
 Fresh unmodified control * HET = O. binodis modified brood ball * CON = D.
 gazella modified brood ball * **plate = treatment + number**: 8-UB1 =
 Unmodified Control incubated for 8 days * **position**: Position in the
 12-well plate A-C, 1-4 * **ID**: Individual identifier * **Date hatched**:
 Date the focal egg hatched * **Day5LW**: Focal larval weight (in grams) 5
 days after hatching * **Day7LW**: Focal larval weight (in grams) 7 days
 after hatching * **AbsoluteGrowth**: Difference in weight (g) between days
 5 and 7 * **GrowthPercent**: Absolute growth as a percentage *
 **Pupation**: Date focal larvae identified as a Pupa * **Adult
 Emergencee**: Emergence the of focal adult from the pupal stage *
 **Devtime_Days**: Time in days from date hatched to adult emergence *
 **ProWid**: Pronotum width (mm) * **Sex**: M = Male, F = Female *
 **datedied**: Date of focal death **ExRuDB2.csv** Survival data for
 hatched individuals * **Event**: 0 = Died, 1 = Alive **ExRuDB3.csv** Event
 data for all eggs used in the experiment * **unhatched**: 0 = unhatched, 1
 = hatched