DOI: 10.5061/dryad.0vt4b8h1d
title: Data from: A multi-tissue view on telomere dynamics and postnatal growth

description: Trade-offs between growth and self-maintenance are common in nature, such
 that early-life effects on growth can generate lasting consequences on
 survival and longevity. Telomeres – putative biomarkers of
 self-maintenance – may link early growth with these later phenotypic
 effects, but evidence for growth-telomere trade-offs is mixed. Null or
 even positive relationships between growth and telomeres may be driven by
 heterogeneity in resource availability or invariable allocation towards
 telomere maintenance within a population. We used nestling tree swallows
 (Tachycineta bicolor) to assess the directionality and timing of
 relationships between growth and telomere length in several tissues. We
 focused on two important phases of growth: first, the peak of postnatal
 growth occurring around 6-days old when nestlings grow by ~33% in a single
 day, and subsequently, the later phase of growth occurring as body mass
 plateaus near adult size at 12-days old. We quantified telomere attrition
 in blood during postnatal growth, as well as telomere length in the blood,
 brain, adrenals, and liver at 12-days old. Growth was unrelated to
 telomere length in the liver and telomere dynamics in blood. However,
 brain telomere length was positively correlated with peak growth, and
 adrenal telomere length was positively related to later growth,
 particularly for chicks that had experienced a temporary stressor. These
 observations suggest that variation in resource availability may mask
 trade-offs, generating positive correlations between growth and telomere
 length at the population level. They also provide insights into complex
 relationships between growth and self-maintenance that can be revealed by
 looking in multiple tissues.
description: We attempted to manipulate chick peak growth by injecting mothers
 with lipopolysaccharide (LPS), which tends to decrease provisioning, in
 order to assess potential intergenerational effects on chick growth and
 telomere dynamics. When chicks were 5 or 6-days old, we injected their
 mothers with either saline or LPS, and quantified changes in maternal mass
 and visitation rate (using RFID) to control for maternal variation in
 responses when looking at the magnitude of effects on chicks.
 For chicks, we measured mass just prior to maternal injections,
 24h after maternal injections, and when chicks were 12-days old. From this
 data, we calculated changes in mass (absolute and/or %), including changes
 during a chick's typical peak of growth (i.e. from 5 to 6-days old)
 and later growth (i.e. from 6 to 12-days old). In order to quantify
 changes in blood telomere length, we also collected blood samples from
 chicks at the start of the study (5 to 6-days old) and when chicks were
 12-days old. To assess the relationship between postnatal growth and
 telomere length in non-blood tissues, we euthanized one median-massed
 chick from each nest at the end of the study and collected blood, brain,
 liver, and adrenals (n = 21 chicks). *While our
 published study does not include this data, we also collected chick wing
 morphology (length, primary feather emergence) as well as molecular
 sex.  DNA from all tissues was extracted using a
 Promega Maxwell RSC instrument, and telomere length was quantified for all
 DNA using qPCR. This dataset uses either 2^deltadelta Ct values (for
 relative telomere length of non-blood tissues) or a corrected change in
 telomere length (corrected for regression to the mean) for blood
 samples. Blood telomere metrics were log-transformed to achieve
 normality. Please see Materials & Methods of
 this paper for further details.