DOI: 10.5061/dryad.7pvmcvdpk
title: Testing Finch’s hypothesis: the role of organismal modularity on the escape from actuarial senescence

description: 1. Until recently, senescence was assumed to be a universal phenomenon.
 Evolutionary theories of senescence predict that no organism may escape
 the physiological decline that results in an increase in mortality risk
 and/or decline in fertility with age. However, evidence both in animals
 and plants has emerged in the last decade defying such predictions.
 Researchers are currently seeking mechanistic explanations for the
 observed variation in ageing trajectories. 2. We argue that the historical
 view on the inevitability of senescence is due, in part, to the
 development of its classical theories, which targeted primarily unitary
 organisms. In unitary species, the integration of resources and functions
 is high, and adult size is determined. In contrast, the architecture of
 modular organisms is indeterminate and built upon repeated modules. The
 isolation of mortality risk in species like hydra (Hydra spp.) or creosote
 brush (Larrea tridentata) may explain their null or even negative
 senescence. 3. Caleb Finch hypothesised three decades ago that species
 with the ability to compartmentalise risk may escape senescence. Here, we
 first revew the evidence on organisms that slow down or even avoid
 senescence in the context of their architecture, along a continuum of
 unitarity-modularity. Then, we use open-access databases to comparatively
 analyse various moments of senescence and link longevity to the degree of
 anatomic modularity. Our analysis compares the pace of senescence across
 138 plants and 151 animals, and the shape of senescence across a subset of
 these. Our comparative analysis reveals that plant species that are more
 modular do indeed tend to escape from senescence more often than those
 that are unitary. The role of modularity in animal senescence is less
 clear. 4. In light of novel support for Finch's hypothesis across a
 large diversity of plant species, and with less conclusive findings in
 animals, we identify new research directions. We highlight opportunities
 related to age-dependent mortality factors. Other areas for further
 research include the role of modularity in relation to endocrine actions,
 and the costs of modular anatomies.
description: This dataset is based on an index for animal anatomies that
 reflects the subdivisionality/multiplicity of organs. The dataset was
 compiled to analyse proxies of anatomic redundancy in unitary animals
 - described in the linked manuscript. The authors of this data relied on a
 combination of review articles and textbooks to identify anatomical
 configurations (detailed below). The scope of the data is limited to renal
 anatomy and the lymphatic system; limitations of this dataset are
 described in the linked manuscript. The two physiological systems selected
 for this dataset were prioritized over other physiological systems because
 a higher-level review showed high variation in the degree to which organs
 in these systems comprise multiple constituent sub-parts (in contrast to
 cardiological systems/respiratory systems/digestive
 systems/etc.). There is opportunity to develop this framework for broader
 physiological applications; to the best of the author's knowledge,
 this is a pioneering effort at applying of subdivision index across a
 broad taxanomic groups. Because this dataset is an early construction, it
 should be approached with caution. Data will be updated/corrected if more
 current information is identified, or if any data infelicities are
 discovered. Detailed notes on changes to this dataset will be annotated.
 Please contact the corresponding author with any questions/discoveries of
 error. More detailed methods and information about the determinations on
 categories (see <em>usage notes</em>) can be found in the
 manuscript. -- Data on lymph
 anatomy is based principally on: Cooper, E., 2019. Advances in Comparative
 Immunology. <i>Springer.</i>
 Cross-validation and additional, detailed information was
 provided by: Budras, K.D., Hullinger, R.L.
 and Rautenfeld, D.B.V., 1987. Lymph heart musculature in
 birds. <i>Journal of
 morphology</i>, <i>191</i>(1), pp.77-87.
 Boehm, T., Hess, I. and Swann, J.B., 2012. Evolution of lymphoid
 tissues. <i>Trends in
 immunology</i>, <i>33</i>(6), pp.315-321.
 Chiba, A., Torroba, M., Honma, Y. and Zapata, A.G., 1988.
 Occurrence of lymphohaemopoietic tissue in the meninges of the stingray
 Dasyatis akajei (Elasmobranchii, Chondricthyes). <i>American journal
 of anatomy</i>, <i>183</i>(3), pp.268-276.
 Owens, L., 2010. Insight into the lymphoid organ of penaeid
 prawns: a review. <i>Fish & shellfish
 immunology</i>, <i>29</i>(3), pp.367-377.
 - Data on Renal Anatomy based
 principally on: Bentley, P.J. (1971). Endocrines and Osmoregulation: A
 Comparative Account in Vertebrates. Heidelberg, Germany:
 Springer. Cross-validation and additional,
 detailed information was provided by: 
 Yokota, E., Kawashima, T., Ohkubo, F., & Sasaki, H.
 (2008). 1348 Comparative anatomical study of the kidney position in
 amniotes using the origin of the renal artery as a landmark. Okajimas
 Folia Anatomica Japonica, 81(6), 135–142. doi:
 10.2535/ofaj.81.135 Williams, T.M., & Worthy,
 G. (2009). Anatomy and physiology: the challenge of aquatic living. In
 Marine Mammal Biology: An Evolutionary Approach. Wiley. Hoelzel, A.R.
 (Ed.). Hoboken, New Jersey, USA. Ortiz, R.M., 2001.
 Osmoregulation in marine mammals. <i>Journal of Experimental
 Biology</i>, <i>204</i>(11), pp.1831-1844.
 Beuchat, C.A., 1999. Kidney structure of a euryhaline mammal,
 the Cape clawless otter (Aonyx capensis). <i>African
 Zoology</i>, <i>34</i>(4), pp.163-165.
description: The levels/factors in the dataset are structured as
 follows: Rank Order Factors: Immune
 Anatomy/Lymphatic Organs #1 - Lymph Nodes
 #2 - Lymph Hearts #3 - Miscelaneous
 multi-constituent lymph tissues #4 - Spleen with no
 lymph peripherals #5 - No centralized immune
 anatomy -- Rank Order Factors:
 Osmoregulatory Organs #1 - Reniculated
 Kidneys #2 - Kidneys + Salt Glands
 <i>or</i> Kidneys + Gills #3 -
 Kidney(s) #4 - Protonephros/Mesonephros
 #5 - Other/None