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Growth control is essential to establish organism size, so organisms must have mechanisms to both sense and adjust growth. Studies of single cells have revealed that size homeostasis can be achieved using distinct control methods: Sizer, Timer, and Adder. In multicellular organisms, mechanisms that regulate body size must not only control single cell growth but also integrate it across organs and tissues during development to generate adult size and shape. To investigate body size and growth control in metazoans, we can leverage the roundworm Caenorhabditis elegans as a scalable and tractable model. We collected precise growth measurements of thousands of individuals throughout larval development, measured feeding behavior to pinpoint larval transitions, and quantified highly accurate changes in animal size and shape during development. We find differences in the growth of animal length and width during larval transitions. Using a combination of quantitative measurements and mathematical modeling, we present two physical mechanisms by which C. elegans can control growth. First, constraints on cuticle stretch generate mechanical signals through which animals sense body size and initiate larval-stage transitions. Second, mechanical control of food intake drives growth rate within larval stages, but between stages, regulatory mechanisms influence growth. These results suggest how physical constraints control developmental timing and growth rate in C. elegans.
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Brain size scaling through development in the whitelined sphinx moth (Hyles lineata) shows mass and cell number comparable to flies, bees, and wasps
Factors regulating larval growth and determinants of adult body size are described for several holometabolous insects, but less is known about brain size scaling through development. Here we use the isotropic fractionation ("brain soup") method to estimate the number of brain cells and cell density for the whitelined sphinx moth (Lepidoptera: Hyles lineata) from the first instar through the adult stage. We measure mass and brain cell number and find that, during the larval stages, body mass shows an exponential relationship with head width, while the total number of brain cells increases asymptotically. Larval brain cell number increases by a factor of ten from nearly 8000 in the first instar to over 80,000 in the fifth instar. Brain cell number increases by another factor of 10 during metamorphosis, with the adult brain containing more than 900,000 cells. This is similar to increases during development in the vinegar fly (Drosophila melanogaster) and the black soldier fly (Hermetia illucens). The adult brain falls slightly below the brain-to-body allometry for wasps and bees but is comparable in the number of cells per unit brain mass, indicating a general conservation of brain cell density across these divergent lineages.
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- Award ID(s):
- 2109598
- PAR ID:
- 10485987
- Publisher / Repository:
- Elsevier Science
- Date Published:
- Journal Name:
- Arthropod Structure & Development
- Volume:
- 78
- Issue:
- C
- ISSN:
- 1467-8039
- Page Range / eLocation ID:
- 101329
- Subject(s) / Keyword(s):
- Brain size Development Isotropic fractionator Lepidoptera Sphingidae
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.asd.2023.101329
