Journal article

Long bone histomorphogenesis of the naked mole-rat: Histodiversity and intraspecific variation


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Publication Details

Author list: Montoya-Sanhueza G, Bennett NC, Oosthuizen MK, Dengler-Crish CM, Chinsamy A

Publisher: Wiley: 12 months

Publication year: 2021

Journal: Journal of Anatomy

Journal name: JOURNAL OF ANATOMY

Volume number: 1

Start page: 1

End page: 25

Total number of pages: 25

ISSN: 0021-8782

eISSN: 1469-7580


Abstract

Lacking fur, living in eusocial colonies and having the longest lifespan of any rodent, makes
naked mole-rats (NMRs) rather peculiar mammals. Although they exhibit a high degree of
polymorphism, skeletal plasticity and are considered a novel model to assess the effects of
delayed puberty on the skeletal system, scarce information on their morphogenesis exists.
Here, we examined a large ontogenetic sample (n = 76) of subordinate individuals to assess
the pattern of bone growth and bone microstructure of fore- and hindlimb bones by
using histomorphological techniques. Over 290 undecalcified thin cross-sections from the
midshaft of the humerus, ulna, femur, and tibia from pups, juveniles and adults were analyzed
with polarized light microscopy. Similar to other fossorial mammals, NMRs exhibited
a systematic cortical thickening of their long bones, which clearly indicates a conserved
functional adaptation to withstand the mechanical strains imposed during digging, regardless
of their chisel-tooth predominance. We describe a high histodiversity of bone matrices
and the formation of secondary osteons in NMRs. The bones of pups are extremely
thin-walled and grow by periosteal bone formation coupled with considerable expansion
of the medullary cavity, a process probably tightly regulated and adapted to optimize the
amount of minerals destined for skeletal development, to thus allow the female breeder
to produce a higher number of pups, as well as several litters. Subsequent cortical thickening
in juveniles involves high amounts of endosteal bone apposition, which contrasts with
the bone modeling of other mammals where a periosteal predominance exists. Adults
have bone matrices predominantly consisting of parallel-fibered bone and lamellar bone,
which indicate intermediate to slow rates of osteogenesis, as well as the development of
poorly vascularized lamellar-zonal tissues separated by lines of arrested growth (LAGs)
and annuli. These features reflect the low metabolism, low body temperature and slow
growth rates reported for this species, as well as indicate a cyclical pattern of osteogenesis.
The presence of LAGs in captive individuals was striking and indicates that postnatal
osteogenesis and its consequent cortical stratification most likely represents a plesiomorphic
thermometabolic strategy among endotherms which has been suggested to be
regulated by endogenous rhythms. However, the generalized presence of LAGs in this
and other subterranean taxa in the wild, as well as recent investigations on variability of
environmental conditions in burrow systems, supports the hypothesis that underground


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Last updated on 2021-10-03 at 13:34