Skull morphometrics of adult male Antartic fur seal, Arctocephalus gazella, and South American fur seal A. australis

Daneri, Gustavo Adolfo; Esponda, César M. García; Santis, Luciano José María De; Pla, Laura

doi:10.1590/s0073-47212005000300006

Cited by 5 publications

(3 citation statements)

References 10 publications

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“…1 ; Table A2 ) were recorded by two operators. The choice of landmarks is inspired by previous morphometric studies of ringed seal ( Pusa hispida ) and Antarctic fur seal ( Arctocephalus gazella ) skulls ( Amano, Hayano & Miyazaki, 2002 ; Daneri et al, 2005 ). Each of the two operators applied two different measurement methods: Direct measurement on the physical skulls using a Microscribe 3D digitizer (Immersion Corporation, San Jose, CA, USA; https://www.immersion.com ; Fig.…”

Section: Methodsmentioning

confidence: 99%

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Measurement error using a SeeMaLab structured light 3D scanner against a Microscribe 3D digitizer

Messer

Svendsen

Galatius

et al. 2021

PeerJ

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Background Geometric morphometrics is a powerful approach to capture and quantify morphological shape variation. Both 3D digitizer arms and structured light surface scanners are portable, easy to use, and relatively cheap, which makes these two capturing devices obvious choices for geometric morphometrics. While digitizer arms have been the “gold standard”, benefits of having full 3D models are manifold. We assessed the measurement error and investigate bias associated with the use of an open-source, high-resolution structured light scanner called SeeMaLab against the popular Microscribe 3D digitizer arm. Methodology The analyses were based on 22 grey seal (Halichoerus grypus) skulls. 31 fixed anatomical landmarks were annotated both directly using a Microscribe 3D digitizer and on reconstructed 3D digital models created from structured light surface scans. Each skull was scanned twice. Two operators annotated the landmarks, each twice on all the skulls and 3D models, allowing for the investigation of multiple sources of measurement error. We performed multiple Procrustes ANOVAs to compare the two devices in terms of within- and between-operator error, to quantify the measurement error induced by device, to compare between-device error with other sources of variation, and to assess the level of scanning-related error. We investigated the presence of general shape bias due to device and operator. Results Similar precision was obtained with both devices. If landmarks that were identified as less clearly defined and thus harder to place were omitted, the scanner pipeline would achieve higher precision than the digitizer. Between-operator error was biased and seemed to be smaller when using the scanner pipeline. There were systematic differences between devices, which was mainly driven by landmarks less clearly defined. The factors device, operator and landmark replica were all statistically significant and of similar size, but were minor sources of total shape variation, compared to the biological variation among grey seal skulls. The scanning-related error was small compared to all other error sources. Conclusions As the scanner showed precision similar to the digitizer, a scanner should be used if the advantages of obtaining detailed 3D models of a specimen are desired. To obtain high precision, a pre-study should be conducted to identify difficult landmarks. Due to the observed bias, data from different devices and/or operators should not be combined when the expected biological variation is small, without testing the landmarks for repeatability across platforms and operators. For any study necessitating the combination of landmark measurements from different operators, the scanner pipeline will be better suited. The small scanning-related error indicates that by following the same scanning protocol, different operators can be involved in the scanning process without introducing significant error.

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Section: Methodsmentioning

confidence: 99%

“… The 31 anatomical landmarks measured on the grey seal skulls in this study. The choice of landmarks is inspired by previous morphometric studies of ringed and Antarctic fur seal skulls ( Amano, Hayano & Miyazaki, 2002 ; Daneri et al, 2005 ). Based on original illustration of a ringed seal by Amano, Hayano & Miyazaki (2002) .…”

Section: Methodsmentioning

confidence: 99%

Measurement error using a SeeMaLab structured light 3D scanner against a Microscribe 3D digitizer

Messer

Svendsen

Galatius

et al. 2021

PeerJ

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“…Because multivariate analyses are sensitive to missing data (Daneri, Esponda, De Santis, & Pla, 2005), specimens were excluded if data were missing for more than one measurement. To estimate the missing value for each specimen with only one missing data point, we used stepwise regression from the remaining subset of cranial variables available for that specimen (Reig, 1992; Reig & Ruprecht, 1989).…”

Section: Methodsmentioning

confidence: 99%

Morphological diversity and ecological niche divergence in goitered and sand gazelles

Hemami

Khosravi

Groves

et al. 2020

Ecology and Evolution

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The phylogeny and species boundaries of Gazella subgutturosa and G. marica have been long debated. The achievements of past conservation efforts have been compromised by a lack of knowledge about the phylogeny and taxonomic status of different populations. We integrated the recent genetic findings by previous studies with morphometric analyses and ecological niche modeling (ENM) to assess discreteness among populations of these gazelle species in Asia. Taxonomic diversity of gazelles was investigated by using principal components analysis (PCA) based on 14 cranial measures of male skulls. Ecological niche divergence was examined based on a PCA on climatic factors and a species distribution modeling (SDM) with environmental variables. Morphometric results indicated substantial differentiation in size between skulls of the western Zagros Mountains including west and south‐western Iran and Arabian Peninsula from all other samples east of the Zagros Mountains from Iran to China. ENM also revealed that gazelles in the east and west of Zagros Mountains occupy distinct niches and that there are apparent areas of disconnection across the goitered gazelle suitable range. A complete divergent niche occupation was also observed between goitered gazelles of northern Mongolia and other populations of the species, except those in China. Taking the inferences from ENM and morphology together with previous genetics results, we conclude that gazelles in the west and south‐west of Iran may represent G. marica . Also, our combined analyses revealed divergence among gazelles of Iran, Central Asia, and Mongolia/China. These results may pave the way for future studies and have conservation implications particularly for reintroduction/supplementation programs.

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Getting Long in the Tooth: A Strong Positive Correlation between Canine Size and Heterozygosity in Antarctic Fur Seals Arctocephalus gazella

Hoffman

Hanson

Forcada

et al. 2010

Journal of Heredity

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Most studies of heterozygosity-fitness correlations (HFCs) in natural populations relate to fitness traits expressed early in life, whereas traits that are often more difficult to measure such as longevity and adult body size remain elusive. Teeth provide a window on an individual's life history, allowing the reliable estimation of both age and body size. Consequently, we collected paired upper canine teeth and tissue samples from 84 adult male Antarctic fur seals Arctocephalus gazella that died of natural causes at Bird Island, South Georgia. Tooth size is a good predictor of skull and body size both within and across taxa, and we similarly find a strong relationship with skull size in our species. In turn, tooth size is itself predicted strongly by genetic heterozygosity estimated using 9 microsatellites. With only 9 loci, the exact mechanisms involved remain unclear, although the observed pattern appears largely attributable to a small subset of loci, suggesting that associative overdominance rather than inbreeding depression provides the proximate mechanism. In addition, locating these markers in the dog genome reveals proximity to genes involved with fat metabolism and growth. Our study illustrates how canine teeth, and potentially other structures such as tympano-periotic bone, waxy inner earplugs, or otoliths, may be used to explore links between genetic variation and important life-history traits in free-ranging vertebrate populations.

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Skull morphometrics of adult male Antartic fur seal, Arctocephalus gazella, and South American fur seal A. australis

Cited by 5 publications

References 10 publications

Measurement error using a SeeMaLab structured light 3D scanner against a Microscribe 3D digitizer

Measurement error using a SeeMaLab structured light 3D scanner against a Microscribe 3D digitizer

Morphological diversity and ecological niche divergence in goitered and sand gazelles

Getting Long in the Tooth: A Strong Positive Correlation between Canine Size and Heterozygosity in Antarctic Fur Seals Arctocephalus gazella

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