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Complete mitochondrial genome and phylogenetic analysis of the Weddell seal, Leptonychotes weddellii.

ABSTRACT: The Weddell seal, Leptonychotes weddellii, which belongs to the family Phocidae, is an abundant pinniped that inhabits the Antarctica. Here, we present the complete mitochondrial genome and phylogeny of L. weddellii. The total length of the mitogenome is 16,762 bp, consisting of 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The base composition of the mitogenome is 34.26% (A), 25.51% (T), 27.09% (C), and 13.11% (G), and 40.22% for overall GC contents. The description of this mitogenome can provide information about variations at the intra-species level and aid phylogenetic studies in family Phocidae.

SUBMITTER: Kim JU

PROVIDER: S-EPMC7783060 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Complete mitochondrial genome and phylogenetic analysis of the Weddell seal, Leptonychotes weddellii.

Kim Jong-U JU Kim Jeong-Hoon JH

Mitochondrial DNA. Part B, Resources 20200915 3

The Weddell seal, Leptonychotes weddellii, which belongs to the family Phocidae, is an abundant pinniped that inhabits the Antarctica. Here, we present the complete mitochondrial genome and phylogeny of L. weddellii. The total length of the mitogenome is 16,762 bp, consisting of 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The base composition of the mitogenome is 34.26% (A), 25.51% (T), 27.09% (C), and 13.11% (G), and 40.22% for overall GC contents. The descrip ...[more]

PMID: 33458160

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Project description:Lactation is the most energy-demanding event in mammals' reproduction. In pinnipeds, females are the only food providers to the young and have developed numerous behavioral and physiological lactation strategies, from capital-breeding to income-breeding. Lactating females' fine-scale foraging strategy, and precise understanding of how females supplement their pup's needs as well as their own are important to understand the species' ecology and energetic balance. Polar pinnipeds, inhabiting extreme environments, are sensitive to climate change and variability, understanding their constraints and foraging strategy during lactation is therefore important. In 2019, three sonar tags were deployed on lactating Weddell seals in Terre Adélie (East Antarctica) for 7 days, to study fine-scale predator-prey interactions. Feeding activity was mostly benthic, reduced, central-placed, and spatially limited. Females spent most of their time hauled-out. A total of 331 prey capture attempts (PrCAs) were recorded using triaxial acceleration data, with 125 prey identified on echograms (5 cm, acoustic size). All PrCAs occurred on the seafloor, shallower than usual records (mean depth of 88 m, vs 280 m after their molt). We also found that they only fed in three of the five identified dive shapes, during the ascent or throughout the dive. Half of the prey were reactive to the seal's approach, either leaving the seafloor, or escaping just above the seafloor, suggesting that the seals hunt by chasing them from the seabed. Seals continuously scanned the area during the approach phase, evoking opportunistic foraging. Our results provide additional evidence that Weddell seal forage during lactation, displaying a mix of capital-breeding and income-breeding strategies during this period of physiological stress. This work sheds light on previously unexplored aspects of their foraging behavior, such as shallow water environments, targeting benthic prey, generally focusing on single prey rather than schools, and evidence of visual scanning through observed head movements.

Project description:Body mass dynamics of animals can indicate critical associations between extrinsic factors and population vital rates. Photogrammetry can be used to estimate mass of individuals in species whose life histories make it logistically difficult to obtain direct body mass measurements. Such studies typically use equations to relate volume estimates from photogrammetry to mass; however, most fail to identify the sources of error between the estimated and actual mass. Our objective was to identify the sources of error that prevent photogrammetric mass estimation from directly predicting actual mass, and develop a methodology to correct this issue. To do this, we obtained mass, body measurements, and scaled photos for 56 sedated Weddell seals (Leptonychotes weddellii). After creating a three-dimensional silhouette in the image processing program PhotoModeler Pro, we used horizontal scale bars to define the ground plane, then removed the below-ground portion of the animal's estimated silhouette. We then re-calculated body volume and applied an expected density to estimate animal mass. We compared the body mass estimates derived from this silhouette slice method with estimates derived from two other published methodologies: body mass calculated using photogrammetry coupled with a species-specific correction factor, and estimates using elliptical cones and measured tissue densities. The estimated mass values (mean ± standard deviation 345±71 kg for correction equation, 346±75 kg for silhouette slice, 343±76 kg for cones) were not statistically distinguishable from each other or from actual mass (346±73 kg) (ANOVA with Tukey HSD post-hoc, p>0.05 for all pairwise comparisons). We conclude that volume overestimates from photogrammetry are likely due to the inability of photo modeling software to properly render the ventral surface of the animal where it contacts the ground. Due to logistical differences between the "correction equation", "silhouette slicing", and "cones" approaches, researchers may find one technique more useful for certain study programs. In combination or exclusively, these three-dimensional mass estimation techniques have great utility in field studies with repeated measures sampling designs or where logistic constraints preclude weighing animals.

Dataset Information

Complete mitochondrial genome and phylogenetic analysis of the Weddell seal, Leptonychotes weddellii.

Publications

Complete mitochondrial genome and phylogenetic analysis of the Weddell seal, <i>Leptonychotes weddellii</i>.

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