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Seals fur reals

Arctocephalus forsteri, a species of fur seal found mainly around southern Australia and New Zealand, is an animal of many a common name. The Māori call it kekeno, the name "New Zealand fur seal" has been commonly used by English speakers in New Zealand, whereas the Australians prefer calling it the long-nosed fur seal. Although the Australian and New Zealand populations show some genetic differences, their morphologies are very similar, and thus they remain (for now at least) classified as a single species.

Photo Description - New Zealand Fur Seal (Arctocephalus forsteri). Photo Credits and acknowledgements – Alexandre Roux (CC BY-NC-SA 2.0), via flickr

The animal is a medium-sized seal with long white whiskers and dark tan ears. Females are metallic on the back and paler underneath with a brown belly. Males have dark grey-brown dorsal fur, a pale muzzle, a pointed snout and a thick mane of long guard hairs. Males are much larger than females and around three times heavier! Pups are dark brown with silvery-grey fur on the head and neck. They feed mainly on fish, cephalopods and seabirds such as penguins.


This eared seal forms breeding colonies in New Zealand and its Subantarctic islands as well as the coasts and islands off southern Australia including Macquarie Island. Non-breeding animals are also known from New South Wales, Queensland and New Caledonia. Mating occurs from mid-November to mid-January and births occur a year later. Females give birth from 4-6 years of age and live for up to 26 years. Males mature at 5-6 years of age, hold territories and mate from 8-9 years, and live up to 15 years in the wild. A small proportion of males defend territories, generally containing around 5-8 females.


In New Zealand, Arctocephalus forsteri was hunted for their fur by Polynesians and Europeans for centuries and nearly to extinction by the 19th century. They are now protected by New Zealand's Marine Mammals Protection Act and are beginning to recover and re-colonize areas in their pre-exploitation range. In Australia, the numbers are now at around 80,000. Known predators include sharks, orcas, leopard seals, New Zealand sea lions, and humans.


Today, we share the chromosome-length genome assembly of a New Zealand fur seal Arctocephalus forsteri. This is a short-read genome assembly from a primary fibroblast cell line. We gratefully acknowledge Dr. Gina Lento for providing a skin sample of the female New Zealand fur seal (ID#: 98VB-05) in 1998 from the School of Biological Sciences, University of Auckland, New Zealand. The primary fibroblast cell line (AFO-5) was established by Mary Thompson at the Laboratory of Genomic Diversity (LGD). We sincerely acknowledge Dr. Stephen J. O’Brien for providing the cell line for this study. The cell line for Hi-C was grown by Polina Perelman and Ruqayya Khan. We are grateful to Drs. Melody Roelke-Parker, Carlos Driscoll, Christina Barr, as well as David Goldman and Stephen Lindell for the preservation of the LGD cell line collection. Passage 4 was used to make the WGS and Hi-C library. We also thank the Pawsey Supercomputing Centre and DNA Zoo Australia team at the University of Western Australia for computational support of this genome assembly.


Check out the contact map below showing the 18 chromosome-length scaffolds, consistent with the previously reported karyotype 2n=36 (Beklemisheva et al., 2020). The karyotypes of seals were formed by one extra fusion of two ancestral carnivoran segments corresponding to three human chromosome segments 1q/7q/16p and one possible inversion or centromere reposition on chromosome 8. Additional heterochromatic blocks are present on several chromosomes of the New Zealand fur seal.


Blog post by Parwinder Kaur, with contributions from Polina Perelman and Gina Lento.


References:

Beklemisheva VR, Perelman PL, Lemskaya NA, Proskuryakova AA, Serdyukova NA, Burkanov VN, Gorshunov MB, Ryder O, Thompson M, Lento G, O'Brien SJ, Graphodatsky AS. Karyotype Evolution in 10 Pinniped Species: Variability of Heterochromatin versus High Conservatism of Euchromatin as Revealed by Comparative Molecular Cytogenetics. Genes (Basel). 2020 Dec 10;11(12):1485. doi: 10.3390/genes11121485.

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