Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis
Information about the reproductive status of free-ranging pinnipeds provides useful insight into their population dynamics, which is essential to their management and conservation. To determine the reproductive status of individual animals, blood sampling is often required despite being impractical...
Published in: | Conservation Physiology |
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Format: | Article in Journal/Newspaper |
Language: | English |
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Online Access: | http://hdl.handle.net/2115/83650 https://doi.org/10.1093/conphys/coab031 |
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fthokunivhus:oai:eprints.lib.hokudai.ac.jp:2115/83650 2023-05-15T18:49:38+02:00 Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis Otsuki, Mayuko Horimoto, Takanori Kobayashi, Motoki Morita, Yuka Ijiri, Shigeho Mitani, Yoko http://hdl.handle.net/2115/83650 https://doi.org/10.1093/conphys/coab031 eng eng Oxford University Press http://hdl.handle.net/2115/83650 Conservation Physiology, 9: 1-11 http://dx.doi.org/10.1093/conphys/coab031 Gas chromatography-flame ionization detection northern fur seal reproductive status steroid hormones testosterone time-resolved fluoroimmunoassay 480 article fthokunivhus https://doi.org/10.1093/conphys/coab031 2022-11-18T01:06:46Z Information about the reproductive status of free-ranging pinnipeds provides useful insight into their population dynamics, which is essential to their management and conservation. To determine the reproductive status of individual animals, blood sampling is often required despite being impractical to collect in open water. Hair as an endocrine marker has been used to less invasively assess the reproductive status of terrestrial animals. However, it is unknown whether pinniped reproductive status can be assessed from hair samples. Here, we examine testosterone levels in hair obtained from 57 male northern fur seals and used it to compare their age class and spermatogenesis during the non-breeding season off Hokkaido. We isolated testosterone from the samples using gas chromatography and measured testosterone levels using time-resolved fluoroimmunoassay. Testosterone levels in hair increased towards the breeding season. In May, testosterone levels were the highest in seals aged between 4 and 7 years, followed by those over the age of 8 years and under the age of 4 years. Spermatids, the final phase of spermatogenesis, werepresent inthe seals sampled between April and June, eventhough testosterone levels were lowin April. The seals with spermatids in May showed the highest testosterone levels. Our results demonstrate that seals with higher testosterone levels in May are likely to be mature males (>= 4 years). Since hair can be collected using biopsy darts in the field, it will be possible to less invasively determine testosterone levels of male seals in the future. Article in Journal/Newspaper Callorhinus ursinus Northern fur seal Hokkaido University Collection of Scholarly and Academic Papers (HUSCAP) Conservation Physiology 9 1 |
institution |
Open Polar |
collection |
Hokkaido University Collection of Scholarly and Academic Papers (HUSCAP) |
op_collection_id |
fthokunivhus |
language |
English |
topic |
Gas chromatography-flame ionization detection northern fur seal reproductive status steroid hormones testosterone time-resolved fluoroimmunoassay 480 |
spellingShingle |
Gas chromatography-flame ionization detection northern fur seal reproductive status steroid hormones testosterone time-resolved fluoroimmunoassay 480 Otsuki, Mayuko Horimoto, Takanori Kobayashi, Motoki Morita, Yuka Ijiri, Shigeho Mitani, Yoko Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
topic_facet |
Gas chromatography-flame ionization detection northern fur seal reproductive status steroid hormones testosterone time-resolved fluoroimmunoassay 480 |
description |
Information about the reproductive status of free-ranging pinnipeds provides useful insight into their population dynamics, which is essential to their management and conservation. To determine the reproductive status of individual animals, blood sampling is often required despite being impractical to collect in open water. Hair as an endocrine marker has been used to less invasively assess the reproductive status of terrestrial animals. However, it is unknown whether pinniped reproductive status can be assessed from hair samples. Here, we examine testosterone levels in hair obtained from 57 male northern fur seals and used it to compare their age class and spermatogenesis during the non-breeding season off Hokkaido. We isolated testosterone from the samples using gas chromatography and measured testosterone levels using time-resolved fluoroimmunoassay. Testosterone levels in hair increased towards the breeding season. In May, testosterone levels were the highest in seals aged between 4 and 7 years, followed by those over the age of 8 years and under the age of 4 years. Spermatids, the final phase of spermatogenesis, werepresent inthe seals sampled between April and June, eventhough testosterone levels were lowin April. The seals with spermatids in May showed the highest testosterone levels. Our results demonstrate that seals with higher testosterone levels in May are likely to be mature males (>= 4 years). Since hair can be collected using biopsy darts in the field, it will be possible to less invasively determine testosterone levels of male seals in the future. |
format |
Article in Journal/Newspaper |
author |
Otsuki, Mayuko Horimoto, Takanori Kobayashi, Motoki Morita, Yuka Ijiri, Shigeho Mitani, Yoko |
author_facet |
Otsuki, Mayuko Horimoto, Takanori Kobayashi, Motoki Morita, Yuka Ijiri, Shigeho Mitani, Yoko |
author_sort |
Otsuki, Mayuko |
title |
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
title_short |
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
title_full |
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
title_fullStr |
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
title_full_unstemmed |
Testosterone levels in hair of free-ranging male northern fur seals (Callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
title_sort |
testosterone levels in hair of free-ranging male northern fur seals (callorhinus ursinus) in relation to sampling month, age class and spermatogenesis |
publisher |
Oxford University Press |
url |
http://hdl.handle.net/2115/83650 https://doi.org/10.1093/conphys/coab031 |
genre |
Callorhinus ursinus Northern fur seal |
genre_facet |
Callorhinus ursinus Northern fur seal |
op_relation |
http://hdl.handle.net/2115/83650 Conservation Physiology, 9: 1-11 http://dx.doi.org/10.1093/conphys/coab031 |
op_doi |
https://doi.org/10.1093/conphys/coab031 |
container_title |
Conservation Physiology |
container_volume |
9 |
container_issue |
1 |
_version_ |
1766243236859346944 |